Formulations for increased shelf life of protein-loaded magnetic particles

Abstract

The invention is directed in a first aspect to an aqueous formulation of a protein-loaded magnetic particle, the formulation comprising (i) at least one protein-loaded magnetic particle present in an aqueous phase in a concentration of ≥ 10 mg / ml; and (ii) at least one non-chelating biocide, wherein the at least one non-chelating biocide is at least partially dissolved respectively in the aqueous phase of (i), and the aqueous formulation, especially the aqueous phase, has a pH value in the range of from 6 to 7. A second aspect of the invention is directed to the use of the aqueous formulation according to the first aspect of the invention for storage, transportation, homogenization, purification, filling, decanting and / or diagnostic purpose.

Description

[0001] Roche Diagnostics GmbH RD39702PC

[0002] Formulations for increased shelf life of protein-loaded magnetic particles

[0003] Technical Field

[0004] The invention is directed in a first aspect to an aqueous formulation of a protein-loaded magnetic particle, the formulation comprising (i) at least one protein-loaded magnetic particle present in an aqueous phase in a concentration of > 10 mg / ml; and (ii) at least one nonchelating biocide, wherein the at least one non-chelating biocide is at least partially dissolved respectively in the aqueous phase of (i), and the aqueous formulation, especially the aqueous phase, has a pH value in the range of from 6 to 7.

[0005] A second aspect of the invention is directed to the use of the aqueous formulation according to the first aspect of the invention for storage, transportation, homogenization, purification, filling, decanting and / or diagnostic purpose.

[0006] Background art

[0007] Antibody-loaded magnetic particles are invaluable tools in diagnostic assays, such as immunoassays, molecular diagnostics, bioseparation applications, such as protein purification and nuleic acid purification. 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).

[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 and sodium azide as a biocide (0.05 - 0.1%), wherein a pH of 7.4 is used. 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 a pH of 7.2. Formulations for higher concentration of protein loaded magnetic particles are described for several commercially available magnetic particles and in several combinations of proteins and magnetic particles. For example, formulations by micromod Partikeltechnologie GmbH for commercialized protein A, streptavidin and avidin protein coated magnetic particles comprise up to 25 mg / ml particle concentrations and sodium azide as biocide, while using PBS buffers adjusted to pH > 7. Commercially available antibody-modified Pierce™ Anti- DYKDDDDK Magnetic Agarose is supplied as a 25% slurry (corresponding to 35 mg / ml particle concentration, as determined by gravimetric analysis) in a formulation containing 0.01% Tween-20 as a detergent, 0.02% sodium azide as a biocide and PBS as a buffering salt, wherein the formulation is adjusted to a pH > 7. Absolute Mag™ Anti-Rat IgG (H&L) Magnetic Particles are stored at 2 mg / ml particle concentration in a formulation containing, 0.02% NaNs as a biocide and PBS as a buffering salt, wherein the formulation is adjusted to a pH > 7. Polysciences, Inc. provides antibody-loaded magnetic particles up to 5 mg / ml particle concentration in a formulation containing sodium azide as a biocide and PBS as a buffering salt, wherein the formulation is adjusted to a pH > 7 and EDTA is used.

[0009] Providing long shelf life of protein-loaded magnetic particles remains challenging, as especially long-term storage of formulations with high concentration (several months up to years) usually causes a loss of functionality. Long-term storage is however important especially for formulations of magnetic particles with higher concentrations, which are intended to be used in an automated workflow - the protein-loaded magnetic particles -in view of packaging, transporting and especially storing before use - have to be stable for weeks up to months or years. Known formulations are not suitable for this purpose, since they are not optimized for long-term storability of protein-loaded and highly magnetic particles. For example, as magnetic particles usually consist of iron oxide, iron of the magnetite core particle leaks into the solution / supernatant upon storage (Biochemical and Biophysical Research Communications 468 (2015) 442-453). In solution, the released iron is known to trigger protein-fragmentation in the presence of histidine buffer or under oxidizing conditions (Analytical Biochemistry 389 (2009) 107-117; mAbs, 3:3, 253-263, DOI: 10.4161 / mabs.3.3.15608), wherein it was understood that the fragmentation could be reduced in the presence of a chelating agent . Consequently, the quality (i.e. protein loading, binding capacity, functionality) of the protein-loaded magnetic particle decreases over time and the shelf life time is severely limited.

[0010] 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 protein-loaded magnetic particles at high particle concentration (> 10 mg / ml). Summary of the invention

[0011] This problem is addressed by an aqueous formulation of a protein-loaded magnetic particle, the formulation comprising (i) at least one protein-loaded magnetic particle present in an aqueous phase; and (ii) at least one non-chelating biocide, wherein the at least one nonchelating biocide is at least partially dissolved respectively in the aqueous phase of (i), and the aqueous formulation, especially the aqueous phase, has a pH value in the range of from 6 to 7, as well as by its use for storage, transportation, homogenization, purification, filling, decanting and / or diagnostic purpose. Preferably, the problem is addressed by an aqueous formulation of a protein-loaded magnetic particle, the formulation comprising (i) at least one protein-loaded magnetic particle present in an aqueous phase in a concentration of > 10 mg / ml; and (ii) at least one non-chelating biocide, wherein the at least one non-chelating biocide is at least partially dissolved respectively in the aqueous phase of (i), and the aqueous formulation, especially the aqueous phase, has a pH value in the range of from 6 to 7, as well as by its use for storage, transportation, homogenization, purification, filling, decanting and / or diagnostic purpose. 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.

[0012] 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.

[0013] 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. 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.

[0014] 1staspect - Aqueous formulation of a protein-loaded magnetic particle

[0015] The problem is addressed by an aqueous formulation of a protein-loaded magnetic particle, the formulation comprising

[0016] (i) at least one protein-loaded magnetic particle present in an aqueous phase;

[0017] (ii) at least one non-chelating biocide, wherein the at least one non-chelating biocide is at least partially dissolved respectively in the aqueous phase of (i), and the aqueous formulation, especially the aqueous phase, has a pH value in the range of from 6 to 7.

[0018] Preferably, 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 present in an aqueous phase in a concentration > 10 mg / ml;

[0020] (ii) at least one non-chelating biocide, wherein the at least one non-chelating biocide is at least partially dissolved respectively in the aqueous phase of (i), and the aqueous formulation, especially the aqueous phase, has a pH value in the range of from 6 to 7.

[0021] The pH of the aqueous formulation is 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.

[0022] A “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 with at least one nitrogen atom or such a structural element -N(OH)-C(=O)-.

[0023] It was surprisingly found that a chelating biocide actively liberates the metal cations from a magnetic particle, as indicated by the increased metal cation concentration in the supernatant (measured, for example, by ICP-MS), and that the combination of chelating biocide with free metal cation causes an increase in protein fragmentation. On the contrary, using a nonchelating biocide and adjusting the pH of the aqueous formulation to be in the range of from 6 to 7, significantly reduces the fragmentation of the protein, which is loaded to the magnetic particle. Consequently, the quality (i.e. protein loading, binding capacity, functionality) of the protein-loaded magnetic particle can be preserved over a longer time and the shelf life time can be increased.

[0024] Non-chelating biocide of (ii)

[0025] In some preferred embodiments of the aqueous formulation, the at least one non-chelating biocide of (ii) is selected from the group of isothiazolinone derivatives, sodium azide, 2- chloroacetamide, sodium benzoate and mixtures thereof. Preferably, the at least one nonchelating biocide of (ii) is 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), benzisothiazoli- none (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-di- chloro-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; more preferably the at least one non-chelating biocide of (ii) 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 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 (ii) more preferably at least comprises MIT.

[0026] Reduced fragmentation

[0027] 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 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. 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% .

[0028] “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. pH of aqueous formulation

[0029] In some preferred embodiments the aqueous formulation has a pH value in the range of from 6.1 to 6.9, more preferably in the range of from 6.2 to 6.8, more preferably in the range of from 6.3 to 6.7, more preferably in the range of from 6.4 to 6.6.

[0030] Buffer system

[0031] In some preferred embodiments the aqueous formulation further comprises (iii) at least one buffer system.

[0032] Preferably, the at least one buffering system 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, more preferably the at least one buffer system is at least MES.

[0033] Magnetic particle

[0034] In some preferred embodiments of the aqueous formulation, the magnetic particle of (i) comprises at least one magnetic core (M), wherein the at least one magnetic core (M) preferably comprises a metal oxide or a metal carbide, more preferably, an iron oxide, in particular an iron oxide selected from the group consisting of FesCU, 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, FesC

[0035] In some preferred embodiments of the aqueous formulation, the magnetic particle of (i) comprises at least a polymer matrix (P) comprising a polysaccharide, preferably agarose, or a crosslinked polymer, wherein the polymer matrix (P) at least partially surrounds the magnetic core (M), 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.

[0036] In some preferred embodiments of the aqueous formulation, the magnetic particle of (i) has a particle size of at least 1 micrometer, preferably in the range of from 1 to 10 micrometer, more preferably in the range of from 1 to 5 micrometer, determined according to ISO 13320.

[0037] In some preferred embodiments of the aqueous formulation, the protein loaded to the magnetic particle of (i) is selected from the group consisting of streptavidin, avidin, protein A, protein G and protein L.

[0038] In some preferred embodiments of the aqueous formulation, the protein loaded to the magnetic particle of (i)is selected from the group consisting of antibody and antibody fragment.

[0039] Preferably, the protein and the magnetic particle are bound to each other by a covalent or a non-covalent bond. 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.

[0040] Protein-loaded magnetic particles (i.e. streptavidin-, avidin-, protein A-, protein G-, protein L-loaded) are commercially available from numerous vendors (i.e. Merck / Sigma-Aldrich, Thermo Fisher, Cytiva, CD-Bioparticles, Micromod Partikeltechnologie GmbH, Sphero- tech). For example, protein-loaded magnetic particles, such as 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). Magnetic particles are per se known to the skilled person.

[0041] For example, protein-loaded magnetic particles, such as antibody-loaded magnetic particles, can be prepared by covalent coupling of proteins / 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 / technicalover- views / public / lodestars-carboxyl-5994-5012en-agilent.pdf and https: / / cdn.cytivalifesci- ences.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 / antibodies on magnetic particles using click chemistry as reported in published procedures (see Molecular Imaging 2009 8:4 (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.

[0042] Preferably, as already indicated above, the magnetic particle comprises at least one magnetic core (M), and at least a polymer matrix (P) comprising a polysaccharide, preferably agarose, or a crosslinked polymer at least partially surrounding the magnetic core (M). In some embodiments, 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, vinylben- zylchloride, divinylbenzene, vinylacetate, methylmethacrylate and acrylic acid.

[0043] 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 of the magnetic particle, 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(vinylbenzyloxy)dodecane, and mixtures of two or more thereof, wherein more preferably the crosslinking agent comprises at least divinylbenzene. Preferably of the magnetic particle, 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. 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.

[0044] 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.

[0045] 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.

[0046] 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‘).

[0047] Preferably, the linker (L) comprises an element (LI)

[0048] • • • X-(CR1R2)xi - [(CR3R4)x2]y-(CR1R2)x3 •••• (LI), wherein

[0049] R1, R2are independently selected from the group consisting of hydrogen atom and Cl to C3 straight or branched alkyl group;

[0050] 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;

[0051] 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;

[0052] X is an -NH- group or an oxygen atom;

[0053] 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)

[0054] ••••X-(CR1R2)xi-[O-(CR3R4)x2]y•••• (L2), wherein

[0055] 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;

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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. Preferably, the at least one magnetic core (M) comprises at least one magnetic nanoparticle, preferably at least one iron oxide nanoparticle, more preferably a FesCU-nan oparticle.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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-hydroxy succinimide).

[0068] Concentration of protein-loaded magnetic particle

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] Detergent

[0075] In some preferred embodiments, the aqueous formulation further comprises (iv) at least one detergent.

[0076] Preferably, the at least one detergent of (iv) is selected from the group consisting of nonionic detergent, ionic detergent, zwitterionic detergent and mixtures of two or more thereof; more preferably, the at least one detergent of (iv) is selected from the group consisting of non-ionic detergent, ionic detergent, zwitterionic detergent and mixtures of non-ionic detergent and ionic detergent; more preferably, the at least one detergent of (iv) is selected from the group consisting of Polidocanol (macrogollaurylether 9, Thesit, CAS: 9002-92-0), Brij 35, Digitonin, dodecyl-B-D-maltoside, octyl-B-D-glucopyranodide, Synperonic F68, Synperonic F108, Tergitol 15-S-9, Tween 20, Tween 80, CTAB, Na-cholate, Na-deoxycho- late, Na-N-lauroylsarcosinate, SDS, ASB-14, ASB-16, CHAPS, SB 3 - 10, SB 12, n-do- decyl-P-D-maltopyranoside (DDM), n-decyl-P-D-maltopyranoside (DM), n-octyl-P-D-glu- copyranoside / 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-chol- amidopropyl)dimethylammonio]-l -propanesulfonate (CHAPS), 3-[(3-cholamidopropyl)di- methylammonio]-2-hydroxy-l -propanesulfonate (CHAPSO), and mixtures of two or more thereof. Reference is made to inhttps: / / www.serva.de / enDE / 275_Information_Center_Deter- gents Cl as sifi cation of Detergents . html .

[0077] In some preferred embodiments, the at least one detergent of (iv) 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), Lau- ryldimethylamine-N-oxide (LDAO), polyoxyethylene dodecyl ether, n-undecyl-P-d-malto- pyranoside (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 (iv) more preferably comprises or is a polyoxyethylene dodecyl ether; more preferably macrogollaurylether 8 (C12E8) and / or macrogollaurylether 9 (Thesit, Polidocanol).

[0078] In some preferred embodiments of the aqueous formulation, the at least one detergent of (iv) is present in a concentration of < 0.04 % (w / v). Preferably, the at least one detergent of (iv) is present in a concentration in the range of from 0.02-0.035 % (w / v).

[0079] “% (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.

[0080] (First) blocking reagent

[0081] In some preferred embodiments, the aqueous formulation further comprises: (v) at least one blocking agent

[0082] Preferably, the at least one blocking reagent of (v) is a protein.

[0083] In some preferred embodiments of the aqueous formulation, the at least one blocking reagent of (v) 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 (v) more preferably comprises at least BSA.

[0084] In some preferred embodiments of the aqueous formulation, the at least one blocking reagent of (v) is a monoclonal antibody, preferably a recombinant antibody. In some preferred embodiments of the aqueous formulation, the at least one blocking reagent of (v) is present in a concentration in the range of from 0.002 to 0.02 mg / ml, more preferably in the range of 0.005 to 0.015 mg / ml.

[0085] Inorganic salt

[0086] In some preferred embodiments, the aqueous formulation further comprises (vi) at least one inorganic salt.

[0087] Preferably, the at least one inorganic salt of (vi) 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.

[0088] In some preferred embodiments of the aqueous formulation, the at least one inorganic salt of (vi) 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.

[0089] 2ndaspect - Use of the aqueous formulation

[0090] A second aspect of the invention is related to the use of an aqueous formulation according to the first aspect as described herein above for storage, transportation, homogenization, purification, filling, decanting and / or diagnostic purpose.

[0091] All details, embodiments and preferred embodiments described herein above with respect to the aqueous formulation of the first aspect of the invention apply also to the use according to the second aspect of the invention.

[0092] In some preferred embodiments, the use aqueous formulation is used for purification, preferably for protein and / or oligonucleotide purification.

[0093] In some preferred embodiments, the aqueous formulation is used 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.

[0094] Mass spectrometric analysis is preferably liquid chromatography-mass spectrometry (LC- MS), more preferably Liquid chromatography-tandem mass spectrometry (LC-MS / MS). 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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). Summarizing and without excluding further possible embodiments, the following embodiments may be envisaged:

[0100] Embodiment 1 : An aqueous formulation of a protein-loaded magnetic particle, the formulation comprising

[0101] (i) at least one protein-loaded magnetic particle present in an aqueous phase;

[0102] (ii) at least one non-chelating biocide, wherein the at least one non-chelating biocide is at least partially dissolved respectively in the aqueous phase of (i), and the aqueous formulation, especially the aqueous phase, has a pH value in the range of from 6 to 7.

[0103] Embodiment 2: The aqueous formulation of embodiment 1, wherein the at least one nonchelating biocide of (ii) is selected from the group of isothiazolinone derivatives, sodium azide, 2-chloroacetamide, sodium benzoate and mixtures thereof.

[0104] Embodiment 3 : The aqueous formulation of embodiment 1 or 2, wherein the at least one non-chelating biocide of (ii) 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.

[0105] Embodiment 4: The aqueous formulation of any one of embodiments 1 to 3, wherein the at least one non-chelating biocide of (ii) 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 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 (ii) more preferably at least comprises MIT.

[0106] Embodiment 5: The aqueous formulation of any one of embodiments 1 to 4, wherein the protein of the at least one protein-loaded magnetic particle of (i) shows a reduced fragmentation of at least 10%less than an aqueous formulation containing a chelating biocide, preferably an iron-chelating biocide, at the same concentration and at a pH >7.4, which has a fragmentation that represents 100%. Embodiment 6: The aqueous formulation of any one of embodiments 1 to 5, having a pH value in the range of from 6.1 to 6.9, preferably in the range of from 6.2 to 6.8, more preferably in the range of from 6.3 to 6.7, more preferably in the range of from 6.4 to 6.6.

[0107] Embodiment 7: The aqueous formulation of any one of embodiments 1 to 6 further comprising

[0108] (iii) at least one buffer system.

[0109] Embodiment 8: The aqueous formulation of embodiment 7, wherein the at least one buffering system 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, more preferably the at least one buffer system is at least MES.

[0110] Embodiment 9: The aqueous formulation of any one of embodiments 1 to 8, wherein the magnetic particle of (i) comprises at least one magnetic core (M), wherein the at least one magnetic core (M) preferably comprises a metal oxide or a metal carbide, more preferably, an iron oxide, in particular an iron oxide selected from the group consisting of FesCU, a- Fe20s, 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, FesCE

[0111] Embodiment 10: The aqueous formulation of embodiment 9, wherein the magnetic particle of (i) comprises at least a polymer matrix (P) comprising a polysaccharide, preferably agarose or a crosslinked polymer, wherein the polymer matrix (P) at least partially surrounds the magnetic core (M). 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.

[0112] Embodiment 11: The aqueous formulation of embodiment 9 or 10, wherein the magnetic particle of (i) has a particle size of at least 1 micrometer, preferably in the range of from 1 to 10 micrometer, more preferably in the range of from 1 to 5 micrometer, determined according to ISO 13320. Embodiment 12: The aqueous formulation of any one of embodiments 9 to 11, wherein the protein loaded to the magnetic particle of (i) is selected from the group consisting of streptavidin, avidin, protein A, protein G and protein L.

[0113] Embodiment 13 : The aqueous formulation of embodiment 12, wherein the protein is selected from the group consisting of antibody and antibody fragment.

[0114] Embodiment 14: The aqueous formulation of any one of embodiments 1 to 13, wherein the protein and the magnetic particle are bound to each other by a covalent or a non-covalent bond.

[0115] Embodiment 15: The aqueous formulation of any one of embodiments 1 to 14, 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.

[0116] Embodiment 16: The aqueous formulation of any one of embodiments 1 to 15, 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.

[0117] Embodiment 17: The aqueous formulation of any one of embodiments 1 to 16, 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.

[0118] Embodiment 18: The aqueous formulation of any one of embodiments 1 to 17, 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.

[0119] Embodiment 19: The aqueous formulation of any one of embodiments 1 to 18, 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.

[0120] Embodiment 20: The aqueous formulation of any one of embodiments 1 to 19, 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.

[0121] Embodiment 21: The aqueous formulation of any one of embodiments 1 to 20, 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.

[0122] Embodiment 22: The aqueous formulation of any one of embodiments 1 to 21 further comprising

[0123] (iv) at least one detergent.

[0124] Embodiment 23 : The aqueous formulation of embodiment 22, wherein the at least one detergent of (iv) is selected from the group consisting of non-ionic detergent, ionic detergent, zwitter-ionic detergent and mixtures of two or more thereof.

[0125] Embodiment 24: The aqueous formulation of embodiment 22 or 23, wherein the at least one detergent of (iv) is selected from the group consisting of non-ionic detergent, ionic detergent, zwitterionic detergent and mixtures of non-ionic detergent and ionic detergent.

[0126] Embodiment 25: The aqueous formulation of any one of embodiments 22to 24, wherein the at least one detergent of (iv) is selected from the group consisting of Polidocanol, Brij 35, Digitonin, dodecyl-B-D-maltoside, octyl-B-D-glucopyranodide, Synperonic F68, Synper- onic 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 maltose neopentyl glycol (LMNG), Triton X-100, Digitonin, cyclic maltosides, 3-[(3-cholamidopropyl)dime- thylammonio]-l -propanesulfonate (CHAPS), 3-[(3-cholamidopropyl)dimethylammonio]-2- hydroxy-1 -propanesulfonate (CHAPSO), and mixtures of two or more thereof.

[0127] Embodiment 26: The aqueous formulation of any one of embodiments 22 to 25, wherein the at least one detergent of (iv) is selected from the group consisting of n-dodecyl-P-D-malto- pyranoside (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 gly- col (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.

[0128] Embodiment 27: The aqueous formulation of any one of embodiments 22 to 26, wherein the at least one detergent of (iv) comprises or is a polyoxyethylene dodecyl ether, preferably macrogollaurylether 8 (CnEs) and / or macrogollaurylether 9 (Thesit, Polidocanol).

[0129] Embodiment 28: The aqueous formulation of any one of embodiments 22 to 27, wherein the at least one detergent of (iv) is present in a concentration of < 0.04 % (w / v).

[0130] Embodiment 29: The aqueous formulation of any one of embodiments 22 to 28, wherein the at least one detergent of (iv) is present in a concentration in the range of from 0.02-0.035 % (w / v).

[0131] Embodiment 30: The aqueous formulation of any one of embodiments 1 to 29 further comprising:

[0132] (v) at least one blocking agent

[0133] Embodiment 31 : The aqueous formulation of embodiment 30, wherein the at least one blocking reagent of (v) is a protein.

[0134] Embodiment 32: The aqueous formulation of embodiment 30 or 31, wherein the at least one blocking reagent of (v) 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.

[0135] Embodiment 33: The aqueous formulation of any one of embodiments 30 to 32, wherein the at least one blocking reagent of (v) comprises at least BSA.

[0136] Embodiment 34: The aqueous formulation of any one of embodiments 30 to 33, wherein the at least one blocking reagent of (v) is a monoclonal antibody, preferably a recombinant antibody.

[0137] Embodiment 35: The aqueous formulation of any one of embodiments 30 to 34, wherein the at least one blocking reagent of (v) is present in a concentration in the range of from 0.002 to 0.02 mg / ml, preferably in the range of 0.005 to 0.015 mg / ml. Embodiment 36: The aqueous formulation of any one of embodiments 1 to 35 further comprising

[0138] (vi) at least one inorganic salt.

[0139] Embodiment 37: The aqueous formulation of embodiment 36, wherein the at least one inorganic salt of (vi) 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.

[0140] Embodiment 38: The aqueous formulation of embodiment 36 or 37, wherein the at least one inorganic salt of (vi) is present at a concentration in the range of from 10 to 300 mM, preferably in the range of from 100 to 245 mM.

[0141] Embodiment 39: Use of an aqueous formulation according to any one of embodiments 1 to 38 for storage, transportation, homogenization, purification, filling, decanting and / or diagnostic purpose.

[0142] Embodiment 40: The use of embodiment 39 for purification, preferably for protein and / or oligonucleotide purification.

[0143] Embodiment 41 : The use of embodiment 39 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.

[0144] The following Examples shall merely illustrate the invention. They shall not be construed, whatsoever, to limit the scope of the invention.

[0145] Examples

[0146] Commercially available antibody-loaded magnetic particles were incubated in different formulations for 8 weeks at 4°C and at elevated temperature (35°C), the latter in order to simulate a long term storage at 4°C over a period of about 64 weeks. The supernatants of the particle suspensions were analysed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS)-Page analysis. The detected antibody fragments in the supernatant are summarized in the figures below. As an example for (“non antibody”) protein-loaded magnetic particles, protein A- and streptavidin-coated magnetic particles were processed and analyzed in a similar manner. The results are summarized below. A storage formulation that enables long-term stability of antibody-coated magnetic beads was required to ensure their long-term functional reliability and system compatibility. Moreover, the suspension volume should ideally be minimized to facilitate storage and transport. Herein analysed were thus the formulation requirements for storing antibody-coated magnetic beads at high concentrations, and in the presence of biocide to prevent microbial growth while ensuring their long-term stability.

[0147] Reference Example 1: Evaluation of the long-term stability of protein-loaded magnetic particles by monitoring the protein fragmentation using an accelerated stability model

[0148] According to the Arrhenius equation (Equation 1) and common knowledge (Connors, Kenneth (1990). Chemical Kinetics: The Study of Reaction Rates in Solution. VCH Publishers, p. 14. ISBN 978-0-471-72020-1) for the temperature dependence of reaction rates, storage of samples for, for example, 8 weeks at 35°C equals roughly 1 year of storage at 4°C. k Equation 1 where: k = rate constant

[0149] A=pre-exponential factor

[0150] Ea= activation energy

[0151] R = universal gas constant

[0152] T = temperature (in K)

[0153] The long-term stability of protein-loaded magnetic particles was, therefore, assessed based on this accelerated stability model, upon storage of protein-loaded magnetic particle samples in the respective formulations, at 35°C in an incubator (Memmert GmbH, Buchenbach, Germany) with a 50 mg / mL particle concentration, unless stated otherwise. The pH values of the different formulations assessed, were determined using a pH meter with a pH sensitive glass elektrode (inoLab® pH 7310 of company InoLab) at a temperature in the range of from 22 to 25°C and atmospheric pressure (1 bar). The concentration of the magnetic particles was, when required, determined by gravimetric analysis. For this, 50 pL magnetic particle suspension were placed in pre-weighted 2 mL screw-cap vials and were washed, upon magnetic separation with a DynaMag™-2 magnet (Invitrogen, Thermo Fisher Scientific, Inc), two times with 0.2 mL ultra pure water and two times with 0.2 mL absolute ethanol. Magnetic particle samples were dried for 16 h in the fumehood and were then weighed using an analytical balance (CPA225D, Sartorius, Germany). After storage of antibody-loaded magnetic particles at 35°C for 8 weeks, and upon magnetic separation with a DynaMag™-2 magnet (Invitrogen, Thermo Fisher Scientific, Inc), magnetic-particle supernatant samples were subjected to SDS-PAGE analysis to follow potential undesired protein degradation processes, for instance antibody fragmentation. For this analysis, 10 pL of magnetic particle supernatant were mixed with 5 pL of Pierce™ non-reducing lane marker sample buffer (Thermo Fisher Scientific, Inc), were denatured at 95°C for 10 minutes, and 12 pL of each sample were loaded and analysed on 12-well NuPAGE™ 4-12 % Bis-Tris, 1,0 mm gels (Thermo Fisher Scientific, Inc) according to the manufacturer’s instructions. Protein bands were stained with Sypro Ruby (Thermo Fisher Scientific, Inc) according to the manufacturer’s instruction, gels were visualized using an Azure 400 gel documentation system (Azure Biosystems Inc.) and protein bands were quantified using the Azure Spot Pro software (Azure Biosystems Inc.). Selected protein fragments as assessed and graphically identified were named fragments 1, 2, 3 and optionally 4, wherein fragment 1 had a molecular weight MW(1), fragment 2 had a molecular weight MW(2), fragment 3 had a molecular weight MW (3) and optionally fragment 4 had a molecular weight MW(4) with MW(1) > MW (2) > MW(3) and optionally > MW(4). Since protein fragmentation is a protein degradation pathway, it is obvious, that formulations which helped to reduce this undesired product degradation process during storage, were highly beneficial for long-term stability. The Magnetic particle supernatant samples were also analysed by inductively coupled plasma mass spectrometry (ICP-MS) for their iron content to assess potential iron leakage from the magnetic particle core. ICP-MS measurements were carried out at the Institut fur Analytik und Um- weltchemie GmbH according to DIN EN ISO 11885 09 / 2009.

[0154] Example 1: Influence of pH value

[0155] Pierce™ Anti-DYKDDDDK Magnetic Agarose (Thermo Fisher Scientific, Inc) samples at a particle concentration of 50 mg / mL in an aqueous suspension with potassium chloride (KC1, 150 mM), Thesit (0.1 weight-%), 2-methyl-l,2-thiazol-3(2H)-one (MIT, 9 mM) and MES or MOPS buffer (25 mM) were subjected to accelerated stability analysis according to Reference Example 1, in formulations that only differ in their pH value. The formulations’ pH was adjusted using a glass electrode and upon addition of the required amount of a 2 M potassium hydroxide (KOH) solution. This analysis revealed that with increasing pH, increasing amounts of antibody fragments were formed, according to the SDS-page analysis of the supernatant of the particle suspension (Fig. 1). Consequently, decreasing the pH was beneficial for achieving a reduced antibody fragmentation and thereby helpful to increase the shelf-life of this product types. Example 2: variations of biocide

[0156] Analysis of Pierce™ Anti-DYKDDDDK Magnetic Agarose samples at a particle concentration of 50 mg / mL in an aqueous suspension with potassium chloride (KC1, 150 mM), bovine serum albumin (BSA, 0.005 mg / mL), Thesit (0.1 weight-%), 2-methyl-l,2-thiazol-3(2H)- one (MIT, 0.5 mg / mL) and MES buffer (25 mM) according to Reference Example 1 at the same pH value of 7.4 but in the presence and absence of the biocide OxyPyrion (2-hydrox- ypyridine-N-oxide) revealed increased fragmentation of the antibody, according to the SDS- page analysis of the supernatants, when the iron-chelating biocide was present while iron content was also increased, as determined by ICP-MS measurements (Fig. 2). Consequently, the use of a non-(iron)chelating biocide was beneficial for achieving a reduced antibody fragmentation and thereby helpful to increase the shelf-life of this product types. According to present data, it could be concluded, that the iron-chelating biocide surprisingly was extracting iron from the core of the magnetic particle into the aqueous phase (formulation) and surprisingly that the iron-biocide complex (or the presence / combination of iron and a chelating biocide) promoted the fragmentation of the antibody.

[0157] It was also apparent that the presence of bovine serum albumin (BSA) in the formulation was beneficial, as antibody fragmentation was substantially more, when BSA was not present (Fig. 2). Consequently, the use of a protein-based blocking reagent was beneficial for achieving a reduced antibody fragmentation and thereby helped to increase the shelf-life of this product types.

[0158] Example 3: variations of protein-loaded magnetic beads

[0159] As the MIT and OxyPyrion biocides effectively prevented microorganism growth at different concentrations, their effect on protein fragmentation at equimolar biocide concentrations was next examined in 25 mM MES, 150 mM KC1, 0.1% Thesit, according to Reference Example 1, using antibody loaded magnetic agarose (Pierce™ anti-DYKDDDDK Magnetic Agarose)- but also protein A-coated magnetic beads (MagnaBind™ Protein A Beads) and streptavidin-coated magnetic beads (MagnaBind™ Streptavidin Beads) (Fig. 3-5) at 50 mg / mL particle concentration.

[0160] The SDS-page analysis of the supernatants revealed, that also at equimolar biocide concentrations, the combination of OxyPyrion and pH 7.5 led to the highest degree of fragmentation that was more or less pronounced, depending on the protein coating the magnetic particles. It was here apparent that for anti-DYKDDDDK magnetic agarose, 300% more fragments were generated at pH 7.5 + 9 mM OxyPyrion, and 75 % more fragments were generated for streptavidin-coated magnetic beads, whereas > 2300% more fragments were observed under the same conditions for protein A-coated magnetic beads.

[0161] Consequently, the use of a slightly acid pH and a non-chelating biocide was beneficial for achieving a reduced antibody fragmentation and thereby helped to increase the shelf-life of this protein-loaded magnetic particles.

[0162] Example 4: further variation of biocide

[0163] Accelerated stability analysis was assessed according to Reference Example 1 wherein_frag- mentation was followed by SDS-PAGE analysis and % fragmentation was calculated based on the fragmentation determined in 25 mM MES, 150 mM KC1, 0.1% Thesit, pH 7.5, 9 mM MIT and at 50 mg / mL magnetic particle concentration. Fragmentation was also analysed in the presence of other biocides, namely sodium benzoate (Na benzoate), ethylenediaminetetraacetic acid (EDTA), sodium azide (NaNs) and 2-chloroacetamide (CAA) (Fig. 6), each at 9mM with the remaining composition as for MIT. This analysis showed that fragmentation at pH 7.5 was increased, when the iron-chelating biocide EDTA was employed, as observed for the iron-chelating biocide OxyPyrion. As expected, the use of non-chelating biocides led to significantly less fragmentation compared to the use of EDTA and OxyPyrion as biocides and thereby helped to increase the shelf-life of this protein-loaded magnetic particles.

[0164] Example 5: variation of concentration of protein-loaded magnetic beads

[0165] The influence of particle concentration on antibody fragmentation was also assessed according to Reference Example 1 upon storage of Pierce™ Anti-DYKDDDDK Magnetic Agarose for 8 weeks at 35°C in 25 mM MES, 150 mM KC1, 0.1% Thesit, 9 mM MIT, pH 6.5 or 25 mM MES, 150 mM KC1, 0.1% Thesit, pH 7.5, 9 mM OxyPyrion at a concentration of 50 mg / mL and at a concentration of 1 mg / mL. After 8 weeks, supernatants of the suspensions stored at 1 mg / mL particle concentration (3 biological replicates for each condition) were concentrated 50 times on a centrifugal filter with 10 kDa molecular weight cut-off (MWCO, Merck Millipore). Upon this treatment, the viscous Thesit detergent was also concentrated, despite its 600 Da molecular mass, making the respective samples unsuitable for SDS-PAGE analysis. Therefore, samples were in this case analyzed by a bicinchoninic acid assay (BCA assay) (Fig. 7).

[0166] The SDS-page analysis of the supernatants indicated an increased degree of antibody fragmentation upon storage of Pierce™ Anti-DYKDDDDK Magnetic Agarose at 50 mg / mL compared to 1 mg / mL, for both biocides. Again, when the employed biocide was a chelating biocide, in this case OxyPyrion, substantially more fragmentation was observed compared to the non-chelating biocide (in this example MIT).

[0167] These findings underline that 1) the storage of magnetic particles at high particle concentration was a technical challenge due to the overall increased protein fragmentation processes and 2) the application of a non-chelating biocide (in this example MIT) was useful at such high particle concentrations for extending the protein-loaded particle shelf-life compared to (iron)-chelating biocides (in this example OxyPyrion) and importantly, enabled long-term storage at high particle concentration.

[0168] Description of Figures

[0169] Fig- 1 Increased antibody fragmentation in the supernatant of Pierce™ Anti-DYKDDDDK Magnetic Agarose suspensions is observed with increasing pH value of a formulation containing 25 mM MES or 25 mM MOPS to ensure the desired buffering range, 150 mM KC1, 0.1% Thesit, 9mM MIT. % fragmentation was calculated in relation to the minimal fragmentation observed at pH 5.5 (= 100%), as determined by SDS-PAGE analysis.

[0170] Fig- 2 Accelerated stability analysis carried out with Pierce™ Anti-DYKDDDDK Magnetic Agarose. Fragmentation was assessed in the above indicated formulations by SDS-PAGE analysis and % fragmentation was calculated in relation to the fragmentation observed at pH 6.3 (= 100%).

[0171] Fig- 3 Accelerated stability analysis carried out with Pierce™ Anti-DYKDDDDK Magnetic Agarose. Fragmentation was assessed by SDS-PAGE analysis in formulations with a pH value and biocide content as indicated in the legend that additionally contain 25 mM MES, 150 mM KC1, 0.1% Thesit. % fragmentation was calculated in relation to the fragmentation observed at pH 6.5 in the presence of MIT (= 100%).

[0172] Fig. 4 Accelerated stability analysis carried out with Pierce™ Protein A Magnetic Beads. Fragmentation was assessed by SDS-PAGE analysis in formulations with a pH value and biocide content as indicated in the legend that additionally contain 25 mM MES, 150 mM KC1, 0.1% Thesit. % fragmentation was calculated in relation to the fragmentation observed at pH 6.5 in the presence of MIT (= 100%).

[0173] Fig. 5 Accelerated stability analysis carried out with MagnaBind™ Streptavidin Beads. Fragmentation was assessed by SDS-PAGE analysis in formulations with a pH value and biocide content as indicated in the legend that additionally contain 25 mM MES, 150 mM KC1, 0.1% Thesit. % fragmentation was calculated in relation to the fragmentation observed at pH 6.5 in the presence of MIT (= 100%). Fig. 6 Accelerated stability analysis carried out with Pierce™ Anti-DYKDDDDK Magnetic Agarose stored in 25 mM MES, 150 mM KC1, 0.1% Thesit, pH 7.5 and 9 mM of the above indicated iron chelating or non-chelating biocides. Fragmentation was assessed by SDS-PAGE analysis and % fragmentation was calculated in relation to the fragmentation determined in 25 mM MES, 150 mM KC1, 0.1% Thesit, pH 7.5, 9 mM MIT (= 100%).

[0174] Fig- 7 BCA assay with colorimetric absorption analysis at 562 nm following fragmentation of Pierce™ Anti-DYKDDDDK Magnetic Agarose in 25 mM MES, 150 mM KC1, 0.1% Thesit, 9 mM MIT, pH 6.5 or 25 mM MES, 150 mM KC1, 0.1% Thesit, pH 7.5 + 9 mM OxyPyrion stored at 50 or 1 mg / mL particle concentration. Supernatants of the latter suspensions (three biological replicates for each condition) were concentrated 50 times in a centrifugal filter. Error bars represent the standard deviation of three independent measurements (n = 3).

Claims

Roche Diagnostics GmbH RD39702PCClaims1. An aqueous formulation of a protein-loaded magnetic particle, the formulation comprising(i) at least one protein-loaded magnetic particle present in an aqueous phase in a concentration of > 10 mg / ml;(ii) at least one non-chelating biocide, wherein the at least one non-chelating biocide is at least partially dissolved respectively in the aqueous phase of (i), and the aqueous formulation, especially the aqueous phase, has a pH value in the range of from 6 to 7.

2. The aqueous formulation of claim 1, wherein the at least one non-chelating biocide of (ii) is selected from the group of isothiazolinone derivatives, sodium azide, 2-chloro- acetamide, sodium benzoate and mixtures thereof; preferably from the group consisting of methylisothiazolinone (2-methyl-l,2-thiazol-3(2H)-one, MIT), methylchloroi- sothiazolinone (5-chloro-2-methyl-l,2-thiazol-3(2H)-one, MCI), benzisothiazoli- none (l,2-benzothiazol-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 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 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(ii) more preferably at least comprises MIT.

3. The aqueous formulation of claim 1 or 2, having a pH value in the range of from 6.1 to 6.9, preferably in the range of from 6.2 to 6.8, more preferably in the range of from 6.3 to 6.7, more preferably in the range of from 6.4 to 6.6.

4. The aqueous formulation of any one of claims 1 to 3 further comprising(iii) at least one buffer system;wherein the at least one buffering system is preferably 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, more preferably the at least one buffer system is at least MES.

5. The aqueous formulation of any one of claims 1 to 4, comprising the at least one protein-loaded magnetic particle in a concentration of > 11 mg / ml, preferably of > 12 mg / ml.

6. The aqueous formulation of any one of claims 1 to 5 further comprising (iv) at least one detergent; wherein the at least one detergent of (iv) is preferably selected from the group consisting of non-ionic detergent, ionic detergent, zwitter-ionic detergent and mixtures of two or more thereof; more 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, Digitonin, dodecyl-B-D-maltoside, octyl-B-D-glucopyranodide, Synperonic F68, Synper- onic F108, Tergitol 15-S-9, Tween 20, Tween 80, CTAB, Na-cholate, Na-deoxycho- late, 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 maltose neopentyl glycol (LMNG), Triton X-100, Digitonin, cyclic maltosides, 3-[(3-cholamidopropyl)dimethylammonio]-l-propanesulfonate(CHAPS), 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-l-propanesulfonate (CHAPSO), and mixtures of two or more thereof; more preferably 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), lau- ryldimethylamine-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-propanesul- fonate (CHAPS), 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-l-propane- sulfonate (CHAPSO), and mixtures of two or more thereof; wherein the at least one detergent of (iv) more preferably comprises or is a polyoxyethylene dodecyl ether,more preferably macrogollaurylether 8 (CnEs) and / or macrogollaurylether 9 (Thesit, Polidocanol); and / or wherein the at least one detergent of (iv) is preferably present in a concentration of < 0.04 % (w / v).

7. The aqueous formulation of any one of claims 1 to 6 further comprising:(v) at least one blocking agent; wherein the at least one blocking reagent of (v) is preferably a protein.

8. The aqueous formulation of claim 7, wherein the protein is selected from the group consisting of bovine serum albumin (BSA), human serum albumin (EISA), lactalbumin, casein, skim milk, serum proteins, and mixtures thereof; wherein the at least one blocking reagent of (v) more preferably comprises at least BSA; or is a monoclonal antibody, preferably a recombinant antibody.

9. The aqueous formulation of claim 7 or 8, wherein the at least one blocking reagent of(v) is present in a concentration in the range of from 0.002 to 0.02 mg / ml, more preferably in the range of 0.005 to 0.015 mg / ml.

10. The aqueous formulation of any one of claims 1 to 9 further comprising(vi) at least one inorganic salt; wherein the at least one inorganic salt of (vi) is preferably 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; and / or wherein the at least one inorganic salt of (vi) is preferably present at a concentration in the range of from 10 to 300 mM, more preferably in the range of from 100 to 245 mM.

11. The aqueous formulation of any one of claims 1 to 10, wherein the magnetic particle of (i) has a particle size of at least 1 micrometer, preferably in the range of from 1 to 10 micrometer, more preferably in the range of from 1 to 5 micrometer, determined according to ISO 13320.

12. The aqueous formulation of any one of claims 1 to 11, wherein the protein loaded to the magnetic particle of (i) is selected from the group consisting of streptavidin, avidin,protein A, protein G and protein L, or wherein the protein loaded to the magnetic particle of (i) is selected from the group consisting of antibody and antibody fragment.

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

14. The use of claim 13 for purification, preferably for protein and / or oligonucleotide purification.

15. 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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