Formulations of protein-loaded magnetic particles with optimal adhesion and foaming properties

Abstract

A first aspect of the invention relates to an aqueous formulation of a protein-loaded magnetic particle, the formulation comprising: (i) at least one protein-loaded magnetic particle; (ii) at least one aqueous phase; wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising: (iii) at least one detergent in a concentration of in the range of from 0.01 to 0.04 % (w / v); (iv) at least one blocking reagent in a concentration ≤ 0.02 mg / ml; (v) at least one inorganic salt in a concentration ≤ 300 mM; and (vi) at least one buffering system; wherein the at least one protein-loaded magnetic particle of (i) is present in the aqueous formulation in a concentration of ≥ 10 mg / ml; and the aqueous formulation has a pH in the range of from 6 to 7. In a second aspect, the invention relates to the use of an aqueous formulation according to the first aspect of the invention for storage, transportation, homogenization, filling, decanting and / or diagnostic purpose. A third aspect of the invention is directed to an aqueous composition, preferably for containing a protein-loaded magnetic particle, the composition comprising water and in dissolved and / or suspended form (iii), (iv), (v) and (vi) as in the formulation of the first aspect of the invention, wherein the aqueous composition has a pH in the range of from 6 to 7. A fourth aspect of the invention relates to the use of the aqueous composition of the third aspect for suspending at least one protein-loaded magnetic particle.

Description

[0001] Roche Diagnostics GmbH RD39645PC

[0002] Formulations of protein-loaded magnetic particles with optimal adhesion and foaming properties

[0003] Technical Field

[0004] A first aspect of the invention relates to an aqueous formulation of a protein-loaded magnetic particle, the formulation comprising: (i) at least one protein-loaded magnetic particle; (ii) at least one aqueous phase; wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising: (iii) at least one detergent in a concentration of in the range of from 0.01 to 0.04 % (w / v); (iv) at least one blocking reagent in a concentration < 0.02 mg / ml; (v) at least one inorganic salt in a concentration < 300 mM; and (vi) at least one buffering system; wherein the at least one protein-loaded magnetic particle of (i) is present in the aqueous formulation in a concentration of > 10 mg / ml; and the aqueous formulation has a pH in the range of from 6 to 7.

[0005] In a second aspect, the invention relates to the use of an aqueous formulation according to the first aspect of the invention for storage, transportation, homogenization, filling, decanting and / or diagnostic purpose. A third aspect of the invention is directed to an aqueous composition, preferably for containing a protein-loaded magnetic particle, the composition comprising water and in dissolved and / or suspended form (iii), (iv), (v) and (vi) as in the formulation of the first aspect of the invention, wherein the aqueous composition has a pH in the range of from 6 to 7. A fourth aspect of the invention relates to the use of the aqueous composition of the third aspect for suspending at least one protein-loaded magnetic particle.

[0006] Background art

[0007] Antibody-loaded magnetic particles are invaluable tools in diagnostic assays, such as immunoassay (i.e. Meza, M. (1997). Application of Magnetic Particles in Immunoassays. In: Hafeli, U., Schutt, W., Teller, J., Zborowski, M. (eds) Scientific and Clinical Applications of Magnetic Carriers. Springer, Boston, MA) and molecular diagnostics (i.e. Materials 2019, 12, 2158), and bioseparation applications, such as protein purification (i.e. Appl Microbiol Biotechnol. 2006 May;70(5):505-16) and nuleic acid purification (i.e. Appl Microbiol Bio- technol. 2006 Oct 25;73(3):495-504). These type of reagents enable automated, rapid and selective enrichment of low-concentrated analytes from complex biological samples, which is a central prerequisite for automated high-throughput diagnostic platforms. Such antibody- loaded magnetic particles are stored in aqueous formulations, which usually contain buffering agents, inorganic salts, biocides, blocking reagents and detergents (see, for example, CN 111044724 A or Haghighi et al. (A. H. Haghighi, M. T. Khorasani, Z. Faghih, F. Far- jadian, Heliyon 6 (2020) e03677). In order to avoid unspecific binding antibody-& protein- loaded magnetic particles during storage and use, these particles are preferably stored in formulations containing blocking reagents (i.e. see J. Mol. Recognit. 2009; 22: 77-82; Anal. Chem. 2009, 81, 21, 8774-8782; Biosensors & Bioelectronics 16 (2001) 989-993; https: / / www.thermofisher.com / blog / behindthebench / dynabeads-magnetic-beads-tips-and- tricks / ).

[0008] CN 101639478 A, CN 101614742 A and CN 101639481 A describe formulations suitable for antibody-coated magnetic particles up to 10 mg / ml particle concentrations. However, high concentrations of detergents (0.1 - 0.3 % Tween) and pH of 7.4 are used.

[0009] CN 102707060 B describes streptavidin protein coated magnetic particles stored up to 5 mg / ml in a formulation containing high concentrations of blocking proteins (0.5% BSA, 1% casein) and having a pH of 7.2.

[0010] WO 2019 / 242474 Al describes formulations suitable for antibody-coated magnetic particles in a range of 0.5 to 1 mg / mL antibody coated magnetic particle in a formulation containing a rather low content of detergent (0.04 to 0.06% (w / v)), but high concentrations of 8 to 12% (w / v; equals 233-350 mM) sucrose in a phosphate buffer adjusted to a pH in the range of from 7.0 to 8.0.

[0011] Known formulations are however not suitable for long-term storage (several months up to years) of antibody-loaded magnetic particles at high concentration of more than 10 mg / ml. Common formulations for magnetic particles are only able to provide solutions for storage at rather low particle concentration (< 10 mg / ml). At higher concentrations than 10 mg / ml, an undesired adhesion on storage materials as well as on transfer and (intermediate) transportation means (glass, plastic, metal) becomes a major problem. Undesired adhesion at high particle concentration is usually countered by the use of detergents or blocking reagents at high concentrations, which is also disadvantageous as outlined below. Another important aspect is that, with a view towards mass spectrometry (MS) analysis, known formulations for magnetic particles have to meet the requirements in terms of MS- compatibility. As on one hand the use of detergents is essential to avoid particle adhesion, detergents on the other hand can lead to ion suppression in MS and therefore their use is usually undesired for MS applications. A common solution to this problem is the use of cleavable detergents, which are converted into MS-compatible fragments prior to analysis. These cleavable detergents are mainly developed for proteomics and usually cleaved during the digestion of the protein sample (Journal of Proteome Research 2007, 6, 2529-2538). However, since these cleavable detergents require specific workflow steps to ensure cleavage prior MS analysis, this class of detergents are not generally applicable for the formulation of antibody-loaded magnetic particles. In other words, cleavable detergents are useful for the formulation of antibody-loaded magnetic particles, which are intended to be subjected to a digestion workflow or other workflows which ensure cleavage of detergent prior MS- analyis. Another drawback of cleavable detergents is their inherent limited stability, which causes aging effects upon longtime storage, such as increasing undesired adhesion of the stored particles over time.

[0012] Another important aspect is that known formulations for magnetic particles, if intended to be used in a workflow, which is intended for automation (i.e. for diagnostic testing) and for enabling a high throughput, do have to meet the requirements in terms of system-compatibility. A perfect formulation in this context should provide low adhesion of the antibody- loaded particles to its surrounding surfaces and should also enable low foam-formation during and after stirring / agitation (to allow, for example, subsequent pipetting after stirring and homogenization). Typical formulations do however not offer this specific features, since the usually contain a high amount of detergent or blocking reagents (i.e. bovine serum albumin). This might be beneficial for lowering the particle adhesion, but provokes foam-formation and causes MS-interferences.

[0013] The objective problem underlying the present invention was thus the provision of an aqueous formulation of a protein-loaded magnetic particle, which overcome the disadvantages indicated above. Especially, an aqueous formulation of a protein-loaded magnetic particle should be provided, which enables the storage of magnetic particles at high particle concentration (> 10 mg / ml), does not adhere to its surrounding surfaces, is stable even if stored for a long time (no adhesion, aggregation etc.) and which further has a low tendency towards foaming.

[0014] Summary of the invention This problem is addressed by an aqueous formulation of a protein-loaded magnetic particle, as well as by the use of said aqueous formulation for storage, transportation, homogenization, filling, decanting and / or diagnostic purpose, an aqueous composition, preferably for containing a protein-loaded magnetic particle, and its use for suspending at least one protein- loaded magnetic particle. Advantageous embodiments which might be realized in an isolated fashion or in any arbitrary combinations are listed in the dependent claims as well as throughout the specification.

[0015] As used in the following, the terms “have”, “comprise” or “include” or any arbitrary grammatical variations thereof are used in a non-exclusive way. Thus, these terms may both refer to a situation in which, besides the feature introduced by these terms, no further features are present in the entity described in this context and to a situation in which one or more further features are present. As an example, the expressions “A has B”, “A comprises B” and “A includes B” may both refer to a situation in which, besides B, no other element is present in A (i.e. a situation in which A solely and exclusively consists of B) and to a situation in which, besides B, one or more further elements are present in entity A, such as element C, elements C and D or even further elements.

[0016] Further, it shall be noted that the terms “at least one”, “one or more” or similar expressions indicating that a feature or element may be present once or more than once, typically will be used only once when introducing the respective feature or element. In the following, in most cases, when referring to the respective feature or element, the expressions “at least one” or “one or more” will not be repeated, notwithstanding the fact that the respective feature or element may be present once or more than once.

[0017] Further, as used in the following, the terms "preferably", "more preferably", "particularly", "more particularly", "specifically", "more specifically" or similar terms are used in conjunction with optional features, without restricting alternative possibilities. Thus, features introduced by these terms are optional features and are not intended to restrict the scope of the claims in any way. The invention may, as the skilled person will recognize, be performed by using alternative features. Similarly, features introduced by "in an embodiment of the invention" or similar expressions are intended to be optional features, without any restriction regarding alternative embodiments of the invention, without any restrictions regarding the scope of the invention and without any restriction regarding the possibility of combining the features introduced in such a way with other optional or non-optional features of the invention. 1staspect - Aqueous formulation of a protein-loaded magnetic particle

[0018] The problem is addressed by an aqueous formulation of a protein-loaded magnetic particle, the formulation comprising:

[0019] (i) at least one protein-loaded magnetic particle;

[0020] (ii) at least one aqueous phase; wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0021] (iii) at least one detergent in a concentration of in the range of from 0.01 to 0.04 % (w / v);

[0022] (iv) at least one blocking reagent in a concentration < 0.02 mg / ml;

[0023] (v) at least one inorganic salt in a concentration < 300 mM; and

[0024] (vi) at least one buffering system; wherein the at least one protein-loaded magnetic particle of (i) is present in the aqueous formulation in a concentration of > 10 mg / ml; and the aqueous formulation has a pH in the range of from 6 to 7.

[0025] Surprisingly, it was found that the inventive aqueous formulation of a protein-loaded magnetic particles allows for high concentrations of protein-loaded magnetic particle within the aqueous formulation while enabling a significant reduction of foam formation as well as a significant reduction of the adherence to surfaces (glass, metal, plastic).

[0026] In some preferred embodiments, the aqueous formulation further comprises

[0027] (vii) at least one biocide.

[0028] Detergent of (iii)

[0029] In some preferred embodiments of the aqueous formulation, the at least one detergent of (iii) is selected from the group consisting of non-ionic detergent, ionic detergent, zwitterionic detergent and mixtures of two or more thereof.

[0030] Preferably, the at least one detergent of (iii) is selected from the group consisting of nonionic detergent, ionic detergent, zwitterionic detergent and mixtures of non-ionic detergent and ionic detergent. In some preferred embodiments of the aqueous formulation, the at least one detergent of (iii) is selected from the group consisting of Polidocanol (CAS no. 3055-99-0), Brij 35 (polyethylene glycol lauryl ether, CAS no. 9002-92-0), Synperonic F68 (poly-(ethylene glycol)- Z> / oc -poly-(propylene glycol)-Z> / oc -poly-(ethylene glycol), CAS no. 9003-11-6), Synperonic F108 (poly-(ethylene glycol )-Z> / ocA poly-(propylene glycol )- xA-poly-(ethylene glycol), CAS no. 68131-40-8), Tergitol 15-S-9 (sec-alkoxy poly ethylene glycol, CAS no. 84133-50-6), Tween 20 (poly oxyethylene-20-sorbitanmonolaurat, CAS no. 9005-64-5), Tween 80 (polyoxyethylene-80-sorbitan monooleat, CAS no. 9005-65-6), CTAB (cetyl trimethyl ammonium bromide, CAS no. 57-09-0), Na-cholate (CAS no. 361-09 -1), Na-deox- ycholate (CAS no. 302-95-4), Na-N-lauroylsarcosinate (CAS no. 137-16-6), SDS (sodium dodecyl sulfate, CAS no. 151-21-3), ASB-14 (amidosulfobetaine- 14, CAS no. 216667-08- 2), ASB-16 (amidosulfobetaine- 16, CAS no. 52562-29-5), SB 3 - 10 (caprylyl sulfobetaine, CAS no. 15163-36-7), SB 12 ( / / -dodecyl-N,N-dimethyl-3-ammonio- l -propanesulfonate, CAS no. 14933-08-05), n-dodecyl-P-D-maltopyranoside (DDM, CAS no. 69227-93-6), n- decyl-P-D-maltopyranoside (DM, CAS no. 82494-09-05), n-octyl-P-D-glucopyranoside / n- nonyl-P-D-glucopyranoside (OG (CAS no. 29836-26-8) / NG (CAS no. 69984-73-2)), lauryl dimethylamine-N-oxide (LDAO, CAS no. 1643-20-5), polyoxyethylene dodecyl ether (CAS no. 9002-92-0), n-undecyl-P-D-maltopyranoside (UDM, CAS no. 253678-67-0), lauryl maltose neopentyl glycol (LMNG, CAS no. 1257852-96-2), Triton X-100 ( / -octyl phe- noxypolyethoxyethanol, CAS no. 9036-19-5), Digitonin, cyclic maltosides (CAS no. 11024- 24-1), 3-[(3-cholamidopropyl)dimethylammonio]-l-propanesulfonate (CHAPS, CAS no. 75621-03-03), 3 -[(3 -cholamidopropyl)dimethylammonio] -2-hy droxy- 1 -propanesulfonate (CHAPSO, CAS no. 82473-24-3), and mixtures of two or more thereof. Reference is made to inhttps: / / www.serva.de / enDE / 275_Information_Center_Detergents_Classifica- tion_of_Detergents.html .

[0031] In some preferred embodiments of the aqueous formulation, the at least one detergent of (iii) is selected from the group consisting of n-dodecyl-P-D-maltopyranoside (DDM), n-decyl-P- d-maltopyranoside (DM), n-octyl-P-d-glucopyranoside / n-nonyl-P-d-glucopyranoside (OG / NG), lauryldimethylamine-N-oxide (LDAO), polyoxyethylene dodecyl ether, n-un- decyl-P-d-maltopyranoside (UDM), lauryl maltose neopentyl glycol (LMNG), Triton X- 100, Digitonin, cyclic maltoside, 3-[(3-cholamidopropyl)dimethylammonio]-l-propanesul- fonate (CHAPS), 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-l-propanesul- fonate (CHAPSO), and mixtures of two or more thereof. In some preferred embodiments of the aqueous formulation, the at least one detergent of (iii) comprises or is a polyoxyethylene dodecyl ether, preferably macrogollaurylether 8 (CnEs) and / or macrogollaurylether 9 (Thesit, Polidocanol, CAS: 9002-92-0).

[0032] In some preferred embodiments of the aqueous formulation, the at least one detergent of (iii) is present in a concentration of < 0.04 % (w / v). Preferably, the at least one detergent of (iii) is present in a concentration in the range of from 0.02-0.035 % (w / v).

[0033] “% (w / v)” means weight of detergent per volume of the aqueous formulation, for example, 1% (w / v) means that 10 mg of detergent are present per 1 milliliter of aqueous formulation.

[0034] (First) blocking reagent of (iv)

[0035] In some preferred embodiments of the aqueous formulation, the at least one blocking reagent of (iv) is a protein.

[0036] Preferably, the at least one blocking reagent of (iv) is a protein selected from the group consisting of bovine serum albumin (BSA), human serum albumin (HSA), lactalbumin, casein, skim milk, serum proteins, and mixtures thereof, wherein the at least one blocking reagent of (iv) more preferably comprises at least BSA.

[0037] In some preferred embodiments of the aqueous formulation, the at least one blocking reagent of (iv), i.e. the protein, is a monoclonal antibody, preferably a recombinant antibody.

[0038] In some preferred embodiments of the aqueous formulation, the at least one blocking reagent of (iv) is present in a concentration in the range of from 0.001 to 0.02 mg / ml, more preferably in the range of 0.001 to 0.015 mg / ml, more preferably in the range of from 0.01 to 0.014 mg / ml (for vitamin D specific antibody-loaded magnetic particle) or in the range of from 0.001 to 0.01 mg / ml (or steroid specific antibody-loaded magnetic particle).

[0039] Inorganic salt of (v)

[0040] In some preferred embodiments of the aqueous formulation, the at least one inorganic salt of (v) is selected from the group of earth alkali metal salt, alkali metal salt and mixtures of earth alkali metal salt and alkali metal salt, more preferably at least one alkali metal salt, more preferably at least one alkali metal halogenide, more preferably at least potassium chloride. In some preferred embodiments of the aqueous formulation, the at least one inorganic salt of (v) is present at a concentration in the range of from 10 to 300 mM, more preferably in the range of from 100 to 245 mM, more preferably in the range of from 100 to 140 mM (for vitamin D specific antibody-loaded magnetic particle) or in the range of 200 to 245 mM (for steroid specific antibody-loaded magnetic particle).

[0041] Buffer system of (vi)

[0042] In some preferred embodiments of the aqueous formulation, the at least one buffering system of (vi) is selected from the group of potassium phosphate buffer (K2HPO4 / KH2PO4), MES, ADA, PIPES, ACES, MOPSO, cholamine chloride, MOPS, TES, HEPES, DiPSO, TAPSO and mixtures of two or more thereof, more preferably selected from the group of potassium phosphate buffer (K2HPO4 / KH2PO4), MES, MOPS and mixtures of two or three thereof, wherein the at least one buffering system of (vi) more preferably comprises at least MES.

[0043] Biocide of (vii)

[0044] In some preferred embodiments of the aqueous formulation, the at least one biocide of (vii) is selected from the group consisting of (metal cation) chelating biocide, (metal cation) nonchelating biocide and mixtures of two or more thereof.

[0045] Preferably, the at least one biocide of (vii) is selected from the group of (metal cation) nonchelating biocides, wherein the at least one biocide of (vii) is preferably selected from the group of isothiazolinone derivative, sodium azide, chloroacetamide, sodium benzoate and mixtures thereof; wherein the at least one biocide of (vii) is more preferably selected from the group consisting of methylisothiazolinone (2-methyl-l,2-thiazol-3(2H)-one, MIT, CAS no. 2682-20-4), methylchloroisothiazolinone (5-chloro-2-methyl-l,2-thiazol-3(2H)-one, MCI, CAS no. 26172-55-4), benzisothiazolinone (l,2-benzothiazol-3(2H)-one, BIT, CAS no. 2634-33-5), octylisothiazolinone (2-octyl-l,2-thiazol-3(2H)-one, OIT, CAS no. 26530- 20-1), dichlorooctylisothiazolinone (4,5-dichloro-2-octyl-l,2-thiazol-3(2H)-one, DCOIT, CAS no. 64359-81-5), sodium azide (CAS no. 26628-22-8), 2-chloroacetamide (CAS no. 79-07-2), sodium benzoate (CAS no. 532-32-1), and mixtures of two or more thereof; wherein the at least one biocide of (vii) is more preferably selected from the group consisting of methylisothiazolinone (2-methyl-l,2-thiazol-3(2H)-one, MIT), methylchloroisothiazolinone (5-chloro-2-methyl-l,2-thiazol-3(2H)-one, MCI), sodium azide, 2-chloroacetamide, sodium benzoate, and mixtures of two or more thereof, preferably from the group consisting of methylisothiazolinone (2-methyl-l,2-thiazol-3(2H)-one, MIT), methylchloroisothiazoli- none (5-chloro-2-methyl-l,2-thiazol-3(2H)-one, MCI), sodium azide, and mixtures of two or more thereof.

[0046] In some preferred embodiments of the aqueous formulation, the at least one biocide of (vii) at least comprises MIT.

[0047] In some preferred embodiments of the aqueous formulation, the at least one biocide of (vii) is present in a concentration in the range of from 0.001 to 0.5 mg / ml, more preferably in the range of from 0.1 to 0.4 mg / ml, more preferably in the range of from 0.15 to 0.35 mg / ml.

[0048] In some preferred embodiments, the aqueous formulation comprises less than 100 weight- ppm, preferably less than 50 weight-ppm, more preferably less than 10 weight-ppm of a (metal cation) chelating biocide, based on the total weight of the aqueous formulation being 100 weight-%. A “(metal cation) chelating biocide” is a compound with biocide activity, which comprises within its structure at least two free electron pairs by which the compound can form at least two chelate bonds to a metal cation, preferably to an iron cation. Preferably, a chelating biocide comprises within its structure at least two COOH groups and at least one nitrogen atom, such as ethylenediaminetetraacetic acid (EDTA), or the chelating biocide comprises within its structure at least one structural element -N(OH)-C(=O)-, which is part of a linear structure or of a cyclic structure, wherein the structure is either aliphatic or aromatic. Such a structural element -N(OH)-C(=O)- can be, for example, found in the biocide OxyPyrion (Hydroxyl-2-pyridone, CAS 822-89-9). A ”non-chelating biocide” does not have these at least two COOH groups and at least one nitrogen atom or structural element -N(OH)- C(=O)-.

[0049] Preferably, the protein of the at least one protein-loaded magnetic particle of (i) within the aqueous formulation according to the present invention shows a reduced fragmentation of at least 10% less than the same protein-loaded magnetic particle of (i) within an aqueous formulation containing a chelating biocide, preferably an iron-chelating biocide, at the same concentration and at a pH > 7. For example, if the fragmentation of the protein of the at least one protein-loaded magnetic particle of (i) within the aqueous formulation according to the present invention is normalized to a value of 100%, the value of the fragmentation of the same protein on the same protein-loaded magnetic particle of (i) within an aqueous formulation containing a chelating biocide, preferably an iron-chelating biocide, at the same concentration and at a pH >7, is > 110%. “Fragmentation” refers to any protein species / fragment that originates from cleavage of the protein loaded to the magnetic particle, wherein the protein initially had a molecular weight MW(0) and thus is characterized by a smaller molecular weight MW(i) of the protein loaded to the magnetic particle compared to the intact protein, i.e. MW(i) < MW(0). Preferably, the protein of the at least one protein-loaded magnetic particle of (i) within the aqueous formulation according to the present invention shows said reduced fragmentation while being in the aqueous formulation / phase for a period of time of at least 8 weeks and / or at a temperature in the range of from 35 to 40°C.

[0050] Second blocking reagent

[0051] In some preferred embodiments, the aqueous formulation further comprises (viii) at least one second blocking reagent.

[0052] Preferably, the at least one second blocking reagent of (viii) is selected from the group consisting of polyol, carbohydrate and mixtures of two or more thereof; more preferably selected from the group consisting of trehalose, sucrose, glycerol, threitol, sorbitol, maltitol and mixtures of two or more thereof; wherein the at least one second blocking reagent of (viii) comprises more preferably at least trehalose.

[0053] In some preferred embodiments of the aqueous formulation, the at least one second blocking reagent of (viii) is present in a concentration in the range of from of 10 to 500 mM, more preferably in the range of from 50 to 250 mM, more preferably in the range of from 70 to 150 mM, more preferably in the range of from 80 to 125 mM (for vitamin D specific-anti- body) or in the range of from 110 to 140 mM (for steroid-specific antibody). pH of aqueous formulation

[0054] In some preferred embodiments, the aqueous formulation, especially the aqueous phase of (ii) of the aqueous formulation as described herein above, has a pH value in the range of from 6 to 7. The pH of the aqueous formulation is preferably determined by using a pH sensitive glass electrode, preferably at a temperature in the range of from 20 to 30°C and / or, preferably and, at a pressure in the range of from 800 to 1300 hPa. In some preferred embodiments, the aqueous formulation has a pH in the range of from 6.0 to 6.9, preferably in the range of from 6.0 to 6.8, more preferably in the range of from 6.0 to 6.7, more preferably in the range of from 6.0 to 6.6, more preferably in the range of from 6.0 to 6.5. Protein of the at least one protein-loaded magnetic particle

[0055] In some preferred embodiments of the aqueous formulation, the protein of the at least one protein-loaded magnetic particle of (i) is an antibody or a fragment thereof. Preferably, the antibody or fragment thereof is selected from the group consisting of vitamin D specific antibody, fragment of vitamin D specific antibody, steroid specific antibody, and fragment of steroid specific antibody.

[0056] Preferably, the vitamin D specific antibody or fragment thereof is selected from the group consisting of vitamin DI specific antibody, vitamin D2 specific antibody, vitamin D3 specific antibody, vitamin D4 specific antibody, vitamin D5 specific antibody, 25-hydroxy-vit- amin D2 specific antibody, 25-hydroxy vitamin D3 specific antibody, 24, 25-dihydroxy- vitamin D2 specific antibody, and 24, 25-dihydroxy-vitamin D3 specific antibody.

[0057] Vitamin D- and steroid-specific antibodies are available from numerous vendors such as (i.e. Merck, Thermo Fisher, Bioventix, Bio-Rad, antibodies-online.com). Also specifically developed antibodies can be used, which can be developed by known procedures (i.e. according to WO 2018 / 122205 A2).

[0058] For example, antibodies precursors from commercialized Roche products (Elecsys® vitamin D total III; Elecsys® Estradiol III) can be used. Monoclonal antibodies were developed as known to the skilled person and as described in the state of the art (see, for example, Waller- Pulido Alejandra, Jimenez-Perez Miriam Irene, Gonzalez- Sanchez Fabio Antonio, Rojo- Gutierrez Rocio Patricia, Torres- Anguiano Elizabeth, Juan Pablo Al eman- Aguilar, Garcia- Varela Rebeca; Production of monoclonal antibodies for therapeutic purposes: A review“; International Immunopharmacology, Vol. 120, July 2023, 110376; Rohit Singh, Pankaj Chandley, Soma Rohatgi , „Recent Advances in the Development of Monoclonal Antibodies and Next-Generation Antibodies“, ImmunoHorizons, (2023) 7 (12): 886-897; WO 2018 / 122205 A2). Antibody-magnetic particle conjugates can be prepared by know procedures using different conjugation chemistries (i.e. see review Beilstein J. Nanotechnol. 2023, 14, 912-926; The AAPS Journal (2021) 23: 43 (DOI: 10.1208 / sl2248-021-00561-5).

[0059] In some preferred embodiments of the aqueous formulation, the protein and the magnetic particle are bound to each other by a covalent or a non-covalent bond.

[0060] In some preferred embodiments of the aqueous formulation, the at least one protein-loaded magnetic particle of (i) comprises at least two protein-loaded magnetic particles, wherein at least a first magnetic particle is loaded with a first protein and at least a second magnetic particle is loaded with a second protein, wherein at least the first protein and the second protein are different from each other. In other words, the aqueous formulation of the present invention may comprises not only one kind of magnetic particle loaded with protein but may rather comprises also mixtures of magnetic particles loaded with different proteins, wherein each magnetic particle is only loaded with one kind of protein.

[0061] Magnetic particles are per se known to the skilled person. For example, protein-loaded magnetic particles, such as antibody-loaded magnetic particles, can be prepared by covalent coupling of proteins, such as antibodies, on amine or carboxylated magnetic particles using published procedures (i.e. Anal Bioanal Chem 408, 8325-8332 (2016); protocols by Agilent and Cytiva https: / / www.agilent.com / cs / library / technicaloverviews / public / lodestars-carboxyl- 5994-5012en-agilent.pdf and https: / / cdn.cytivalifesciences.com / api / public / content / digi- 33629-original). Suitable carboxylated magnetic particles for protein / antibody conjugation are commercially available from numerous vendors (i.e. Merck / Sigma-Aldrich, Thermo Fisher, Cytiva, Agilent, CD Bioparticles) or can be prepared by known protocols (i.e. ACS Omega 2018, 3, 12, 17904-17913; Colloid Polym Sci 302, 695-709 (2024); Journal of Magnetism and Magnetic Materials 265 (2003) 98-105). As another example, protein-loaded magnetic particles, such as antibody-loaded magnetic particles, can be prepared by covalent coupling of proteins, such as antibodies, on magnetic particles using click chemistry as reported in published procedures (see Molecular Imaging 2009 8:4

[0062] (https: / / doi.org / 10.2310 / 7290.2009.00021); ACS Nano 2013, 7, 11, 9655-9663). Suitable azide-or alkyne-modified magnetic particles for protein / antibody conjugation are commercially available from numerous vendors (i.e. NANOCS, CD Bioparticles) or can be prepared by known protocols (i.e Ind. Eng. Chem. Res. 2014, 53, 12, 4554-4564; ACS Nano 2013, 7, 11, 9655-9663; M. B. Coppock, D. N. Strati s-Cullum, Methods 158 (2019) 12-1.).

[0063] Preferably, the magnetic particle comprises at least one magnetic core (M), and at least a polymer matrix (P) comprising a crosslinked polymer at least partially surrounding the magnetic core (M). Preferably, the polymer matrix (P) comprises a crosslinked polymer, wherein the crosslinked polymer preferably comprises a co-polymer obtained or obtainable by a method comprising a polymerization of at least one, preferably at least two different, monomeric building block(s) selected from the group consisting of styrene, functionalized styrenes, vinylbenzylchloride, divinylbenzene, vinylacetate, methylmethacrylate and acrylic acid. Preferably, the at least one monomeric building block used has one or more functional group(s) reactive towards amine groups or amine groups, wherein the functional group reactive towards amine groups and / or hydroxyl groups is preferably selected from the group of halogenated Cl-C3-alkyl group, halogen atom, epoxy group and activated carboxy group, more preferably the functional group reactive towards amine groups and / or hydroxyl groups is a halogenated Cl-C3-alkyl group, more preferably a -CH2-CI group. Preferably, vinylben- zyl chloride is employed as monomeric building block having functional groups reactive towards amine groups and / or hydroxyl groups. Preferably, the at least one further monomeric building block is a crosslinking agent, preferably selected from the group consisting of divinylbenzene, bis(vinylphenyl)ethane, bis(vinylbenzyloxy)hexane, bis(vinylben- zyloxy)dodecane, and mixtures of two or more thereof, wherein more preferably the crosslinking agent comprises at least divinylbenzene. Preferably, the co-polymer is obtained or obtainable by a method comprising a polymerization of at least two different monomeric building blocks selected from the group consisting of the following monomers: with Rv, Rw, Rx, Ryand Rz, are, independently of each other selected from the group consisting of -N3, -NH2, -Br, -I, -F, -NR’R”, -NR’R”R”’, -COOH, -CN, -OH, -OR’, -COOR’, - NO2, -SH2, -SO2, -R’(OH)X, -R’(COOH)X, -R’(COOR”)X, -R’(OR”)X, -R’(NH2)X, - R’(NHR”)X, -R’(NR”R”’)X, -R’(C1)X, -R’(I)X, -R’(Br)x, -R’(F)X, R’(CN)X, -R’(N3)X, - R’(NO2)X, -R’(SH2)X, -R’(SO2)X, alkyl, aryl, cycloalkyl, heteroaryl, heterocycloalkyl and with R’, R” and R’” being, independently of each other, selected from the group consisting of alkyl, aryl, cycloalkyl, heteroaryl, heterocycloalkyl, halides, hydrogen, sulfides, nitrates and amines, and wherein x is an integer in the range of from 1 to 3.

[0064] Preferably, the polymer matrix is obtained or obtainable by a method comprising co-poly- merizing at least one monomeric building block, which is a crosslinking agent, and at least one monomeric building block having functional groups reactive towards amine groups and / or hydroxyl groups, wherein the molar ratio of crosslinking agent : monomeric building block having functional groups reactive towards amine groups and / or hydroxyl groups is in the range of from 10: 1 to 1 :10, preferably in the range of from 5:1 to 1 :5, more preferably in the range of from 2: 1 to 1 :2, more preferably in the range of from 1.5: 1 to 1 : 1.5, more preferably in the range of from 1.2: 1 to 1 : 1.2.

[0065] Preferably, at least divinylbenzene is employed as crosslinking agent and at least vinylbenzyl chloride is employed as monomeric building block having functional groups reactive towards amine groups and / or hydroxyl groups.

[0066] Preferably, the functional group reactive towards amine groups and / or hydroxyl groups is modified in the polymer matrix (P), wherein a modified functional group is still reactive towards amine groups and / or hydroxyl groups and is preferably a carboxyl group and / or an amine group. For example, if vinylbenzyl chloride has been employed as monomeric building block, the functional group is modified into a hydroxyl group, for example, by application of a strong base such as KOH and heat, and, subsequently, the hydroxyl group is transformed into a carboxylic group by oxidation, for example, by using sodium hypochlorite.

[0067] Preferably, a linker (L) is attached to the polymer matrix (P), preferably via a covalent bond to a functional, optionally modified, group reactive towards amine groups and / or hydroxyl groups. Said linker (L) links the magnetic particle to a further functional, optionally modified, group (FG), which is preferably selected from azide group (-N=N+-N‘) and carboxyl group (-COO(H)), and is more preferably an azide group (-N=N+-N‘).

[0068] Preferably, the linker (L) comprises an element (LI)

[0069] • • • X-(CR1R2)xi - [(CR3R4)x2]y-(CR1R2)x3 •••• (LI), wherein

[0070] R1, R2are independently selected from the group consisting of hydrogen atom and Cl to C3 straight or branched alkyl group;

[0071] R3is selected from the group consisting of hydrogen atom and Cl to C3 straight or branched alkyl group, and is preferably a Cl to C3 straight or branched alkyl group;

[0072] R4is a C(=O)-X1-(CH2)zi-N+(CH3)2-(CH2)z2-SO3- group; xl, x2, x3 are each independently an integer selected from the range of from 1 to 10; y is an integer selected from the range of from 1 to 500;

[0073] X is an -NH- group or an oxygen atom;

[0074] XIis an -NH- group or an oxygen atom, preferably an oxygen atom; wherein the dotted lines •••• indicate the covalent bond(s) to the polymer matrix (P) and to the further functional group (FG) respectively; or the linker (L) comprises an element (L2)

[0075] ••••X-(CR1R2)xi-[O-(CR3R4)x2]y•••• (L2), wherein

[0076] R1, R2, R3, R4are independently selected from the group consisting of hydrogen atom and Cl to C3 straight or branched alkyl group; xl, x2 are each independently an integer selected from the range of from 1 to 10; y is an integer selected from the range of from 1 to 500;

[0077] X is an -NH- group or an oxygen atom; wherein the dotted lines •••• indicate the covalent bond(s) to the polymer matrix (P) and to the further functional group (FG) respectively.

[0078] Preferably, at least one of R3, R4is a hydrogen atom, preferably R3and R4are both hydrogen atoms. Preferably, at least one of R1, R2is a hydrogen atom, preferably R1and R2are both hydrogen atoms. Preferably, xl, x2 and optionally x3 are independently an integer selected from the range of from 2 to 6, preferably 2 or 3. Preferably, y is an integer selected from the range of from 2 to 450, preferably from the range of from 2 to 225, more preferably from the range of from 2 to 110; or wherein y is an integer selected preferably from the range of from 2 to 50, more preferably from the range of from 3 to 40.

[0079] Preferably, the at least one magnetic core (M) comprises a compound selected from the group consisting of metal, metal carbide, metal nitride, metal sulfide, metal phosphide, metal oxide, metal chelate and a mixture of two or more thereof.

[0080] Preferably, the at least one magnetic core (M) comprises a metal oxide or a metal carbide, more preferably, an iron oxide, in particular an iron oxide selected from the group consisting of Fe3O4, a-Fe2O3, y-Fe2O3, MnFepOq, CoFepOq, NiFepOq, CuFepOq, ZnFepOq„ CdFepOq, BaFepO and SrFepO, wherein p and q vary depending on the method of synthesis, and wherein p is preferably an integer of from 1 to 3, more preferably 2, and wherein q is preferably 3 or 4 most preferably, Fe3O4.

[0081] Preferably, the at least one magnetic core (M) comprises at least one magnetic nanoparticle, preferably at least one iron oxide nanoparticle, more preferably a Fe3O4-nan oparticle. Preferably, the at least one magnetic core (M) comprises, more preferably consists of a magnetic nanoparticle and a coating (C). Preferably, the magnetic particle has a coating (C) on at least a part of the surface of the magnetic core (M), preferably on at least 90 % of the surface of the magnetic core (M), more preferably on the whole surface of the magnetic core (M). Preferably, the coating (C) is selected from the group consisting of silica, silicate, silane, phosphate, phosphonate, phosphonic acid, fatty acid, and mixtures of two or more thereof.

[0082] Preferably, the coating (C) is selected from the group consisting of silica, tetraethyl orthosilicate, 3 -(trimethoxy silyl)propyl methacrylate, vinyltrimethoxy silane, vinyltri ethoxysilane, allyltrimethoxysilane, allyltri ethoxy silane, triethoxy vinylsilane, 3 -(trimethoxy si - lyl)propyl acrylate, trimethoxy(7-octen-l-yl)silane, trimethoxymethylsilane, triethoxymethylsilane, ethyltrimethoxysilane, triethoxy(ethyl)silane, trimethoxyphenylsilane, tri- methoxy(2-phenylethyl)silane trimethoxy(propyl)silane, n-propyltriethoxysilane, isobu- tyl(trimethoxy)silane, isobutyltriethoxysilane, vinylphosphonic acid, dimethyl vi- nylphosphonate, diethyl vinylphosphonate, diethyl allylphosphonate, diethyl allyl phosphate, diethyl (2-methylallyl)phosphonate, octylphosphonic acid, butylphosphonic acid, decylphosphonic acid, hexylphosphonic acid, hexadecylphosphonic acid, n-do- decylphosphonic acid, lauric acid, myristic acid, palmitic acid, stearic acid, and arachidic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecylic acid, tridecylic acid, pentadecylic acid, margaric acid, nonadecylic acid, heneicosylic acid, behenic acid, tricosylic acid, lignoceric acid, pentaco- sylic acid, cerotic acid, heptacosylic acid, montanic acid, nonacosylic acid, melissic acid, henatriacontylic acid, lacceroic acid, psyllic acid, geddic acid, ceroplastic acid, hexatriac- ontylic acid, heptatriacontanoic acid, octatriacontanoic acid, oleic acid, linoleic acid, linolenic acid, arachidonic acid, hexadecatrienoic acid, stearidonic acid, eicosatrienoic acid, eicosatetraenoic acid, eicosapentaenoic acid, heneicosapentaenoic acid, docosapentaenoic acid, clupanodonic acid, docosahexaenoic acid, tetracosapentaenoic acid, tetracosahex- aenoic acid, calendic acid, eicosadienoic acid, docosadienoic acid, adrenic acid, docosapentaenoic acid, tetraco-satetraenoic acid, tetracosapentaenoic acid, 5-dodecenoic acid, 7- tetradecenoic acid, pal-mitoleic acid, vaccenic acid, paullinic acid, 15-docosenoic acid, 17- tetracosenoic acid, elaidic acid, gondoic acid, mead acid, erucic acid, nervonic acid, rumenic acid, calendic acid, jacaric acid, eleostearic acid, catalpic acid, punicic acid, rumelenic acid, parinaric acid, bosseopentaenoic acid, pinolenic acid, podocarpic acid and mixtures of two or more thereof. Preferably, the magnetic particles have a median of particle size distribution x50 in the range of from 1 to 10 pm, more preferably in the range of from 2 to 5 micrometers, as determined according to DIN ISO 9276-2:2018-09.

[0083] Preferably, the median of particle size distribution x50 has a standard deviation (span), calculated according to (x90 - xlO) / x50, of < 1.1 micrometer, wherein x90, x50 and xlO are determined according to DIN ISO 9276-2:2018-09.

[0084] Preferably, the magnetic particle has a density in the range of from 1.2 to 1.7 g / cm3, determined by gas pycnometry. The determination of the density by gas pycnometry is preferably done according to the method indicated in the European Pharmacopoeia (Ph. Eur.), 11thedition, Chapter 2.9.23.

[0085] Preferably, the magnetic particle has a saturation magnetization in the range of from 15 to 25 Am2 / kg, determined by vibrating sample magnetometry, preferably according to ASTM A 894 / A 894M.

[0086] Preferably, the magnetic particle has a BET specific surface area in the range of from 2 to 60 m2 / g, determined by nitrogen physisorption according to DIN 66131 : 1993-07.

[0087] Preferably, the protein is bonded to the magnetic particle via a functional group of the magnetic particle, preferably the functional group (FG) indicated above and a corresponding functional group of the protein, for example by “click” chemistry or via NHS chemistry (NHS: N-hydroxysuccinimide).]

[0088] Concentration of protein-loaded magnetic particle

[0089] In some preferred embodiments, the aqueous formulation comprises the at least one protein- loaded magnetic particle in a concentration in the range of > 10 mg / ml, more preferably of > 11 mg / ml, more preferably of> 12 mg / ml.

[0090] In some preferred embodiments, the aqueous formulation comprises the at least one protein- loaded magnetic particle in a concentration in the range of from 10 to 100 mg / ml, more preferably in the range of from 10 to 50 mg / ml. In some preferred embodiments, the aqueous formulation comprises the at least one protein- loaded magnetic particle in a concentration in the range of from 11 to 100 mg / ml, more preferably in the range of from 11 to 50 mg / ml.

[0091] In some preferred embodiments, the aqueous formulation comprises the at least one protein- loaded magnetic particle in a concentration in the range of from 12 to 100 mg / ml, more preferably in the range of from 12 to 50 mg / ml.

[0092] In some preferred embodiments, the aqueous formulation comprises the at least one protein- loaded magnetic particle in a concentration in the range of from 12 to 13 mg / ml, or in a concentration in the range of from 18 to 22 mg / ml, or in a concentration in the range of from 25 to 29 mg / ml, or in a concentration in the range of from 48 to 52 mg / ml.

[0093] In some preferred embodiments, the aqueous formulation comprises the at least one protein- loaded magnetic particle in a concentration of 12.5 mg / ml, or in a concentration of 20 mg / ml, or in a concentration of 27 mg / ml, or in a concentration of 50 mg / ml.

[0094] Specific embodiments of aqueous formulation

[0095] In some preferred embodiments, the aqueous formulation comprises

[0096] (i) at least one protein-loaded magnetic particle, wherein the protein is preferably an antibody or fragment thereof, said antibody preferably being selected from vitamin D specific antibody, fragment of vitamin D specific antibody, and steroid-specific antibody, fragment of steroid-specific antibody;

[0097] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0098] (iii) at least one detergent, which preferably comprises or is Thesit, in a concentration of in the range of from 0.01 to 0.04 % (w / v);

[0099] (iv) at least one blocking reagent, which preferably comprises BSA, in a concentration < 0.02 mg / ml;

[0100] (v) at least one inorganic salt, which preferably comprises or is KC1, in a concentration < 300 mM; and

[0101] (vi) at least one buffering system, which preferably comprises or is KH2PO4 / K2HPO4 (K- PO4) or MOPS or MES; wherein the aqueous formulation has a pH value in the range of from 6 to 7 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of > 10 mg / ml, preferably of> 11 mg / ml, more preferably of> 12 mg / ml.

[0102] In some preferred embodiments, the aqueous formulation comprises

[0103] (i) at least one protein-loaded magnetic particle, wherein the protein is preferably an antibody or fragment thereof, said antibody preferably being selected from vitamin D specific antibody, fragment of vitamin D specific antibody, steroid-specific antibody, and fragment of steroid-specific antibody;

[0104] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0105] (iii) at least one detergent, which preferably comprises or is Thesit, in a concentration of in the range of from 0.01 to 0.04 % (w / v);

[0106] (iv) at least one blocking reagent, which preferably comprises BSA, in a concentration < 0.02 mg / ml;

[0107] (v) at least one inorganic salt, which preferably comprises or is KC1, in a concentration < 300 mM;

[0108] (vi) at least one buffering system, which preferably comprises or is KH2PO4 / K2HPO4 (K- PO4) or MOPS or MES;

[0109] (vii) at least one biocide, which preferably comprises or is MIT;

[0110] (viii) at least one second blocking reagent, which preferably comprises or is trehalose; wherein the aqueous formulation has a pH value in the range of from 6 to 7 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of > 10 mg / ml, preferably of> 11 mg / ml, more preferably of> 12 mg / ml.

[0111] In some preferred embodiments, the aqueous formulation comprises

[0112] (i) at least one protein-loaded magnetic particle, wherein the protein is preferably an antibody or fragment thereof, said antibody preferably being selected from vitamin D specific antibody, fragment of vitamin D specific antibody, steroid-specific antibody, and fragment of steroid-specific antibody;

[0113] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising: (iii) at least one detergent, which preferably comprises or is Thesit, in a concentration of in the range of from 0.01 to 0.04 % (w / v);

[0114] (iv) at least one blocking reagent, which preferably comprises BSA, in a concentration < 0.02 mg / ml;

[0115] (v) at least one inorganic salt, which preferably comprises or is KC1, in a concentration < 300 mM; and

[0116] (vi) at least one buffering system, which preferably comprises or is KH2PO4 / K2HPO4 (K- PO4) or MOPS or MES; wherein the aqueous formulation has a pH value in the range of from 6 to 7 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of > 10 mg / ml, preferably of> 11 mg / ml, more preferably of> 12 mg / ml.

[0117] In some preferred embodiments, the aqueous formulation comprises

[0118] (i) at least one protein-loaded magnetic particle, wherein the protein is preferably an antibody or fragment thereof, said antibody preferably being selected from vitamin D specific antibody, fragment of vitamin D specific antibody, steroid-specific antibody, and fragment of steroid-specific antibody;

[0119] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0120] (iii) at least one detergent, which preferably comprises or is Thesit, in a concentration of in the range of from 0.01 to 0.04 % (w / v);

[0121] (iv) at least one blocking reagent, which preferably comprises BSA, in a concentration < 0.02 mg / ml;

[0122] (v) at least one inorganic salt, which preferably comprises or is KC1, in a concentration < 300 mM; and

[0123] (vi) at least one buffering system, which preferably comprises or is KH2PO4 / K2HPO4 (K- PO4) or MOPS or MES;

[0124] (vii) at least one biocide, which preferably comprises or is MIT, in a concentration < 0.5 mg / ml;

[0125] (viii) at least one second blocking reagent, which preferably comprises or is trehalose, in a concentration in the range of from of 10 to 500 mM; wherein the aqueous formulation has a pH value in the range of from 6 to 7 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of > 10 mg / ml, preferably of> 11 mg / ml, more preferably of> 12 mg / ml. In some preferred embodiments, the aqueous formulation comprises

[0126] (i) at least one protein-loaded magnetic particle, wherein the protein is a vitamin D specific antibody, or a fragment of vitamin D specific antibody;

[0127] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0128] (iii) at least one detergent, which is Thesit, in a concentration of 0.03 % (w / v);

[0129] (iv) at least one blocking reagent, which is BSA, in a concentration of 0.0125 mg / ml;

[0130] (v) at least one inorganic salt, which is KC1, in a concentration of 125 mM; and

[0131] (vi) at least one buffering system, which is MOPS;

[0132] (vii) at least one biocide, which is MIT, in a concentration of 0.25 mg / ml;

[0133] (viii) at least one second blocking reagent, which is trehalose, in a concentration of 105 mM; wherein the aqueous formulation has a pH value of 7.4 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of 20 mg / ml.

[0134] In some preferred embodiments, the aqueous formulation comprises

[0135] (i) at least one protein-loaded magnetic particle, wherein the protein is a vitamin D specific antibody, or a fragment of vitamin D specific antibody;

[0136] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0137] (iii) at least one detergent, which is Thesit, in a concentration of 0.035 % (w / v);

[0138] (iv) at least one blocking reagent, which is BSA, in a concentration of 0.0125 mg / ml;

[0139] (v) at least one inorganic salt, which is KC1, in a concentration of 125 mM; and

[0140] (vi) at least one buffering system, which is MOPS;

[0141] (vii) at least one biocide, which is MIT, in a concentration of 0.25 mg / ml;

[0142] (viii) at least one second blocking reagent, which is trehalose, in a concentration of 125 mM; wherein the aqueous formulation has a pH value of 7.4 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of 20 mg / ml.

[0143] In some preferred embodiments, the aqueous formulation comprises

[0144] (i) at least one protein-loaded magnetic particle, wherein the protein is a vitamin D specific antibody, or a fragment of vitamin D specific antibody;

[0145] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0146] (iii) at least one detergent, which is Thesit, in a concentration of 0.035 % (w / v);

[0147] (iv) at least one blocking reagent, which is BSA, in a concentration of 0.014 mg / ml;

[0148] (v) at least one inorganic salt, which is KC1, in a concentration of 135 mM; and

[0149] (vi) at least one buffering system, which is MOPS;

[0150] (vii) at least one biocide, which is MIT, in a concentration of 0.25 mg / ml;

[0151] (viii) at least one second blocking reagent, which is trehalose, in a concentration of 125 mM; wherein the aqueous formulation has a pH value of 7.4 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of 20 mg / ml.

[0152] In some preferred embodiments, the aqueous formulation comprises

[0153] (i) at least one protein-loaded magnetic particle, wherein the protein is a vitamin D specific antibody, or a fragment of vitamin D specific antibody;

[0154] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0155] (iii) at least one detergent, which is Thesit, in a concentration of 0.03 % (w / v);

[0156] (iv) at least one blocking reagent, which is BSA, in a concentration of 0.005 mg / ml;

[0157] (v) at least one inorganic salt, which is KC1, in a concentration of 235 mM; and

[0158] (vi) at least one buffering system, which is MES, preferably in a concentration of 25 mM;

[0159] (vii) at least one biocide, which is MIT, in a concentration of 0.25 mg / ml;

[0160] (viii) at least one second blocking reagent, which is trehalose, in a concentration of 125 mM; wherein the aqueous formulation has a pH value of 6.3 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of >10 mg / ml, preferably 20 mg / ml.

[0161] In some preferred embodiments, the aqueous formulation comprises

[0162] (i) at least one protein-loaded magnetic particle, wherein the protein is a steroid-specific antibody, or a fragment of steroid-specific antibody;

[0163] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0164] (iii) at least one detergent, which is Thesit, in a concentration of 0.025 % (w / v); (iv) at least one blocking reagent, which is BSA, in a concentration of 0.005 mg / ml;

[0165] (v) at least one inorganic salt, which is KC1, in a concentration of 230 mM; and

[0166] (vi) at least one buffering system, which is MOPS;

[0167] (vii) at least one biocide, which is MIT, in a concentration of 0.25 mg / ml;

[0168] (viii) at least one second blocking reagent, which is trehalose, in a concentration of 100 mM; wherein the aqueous formulation has a pH value of 7.4 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of 12.5 mg / ml.

[0169] In some preferred embodiments, the aqueous formulation comprises

[0170] (i) at least one protein-loaded magnetic particle, wherein the protein is a steroid-specific antibody, or a fragment of steroid-specific antibody;

[0171] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0172] (iii) at least one detergent, which is Thesit, in a concentration of 0.025 % (w / v);

[0173] (iv) at least one blocking reagent, which is BSA, in a concentration of 0.009 mg / ml;

[0174] (v) at least one inorganic salt, which is KC1, in a concentration of 230 mM; and

[0175] (vi) at least one buffering system, which is MOPS;

[0176] (vii) at least one biocide, which is MIT, in a concentration of 0.25 mg / ml;

[0177] (viii) at least one second blocking reagent, which is trehalose, in a concentration of 100 mM; wherein the aqueous formulation has a pH value of 7.4 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of 12.5 mg / ml.

[0178] In some preferred embodiments, the aqueous formulation comprises

[0179] (i) at least one protein-loaded magnetic particle, wherein the protein is a steroid-specific antibody, or a fragment of steroid-specific antibody;

[0180] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0181] (iii) at least one detergent, which is Thesit, in a concentration of 0.025 % (w / v);

[0182] (iv) at least one blocking reagent, which is BSA, in a concentration of 0.01 mg / ml;

[0183] (v) at least one inorganic salt, which is KC1, in a concentration of 235 mM; and

[0184] (vi) at least one buffering system, which is MOPS;

[0185] (vii) at least one biocide, which is MIT, in a concentration of 0.25 mg / ml;

[0186] (viii) at least one second blocking reagent, which is trehalose, in a concentration of 125 mM; wherein the aqueous formulation has a pH value of 7.4 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of 12.5 mg / ml.

[0187] In some preferred embodiments, the aqueous formulation comprises

[0188] (i) at least one protein-loaded magnetic particle, wherein the protein is a steroid-specific antibody, or a fragment of steroid-specific antibody;

[0189] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0190] (iii) at least one detergent, which is Thesit, in a concentration of 0.03 % (w / v);

[0191] (iv) at least one blocking reagent, which is BSA, in a concentration of 0.005 mg / ml;

[0192] (v) at least one inorganic salt, which is KC1, in a concentration of 235 mM; and

[0193] (vi) at least one buffering system, which is MOPS;

[0194] (vii) at least one biocide, which is MIT, in a concentration of 0.25 mg / ml;

[0195] (viii) at least one second blocking reagent, which is trehalose, in a concentration of 125 mM; wherein the aqueous formulation has a pH value of 7.4 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of 12.5 mg / ml.

[0196] In some preferred embodiments, the aqueous formulation comprises

[0197] (i) at least one protein-loaded magnetic particle, wherein the protein is a steroid-specific antibody, or a fragment of steroid-specific antibody;

[0198] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0199] (iii) at least one detergent, which is Thesit, in a concentration of 0.035 % (w / v);

[0200] (iv) at least one blocking reagent, which is BSA, in a concentration of 0.005 mg / ml;

[0201] (v) at least one inorganic salt, which is KC1, in a concentration of 235 mM; and

[0202] (vi) at least one buffering system, which is MOPS;

[0203] (vii) at least one biocide, which is MIT, in a concentration of 0.25 mg / ml;

[0204] (viii) at least one second blocking reagent, which is trehalose, in a concentration of 125 mM; wherein the aqueous formulation has a pH value of 7.4 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of 12.5 mg / ml.

[0205] In some preferred embodiments, the aqueous formulation comprises (i) at least one protein-loaded magnetic particle, wherein the protein is a steroid-specific antibody, or a fragment of steroid-specific antibody;

[0206] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0207] (iii) at least one detergent, which is Thesit, in a concentration of 0.025 % (w / v);

[0208] (iv) at least one blocking reagent, which is BSA, in a concentration of 0.025 mg / ml;

[0209] (v) at least one inorganic salt, which is KC1, in a concentration of 245 mM; and

[0210] (vi) at least one buffering system, which is potassium phosphate buffer (K2HPO4 / KH2PO4;

[0211] K-PO4);

[0212] (vii) at least one biocide, which is MIT, in a concentration of 0.25 mg / ml;

[0213] (viii) at least one second blocking reagent, which is trehalose, in a concentration of 125 mM; wherein the aqueous formulation has a pH value of 7.4 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of 12.5 mg / ml.

[0214] In some preferred embodiments, the aqueous formulation comprises

[0215] (i) at least one protein-loaded magnetic particle, wherein the protein is a steroid-specific antibody, or a fragment of steroid-specific antibody;

[0216] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0217] (iii) at least one detergent, which is Thesit, in a concentration of 0.03 % (w / v);

[0218] (iv) at least one blocking reagent, which is BSA, in a concentration of 0.005 mg / ml;

[0219] (v) at least one inorganic salt, which is KC1, in a concentration of 235 mM; and

[0220] (vi) at least one buffering system, which is MES, preferably in a concentration of 25 mM;

[0221] (vii) at least one biocide, which is MIT, in a concentration of 0.25 mg / ml;

[0222] (viii) at least one second blocking reagent, which is trehalose, in a concentration of 125 mM; wherein the aqueous formulation has a pH value of 6.3 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of > 10 mg / ml, preferably of 12.5 mg / ml.

[0223] Properties of aqueous formulation

[0224] In some preferred embodiments, the aqueous formulation has an initial foam height of less than 4 mm, more preferably determined according to the procedure of Example 1). In some preferred embodiments, the aqueous formulation has a final foam height of less than 1mm, more preferably determined according to the procedure of Example 1).

[0225] In some preferred embodiments, the aqueous formulation has a bottle AdhesClass with respect to metallic surface, more preferably a steel surface, of 2 or less preferably determined according to the procedure of Example 1).

[0226] In some preferred embodiments, the aqueous formulation has a bottle AdhesClass with respect to polymeric surface, more preferably polypropylene surface, of 2 or less, preferably determined according to the procedure of Example 1).

[0227] 2ndaspect - Use of the aqueous formulation

[0228] A second aspect of the invention is directed to the use of an aqueous formulation according to the first aspect of the invention as described herein above for storage, transportation, homogenization, filling, decanting and / or diagnostic purpose. All details, embodiments and preferred embodiments described herein above with respect to the aqueous formulation of the first aspect apply also to the use of the second aspect of the invention.

[0229] Preferably, the aqueous formulation is used for diagnostic purpose, more preferably for determining an analyte of interest in a sample, more preferably for determining an analyte of interest in a sample by mass spectrometry.

[0230] Mass spectrometric analysis is preferably liquid chromatography-mass spectrometry (LC- MS), more preferably Liquid chromatography-tandem mass spectrometry (LC-MS / MS).

[0231] The term "analyte of interest" is used for a compound, which is analyzable or analyzed via mass spectrometry. An analyte of interest can be any kind of molecule present in a living organism, without any limitation as long as it is analyzable via mass spectrometry.

[0232] In some preferred embodiments of the method, the analyte of interest is selected from the group consisting of nucleic acid (e.g. DNA, mRNA, miRNA, rRNA etc.), amino acid, peptide, protein (e.g. cell surface receptor, cytosolic protein), metabolite or hormone (e.g. testosterone, estrogen, estradiol), fatty acid, lipid, carbohydrate, steroid, ketosteroid, secosteroid (e.g. vitamin D), molecule characteristic of a certain modification of another molecule (e.g. sugar moieties or phosphoryl residues on proteins, methyl residues on genomic DNA) or a substance that has been internalized by the organism (e.g. therapeutic drug, drug of abuse, toxin) or a metabolite of such a substance, and mixtures of two or more thereof, preferably, the analyte of interest is selected from the group consisting of testosterone, estradiol, aldosterone, androstendione, vitamin DI, vitamin D2, vitamin D3, vitamin D4, vitamin D5, 25-hydroxy-vitamin D2, 25-hydroxy vitamin D3, 24, 25-dihydroxy-vitamin D3, 24, 25-di- hydroxy- vitamin D3, progesterone, 17-hydroxy-progesterone, cortisol, cortison, dehydroepiandrosterone, dehydroepiandrosterone-sulfate and mixtures of two or more thereof.

[0233] In some preferred embodiments of the method, the liquid sample as used herein refers to a biological sample obtained for the purpose of evaluation in vitro. In the methods of the present invention, the liquid sample preferably may comprise any body fluid. Preferred fluid samples are whole blood, serum, plasma, bronchioalveolar lavage (BAL), epithelial lining fluid (ELF), urine or sputum, with plasma or serum being most preferred.

[0234] The term liquid sample includes biological fluid samples that have been manipulated in any way after their procurement, such as by treatment with reagents, solubilization, or enrichment for certain components, such as proteins or polynucleotides.

[0235] The aforementioned uses for determining analytes in liquid samples may, preferably, be applied or are involved in diagnostic purposes, drug of abuse testing, environmental control, food safety, quality control, purification or manufacturing processes. In diagnostic applications, the qualitative or quantitative determination of an analyte may allow aiding the diagnosis if the analyte is, e.g., a biomarker for a disease or medical condition. Similarly, the qualitative or quantitative assessment of an analyte being an indicator for environmental changes may help to identify pollution or to make assessments of environmental changes. Food safety as well as manufacturing or purification processes may be controlled by qualitative or quantitative determination of indicator analytes. Such indicators may also be determined in connection with general aspects of quality control, e.g., also in storage stability assessments of products and the like.

[0236] The use(s), especially the use for diagnostic purposes, preferably for determining an analyte of interest in a sample, more preferably for determining an analyte of interest in a sample by mass spectrometry, are / is in vitro use(s).

[0237] 3rdaspect - Aqueous composition A third aspect of the invention is direct to an aqueous composition, preferably for containing a protein-loaded magnetic particle, the composition comprising water and in dissolved and / or suspended form:

[0238] (iii) at least one detergent in a concentration of in the range of from 0.01 to 0.04 % (w / v);

[0239] (iv) at least one blocking reagent in a concentration < 0.02 mg / ml;

[0240] (v) at least one inorganic salt in a concentration < 300 mM; and

[0241] (vi) at least one buffering system; wherein the aqueous composition has a pH in the range of from 6 to 7.

[0242] All details described herein above with respect to the aqueous formulation of the first aspect of the invention and its components (iii), (iv), (v) and (vi), as well as with respect to its optional further components (vii), i.e. the at least one biocide, and (viii), i.e. the at least one second blocking reagent, also apply for the aqueous composition of the third aspect of the present invention. The same applies also for the pH values described herein above with respect to the aqueous formulation of the first aspect of the invention.

[0243] 4thaspect - Use of the aqueous composition

[0244] A fourth aspect of the invention is related to the use of the aqueous composition of the third aspect of the present invention described herein above for suspending at least one protein- loaded magnetic particle, preferably for storage, transportation, homogenization, filling, decanting and / or diagnostic purpose involving the at least one protein-loaded magnetic particle. Regarding the suspending at least one protein-loaded magnetic particle in the aqueous composition of the third aspect of the present invention, especially the concentration limits and ranges described herein above with respect to the aqueous formulation of the first aspect of the invention apply also for the use of the fourth aspect of the invention. Furthermore, all details, embodiments and preferred embodiments described herein above with respect to the aqueous formulation of the first aspect of the invention in view of the protein of the protein- loaded magnetic particle and the magnetic particle itself also apply for the use of the aqueous composition of the fourth aspect of the invention.

[0245] Summarizing and without excluding further possible embodiments, the following embodiments may be envisaged:

[0246] Embodiment 1 : An aqueous formulation of a protein-loaded magnetic particle, the formulation comprising:

[0247] (iii) at least one protein-loaded magnetic particle; (iv) at least one aqueous phase; wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0248] (iii) at least one detergent in a concentration of in the range of from 0.01 to 0.04 % (w / v);

[0249] (iv) at least one blocking reagent in a concentration < 0.02 mg / ml;

[0250] (v) at least one inorganic salt in a concentration < 300 mM; and

[0251] (vi) at least one buffering system; wherein the at least one protein-loaded magnetic particle of (i) is present in the aqueous formulation in a concentration of > 10 mg / ml; and the aqueous formulation has a pH in the range of from 6 to 7.

[0252] Embodiment 2: The aqueous formulation of embodiment 1 further comprising

[0253] (vii) at least one biocide.

[0254] Embodiment 3 : The aqueous formulation of embodiment 1 or 2, wherein the at least one detergent of (iii) is selected from the group consisting of non-ionic detergent, ionic detergent, zwitter-ionic detergent and mixtures of two or more thereof.

[0255] Embodiment 4: The aqueous formulation of any one of embodiments 1 to 3, wherein the at least one detergent of (iii) is selected from the group consisting of non-ionic detergent, ionic detergent, zwitterionic detergent and mixtures of non-ionic detergent and ionic detergent.

[0256] Embodiment 5: The aqueous formulation of any one of embodiments 1 to 4, wherein the at least one detergent of (iii) is selected from the group consisting of Polidocanol, Brij 35, Octyl-B-D-glucopyranodide, Synperonic F68, Synperonic F108, Tergitol 15-S-9, Tween 20, Tween 80, CTAB, Na-cholate, Na-deoxycholate, Na-N-lauroylsarcosinate, SDS, ASB-14, ASB-16, SB 3 - 10, SB 12, n-Dodecyl-P-D-Maltopyranoside (DDM), n-Decyl-P-D-Malto- pyranoside (DM), n-Octyl-P-D-Glucopyranoside / n-Nonyl-P-D-Glucopyranoside (OG / NG), Lauryldimethylamine-N-oxide (LDAO), Polyoxyethylene dodecyl ether, n-Undecyl-P-D- maltopyranoside (UDM), Lauryl maltose neopentyl glycol (LMNG), Triton X-100, Digitonin, cyclic maltosides, 3-[(3-cholamidopropyl)dimethylammonio]-l-propanesulfonate (CHAPS), 3 - [(3 -cholamidopropyl)dimethylammonio] -2-hy droxy- 1 -propanesulfonate (CHAPSO), and mixtures of two or more thereof. Embodiment 6: The aqueous formulation of any one of embodiments 1 to 5, wherein the at least one detergent of (iii) is selected from the group consisting of n-Dodecyl-P-D-Maltopy- ranoside (DDM), n-Decyl-P-d-Maltopyranoside (DM), n-Octyl-P-d-Glucopyranoside / n- Nonyl-P-d-Glucopyranoside (OG / NG), Lauryldimethylamine-N-oxide (LDAO), polyoxyethylene dodecyl ether, n-undecyl-P-d-maltopyranoside (UDM), lauryl maltose neopentyl glycol (LMNG), Triton X-100, Digitonin, cyclic maltoside, 3-[(3-cholamidopropyl)dime- thylammonio]-l -propanesulfonate (CHAPS), 3-[(3-cholamidopropyl)dimethylammonio]-2- hydroxy-1 -propanesulfonate (CHAPSO), and mixtures of two or more thereof.

[0257] Embodiment 7: The aqueous formulation of any one of embodiments 1 to 6, wherein the at least one detergent of (iii) comprises or is a polyoxyethylene dodecyl ether, preferably mac- rogollauryl ether 8 (CnEs) and / or macrogollaurylether 9 (Thesit, Polidocanol).

[0258] Embodiment 8: The aqueous formulation of any one of embodiments 1 to 7, wherein the at least one detergent of (iii) is present in a concentration of < 0.04 % (w / v).

[0259] Embodiment 9: The aqueous formulation of any one of embodiments 1 to 8, wherein the at least one detergent of (iii) is present in a concentration in the range of from 0.02-0.035 % (w / v).

[0260] Embodiment 10: The aqueous formulation of any one of embodiments 1 to 9, wherein the at least one blocking reagent of (iv) is a protein.

[0261] Embodiment 11 : The aqueous formulation of any one of embodiments 1 to 10, wherein the at least one blocking reagent of (iv) is a protein selected from the group consisting of bovine serum albumin (BSA), human serum albumin (HSA), lactalbumin, casein, skim milk, serum proteins, and mixtures thereof.

[0262] Embodiment 12: The aqueous formulation of any one of embodiments 1 to 11, wherein the at least one blocking reagent of (iv) comprises at least BSA.

[0263] Embodiment 13 : The aqueous formulation of any one of embodiments 1 to 12, wherein the at least one blocking reagent of (iv) is a monoclonal antibody, preferably a recombinant antibody.

[0264] Embodiment 14: The aqueous formulation of any one of embodiments 1 to 13 wherein the at least one blocking reagent of (iv) is present in a concentration in the range of from 0.001 to 0.02 mg / ml, preferably in the range of 0.001 to 0.015 mg / ml, more preferably in the range of from 0.01 to 0.014 mg / ml (for vitamin D specific antibody-loaded magnetic particle) or in the range of from O.OOlto 0.01 mg / ml (or steroid specific antibody-loaded magnetic particle).

[0265] Embodiment 15: The aqueous formulation of any one of embodiments 1 to 14, wherein the at least one inorganic salt of (v) is selected from the group of earth alkali metal salt, alkali metal salt and mixtures of earth alkali metal salt and alkali metal salt, preferably at least one alkali metal salt, more preferably at least one alkali metal halogenide, more preferably at least potassium chloride.

[0266] Embodiment 16: The aqueous formulation of any one of embodiments 1 to 15, wherein the at least one inorganic salt of (v) is present at a concentration in the range of from 10 to 300 mM, preferably in the range of from 100 to 245 mM, more preferably in the range of from 100 to 140 mM (for vitamin D specific antibody-loaded magnetic particle) or in the range of 200 to 245 mM (for steroid specific antibody-loaded magnetic particle).

[0267] Embodiment 17: The aqueous formulation of any one of embodiments 1 to 16, wherein the at least one buffering system of (vi) is selected from the group of potassium phosphate buffer (K2HPO4 / KH2PO4), MES, ADA, PIPES, ACES, MOPSO, cholamine chloride, MOPS, TES, HEPES, DiPSO, TAPSO and mixtures of two or more thereof, preferably selected from the group of potassium phosphate buffer (K2HPO4 / KH2PO4), MES, MOPS and mixtures of two or three thereof, wherein the at least one buffering system of (vi) more preferably comprises at least MES.

[0268] Embodiment 18: The aqueous formulation of any one of embodiments 2 to 17, wherein the at least one biocide of (vii) is selected from the group consisting of (metal cation) chelating biocide, (metal cation) non-chelating biocide and mixtures of two or more thereof.

[0269] Embodiment 19: The aqueous formulation of embodiment 18, wherein the at least one biocide of (vii) is selected from the group of (metal cation) non-chelating biocides.

[0270] Embodiment 20: The aqueous formulation of embodiment 18 or 19, wherein the at least one biocide of (vii) is selected from the group of isothiazolinone derivative, sodium azide, 2- chloroacetamide, sodium benzoate and mixtures thereof. Embodiment 21 : The aqueous formulation of any one of embodiments 18 to 20, wherein the at least one biocide of (vii) is selected from the group consisting of methylisothiazolinone (2-methyl-l,2-thiazol-3(2H)-one, MIT), methylchloroisothiazolinone (5-chloro-2-methyl- l,2-thiazol-3(2H)-one, MCI), benzisothiazolinone (l,2-benzothiazol-3(2H)-one, BIT), oc- tylisothiazolinone (2-octyl-l,2-thiazol-3(2H)-one, OIT), dichlorooctylisothiazolinone (4,5- dichloro-2-octyl-l,2-thiazol-3(2H)-one, DCOIT), sodium azide, 2-chloroacetamide, sodium benzoate, and mixtures of two or more thereof.

[0271] Embodiment 22: The aqueous formulation of any one of embodiments 18 to 21, wherein the at least one biocide of (vii) is selected from the group consisting of methylisothiazolinone (2-methyl-l,2-thiazol-3(2H)-one, MIT), methylchloroisothiazolinone (5-chloro-2-methyl- l,2-thiazol-3(2H)-one, MCI), sodium azide, 2-chloroacetamide, sodium benzoate, and mixtures of two or more thereof, preferably from the group consisting of methylisothiazolinone (2-methyl-l,2-thiazol-3(2H)-one, MIT), methylchloroisothiazolinone (5-chloro-2-methyl- l,2-thiazol-3(2H)-one, MCI), sodium azide, and mixtures of two or more thereof.

[0272] Embodiment 23: The aqueous formulation of any one of embodiments 18 to 22, wherein the at least one biocide of (vii) at least comprises MIT.

[0273] Embodiment 24: The aqueous formulation of any one of embodiments 2 to 23, wherein the at least one biocide of (vii) is present in a concentration in the range of from 0.001 to 0.5 mg / ml, preferably in the range of from 0.1 to 0.4 mg / ml, more preferably in the range of from 0.15 to 0.35 mg / ml.

[0274] Embodiment 25: The aqueous formulation of any one of embodiments 1 to 24, comprising less than 100 weight-ppm, preferably less than 50 weight-ppm, more preferably less than 10 weight-ppm of a (metal cation) chelating biocide, based on the total weight of the aqueous formulation being 100 weight-%.

[0275] Embodiment 26: The aqueous formulation of any one of embodiments 1 to 25, further comprising

[0276] (viii) at least one second blocking reagent.

[0277] Embodiment 27: The aqueous formulation of embodiment 26, wherein the at least one second blocking reagent of (viii) is selected from the group consisting of polyol, carbohydrate and mixtures of two or more thereof. Embodiment 28: The aqueous formulation of embodiment 26 or 27, wherein the at least one second blocking reagent of (viii) is selected from the group consisting of trehalose, sucrose, glycerol, threitol, sorbitol, maltitol and mixtures of two or more thereof.

[0278] Embodiment 29: The aqueous formulation of any one of embodiments 26 to 28, wherein the at least one second blocking reagent of (viii) comprises at least trehalose.

[0279] Embodiment 30: The aqueous formulation of any one of embodiments 26 to 29, wherein the at least one second blocking reagent of (viii) is present in a concentration in the range of from of 10 to 500 mM, preferably in the range of from 50 to 250 mM, more preferably in the range of from 70 to 150 mM, more preferably in the range of from 80 to 125 mM (for vitamin D specific-antibody) or in the range of from 110 to 140 mM (for steroid-specific antibody).

[0280] Embodiment 31 : The aqueous formulation of any one of embodiments 1 to 30, especially the aqueous phase of (ii) of the aqueous formulation of any one of embodiments 1 to 30, having a pH value in the range of from 6 to 7.

[0281] Embodiment 32: The aqueous formulation of any one of embodiments 1 to 31, wherein the protein of the at least one protein-loaded magnetic particle of (i) is an antibody or a fragment thereof.

[0282] Embodiment 33: The aqueous formulation of embodiment 32, wherein the antibody or fragment thereof is selected from the group consisting of vitamin D specific antibody, fragment of vitamin D specific antibody, steroid specific antibody, and fragment of steroid specific antibody.

[0283] Embodiment 34: The aqueous formulation of embodiment 33, wherein the vitamin D specific antibody or fragment thereof is selected from the group consisting of vitamin DI specific antibody, vitamin D2 specific antibody, vitamin D3 specific antibody, vitamin D4 specific antibody, vitamin D5 specific antibody, 25-hydroxy-vitamin D2 specific antibody, 25- hydroxy vitamin D3 specific antibody, 24, 25-dihydroxy-vitamin D3 specific antibody, and 24, 25-dihydroxy-vitamin D3 specific antibody.

[0284] Embodiment 35: The aqueous formulation of any one of embodiments 1 to 34, wherein the protein and the magnetic particle are bound to each other by a covalent or a non-covalent bond. Embodiment 36: The aqueous formulation of any one of embodiments 1 to 35, wherein the at least one protein-loaded magnetic particle of (i) comprises at least two protein-loaded magnetic particles, wherein at least a first magnetic particle is loaded with a first protein and at least a second magnetic particle is loaded with a second protein, wherein at least the first protein and the second protein are different from each other.

[0285] Embodiment 37: The aqueous formulation of any one of embodiments 1 to 36, comprising the at least one protein-loaded magnetic particle in a concentration in the range of > 10 mg / ml, preferably of> 11 mg / ml, more preferably of > 12 mg / ml.

[0286] Embodiment 38: The aqueous formulation of any one of embodiments 1 to 37, comprising the at least one protein-loaded magnetic particle in a concentration in the range of from 10 to 100 mg / ml, preferably in the range of from 10 to 50 mg / ml.

[0287] Embodiment 39: The aqueous formulation of any one of embodiments 1 to 38, comprising the at least one protein-loaded magnetic particle in a concentration in the range of from 11 to 100 mg / ml, preferably in the range of from 11 to 50 mg / ml.

[0288] Embodiment 40: The aqueous formulation of any one of embodiments 1 to 39, comprising the at least one protein-loaded magnetic particle in a concentration in the range of from 12 to 100 mg / ml, preferably in the range of from 12 to 50 mg / ml.

[0289] Embodiment 41 : The aqueous formulation of any one of embodiments 1 to 40, comprising the at least one protein-loaded magnetic particle in a concentration in the range of from 12 to 13 mg / ml, or in a concentration in the range of from 18 to 22 mg / ml, or in a concentration in the range of from 25 to 29 mg / ml, or in a concentration in the range of from 48 to 52 mg / ml.

[0290] Embodiment 42: The aqueous formulation of any one of embodiments 1 to 41, comprising the at least one protein-loaded magnetic particle in a concentration of 12.5 mg / ml, or in a concentration of 20 mg / ml, or in a concentration of 27 mg / ml, or in a concentration of 50 mg / ml.

[0291] Embodiment 43: The aqueous formulation of any one of embodiments 1 to 42, having a pH in the range of from 6.0 to 6.9, preferably in the range of from 6.0 to 6.8, more preferably in the range of from 6.0 to 6.7, more preferably in the range of from 6.0 to 6.6, more preferably in the range of from 6.0 to 6.5.

[0292] Embodiment 44: The aqueous formulation of any one of embodiments 1 to 43, comprising

[0293] (i) at least one protein-loaded magnetic particle, wherein the protein is preferably an antibody or fragment thereof, said antibody preferably being selected from vitamin D specific antibody, fragment of vitamin D specific antibody, and steroid-specific antibody, fragment of steroid-specific antibody;

[0294] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0295] (iii) at least one detergent, which preferably comprises or is Thesit, in a concentration of in the range of from 0.01 to 0.04 % (w / v);

[0296] (iv) at least one blocking reagent, which preferably comprises BSA, in a concentration < 0.02 mg / ml;

[0297] (v) at least one inorganic salt, which preferably comprises or is KC1, in a concentration < 300 mM; and

[0298] (vi) at least one buffering system, which preferably comprises or is KH2PO4 / K2HPO4 (K- PO4) or MOPS or MES; wherein the aqueous formulation has a pH value in the range of from 6 to 7 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of > 10 mg / ml, preferably of> 11 mg / ml, more preferably of> 12 mg / ml.

[0299] Embodiment 45: The aqueous formulation of embodiment 44, the formulation comprising

[0300] (i) at least one protein-loaded magnetic particle, wherein the protein is preferably an antibody or fragment thereof, said antibody preferably being selected from vitamin D specific antibody, fragment of vitamin D specific antibody, steroid-specific antibody, and fragment of steroid-specific antibody;

[0301] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0302] (iii) at least one detergent, which preferably comprises or is Thesit, in a concentration of in the range of from 0.01 to 0.04 % (w / v);

[0303] (iv) at least one blocking reagent, which preferably comprises BSA, in a concentration < 0.02 mg / ml; (v) at least one inorganic salt, which preferably comprises or is KC1, in a concentration < 300 mM;

[0304] (vi) at least one buffering system, which preferably comprises or is KH2PO4 / K2HPO4 (K- PO4) or MOPS or MES;

[0305] (vii) at least one biocide, which preferably comprises or is MIT;

[0306] (viii) at least one second blocking reagent, which preferably comprises or is trehalose; wherein the aqueous formulation has a pH value in the range of from 6 to 7 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of > 10 mg / ml, preferably of> 11 mg / ml, more preferably of> 12 mg / ml.

[0307] Embodiment 46: The aqueous formulation of embodiment 44 or 45, comprising

[0308] (i) at least one protein-loaded magnetic particle, wherein the protein is preferably an antibody or fragment thereof, said antibody preferably being selected from vitamin D specific antibody, fragment of vitamin D specific antibody, steroid-specific antibody, and fragment of steroid-specific antibody;

[0309] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0310] (iii) at least one detergent, which preferably comprises or is Thesit, in a concentration of in the range of from 0.01 to 0.04 % (w / v);

[0311] (iv) at least one blocking reagent, which preferably comprises BSA, in a concentration < 0.02 mg / ml;

[0312] (v) at least one inorganic salt, which preferably comprises or is KC1, in a concentration < 300 mM; and

[0313] (vi) at least one buffering system, which preferably comprises or is KH2PO4 / K2HPO4 (K- PO4) or MOPS or MES; wherein the aqueous formulation has a pH value in the range of from 6 to 7 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of > 10 mg / ml, preferably of> 11 mg / ml, more preferably of> 12 mg / ml.

[0314] Embodiment 47: The aqueous formulation of any one of embodiments 44 to 46, comprising

[0315] (i) at least one protein-loaded magnetic particle, wherein the protein is preferably an antibody or fragment thereof, said antibody preferably being selected from vitamin D specific antibody, fragment of vitamin D specific antibody, steroid-specific antibody, and fragment of steroid-specific antibody;

[0316] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0317] (iii) at least one detergent, which preferably comprises or is Thesit, in a concentration of in the range of from 0.01 to 0.04 % (w / v);

[0318] (iv) at least one blocking reagent, which preferably comprises BSA, in a concentration < 0.02 mg / ml;

[0319] (v) at least one inorganic salt, which preferably comprises or is KC1, in a concentration < 300 mM; and

[0320] (vi) at least one buffering system, which preferably comprises or is KH2PO4 / K2HPO4 (K- PO4) or MOPS or MES;

[0321] (vii) at least one biocide, which preferably comprises or is MIT, in a concentration < 0.5 mg / ml;

[0322] (viii) at least one second blocking reagent, which preferably comprises or is trehalose, in a concentration in the range of from of 10 to 500 mM; wherein the aqueous formulation has a pH value in the range of from 6 to 7 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of > 10 mg / ml, preferably of> 11 mg / ml, more preferably of> 12 mg / ml.

[0323] Embodiment 48: The aqueous formulation of any one of embodiments 44 to 47, comprising

[0324] (i) at least one protein-loaded magnetic particle, wherein the protein is a vitamin D specific antibody, or a fragment of vitamin D specific antibody;

[0325] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0326] (iii) at least one detergent, which is Thesit, in a concentration of 0.03 % (w / v);

[0327] (iv) at least one blocking reagent, which is BSA, in a concentration of 0.0125 mg / ml;

[0328] (v) at least one inorganic salt, which is KC1, in a concentration of 125 mM; and

[0329] (vi) at least one buffering system, which is MOPS;

[0330] (vii) at least one biocide, which is MIT, in a concentration of 0.25 mg / ml;

[0331] (viii) at least one second blocking reagent, which is trehalose, in a concentration of 105 mM; wherein the aqueous formulation has a pH value of 7.4 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of 20 mg / ml.

[0332] Embodiment 49: The aqueous formulation of any one of embodiments 44 to 47, comprising (i) at least one protein-loaded magnetic particle, wherein the protein is a vitamin D specific antibody, or a fragment of vitamin D specific antibody;

[0333] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0334] (iii) at least one detergent, which is Thesit, in a concentration of 0.035 % (w / v);

[0335] (iv) at least one blocking reagent, which is BSA, in a concentration of 0.0125 mg / ml;

[0336] (v) at least one inorganic salt, which is KC1, in a concentration of 125 mM; and

[0337] (vi) at least one buffering system, which is MOPS;

[0338] (vii) at least one biocide, which is MIT, in a concentration of 0.25 mg / ml;

[0339] (viii) at least one second blocking reagent, which is trehalose, in a concentration of 125 mM; wherein the aqueous formulation has a pH value of 7.4 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of 20 mg / ml.

[0340] Embodiment 50: The aqueous formulation of any one of embodiments 44 to 47, comprising

[0341] (i) at least one protein-loaded magnetic particle, wherein the protein is a vitamin D specific antibody, or a fragment of vitamin D specific antibody;

[0342] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0343] (iii) at least one detergent, which is Thesit, in a concentration of 0.035 % (w / v);

[0344] (iv) at least one blocking reagent, which is BSA, in a concentration of 0.014 mg / ml;

[0345] (v) at least one inorganic salt, which is KC1, in a concentration of 135 mM; and

[0346] (vi) at least one buffering system, which is MOPS;

[0347] (vii) at least one biocide, which is MIT, in a concentration of 0.25 mg / ml;

[0348] (viii) at least one second blocking reagent, which is trehalose, in a concentration of 125 mM; wherein the aqueous formulation has a pH value of 7.4 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of 20 mg / ml.

[0349] Embodiment 51 : The aqueous formulation of any one of embodiments 44 to 47, comprising

[0350] (i) at least one protein-loaded magnetic particle, wherein the protein is a vitamin D specific antibody, or a fragment of vitamin D specific antibody;

[0351] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0352] (iii) at least one detergent, which is Thesit, in a concentration of 0.03 % (w / v);

[0353] (iv) at least one blocking reagent, which is BSA, in a concentration of 0.005 mg / ml;

[0354] (v) at least one inorganic salt, which is KC1, in a concentration of 235 mM; and

[0355] (vi) at least one buffering system, which is MES, preferably in a concentration of 25 mM;

[0356] (vii) at least one biocide, which is MIT, in a concentration of 0.25 mg / ml;

[0357] (viii) at least one second blocking reagent, which is trehalose, in a concentration of 125 mM; wherein the aqueous formulation has a pH value of 6.3 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of >10 mg / ml.

[0358] Embodiment 52: The aqueous formulation of any one of embodiments 44 to 47, comprising

[0359] (i) at least one protein-loaded magnetic particle, wherein the protein is a steroid-specific antibody, or a fragment of steroid-specific antibody;

[0360] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0361] (iii) at least one detergent, which is Thesit, in a concentration of 0.025 % (w / v);

[0362] (iv) at least one blocking reagent, which is BSA, in a concentration of 0.005 mg / ml;

[0363] (v) at least one inorganic salt, which is KC1, in a concentration of 230 mM; and

[0364] (vi) at least one buffering system, which is MOPS;

[0365] (vii) at least one biocide, which is MIT, in a concentration of 0.25 mg / ml;

[0366] (viii) at least one second blocking reagent, which is trehalose, in a concentration of 100 mM; wherein the aqueous formulation has a pH value of 7.4 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of 12.5 mg / ml.

[0367] Embodiment 53: The aqueous formulation of any one of embodiments 44 to 47, comprising

[0368] (i) at least one protein-loaded magnetic particle, wherein the protein is a steroid-specific antibody, or a fragment of steroid-specific antibody;

[0369] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0370] (iii) at least one detergent, which is Thesit, in a concentration of 0.025 % (w / v);

[0371] (iv) at least one blocking reagent, which is BSA, in a concentration of 0.009 mg / ml;

[0372] (v) at least one inorganic salt, which is KC1, in a concentration of 230 mM; and

[0373] (vi) at least one buffering system, which is MOPS; (vii) at least one biocide, which is MIT, in a concentration of 0.25 mg / ml;

[0374] (viii) at least one second blocking reagent, which is trehalose, in a concentration of 100 mM; wherein the aqueous formulation has a pH value of 7.4 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of 12.5 mg / ml.

[0375] Embodiment 54: The aqueous formulation of any one of embodiments 44 to 47, comprising

[0376] (i) at least one protein-loaded magnetic particle, wherein the protein is a steroid-specific antibody, or a fragment of steroid-specific antibody;

[0377] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0378] (iii) at least one detergent, which is Thesit, in a concentration of 0.025 % (w / v);

[0379] (iv) at least one blocking reagent, which is BSA, in a concentration of 0.01 mg / ml;

[0380] (v) at least one inorganic salt, which is KC1, in a concentration of 235 m ; and

[0381] (vi) at least one buffering system, which is MOPS;

[0382] (vii) at least one biocide, which is MIT, in a concentration of 0.25 mg / ml;

[0383] (viii) at least one second blocking reagent, which is trehalose, in a concentration of 125 mM; wherein the aqueous formulation has a pH value of 7.4 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of 12.5 mg / ml.

[0384] Embodiment 55: The aqueous formulation of any one of embodiments 44 to 47, comprising

[0385] (i) at least one protein-loaded magnetic particle, wherein the protein is a steroid-specific antibody, or a fragment of steroid-specific antibody;

[0386] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0387] (iii) at least one detergent, which is Thesit, in a concentration of 0.03 % (w / v);

[0388] (iv) at least one blocking reagent, which is BSA, in a concentration of 0.005 mg / ml;

[0389] (v) at least one inorganic salt, which is KC1, in a concentration of 235 mM; and

[0390] (vi) at least one buffering system, which is MOPS;

[0391] (vii) at least one biocide, which is MIT, in a concentration of 0.25 mg / ml;

[0392] (viii) at least one second blocking reagent, which is trehalose, in a concentration of 125 mM; wherein the aqueous formulation has a pH value of 7.4 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of 12.5 mg / ml. Embodiment 56: The aqueous formulation of any one of embodiments 44 to 47, comprising

[0393] (i) at least one protein-loaded magnetic particle, wherein the protein is a steroid-specific antibody, or a fragment of steroid-specific antibody;

[0394] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0395] (iii) at least one detergent, which is Thesit, in a concentration of 0.035 % (w / v);

[0396] (iv) at least one blocking reagent, which is BSA, in a concentration of 0.005 mg / ml;

[0397] (v) at least one inorganic salt, which is KC1, in a concentration of 235 mM; and

[0398] (vi) at least one buffering system, which is MOPS;

[0399] (vii) at least one biocide, which is MIT, in a concentration of 0.25 mg / ml;

[0400] (viii) at least one second blocking reagent, which is trehalose, in a concentration of 125 mM; wherein the aqueous formulation has a pH value of 7.4 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of 12.5 mg / ml.

[0401] Embodiment 57: The aqueous formulation of any one of embodiments 44 to 47, comprising

[0402] (i) at least one protein-loaded magnetic particle, wherein the protein is a steroid-specific antibody, or a fragment of steroid-specific antibody;

[0403] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0404] (iii) at least one detergent, which is Thesit, in a concentration of 0.025 % (w / v);

[0405] (iv) at least one blocking reagent, which is BSA, in a concentration of 0.025 mg / ml;

[0406] (v) at least one inorganic salt, which is KC1, in a concentration of 245 mM; and

[0407] (vi) at least one buffering system, which is potassium phosphate buffer (K2HPO4 / KH2PO4; K-PO4);

[0408] (vii) at least one biocide, which is MIT, in a concentration of 0.25 mg / ml;

[0409] (viii) at least one second blocking reagent, which is trehalose, in a concentration of 125 mM; wherein the aqueous formulation has a pH value of 7.4 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of 12.5 mg / ml.

[0410] Embodiment 58: The aqueous formulation of any one of embodiments 44 to 47, comprising

[0411] (i) at least one protein-loaded magnetic particle, wherein the protein is a steroid-specific antibody, or a fragment of steroid-specific antibody;

[0412] (ii) at least one aqueous phase, wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:

[0413] (iii) at least one detergent, which is Thesit, in a concentration of 0.03 % (w / v);

[0414] (iv) at least one blocking reagent, which is BSA, in a concentration of 0.005 mg / ml;

[0415] (v) at least one inorganic salt, which is KC1, in a concentration of 235 mM; and

[0416] (vi) at least one buffering system, which is MES, preferably in a concentration of 25 mM;

[0417] (vii) at least one biocide, which is MIT, in a concentration of 0.25 mg / ml;

[0418] (viii) at least one second blocking reagent, which is trehalose, in a concentration of 125 mM; wherein the aqueous formulation has a pH value of 6.3 and comprises the at least one protein loaded magnetic particle of (i) in a concentration of > 10 mg / ml.

[0419] Embodiment 59: The aqueous formulation of any one of embodiments 1 to 58, having an initial foam height of less than 4 mm, preferably determined according to the procedure of Example 1).

[0420] Embodiment 60: The aqueous formulation of any one of embodiments 1 to 59, having a final foam height of less than 1 mm, preferably determined according to the procedure of Example 1).

[0421] Embodiment 61 : The aqueous formulation of any one of embodiments 1 to 60, having a bottle AdhesClass with respect to metallic surface, preferably a steel surface, of 2 or less preferably determined according to the procedure of Example 1).

[0422] Embodiment 62: The aqueous formulation of any one of embodiments 1 to 61, having a bottle AdhesClass with respect to polymeric surface, preferably polypropylene surface, of 2 or less, preferably determined according to the procedure of Example 1).

[0423] Embodiment 63: Use of an aqueous formulation according to any one of embodiments 1 to 62 for storage, transportation, homogenization, filling, decanting and / or diagnostic purpose.

[0424] Embodiment 64: The use of embodiment 63 for diagnostic purpose, preferably for determining an analyte of interest in a sample, more preferably for determining an analyte of interest in a sample by mass spectrometry.

[0425] Embodiment 65: An aqueous composition, preferably for containing a protein-loaded magnetic particle, the composition comprising water and in dissolved and / or suspended form: (iii) at least one detergent in a concentration of in the range of from 0.01 to 0.04 % (w / v);

[0426] (iv) at least one blocking reagent in a concentration < 0.02 mg / ml;

[0427] (v) at least one inorganic salt in a concentration < 300 mM; and

[0428] (vi) at least one buffering system; wherein the aqueous composition has a pH in the range of from 6 to 7.

[0429] Embodiment 66: Use of the aqueous composition of embodiment 65 for suspending at least one protein-loaded magnetic particle, preferably for storage, transportation, homogenization, filling, decanting and / or diagnostic purpose involving the at least one protein-loaded magnetic particle.

[0430] The following Examples shall merely illustrate the invention. They shall not be construed, whatsoever, to limit the scope of the invention.

[0431] Examples

[0432] In the following, all pH values indicated were determined by using a pH sensitive glass electrode, preferably at a temperature in the range of from 20 to 25 °C and / or, preferably and, at a pressure in the range of from 800 to 1300 hPa.

[0433] Example 1: Development and optimization of a formulation

[0434] In order to develop an optimal formulation for vitamin D- and steroid-specific antibody- loaded magnetic particles a design-of-experiment (DoE) approach was employed. The desired final formulation should enable the storage of functionally reliable and system-compatible antibody-loaded magnetic particles, which requires minimal adhesion on polypro- pylene(PP)-coated surfaces (i.e. storage material), minimal foaming to enable automated liquid-level-detection aided pipetting and low adhesion to common pipetting needles (for example, electropolished steel, PROBE SET INTEGRA 400 / 400plus from Roche Diagnostics).

[0435] Commercially available vitamin D-and steroids specific antibodies were purchased from numerous vendors such as (i.e. Merck, Thermo Fisher, Bioventix, Bio-Rad, antibodies- online.com). Also internally developed antibodies were used, which were developed by known procedures (i.e. according to WO 2018 / 122205 A2). Furthermore, available antibodies precursors from commercialized Roche products (Elecsys® vitamin D total III; Elecsys® Estradiol III) were used. Antibody particle conjugates were prepared, wherein as vitamin D-specific antibody-loaded magnetic particle, a magnetic particle with a FesC core and a polymeric matrix, loaded with a vitamin D-specific antibody, was used. As steroid-specific antibody-loaded magnetic particle, a magnetic particle with a FesCU core and a polymeric matrix, loaded with a steroidspecific antibody (estradiol-, testosterone-, aldosterone- and androstenedione-specific antibody), was used.

[0436] The following six variables were included and screened in the DoE:

[0437] 1) Different concentration ranges of bovine serum albumin (BSA; in the range of from 0 to 0.2 mg / ml),

[0438] 2) a monoclonal mouse antibody (MAB33; in the range of from 0 to 0.1 mg / ml)),

[0439] 3) Thesit (in the range of from 0 to 0.35 % (w / v)),

[0440] 4) trehalose (in the range of from 0 to 250 mM),

[0441] 5) KC1 (in the range of from 0 to 300 mM) and

[0442] 6) 2 different buffer systems (Potassium phosphate buffer (mixture of KH2PO4 and K2HPO4, K-PO4) and 3-(N-morpholino)propanesulfonic acid (MOPS), each at 25 mM).

[0443] The monoclonal mouse antibody MA33 was Monomeric IgG of commercially available MAB33 IgGl / IgGl Poly (https: / / custombiotech.roche.com / global / en / products / cb / mab33- iggl-iggl-poly-3796120.html).

[0444] The DoE model was calculated using the JMP software (custom designed, reactive surface model, JMP 15), whereby the number of experiments was limited to 30 formulations (see table 1). For the screening, the antibody-loaded magnetic particles and the metal test samples (electropolished steel, PROBE SET INTEGRA 400 / 400plus from Roche Diagnostics) were suspended in the respective formulations (see table 1).

[0445] All formulations used 25 mM of the target buffer salt (MOPS; K-PO4), 0.25mg / ml MIT as a biocide and were adjusted to pH 7.4 and transferred to the desired PP -based storage bottles.

[0446] Tested particle concentrations were 12.5 mg / ml and 20.0 mg / ml for the steroid-and the vitamin specific particles, respectively. The formulated antibody-loaded magnetic particles were stored for 24 h at room temperature (23° C) and then subjected to a foam evaluation.

[0447] Table 1 suggested and executed compositions for the DoE-guided formulation optimization.

[0448]

[0449] Evaluation methods:

[0450] As readout-methods the following properties of the formulated antibody-loaded magnetic particles were selected, each at room temperature (23° C) and at a pressure of 1013 mbar: ) Foam formation properties (Initial foam height, foam decomposition rate and final foam height):

[0451] The particle suspensions were shaken in the storage bottle for 5 min at 100 rpm. The initial foam height, the foam decomposition rate and the final foam height were examined and evaluated. The measured values were fitted non-linearly using the JMP software with the following model: a = final foam (height) [mm], b = amplitude [mm], c = foam decay [1 / min], and a+b = initial foam (height) [mm],

[0452] Depending on the formulation, a strongly fluctuating foam behavior was observed, whereby a stable foam was generated with some formulation compositions. ) Adhesion on storage bottle:

[0453] To evaluate the adhesion to the desired PP -based storage bottle, the antibody-loaded magnetic particles were stored in the respective formulation in the PP -based storage bottle for one week (see above). The sedimented magnetic particles were then subjected to an optical evaluation and the degree of adhesion was classified based on a suitable classification system (see table 2), which is designated as the “bottle adhesion class (bottle AdhesClass)” in the following descriptions and figures.

[0454] Table 2

[0455] Description of the herein used adhesion classification system for the bottle and metal adhesion classes. In addition to the above described visual evaluation, a data-based adhesion evaluation process was established using the following procedure: The state of the storage material containing the antibody-loaded magnetic particles stored in the different formulations, was documented photographically. Next, the particle suspensions were vortexed and removed from the storage bottle. The remaining sample for testing the metal adhesion (electropolished steel, PROBE SET INTEGRA 400 / 400plus from Roche Diagnostics) was also removed and subjected to adhesion analysis (see below). The storage bottles were rinsed with 5 mL of water and the residual (adhesively bound) magnetic particles on the PP-storage material was again documented photographically. Analysis of the obtained samples was done semi-automated using the Imaged software by calculating an RGB-profile from relevant areas (marked by “makeRectangle” function) of the recorded picture. The obtained profiles were exported to Microsoft Excel, subtracted by the profile of a clean storage bottle ( = blank value) and the sign exchanged to generate a blanked pixel intensity profile where high values correspond to magnetic particles present, bottle-water boundaries (including formulation droplets), formulation-air and / or bottle-air boundaries. The profiles were subtracted from the pixel average below the bottom of the bottle where the paper background pixel intensities were located, essentially uniformly zeroing the pixel intensities of the photographic area without the bottle. The adhesion scores (“Adhes Score”) both with the magnetic particle formulation still in one bottle (“Ad- hesScore Pre”) and the washed out bottles (“AdhesScore Post) were calculated as follows: The average pixel intensities over thee ranges (region above the sedimented magnetic particle bulk, the region directly above the liquid level and the region higher above the liquid level) were added and thus condensed into two scores per formulation (“AdhesScore Pre and Post”). Low values of the adhesion scores translate into low amount of adhesively bound magnetic particles and are thereby preferred over high values of adhesion scores, which indicate strong particle adhesion in the relevant areas.

[0456] 3) Adhesion on metal (bottle AdhesClass): For the optical evaluation of the particle adhesion to metallic surfaces, the obtained metal samples (see above, electropolished steel, PROBE SET INTEGRA 400 / 400plus from Roche Diagnostics) were again optically assessed and classified in the above-mentioned adhesion classification system (table 2) to obtain the bottle AdhesClass values.

[0457] Data analysis and modelling: Analysis of the obtained data was done using JMP 15. Responses were minimized and weighting of the desirability function was set to as described below. A stepwise-algorithm was used to generate the model by the following settings: Stopping Rule = Minimum BIC, Direction = Forward und Rules = Combine All. All models were fine-adjusted in terms of Plot Actual by Predicted and Plot Residual by Normal Quantile Tool, effects with a P-value < 5 % were removed. In some cased non-significant effects were manually removed if the effects were identified to cause biases (overfitting or deviation of the residuals from a normal distribution) to generate an acceptable and meaningful model (all selected models for each response are listed below). Next, the modelling of all the responses as a function of the tested factors for both types of antibody-loaded magnetic particles was conducted. The weighting of the desirability function was adjusted by using the following importance values: l / 7:2.5%:0:7.15%:7.15%: 5%:7.125% (initial foam height : foam decay: final foam height: bottle AdhesClass: AdhesScore Pre: AdhesScore Post : metal AdhesClass). The desirability functions were mostly adjusted from a linear to a non-linear form to overproportionally penalize high values (see desirability function in the accompanying graphs). Finally, the desirability was maximized and the corresponding factors were identified (reported results are rounded numbers to ease readability, handling and manufacturing).

[0458] Fig. 1 shows the model of the vitamin D-specific antibody-loaded magnetic particles with the proposed optimal concentrations for each tested formulation ingredient. According to the statistical analysis of the first DoE, the following conclusions and advantageous concentrations for the respective formulation ingredients were identified: KC1 enabled a minimal foaming properties and metal adhesion at a concentration of 125 mM. Trehalose concentration for optimal low foaming and adhesion was identified around 125 mM. Thesit offers an optimal low initial foam height and slight reduction in adhesion around 0.03 % (w / v). BSA showed a tendency towards strong foaming and a positive influence on the adhesion behavior, with the best results being achieved at a concentration around 0.0125 mg / mL. The use of MAB33 only slightly reduced the adhesion of the magnetic particles and contributed overall to undesired foam formation. Compared to potassium phosphate, MOPS is the preferred buffer type due to in general reduced adhesion behavior and foam formation.

[0459] Fig. 2 shows the model of the steroid-specific antibody-loaded magnetic particles with the proposed optimal concentrations for each tested formulation ingredient. The following conclusions and advantageous concentrations for the respective formulation ingredients were identified: KC1 leads to a foam-and adhesion-minimum at a concentration around 230 mM. Thesit facilitates a saturation-like minimum of adhesion properties, while maintaining an optimal low foaming feature around 0.025 % (w / v) Thesit content. Trehalose is optimal balanced in terms of bottle adhesion, anti-foam properties and metal adhesion at a concentration around 100 mM. Optimal results with BSA were achieved at a concentration of 0.005 mg / mL. Again, the use of MAB33 only slightly reduced the adhesion of the magnetic particles and contributed overall to undesired foam formation. With regard to adhesion and anti-foam behaviour, MOPS was again the preferred buffer type.

[0460] A subsequent DoE-assisted screening to develop optimal formulation compositions for antibody-loaded magnetic particles was conducted to 1) verify the above described findings and 2) to identify additional or even improved formulation compositions and 3) to enable a more precise determination of the individual optimal ingredient concentrations. Forthat purpose, the second round of optimization focused on relevant formulation ingredient concentrations ranges as identified in the first screening experiments (see above). For the second round of optimization, the DoE model of the first screening was extended by 16 additional experiments. The suggested experiments were again calculated by the JMP software (custom designed, reactive surface model) (see table 3). According to the above described findings, the concentrations ranges of interests were defined as follows: 50-250 mM KC1, 0.01-0.0225 m / v Thesit, 50-150 mM threhalose, 0-0.01 mg / ml BSA and 0-0.1 mg / ml MAB33. Again the two potential buffer salts K-PO4 and MOPS were tested and all prepared formulations were again supplemented with 25 mM of the respective buffer (MOPS or K-PO4), 0.25mg / ml MIT as a biocide and were adjusted to pH 7.4.

[0461] Table 3

[0462] Extension of the DoE model of the first screening by a second optimization round of DoE- guided formulation optimization. Overview of the 16 suggested, executed and evaluated compositions.

[0463]

[0464] The subsequent experiments and analysis was conducted as described above for the first screening of the DoE-based formulation optimization. For subsequent modelling, all responses and factors of the first (30 experiments) and the second screening (16 additional experiments) were united and modelled as described above.

[0465] Fig. 3 shows the model of the vitamin D-specific antibody-loaded magnetic particles with the proposed optimal concentrations for each tested formulation ingredient. According to the statistical analysis of the extended DoE, the following conclusions and advantageous concentrations for the respective formulation ingredients were identified: KC1 enabled a minimal foaming properties and metal adhesion at a concentration around 141 mM. Trehalose concentration for optimal low foaming and adhesion was confirmed to be around 125 mM. Thesit offers also optimal low initial foam height and slight reduction in adhesion around 0.035 % (w / v). BSA showed a tendency towards strong foaming and a positive influence on the adhesion behavior, with the best results being achieved at a concentration around 0.0139 mg / mL. The use of MAB33 only slightly reduced the adhesion of the magnetic particles and contributed overall to undesired foam formation, which results in a preferred absence of MAB33. Again, compared to potassium phosphate, MOPS is the preferred buffer type due to in general reduced adhesion behavior.

[0466] Three additional favorable formulations calculated and suggested by the model for the first and second round of DoE-guided optimization for the vitamin D specific antibody-loaded magnetic particles are summarized in the table 4 below. In summary, for this particle type KC1 concentrations in the range of 120-140 mM, Thesit content from 0.03-0.035 % (w / v), threhalose concentration of 105-125 mM and BSA content of 0.0125 - 0.014 mg / ml are most preferred. Table 4

[0467] Representative examples of three calculated highly desirable particle formulations (VI, V2,

[0468] V3) for the vitamin D specific antibody- loaded magnetic particle.

[0469] Fig. 4 shows the model of the magnetic particles with the proposed optimal concentrations for each tested formulation ingredient. According to the statistical analysis of the extended DoE, the following conclusions and advantageous concentrations for the respective formulation ingredients were identified: KC1 enabled a minimal foaming properties and metal adhesion at a concentration around 229 mM. Trehalose concentration for optimal low foaming and adhesion was confirmed to be around 125 mM. Thesit offers also optimal low initial foam height and slight reduction in adhesion around 0.022 % (w / v). BSA showed again a tendency to generate strong initial foam and little, but in general, positive influence on the adhesion behavior. The use of MAB33 contributed overall in no significant improvements in the formulation properties, which results in a preferred absence of this ingredient. Again, compared to potassium phosphate, MOPS is the preferred buffer type in this case mainly due reduced adhesion towards the PP -based bottle.

[0470] Six additional favorable formulations calculated and suggested by the model for the first and second round of DoE-guided optimization for the steroid specific antibody-loaded magnetic particles are summarized in the table 5 below. In summary, for this particle type KC1 concentrations in the range of 230-245 mM, Thesit content from 0.025-0.035 w / v, threhalose concentration of 100-125 mM and BSA content of 0.005 - 0.01 mg / ml are most preferred. Table 5

[0471] Representative examples of six calculated highly desirable particle formulations (S1-S6) for the steroid specific antibody-loaded magnetic particle.

[0472]

[0473] Example 2: Adhesion behaviour of antibody-loaded magnetic particles on metal and silicone surfaces

[0474] 2.1 Adhesion on metal

[0475] In order to find a suitable pH of the formulation comprising antibody loaded magnetic beads in terms of low unspecific binding (undesired adhesion) towards metallic surfaces, the following experiments were conducted: The metal sample (electropolished stainless steel) was incubated for 8 h in 80 ml of different magnetic particle suspension. The following particle suspensions were tested:

[0476] 1) Vitamin D-specific antibody-loaded magnetic at a concentration of 20 mg / mL in aqueous formulations containing 125 mM KC1, 105 mM Trehalose, 0.0125 mg / mL BSA, 0.03 wt.% Thesit, 0.25 mg / mL MIT, 25 mM MOPS adjusted to pH 7.0 and 7.4, and formulations containing 125 mM KC1, 105 mM Trehalose, 0.0125 mg / mL BSA, 0.03 wt.% Thesit, 0.25 mg / mL MIT, 25 mM MES adjusted to pH 6.0 and pH 6.5

[0477] 2) A mixture of 4 steroid-specific antibody-loaded magnetic particles (steroid specific with respect to testosterone, estradiol, aldosterone, androstenedione) at concentration of 12.5 mg / mL in aqueous formulations containing 235 mM KC1, 125 mM Trehalose, 0.005 mg / mL BSA, 0.03 wt.% Thesit, 0.25 mg / mL MIT, 25 mM MOPS, adjusted to pH 7.4, and formulations containing 235 mM KC1, 125 mM Trehalose, 0.005 mg / mL BSA, 0.03 wt.% Thesit, 0.25 mg / mL MIT, 25 mM MES, adjusted to pH 5.5, 6.0 and 6.5.

[0478] After incubation of the metal piece with the magnetic particle suspensions, the samples were immersed in water and then allowed to drip off. To quantify the amount of magnetic particles on the metal piece, the metal sample was transferred to a falcon tube with 30 mL ethanol and placed in an ultrasonic bath for 30 min. The resulting magnetic particle suspension was then magnetically separated and a gravimetric mass determination was carried out. As depicted in Figure 5 the undesired adhesion of the steroid-specific antibody-loaded magnetic particles can be reduced significantly (5-10 fold) by using an 2-(A-morpholino)ethanesulfonic acid (MES) buffer adjusted to an acidic pH (<7). A similar behavior was observed for the vitamin D-specific antibody-loaded magnetic particles, an optimal, minimal binding was observed by using (again) slightly acidic conditions (MES-based formulations adjusted to pH 6.5); see Fig. 6. It is important to note, that the vitamin D-specific antibody-loaded magnetic particles showed in general a lower adhesion to the tested metal surface.

[0479] 2.1 Adhesion on silicon tubing

[0480] In order to find a suitable pH of the formulation comprising antibody loaded magnetic beads in terms of low unspecific binding (undesired adhesion) towards silicone surfaces, the following experiments were conducted: A masterflex squeeze tubing (collapse-protected) was placed in a peristaltic pump and the silicone tubing was attached to the squeeze tubing on both sides. Antibody loaded magnetic particles (suspended in different formulations, see below) were stirred by using an overhead stirring system and the particle suspension was continually pumped / recirculated through the silicone tubings for 8 h.

[0481] The following particle suspensions were tested:

[0482] 1) Vitamin D-specific antibody-loaded magnetic at a concentration of 20 mg / mL in aqueous formulations containing 125 mM KC1, 105 mM Trehalose, 0.0125 mg / mL BSA, 0.03 wt.% Thesit, 0.25 mg / mL MIT, 25 mM MOPS adjusted to 7.4, and formulations containing 125 mM KC1, 105 mM Trehalose, 0.0125 mg / mL BSA, 0.03 wt.% Thesit, 0.25 mg / mL MIT, 25 mM MES adjusted to pH 6.0 and pH 6.5

[0483] 2) A mixture of 4 steroid-specific antibody-loaded magnetic particles (steroid specific with respect to testosterone, estradiol, aldosterone, androstendione) at concentration of 12.5 mg / mL in aqueous formulations containing 235 mM KC1, 125 mM Trehalose, 0.005 mg / mL BSA, 0.03 wt.% Thesit, 0.25 mg / mL MIT, 25 mM MOPS, adjusted to pH 7.4, and formulations containing 235 mM KC1, 125 mM Trehalose, 0.005 mg / mL BSA, 0.03 wt.% Thesit, 0.25 mg / mL MIT, 25 mM MES, adjusted to pH 6.0 and 6.5.

[0484] Then 8 cm of the test material was removed, dipped in demineralized water with tweezers and allowed to dry. The material sample was placed in a Falcon tube with ethanol and placed in an ultrasonic bath for 30 min. Under these conditions, magnetic particles bound to the surface of the sample material were detached. Finally, the magnetic particles were magnetically separated, dried and the amount of adhesively bound particles was quantified gravi- metrically.

[0485] The experiments indicated that silicone might be a suitable tubing material for production of antibody-loaded magnetic particles and products containing these particles. Relevant adhesion of the antibody-loaded magnetic particles (vitamin D and steroid specific) to silicone tubes using a MOPS-buffer formulation pH 7.4 (see Fig. 7) was observed and thus required further optimization in order to reduce particle loss and to prevent clogging of silicone-hoses, both possible during the production of antibody-loaded magnetic particles-based products using silicone-based hoses. By using MES as a buffer substance at pH values from 6.0 to 6.5, adhesion could be reduced in all cases by at least 33% and in some cases by more than 80-90% (see Table 4). In summary, the results show very clearly that MES-based acidic formulations have a beneficial effect on the adhesion behavior of the antibody-loaded magnetic particles compared to rather neutral MOPS-based formulations.

[0486] Summary: Final formulation based on the results

[0487] Considering the findings of the above-described experiments, the two following formulations were identified to be most suitable for particle storage, production and application on high throughput diagnostic analyzers (i.e. cobas i601) :

[0488] Formulation steroid specific antibody-loaded magnetic particle: 235 mM KC1, 125 mM Trehalose, 0.005 mg / mL BSA, 0.03 wt.% Thesit, 0.25 mg / mL MIT, 25 mM MES, pH 6.3 in fully demineralized water (VE water)

[0489] Formulation vitamin D specific antibody-loaded magnetic particle: 125 mM KC1, 105 mM Trehalose, 0.0125 mg / mL BSA, 0.03 wt.% Thesit, 0.25 mg / mL MIT, 25 mM MES, pH 6.3 in VE water.

[0490] Short description of the Figures

[0491] Fig- 1 shows optimal formulation ingredient concentrations (red lines & values) suggested by DoE-analysis for the vitamin D-specific antibody-loaded magnetic particles. Magnetic particle concentration = 20 mg / mL.

[0492] Fig- 2 shows optimal formulation ingredient concentrations (red lines & values) suggested by the DoE-analysis for the steroid-specific antibody-loaded magnetic particles. Magnetic particle concentration = 12.5 mg / mL. Fig. 3 shows optimal formulation ingredient concentrations (red lines & values) suggested by DoE-analysis for the vitamin D-specific antibody-loaded magnetic particles after extending the first screening model.

[0493] Fig- 4 shows optimal formulation ingredient concentrations (red lines & values) suggested by DoE-analysis for the steroid-specific antibody-loaded magnetic particles after extending the first screening model.

[0494] Fig. 5 shows determined adhesion of steroid-specific antibody-loaded magnetic particles in different formulations on electropolished stainless steel.

[0495] Fig- 6 shows determined adhesion of vitamin D-specific antibody-loaded magnetic particles in different formulations on electropolished stainless steel.

[0496] Fig. 7 shows mass loss of the antibody-loaded magnetic particles (MP) per surface at different pH values and with different hose material: Silicone tubing 1.5 cm = Watson Marlow Pumpsil platinum-cured silicone hose with 16 mm inner diameter; Silicone tubing 0.5 cm = Watson Marlow Pumpsil platinum cured silicone hose with 5 mm inner diameter; Formulation mixture of 4 steroid specific magnetic particles (MP): pH7.4 = 235 mM KC1, 125 mM Trehalose, 0.005 mg / mL BSA, 0.03 % (w / v) Thesit, 0.25 mg / mL MIT, 25 mM MOPS, pH 7.4; pH 6.5 and pH 6.0 = 235 mM KC1, 125 mM Trehalose, 0.005 mg / mL BSA, 0.03 wt.% (w / v) Thesit, 0.25 mg / mL MIT, 25 mM MES, pH 6.0-6.5; Formulation vitamin D specific magnetic particle (MP): pH 7.4 = 125 mM KC1, 105 mM Trehalose, 0.0125 mg / mL BSA, 0.03 % (w / v) Thesit, 0.25 mg / mL MIT, 25 mM MOPS, pH 7.4 in VE water; pH 6.0 - 6.5: 125 mM KC1, 105 mM Trehalose, 0.0125 mg / mL BSA, 0.03 % (w / v) Thesit, 0.25 mg / mL MIT, 25 mM MOPS or MES, pH 6.0-7.5.

Claims

Roche Diagnostics GmbH RD39645PCClaims1. An aqueous formulation of a protein-loaded magnetic particle, the formulation comprising:(i) at least one protein-loaded magnetic particle;(ii) at least one aqueous phase; wherein the at least one protein-loaded magnetic particle of (i) is at least partially suspended in the at least one aqueous phase of (ii), the formulation further comprising:(iii) at least one detergent in a concentration of in the range of from 0.01 to 0.04 % (w / v);(iv) at least one blocking reagent in a concentration < 0.02 mg / ml;(v) at least one inorganic salt in a concentration < 300 mM; and(vi) at least one buffering system; wherein the at least one protein-loaded magnetic particle of (i) is present in the aqueous formulation in a concentration of > 10 mg / ml; and the aqueous formulation has a pH in the range of from 6 to 7.

2. The aqueous formulation of claim 1 further comprising(vii) at least one biocide.

3. The aqueous formulation of claim 1 or 2, wherein the at least one detergent of (iii) is selected from the group consisting of non-ionic detergent, ionic detergent, zwitterionic detergent and mixtures of two or more thereof; preferably from the group consisting of non-ionic detergent, ionic detergent, zwitterionic detergent and mixtures of non-ionic detergent and ionic detergent; more preferably from the group consisting of Polidocanol, Brij 35, Synperonic F68, Synperonic F108, Tergitol 15-S-9, Tween 20, Tween 80, CTAB, Na-cholate, Na-deoxycholate, Na-N-lauroylsarcosinate, SDS, ASB-14, ASB-16, CHAPS, SB 3 - 10, SB 12, n-dodecyl-P-D-maltopyranoside (DDM), n-decyl-P-D-maltopyranoside (DM), n-Octyl-P-D-Glucopyranoside / n- nonyl-P-D-glucopyranoside (OG / NG), lauryldimethylamine-N-oxide (LDAO), polyoxyethylene dodecyl ether, n-undecyl-P-D-maltopyranoside (UDM), lauryl maltoseneopentyl glycol (LMNG), Triton X-100, Digitonin, cyclic maltosides, 3-[(3-chol- amidopropyl)dimethylammonio]-2-hydroxy-l -propanesulfonate (CHAPSO), and mixtures of two or more thereof; more preferably from the group consisting of n-do- decyl-P-D-maltopyranoside (DDM), n-decyl-P-d-maltopyranoside (DM), n-octyl-P- d-glucopyranoside / n-nonyl-P-d-glucopyranoside (OG / NG), lauryldimethylamine-N- oxide (LDAO), polyoxyethylene dodecyl ether, n-undecyl-P-d-maltopyranoside (UDM), lauryl maltose neopentyl glycol (LMNG), Triton X-100, Digitonin, cyclic maltoside, 3-[(3-cholamidopropyl)dimethylammonio]-l-propanesulfonate (CHAPS), 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-l-propanesulfonate (CHAPSO), and mixtures of two or more thereof; wherein the at least one detergent of (iii) more preferably comprises or is a polyoxyethylene dodecyl ether, preferably macrogollaurylether 8 (CnEs) and / or macrogollaurylether 9 (Thesit, Polidocanol); and / or wherein the at least one detergent of (iii) is present in a concentration in the range of from 0.02-0.035 % (w / v).

4. The aqueous formulation of any one of claims 1 to 3, wherein the at least one blocking reagent of (iv) is a protein; preferably selected from the group consisting of bovine serum albumin (BSA), human serum albumin (HSA), lactalbumin, casein, skim milk, serum proteins, and mixtures thereof; wherein the at least one blocking reagent of (iv) more preferably comprises at least BSA; or preferably a monoclonal antibody, more preferably a recombinant antibody; and / or, preferably and, wherein the at least one blocking reagent of (iv) is present in a concentration in the range of from 0.001 to 0.02 mg / ml, preferably in the range of 0.001 to 0.015 mg / ml.

5. The aqueous formulation of any one of claims 1 to 4, wherein the at least one inorganic salt of (v) is selected from the group of earth alkali metal salt, alkali metal salt and mixtures of earth alkali metal salt and alkali metal salt, preferably at least one alkali metal salt, more preferably at least one alkali metal halogenide, more preferably at least potassium chloride; and / or, preferably and, wherein the at least one inorganic salt of (v) is present at a concentration in the range of from 10 to 300 mM, preferably in the range of from 100 to 245 mM.

6. The aqueous formulation of any one of claims 1 to 5, wherein the at least one buffering system of (vi) is selected from the group of potassium phosphate buffer (K2HPO4 / KH2PO4), MES, ADA, PIPES, ACES, MOPSO, cholamine chloride, MOPS, TES, HEPES, DiPSO, TAPSO and mixtures of two or more thereof, preferably selected from the group of potassium phosphate buffer (K2HPO4 / KH2PO4), MES, MOPS and mixtures of two or three thereof, wherein the at least one buffering system of (vi) more preferably comprises at least MES.

7. The aqueous formulation of any one of claims 2 to 6, wherein the at least one biocide of (vii) is selected from the group consisting of (metal cation) chelating biocide, (metal cation) non-chelating biocide and mixtures of two or more thereof; preferably selected from the group of (metal cation) non-chelating biocides; more preferably selected from the group of isothiazolinone derivative, sodium azide, 2-chloroacetamide, sodium benzoate and mixtures thereof; more preferably selected from the group consisting of me- thylisothiazolinone (2-methyl-l,2-thiazol-3(2H)-one, MIT), methylchloroisothiazoli- none (5-chloro-2-methyl-l,2-thiazol-3(2H)-one, MCI), benzisothiazolinone (1,2-ben- zothiazol-3(2H)-one, BIT), octylisothiazolinone (2-octyl-l,2-thiazol-3(2H)-one, OIT), dichlorooctylisothiazolinone (4,5-dichloro-2-octyl-l,2-thiazol-3(2H)-one, DCOIT), sodium azide, 2-chloroacetamide, sodium benzoate, and mixtures of two or more thereof; more preferably selected from the group consisting of methylisothiazoli- none (2-methyl-l,2-thiazol-3(2H)-one, MIT), methylchloroisothiazolinone (5-chloro- 2-methyl-l,2-thiazol-3(2H)-one, MCI), sodium azide, 2-chloroacetamide, sodium benzoate, and mixtures of two or more thereof, preferably from the group consisting of methylisothiazolinone (2-methyl-l,2-thiazol-3(2H)-one, MIT), methylchloroisothiazolinone (5-chloro-2-methyl-l,2-thiazol-3(2H)-one, MCI), sodium azide, and mixtures of two or more thereof; wherein the at least one biocide of (vii) more preferably at least comprises MIT; and / or, preferably and, wherein the at least one biocide of (vii) is present in a concentration in the range of from 0.001 to 0.5 mg / ml, preferably in the range of from 0.1 to 0.4 mg / ml, more preferably in the range of from 0.15 to 0.35 mg / ml.

8. The aqueous formulation of any one of claims 1 to 7, further comprising (viii) at least one second blocking reagent; wherein the at least one second blocking reagent of (viii) is preferably selected from the group consisting of polyol, carbohydrate and mixtures of two or more thereof; more preferably selected from the group consisting of trehalose, sucrose, glycerol, threitol,sorbitol, maltitol and mixtures of two or more thereof; wherein the at least one second blocking reagent of (viii) more preferably comprises at least trehalose; and / or, preferably and, wherein the at least one second blocking reagent of (viii) is present in a concentration in the range of from of 10 to 500 mM, preferably in the range of from 50 to 250 mM, more preferably in the range of from 100 to 150 mM.

9. The aqueous formulation of any one of claims 1 to 8, comprising the at least one protein-loaded magnetic particle in a concentration in the range of from 10 to 100 mg / ml, preferably in the range of from 10 to 50 mg / ml.

10. The aqueous formulation of any one of claims 1 to 9, having a pH in the range of from 6.0 to 6.9, preferably in the range of from 6.0 to 6.8, more preferably in the range of from 6.0 to 6.7, more preferably in the range of from 6.0 to 6.6, more preferably in the range of from 6.0 to 6.5.

11. The aqueous formulation of any one of claims 1 to 10, having an initial foam height of less than 4 mm, preferably determined according to the procedure of Example 1); and / or having a final foam height of less than 1mm, preferably determined according to the procedure of Example 1).

12. The aqueous formulation of any one of claims 1 to 11, having a bottle AdhesClass with respect to metallic surface, preferably a steel surface, of 2 or less preferably determined according to the procedure of Example 1); and / or having a bottle AdhesClass with respect to polymeric surface, preferably polypropylene surface, of 2 or less, preferably determined according to the procedure of Example 1).

13. Use of an aqueous formulation according to any one of claims 1 to 12 for storage, transportation, homogenization, filling, decanting and / or diagnostic purpose.

14. The use of claim 13 for diagnostic purpose, preferably for determining an analyte of interest in a sample, more preferably for determining an analyte of interest in a sample by mass spectrometry.

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