Method of manufacturing an analyte sensor and analyte sensor obtained by the method

Abstract

A method of manufacturing at least one analyte sensor (110) for determining at least one analyte in a bodily fluid is proposed. The method comprises the steps of: A) providing at least one substrate (112) comprising a first side (114) and a second side (H6); B) providing at least one first conductive layer (122) at least partially covering the first side (114) of the substrate (112); C) providing at least one second conductive layer (124) at least partially covering at least one of the first side (114) and the second side (116); D) providing at least one working electrode (128) on the first side (114) by providing at least one working electrode material (132) at least partially covering the first conductive layer (122); E) providing at least one further electrode (142) on at least one of the first side (114) and the second side (116) by providing: at least one AgCl-comprising composition (146) at least partially covering the second conductive layer (124); and at least one protective layer (148) covering the AgCl-comprising composition (146) apart from at least one interaction area (150) accessible to the bodily fluid; F) exposing the AgCl-comprising composition (146) at least partially to ultraviolet light.

Description

[0001] Method of manufacturing an analyte sensor and analyte sensor obtained by the method

[0002] Technical Field

[0003] The present invention relates to a method of manufacturing at least one analyte sensor for determining at least one analyte, to an analyte sensor obtained by the method and to a system configured for performing the method. The analyte sensor may, primarily, be used for determining a concentration of at least one analyte in a bodily fluid, in particular a blood glucose level. However, further applications may also be feasible.

[0004] Background art

[0005] Determining a concentration of one or more analytes in a bodily fluid, in particular a blood glucose level, plays an important role in the prevention and treatment of various diseases. Without restricting further possible applications, the invention is described in the following with reference to glucose in an interstitial fluid. However, the invention can also be applied to other types of analytes.

[0006] In subcutaneous glucose biosensors Ag / AgCl-based electrode may be used either as reference electrode (RE), which provides a known reference potential or as combined counter electrode / reference electrode (CERE), which, both, provides a reference potential and acts as an electrons acceptor, thus acting as counter electrode.

[0007] The Ag / AgCl-based electrode is typically made by coating a substrate with paste or ink comprising AgCl powder, a binder, as well as elemental Ag powder and, optionally, further components. Subcutaneous glucose biosensors working in a two-electrode set-up rely on the availability of AgCl in the process of the determination of glucose concentration. In particular, the quantity of AgCl comprised by the CERE should at least correspond to the amount of glucose oxidized during the operating time of the sensor. Depending on sensors sensitivity, considering operating times of many days, e.g. 10 to 14 days, AgCl amounts in the range of several dozens of micrograms will usually be required. Although AgCl, generally, is a poorly soluble salt, the interstitial fluid may comprise different substances, which are able to form soluble forms of silver, e.g. coordination complexes. The complexed Ag+ions may then diffuse out of the analyte sensor and provoke foreign body reactions, which may result in a diminished performance of the analyte sensor and / or which may provoke immune reactions. Thus, while sufficient amounts of AgCl are on the one hand required for proper function of the analyte sensor over the envisaged duration of use, AgCl may on the other hand decrease the analyte sensor’s biocompatibility.

[0008] PCT / EP2021 / 068429 describes an analyte sensor for conducting an analyte measurement in a bodily fluid of a user. The analyte sensor comprises a substrate, at least one working electrode, at least one second electrode and a membrane, wherein the membrane is located on top of the at least one second electrode.

[0009] PCT / EP2021 / 082392 discloses an analyte sensor and a method for manufacturing an analyte sensor. The analyte sensor comprises an electrode comprising a layer of an AgCl-containing composition. The AgCl on an outer surface of the layer of the AgCl-containing composition is at least partially reduced, thus reducing the amount of the exposed AgCl.

[0010] WO2023012138A1 describes an analyte sensor comprising a substrate, at least one first electrode, at least one second electrode and at least one protective layer covering the at least one second electrode. The analyte sensor may mainly be used for conducting analyte measurements in a body fluid of a user.

[0011] Despite the progress that has been made in the field of analyte sensors and their manufacturing, several challenges still remain. In particular, there still is a need for reliable and cost-efficient methods of manufacturing analyte sensors that provide analyte sensors with sufficient amounts of AgCl while at the same time ensuring the analyte sensor’s biocompatibility.

[0012] Problem to be solved

[0013] It is therefore desirable to provide a method of manufacturing at least one analyte sensor for determining at least one analyte in a bodily fluid and an analyte sensor obtained by the method, which at least partially avoid the shortcomings of known methods and analyte sensors and which at least partially address the above-mentioned challenges. In particular, it is desirable to provide an analyte sensor, which combines an increased biocompatibility with a high level of sensitivity towards the analyte and a long duration of use, while the method of manufacturing said analyte sensor should be simple and fast.

[0014] Summary

[0015] This problem is addressed by a method of manufacturing at least one analyte sensor for determining at least one analyte in a bodily fluid and by an analyte sensor obtained by the method with the features of the independent claims. 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.

[0016] 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.

[0017] 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, non-withstanding the fact that the respective feature or element may be present once or more than once.

[0018] 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 way with other optional or non-optional features of the invention.

[0019] In a first aspect of the present invention a method of manufacturing at least one analyte sensor for determining at least one analyte in a bodily fluid is disclosed. The method comprises the following method steps, which may specifically be performed in the given order. However, a different order may also be possible. The method may further comprise additional method steps, which are not listed. Further, one or more or even all of the method steps may be performed only once or repeatedly. The method steps may in particularly be performed in manner, wherein two or more steps may fully or at least partially be overlapping in time. The method comprising the steps of:

[0020] A) providing at least one substrate comprising a first side and a second side;

[0021] B) providing, specifically applying, at least one first conductive layer at least partially covering the first side of the substrate;

[0022] C) providing, specifically applying, at least one second conductive layer at least partially covering at least one of the first side and the second side;

[0023] D) providing at least one working electrode on the first side by providing at least one working electrode material at least partially covering the first conductive layer;

[0024] E) providing at least one further electrode on at least one of the first side and the second side by providing: at least one AgCl-comprising composition at least partially covering the second conductive layer; and at least one protective layer covering the AgCl-comprising composition apart from at least one interaction area accessible to the bodily fluid;

[0025] F) exposing the AgCl-comprising composition at least partially to ultraviolet light.

[0026] The term “analyte sensor” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a sensor configured for detecting quantitatively and / or qualitative at least one analyte. The analyte sensor may in particular be a device configured to perform the detection of the analyte by generating and / or acquiring at least one measurement signal caused by and / or related to the presence, absence or concentration of the analyte. The analyte sensor may be or may comprise at least one electro- chemical sensor. The measurement signal generated and / or acquired by the analyte sensor according to the analyte may in particular be an electrical signal, e.g. at least one current signal or at least one voltage signal.

[0027] The analyte sensor specifically may be configured as an in vivo analyte sensor, configured for determining the at least one analyte in the bodily fluid while the bodily fluid is still contained in a body of a user. Thus, the analyte sensor may specifically be at least partially implantable into the body tissue of a user. Specifically, the analyte sensor may be a subcutaneously implantable analyte sensor or a transcutaneously implantable analyte sensor. Thus, generally, the analyte sensor may comprise at least one implantable portion, such that the analyte sensor may at least partially be in contact with the bodily fluid of a user, e.g. via the implantable portion. The implantable portion, as an example, may fully or partially be flexible or deformable. Specifically, the implantable portion may have a length not exceeding 20 mm, such as not exceeding 10 mm, e.g. a length of 5 mm to 7 mm. The implantable portion may have a width not exceeding 3 mm, e.g. a width not exceeding 1 mm, e.g. a width of 0.5 mm to 0.7 mm. The implantable portion may have a thickness not exceeding 2 mm, e.g. a thickness not exceeding 0.5 mm, e.g. a thickness of 0.1 mm to 0.3 mm. The implantable portion may specifically be rod-shaped. The implantable portion may have a diameter not exceeding 2 mm, e.g. a diameter not exceeding 1 mm, e.g. a diameter of 0.2 mm to 0.5 mm. Besides the implantable portion, the analyte sensor may optionally comprise at least one further part or component that may remain outside of the body tissue, e.g. a contacting portion having one or more electrical contact pads electrically connected to the working electrode and the further electrode, respectively. The implantable portion arranged within the body tissue and the further part or component arranged outside of the body tissue may be electrically connected and / or connectable.

[0028] The analyte sensor may comprise one or more further components, such as one or more electronics units electrically connectable or electrically connected with the electrodes.

[0029] The term “analyte” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an arbitrary element, such as a chemical substance, component or compound, and / or other parameters to be detected and / or measured. As an example, the at least one analyte may be a chemical compound which takes part in metabolism, such as one or more of glucose, cholesterol or triglycerides. Additionally or alternatively, however, other types of analytes may be used and / or any combination of ana- lytes may be determined. The determining of the at least one analyte specifically may, in particular, be an analyte-specific detection. Without restricting further possible applications, the present invention is described herein with particular reference to detecting and / or monitoring of glucose, in particular in an interstitial fluid. The analyte sensor may specifically be a subcutaneous glucose biosensor.

[0030] The term "determining at least one analyte" as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a process of detecting at least one analyte in a qualitative and / or quantitative manner. The process of detecting at least one analyte may in particular comprise generating and / or acquiring at least one measurement signal according to the analyte to be determined. In particular, at least one property such as the presence, absence and / or concentration of the analyte in the bodily fluid may deduced and / or deducible from the measurement signal.

[0031] The term “bodily fluid” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a liquid produced by and / or present in the body of a human or animal. The bodily fluid may e.g. be present in the body tissue of a user. As an example, the bodily fluid may be or may comprise one or more of blood, interstitial fluid, urine, saliva, tear fluid or the like. Other bodily fluids may also be feasible.

[0032] The term “providing” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to the process of supplying and / or making available an object e.g. in order to further process or use the object in one or more subsequent steps. The providing specifically may comprise one or more of making available, manufacturing, adding, coating, dispensing at least one object or component. Thus, as an example, instead of applying the at least one first conductive layer to the first side or applying the at least one second conductive layer to the second side, respectively, the substrate provided for the process may already have applied thereto the first conductive layer and / or the second conductive layer. However, the application of one or both of these first and second conductive layers may also be part of the process itself. The term “applying” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to the process of depositing, printing, dispensing, spreading or arranging at least one first object, such as at least one material or composition, to or onto a second object. In said process, the second object may e.g. be covered fully or partially by the first object.

[0033] The term “covering” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a state where at least one first object, such as at least one material or composition, is placed or has been placed on a second object, e.g. on a surface of the second object. As a result, the second object may be at least partially enveloped and / or coated by the first object, which may act as a layer covering at least one surface of the second object fully or partially. In particular, the first object “at least partially covering” the second object, may cover the second object fully or only in parts, such that certain areas and / or sections of the second object are left free and / or devoid of the first object.

[0034] The term "substrate" as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an arbitrary element configured to carry one or more other elements arranged and / or disposed thereon or therein. As an example, the substrate may carry one or more electrodes, which may e.g. be arranged on different sides of the substrate. The substrate may comprise at least one electrically insulating material, e.g. to prevent an electrical contact between the electrodes arranged on the different sides of the substrate. By way of example, the electrically insulating material may be selected from polyethylene terephthalate (PET) or polycarbonate (PC) or polyimide (PI). Other electrically insulating materials may also be feasible. The substrate may be a planar substrate. The substrate may, specifically, have an elongated shape, such as a strip shape, a bar shape or a rod shape. However, other kinds of shapes may also be feasible.

[0035] The substrate has the at least one first side and the at least one second side. The first side of the substrate and the second side of the substrate may be opposing sides of the substrate facing in opposite directions. In particular, the first side and the second side may be oriented essentially parallel. In particular, the first side and the second side may each comprise at least one surface of the substrate. As part of step B) of the method, the at least one first conductive layer at least partially covering the first side of the substrate is applied. As part of step C) of the method, the at least one second conductive layer at least partially covering at least one of the first side and the second side of the substrate is applied. In particular, in step C) the second conductive layer may be applied to the second side of the substrate such that the second side of the substrate is at least partially covered. The first conductive layer and the second conductive layer may each comprise at least one electrically conductive or semiconducting material. In particular, both the first conductive layer and the second conductive layer may comprise or may be formed by the same conductive material. The conductive material may comprise at least one of: an inorganic electrically conductive material, such as at least one of electrically conductive carbon and a metal, specifically at least one metal selected from the group consisting of: gold; silver; platinum; copper, e.g. gold-plated copper. Additionally or alternatively, at least one organic electrically conductive or semiconducting material may be used, such as at least one electrically conductive polymer, such as PEDOT, wherein PEDOT stands for Poly-3, 4-ethylendi oxythiophen. Other conductive materials may be feasible. Examples of further electrically conductive materials may comprise ITO and FTO, wherein ITO stands for indium tin oxide and FTO stands for fluorine-doped tin oxide Thus, the first conductive layer and the second conductive layer may both be electrically conductive.

[0036] The first conductive layer may be in electrical contact with the working electrode material, which at least partially covers the first conductive layer. The first conductive layer may facilitate an electron transport from the working electrode material. The second conductive layer may be in electrical contact with the AgCl-comprising composition, which is provided on the second conductive layer. The second conductive layer may facilitate an electron transport to and / or into the AgCl-comprising composition. The first conductive layer and the second conductive layer may be separated from each other by the substrate, such that the first conductive layer and the second conductive layer are electrically insulated from one another.

[0037] The terms “first” and “second”, e.g. as used in connection with the terms “side” and “layer”, or any further ordinal numbers used herein, do not imply any sequence or order regarding the provision or application of the objects, nor any difference in significance of the objects. Instead, the terms “first” and “second” or any further ordinal numbers are used for a clear distinction between the numbered objects.

[0038] The term “electrode” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an arbitrary electrically conductive or semiconducting element to which an electrical voltage or an electrical current is applicable. The electrode may comprise at least one electrically conductive material, e.g in the form of an electrically conductive layer. The electrical voltage may be applied e.g. between the electrode and at least one further electrically conductive element by at least one potentiostat and / or by at least one amperometric measurement unit. The potentiostat and / or the at least one amperometric measurement unit may optionally also form part of the analytical sensor and / or of an analytical system comprising the analytical sensor and the at least one potentiostat and / or amperometric measurement unit.

[0039] The term “working electrode” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an electrode that is sensitive to the analyte to be determined.

[0040] Correspondingly, the term “working electrode material” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a material or chemical compound or chemical composition configured for undergoing a detectable chemical reaction with the analyte or in the presence of the analyte, more specifically at least one electrochemical reaction which is electrically detectable, such as by one or more of a potentiostatic measurement and an amperometric measurement.

[0041] Consequently, the working electrode comprises the at least one first electrically conductive layer or at least the part of the first electrically conductive layer covered by the at least one working electrode material, and the at least one working electrode material, such as in a layer setup. A part of the first electrically conductive layer not covered by the at least one working electrode material may form at least one electrical lead for electrically contacting the working electrode. The electrical lead may also comprise at least one electrical contact pad on the substrate.

[0042] Thus, specifically, the working electrode may be configured for changing its electrochemical potential in the presence of the analyte and cause electric current flow at appropriate polarization. The working electrode material, specifically, may comprise at least one material or chemical compound configured for selectively reacting with the analyte, such as at least one enzyme. As an example, in case the analyte is glucose or comprises glucose, the enzyme may comprise one or more of glucose oxidase and glucose dehydrogenase. In addition, the working electrode material may comprise one or more additional components, such as mediator compounds configured for electron transfer and the like. Reference may be made to “Enzyme based amperometric biosensors” by Paolo Bollella and Lo Gorton, Current Opinion in Electrochemistry Volume 10, August 2018, Pages 157-173, https: / / doi.org / 10.1016 / j.coe- lec.2018.06.003.

[0043] Thus, generally, the working electrode may be configured for interacting with the analyte, specifically by a redox reaction. The interaction may e.g. comprise an exchange of at least one electron, such as a transfer of electrons from the analyte to the working electrode in at least one electrochemical detection reaction. The electrochemical detection reaction at the working electrode may be one of two half-reactions, wherein the further of the two half-reaction may take place at the further electrode, such as at one or more of the counter electrode or the CERE. As a result of the potential applied between the working electrode and the at least one further electrode and the electrochemical detection reaction, current may flow between the working electrode and the further electrode via at least one electrolyte, in particular via the bodily fluid. At least one measurement signal may be generated according to the presence, absence and / or concentration of the analyte. The measurement signal may be an electrical signal comprising at least one of: at least one current signal or at least one voltage signal.

[0044] Step D) comprises providing the at least one working electrode on the first side by providing at least one working electrode material at least partially covering the first conductive layer. The working electrode material may comprise at least one reagent layer for detecting the analyte. Thus, step D) may in particular comprise applying the at least one reagent layer to the first conductive layer. The reagent layer may at least partially cover the first conductive layer. In the area in which the reagent layer covers the first conductive layer, the first conductive layer and the reagent layer may form the working electrode. The reagent layer may specifically comprise at least one biorecognition component, particularly an enzyme, adapted to interact with the analyte. The reagent layer may comprise one specific biorecognition component or a mixture of two or more biorecognition components. The biorecognition component, specifically the enzyme, may be capable of catalyzing at least one chemical reaction altering the analyte, e.g. a chemical reaction in which the analyte is oxidized and / or reduced. Specifically, the biorecognition component, particularly the enzyme, may be adapted to oxidize or reduce the analyte. In particular, the biorecognition component, specifically the enzyme, may be at least one of: glucose oxidase (GOx) and glucose dehydrogenase (GDH). Step E) comprises providing the at least one further electrode on at least one of the first side and the second side by providing: at least one AgCl-comprising composition at least partially covering the second conductive layer; and at least one protective layer covering the AgCl-com- prising composition apart from at least one interaction area accessible to the bodily fluid. In particular, in step C) of the method, the second conductive layer may be provided, specifically applied, such that the second conductive layer at least partially covers the second side of the substrate and in step E), the further electrode may be provided on the second side of the substrate. For better readability this embodiment will be referred to in the following. The person skilled in the art will easily be able to transfer the description to an embodiment, wherein both the working electrode and the further electrode are provided on the first side.

[0045] Consequently, the at least one further electrode on the second side of the substrate comprises the at least one second electrically conductive layer or at least the part of the second electrically conductive layer covered by the at least one AgCl-comprising composition, and the at least one AgCl-comprising composition, such as in a layer setup. In addition, the at least one protective layer covering the AgCl-comprising composition apart from at least one interaction area accessible to the bodily fluid may optionally also form part of the at least one further electrode. At least one part of the second conductive layer may remain uncovered by the AgCl-comprising composition. This at least one part, as an example, may form or may comprise at least one conductive lead, e.g. for electrically contacting the at least one further electrode. The at least one conductive lead, as an example, may also form one or more electrical contact pads for electrically contacting the at least one further electrode.

[0046] The at least one further electrode and the working electrode may form part of an electrochemical circuit. Both the working electrode and the further electrode may be part of the implantable portion of the analyte sensor and may be arranged within the body tissue. In particular, thus, the analyte sensor may be used for one or more of a potentiometric or an amperometric measurement. As an example, an electrical voltage or difference in electrical potentials may be measured between the working electrode and the at least one further electrode. Additionally or alternatively, a voltage may be applied between the working electrode and the further electrode, such that an electrical current may flow between the working electrode and the further electrode e.g. via at least one electrolyte, such as the bodily fluid, wherein the electrical current may be measured. Thus, the measurement signal of the analyte sensor may comprise one or more of a voltage measurement signal and a current measurement signal. The measurement signal may be used for the determination of the analyte, such as for detecting the concentration of the analyte. The further electrode may comprise at least one of: a counter electrode, a reference electrode and a combined counter / reference electrode. The type of electrode of the at least one further electrode typically is determined by the measurement setup in which the at least one further electrode is used. Thus, in potentiostatic measurements, as an example, a voltage may be measured between the working electrode and the further electrode. In this setup, typically, the at least one further electrode may be referred to or may at least partially act as a reference electrode, wherein, typically, use may be made of the fact that the electrode potential of the further electrode comprising the Ag / AgCl composition may remain widely unaffected by the concentration of the analyte, such as the concentration of glucose. In amperometric measurements, on the other hand, an electrical current may be measured between the working electrode and the at least one further electrode or at least a part thereof, by applying a known voltage, or alternatively, the voltage between the working electrode and the at least one further electrode or at least a part thereof may be measured which is required for achieving a predetermined electrical current. In this setup, as an example, the at least one further electrode may be referred to as a counter electrode.

[0047] Thus, the term "counter electrode" as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. Specifically, an electrochemical detection reaction taking place at the working electrode may be one of two half reactions, wherein the further of the two half reaction may take place at the counter electrode in form of the counter reaction. In particular, the half reaction taking place at the working electrode may comprise an oxidation of the analyte, specifically glucose, while the half reaction taking place at the counter electrode may comprise a reduction, specifically a reduction of the counter electrode e.g. a reduction of Ag+to elemental Ag. The counter electrode may particularly be configured for balancing a current flow due to the electrochemical detection reaction at the working electrode.

[0048] The term "reference electrode" as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an electrode configured for providing at least one electrical reference potential. The electrochemical reference potential of the reference electrode may be, at least widely, independent of the presence, absence or concentration of the analyte. The reference electrode may be configured for being a reference for measuring and / or controlling a potential of the working electrode. The reference electrode may have a stable and well-known electrode potential. In particular, the further electrode may combine several functionalities. The further electrode may specifically be or comprise a combined counter / reference electrode, also referred to as CERE. Thus, the further electrode may provide the reference potential and balance the current flow from the working electrode.

[0049] The term “AgCl-comprising composition” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a material, such as a solid, fluid or paste-like material, comprising AgCl, which may also be referred to as silver chloride. The AgCl-comprising composition may comprise AgCl in the form of particles with a particle size in the range from 0.5 pm to 80 pm, specifically in the range from 1 pm to 50 pm, more specifically in the range from 2 pm to 20 pm. The analyte sensor, in particular the further electrode, more particularly the AgCl-comprising composition, which at least partially covers the second conductive layer, may comprise a total amount of AgCl in the range from 10 pg to 100 pg, specifically 20 pg to 50 pg, more specifically 25 pg to 35 pg. The AgCl-comprising composition may in particular be provided by applying the AgCl-comprising composition to the second conductive layer in the form of a paste or an ink, e.g. using at least one coating process, specifically a wet-coating process, selected from the group consisting of: doctor-blading; dispensing; slot-dye coating; cannula-coating; printing, e.g. screen printing, specifically rotary screen printing. Thus, the AgCl-comprising composition may be provided in step E) as an AgCl-comprising layer with a thickness in the range from 1 pm to 100 pm, specifically from 5 pm to 60 pm, more specifically from 15 pm to 25 pm.

[0050] The AgCl-comprising composition may comprise at least one further component, specifically a plurality of further components. Specifically, the AgCl-comprising composition may comprise at least one of: elemental Ag and at least one binder, such as an organic binder. A weight per weight ratio, also referred to as w / w, of elemental Ag to AgCl in the AgCl-comprising composition may be in the range from 10: 1 to 1 :20, e.g. in the range from 10: 1 to 1 : 10. The terms elemental Ag and elemental silver may be used interchangeably throughout this document. The binder may specifically comprise a non-conductive polymer, particularly a PVC- based polymer and / or a polyurethan-based polymer, specifically a TPU-based polymer. The expression TPU-based polymer may refer to a thermoplastic polyurethane. The AgCl-compris- ing composition may comprise both elemental Ag and the at least one binder, specifically in a ratio in the range from 1 : 100 to 100: 1, specifically in the range from 1 :50 to 50: 1, more specifically in the range from 1 : 10 to 10: 1. The term protective layer“ as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a material forming a sheet and / or a film extending over an object, e.g. such that at least one surface of the object is fully or partially covered. The protective layer may thus shield the object it covers or partly covers. The protective layer may in particular be or function as a physical barrier that may fully or partially prevent or impede a physical contact between the covered object and its environment. In particular, the protective layer covering the AgCl-comprising composition may prevent a physical contact between the covered parts of the AgCl comprising composition and the bodily fluid and / or the body tissue the analyte sensor is inserted into, while such contact may take place e.g. at the at least one interaction area, which is not covered by the protective layer. The protective layer may in particular be impermeable to the bodily fluid. The protective layer may prevent an interaction between the parts of the AgCl-comprising composition covered by the protective layer and the bodily fluid and / or the body tissue surrounding the AgCl-compris- ing composition, e.g. a chemical, biochemical allergic and / or electrochemical interaction. The protective layer may prevent a leaching of Ag+from the parts of the AgCl-comprising composition covered by the protective layer into the bodily fluid. The protective layer may comprise at least one polymer, such as at least one of: TPU-based polymer, a PVC-based polymer, a polyester-based polymer, a polystyrene-based polymer. The expression PVC-based polymer may refer to a polyvinylchloride-based polymer. Further materials for the protective layer are feasible. As an example, the protective layer may comprise hydrophobic polymers, industrial photoresist, insulating varnish. Further materials, e.g. materials, which can be applied as a thin layer and are not water permeable, may be used.

[0051] The term “interaction area” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a section, a segment and / or a portion of an object, through which an interaction can take place between the object and its surrounding environment. The interaction area of the AgCl-comprising composition may specifically comprise at least one surface section of the AgCl-comprising composition that is devoid of the protective layer. Thus, said surface section may specifically be in physical contact with the bodily fluid thus allowing an interaction to take place between the AgCl-comprising composition and the bodily fluid when the analyte sensor is implanted into the body tissue. The interaction may e.g. be a chemical, specifically an electrochemical interaction. The interaction area may further allow an interaction, e.g. a photochemical interaction, between the surface section of the AgCl-comprising composition that is comprised by the interaction area and electromagnetic radiation, e.g. ultraviolet light, inciding thereon in a state when the analyte sensor is not implanted.

[0052] The at least one interaction area is provided as part of step E). The at least one interaction area may specifically be located on the second side of the substrate and / or at at least one edge of a layer setup comprising the substrate, the second conductive layer, the at least one AgCl-com- prising composition and the at least one protective layer. Thus, specifically, at least one edge of the further electrode may be uncovered by the protective layer, and the uncovered edge may form the at least one interaction area in which the AgCl-comprising composition may get in contact with the bodily fluid.

[0053] The at least one interaction area may specifically be formed by cutting a layer setup comprising the substrate, the working electrode and the at least one further electrode. By the cutting, as an example, at least one edge portion in the layer setup may be generated, wherein the edge portion may comprise the interaction area. The cutting process specifically may comprise one or more of a mechanical cutting and a laser cutting, as described in more detail below. In particular, a plurality of interaction areas may be provided as part of step E), such as two or more interaction areas. Specifically step E) may comprise providing the at least one further electrode comprising exactly two interaction areas. The two interaction areas may be facing in opposite directions. The interaction area may have a surface in the range from 0.01 mm2to 1 mm2, specifically from 0.1 mm2to 0.5 mm2, more specifically from 0.2 mm2to 0.4 mm2.

[0054] Alternatively or in addition to the formation of the interaction area by cutting the layer setup comprising the substrate, the working electrode and the at least one further electrode, the interaction area may be formed by generating at least one opening in the protective layer, such as single opening or a plurality of openings. The opening may also be described as a whole in the protective layer, such that the AgCl-comprising composition is devoid of the protective layer at the at least one opening. For generating the at least one opening a laser may be applied. Specifically, the AgCl -comprising composition may be applied as a spot or bar and covered by the protective layer such that during the following sensor cutting no AgCl-comprising composition is cut and is thus not exposed. In order to create the interaction area the laser can be applied in order to create a single or a plurality of openings in the protection layer. Reference may be made to WO2023012138A1. The interaction areas, e.g. in form of the at least one opening in the protective layer, may allow for mass transport. The term “accessible to the bodily fluid” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to the property of an object that can be brought in direct physical contact with the bodily fluid. Thus, the interaction area, unlike those parts of the AgCl-comprising composition that are covered by the protective layer, may be contactable by the fluid, e.g. be immersed in the bodily fluid specifically when the implantable portion of the analyte sensor is arranged within the tissue.

[0055] The term “exposing to ultraviolet light” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to the process of illuminating an obj ect with ultraviolet light and / or subj ecting the obj ect to ultraviolet light. Step F) comprises exposing the AgCl-comprising composition at least partially to ultraviolet light. Thus, the AgCl-comprising composition may be fully exposed to the ultraviolet light, such as that the entire AgCl-comprising composition, in particular the entire surface of the AgCl-comprising composition, is exposed to the ultraviolet light. Alternatively, the AgCl- comprising composition may be only partially exposed to the ultraviolet light, such that only certain parts, sections or areas of the AgCl-comprising composition, in particular only certain surface areas, are exposed to the ultraviolet light, while other parts, sections or areas of the AgCl-comprising composition, in particular other surface areas, are not illuminated by the ultraviolet light. In particular, step F) may comprise at least partially exposing the interaction area to the ultraviolet light. Specifically, step F) of the method may be performed after the interaction area has been provided.

[0056] The term “ultraviolet light” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a partition of electromagnetic radiation having a wavelength in the range from 10 nm to 400 nm, specifically in the range from 100 nm to 380 nm. In particular, in step F) an artificial ultraviolet light source may be used, specifically an artificial ultraviolet light source having a peak wavelength in the range of 200 nm to 400 nm. As an example, an array of ultraviolet light emitting diodes, also referred to as a UV LED Array, may be used having a peak wavelength of 365 nm. In particular, the ultraviolet light used in step F) may have an intensity in the range of 1 mW / cm2to 200 mW / cm2, specifically 10 mW / cm2to 100 mW / cm2, more specifically 50 mW / cm2to 75 mW / cm2. E.g. the intensity may be 65 mW / cm2. In particular, the AgCl-comprising composition may be at least partially exposed to ultraviolet light as part of step F) by positioning the analyte sensor, specifically the AgCl-comprising composition, at a distance from the ultraviolet light source. Other conditions of irradiations, e.g. regarding the ultraviolet light source, the intensity, and the duration of radiation may be feasible. In particular, the conditions of irradiations may be such that the AgCl-comprising composition exposed to the ultraviolet light receives a predefined radiation dose, specifically a total energy per area.

[0057] Step F) comprises exposing the AgCl-comprising composition at least partially to ultraviolet light. As part of step F), without wishing to be bound by this theory, AgCl may at least partially be photochemically transformed into elemental Ag. Specifically, in step F) elemental Ag may be formed by the ultraviolet light at least partially reducing the AgCl in the interaction area, specifically the AgCl at the surface of the interaction area. Thus, in step F) an amount of AgCl, e.g. a fraction of the AgCl of the AgCl-comprising composition may be reduced to elemental Ag. Electrochemical measurements reveal a 1% to 5% reduction of electrochemically accessible AgCl, depending on treatment conditions, which may be explained by photochemical reduction of this AgCl quantity. Particularly, in step F) the concentration of AgCl may be reduced in the interaction area, specifically at the surface of the interaction area. Thus, at least a partial decomposition and / or disintegration of the AgCl near the surface of the interaction area may be the result of the photochemical treatment with ultraviolet light in step F). This AgCl may otherwise be a source of Ag+ions. The AgCl located more remote from the surface of the interaction area may contribute less to the leaching of Ag+ions. A direct contact of the bodily fluid with the AgCl and a leaching of Ag+into the bodily fluid may thus be reduced and adverse body reactions diminished such that a biocompatibility of the analyte sensor may be increased. Furthermore, the exposition of the AgCl-comprising composition at least partially to the ultraviolet light as performed in step F) of the method may in particular be a dry process, which may allow a simple and fast manufacturing of the analyte sensor.

[0058] As an example, in step F) an amount in the range of 0.1 pg to 2 pg of a total amount of 30 pg of AgCl may be reduced to elemental Ag. Other amounts are feasible. In particular, the given values may design specific and may be different for different designs, shapes and / or embodiments of the analyte sensor, specifically for different designs, shapes and / or embodiments of AgCl-comprising composition.

[0059] Step F) may comprise exposing the AgCl-comprising composition at least partially to the ultraviolet light in a stepwise fashion, wherein each exposition step may comprise exposing the AgCl-comprising composition at least partially to the ultraviolet light for an exposition time in the range from 3 seconds to 2 minute, specifically from 15 seconds to 1 minute, more specifically an exposition time of 30 seconds. Each exposition step may be followed by at least one dissipation step, wherein each dissipation step comprises a radiation break in the range from 1 second to 30 seconds, specifically 3 seconds to 10 seconds, more specifically a radiation break of 5 seconds. In the dissipation step, the AgCl-comprising composition, specifically the interaction area, may not be exposed to the ultraviolet light. Instead, the illumination with the ultraviolet light may be interrupted. Heat dissipation from the AgCl-comprising composition may take place during the dissipation steps, such that thermal stress caused by the exposition to ultraviolet radiation may be reduced. In step F), the AgCl-comprising composition, specifically the interaction area, may be at least partially exposed to the ultraviolet light for a total amount of exposition time in the range from 10 seconds to 1 hour, specifically from 30 seconds to 30 minutes, more specifically from 1 minute to 20 minutes. In particular, step F) may comprise a plurality of exposition steps, each followed by a dissipation step, such that the total amount of exposition time may correspond to a sum of exposition times of each exposition step.

[0060] The method of manufacturing the at least one analyte sensor may specifically comprise forming the at least one analyte sensor by cutting, specifically by laser cutting, a layer setup, e.g. a sheetlike template, comprising the substrate, the first conductive layer, the second conductive layer, the working electrode material, the AgCl-comprising composition and the protective layer. In particular, the interaction area may be formed in the laser cutting process, specifically as a cutting edge of layer setup, e.g. the sheet-like template. Particularly, a plurality of analyte sensors may be manufactured by successively laser cutting each analyte sensor of the plurality of analyte sensors from the layer setup, e.g. the sheet-like template. In the laser cutting process, e.g. at least one of the following lasers may be used: a carbon-dioxide laser and ultra-short pulse laser.

[0061] In a further aspect of the present invention, an analyte sensor for determining at least one analyte in a bodily fluid is proposed. The analyte sensor is obtained by the method of manufacturing at least one analyte sensor for determining at least one analyte in a bodily fluid, as described above and / or as further described below. Accordingly, regarding details of the analyte sensor as well as regarding terms and definitions, reference may be made to the description of the method of manufacturing at least one analyte sensor as given above and / or as further given below.

[0062] The analyte sensor comprises: a) the at least one substrate, wherein the substrate comprises the first side and the second side; b) the at least one first conductive layer, wherein the first conductive layer at least partially covers the first side of the substrate; c) the at least one second conductive layer, wherein the second conductive layer at least partially covers at least one of the first side and the second side; d) the at least one working electrode, wherein the working electrode comprises: at least one part of the first conductive layer; and the at least one working electrode material at least partially covering the at least one part of the first conductive layer; e) the at least one further electrode, wherein the further electrode comprises: at least one part of the second conductive layer; the AgCl-comprising composition at least partially covering the at least one part of the second conductive layer; and the protective layer covering the AgCl-comprising composition apart from the at least one interaction area accessible to the bodily fluid.

[0063] In a further aspect of the present invention a system for manufacturing at least one analyte sensor for determining at least one analyte in a bodily fluid is proposed. The system is configured for performing the method as described above and / or as described in further detail below. Accordingly, regarding details of the system for manufacturing at least one analyte sensor as well as regarding terms and definitions, reference may be made to the description of the method of manufacturing at least one analyte sensor as given above and / or as further given below. The system comprises: i. at least one first application device for applying the at least one first conductive layer at least partially covering the first side of the substrate; ii. an application device for applying the second conductive layer at least partially covering at least one of the first side and the second side; iii. at least one device for providing the at least one working electrode material at least partially covering the first conductive layer; iv. at least one device for providing the at least one AgCl-comprising composition at least partially covering the second conductive layer; v. at least one device for providing the at least one protective layer covering the AgCl-comprising composition apart from at least one interaction area accessible to the bodily fluid; and vi. at least one exposure device for exposing the AgCl-comprising composition at least partially to ultraviolet light. The method of manufacturing the at least one analyte sensor and the analyte sensor obtained by the method provide numerous advantages over methods and analyte sensor as known in the art. Thus, as part of the method, an additional photochemical treatment of the by TPU protected CERE may be proposed in order to convert the AgCl at the open Ag / AgCl areas, e.g. at the at least one the interaction area, to elemental silver. The photochemical treatment may include irradiation of the CERE by UV. The irradiation spectrum may be selected from a broad range, wherein the preferable range may be UV B and / or UV C, e.g, 365 nm. The duration of the irradiation may depend on the spectrum and flux. As an example, the duration may be 15 minutes at 65 mWatt / cm2and the spectrum may have a peak wavelength of 365 nm and a FWHM of 6 nm. The abbreviation FWHM may refer to the expression “Full Width at Half Maximum”. Also, other intensities, spectra and durations may be applicable and may vary on the CERE composition and / or design. Furthermore, the irradiation may occur at different intensities and durations instead of one single irradiation session. This may be useful to reduce the thermal loading of the substrate.

[0064] In particular, the analyte sensor obtained by the method of manufacturing at least one analyte sensor may show an increased biocompatibility as compared to sensors known in the art. In particular, exposing the AgCl-comprising composition at least partially to ultraviolet light may lead to a reduction of AgCl at the interaction area. Thus, a contact of the AgCl with the bodily fluid and a leaching of Ag+into the body fluid may be reduced. This may increase the biocompatibility of the analyte sensor by reducing adverse body reactions. Furthermore, adverse body reactions that may occur due to soluble forms of silver ions diffusing into the bodily fluid. These adverse body reactions may diminish the performance of the analyte sensor. Thus, by reducing such reactions, the analyte sensor may show an increased sensitivity and / or reliability as compared to analyte sensors known in the art, in particular in the time period directly following sensor insertion.

[0065] Further, the analyte sensor obtained by the method may also show an improved sensor performance compared to analyte sensors known in the art, in particular an enhanced CERE performance during a time period after sensor insertion, during which the sensor run-in takes place, such as during a time period of several minutes after insertion.

[0066] Furthermore, the method of manufacturing the analyte sensor may be more cost-efficient than methods known in the art. In particular, the step F) of the method may be performed as a dry method step. In particular, wet method steps may be avoided in step F) of the method. Thus, the method may specifically be performed faster and in a more simple fashion than methods known in the art.

[0067] Summarizing and without excluding further possible embodiments, the following embodiments may be envisaged:

[0068] Embodiment 1 : A method of manufacturing at least one analyte sensor for determining at least one analyte in a bodily fluid, the method comprising the steps of

[0069] A) providing at least one substrate comprising a first side and a second side;

[0070] B) providing, specifically applying, at least one first conductive layer at least partially covering the first side of the substrate;

[0071] C) providing, specifically applying, at least one second conductive layer at least partially covering at least one of the first side and the second side;

[0072] D) providing at least one working electrode on the first side by providing at least one working electrode material at least partially covering the first conductive layer;

[0073] E) providing at least one further electrode on at least one of the first side and the second side by providing: at least one AgCl-comprising composition at least partially covering the second conductive layer; and at least one protective layer covering the AgCl-comprising composition apart from at least one interaction area accessible to the bodily fluid;

[0074] F) exposing the AgCl-comprising composition at least partially to ultraviolet light.

[0075] Embodiment 2: The method according to the preceding embodiment, wherein, in step C), the second conductive layer at least partially covers the second side of the substrate and, wherein in step E), the further electrode is provided on the second side of the substrate.

[0076] Embodiment 3 : The method according to any one of the preceding embodiments, wherein in step F) AgCl is photochemically transformed into elemental Ag.

[0077] Embodiment 4: The method according to any one of the preceding embodiments, wherein in step F) the interaction area is at least partially exposed to the ultraviolet light.

[0078] Embodiment 5 : The method according to any one of the preceding embodiments, wherein in step F) an artificial ultraviolet light source is used, specifically an artificial ultraviolet light source having a peak wavelength in the range of 200 nm to 400 nm. Embodiment 6: The method according to the any one of the preceding embodiments, wherein in step F) the AgCl-comprising composition, specifically the interaction area, is exposed to ultraviolet light having a total intensity of 1 mW / cm2to 200 mW / cm2, specifically 10 mW / cm2to 100 mW / cm2, more specifically 50 mW / cm2to 75 mW / cm2in the spectral range of 200 nm to 400 nm.

[0079] Embodiment 7 : The method according to any one of the preceding embodiments, wherein the interaction area comprises at least one surface section of the AgCl-comprising composition.

[0080] Embodiment 8 : The method according to any one of the preceding embodiments, wherein the interaction area has a surface in the range from 0.01 mm2to 1 mm2.

[0081] Embodiment 9: The method according to any one of the preceding embodiments, wherein in step F) elemental Ag is formed by the ultraviolet light at least partially reducing the AgCl in the interaction area, specifically the AgCl at the surface of the interaction area.

[0082] Embodiment 10 : The method according to any one of the preceding embodiments, wherein in step F) an amount in the range of 0.1 pg to 2 pg of a total amount of 30 pg of AgCl is reduced to elemental Ag.

[0083] Embodiment 11 : The method according to any one of the preceding embodiments, wherein in step F) the AgCl of the AgCl-comprising composition is at least partially decomposed, specifically at the surface of the interaction area.

[0084] Embodiment 12: The method according to any one of the preceding embodiments, wherein the further electrode comprises at least two of the interaction areas, specifically exactly two interaction areas facing in opposite directions.

[0085] Embodiment 13 : The method according to any one of the preceding embodiments, wherein the at least one interaction area is formed by at least one of a mechanical cutting and a laser cutting. Embodiment 14: The method according to any one of the preceding embodiments, wherein the method comprises forming the at least one analyte sensor by cutting a layer setup, specifically a sheet-like template, comprising the substrate, the working electrode, and the further electrode.

[0086] Embodiment 15: The method according to the preceding embodiment, wherein the interaction area is formed in the cutting process, specifically as a cutting edge of the layer setup.

[0087] Embodiment 16: The method according to any one of the two preceding embodiments, wherein a plurality of the analyte sensors is manufactured by successively cutting each of the analyte sensors of the plurality of analyte sensors from the layer setup.

[0088] Embodiment 17: The method according to any one of the three preceding embodiments, wherein in the laser cutting process at least one of the following lasers is used: a carbon-dioxide laser and an ultra-short pulse laser

[0089] Embodiment 18 : The method according to any one of the preceding embodiments, wherein step F) of the method is performed after the interaction area has been provided.

[0090] Embodiment 19 : The method according to any one of the preceding embodiments, wherein step F) comprises exposing the AgCl-comprising composition at least partially to the ultraviolet light in a stepwise fashion, wherein each exposition step comprises exposing the AgCl-com- prising composition at least partially to ultraviolet light for an exposition time in the range from 3 seconds to 2 minute, specifically from 15 seconds to 1 minute, more specifically an exposition time of 30 seconds.

[0091] Embodiment 20 : The method according to the preceding embodiment, wherein each exposition step is followed by at least one dissipation step, wherein each dissipation step comprises a radiation break in the range from 1 second to 30 seconds, specifically 3 seconds to 10 seconds, more specifically a radiation break of 5 seconds.

[0092] Embodiment 21 : The method according to any one of the preceding embodiments, wherein in step F) the AgCl-comprising composition, specifically the interaction area, is at least partially exposed to the ultraviolet light for a total amount of exposition time in the range from 10 seconds to 1 hour, specifically from 30 seconds to 30 minutes, more specifically from 1 minute to 20 minutes. Embodiment 22 : The method according to any one of the preceding embodiments, wherein the working electrode material comprises at least one reagent layer for detecting the analyte.

[0093] Embodiment 23 : The method according to the preceding embodiment, wherein the reagent layer comprises at least one biorecognition component, specifically an enzyme, adapted to interact with the analyte.

[0094] Embodiment 24: The method according to the preceding embodiment, wherein the biorecognition component, specifically the enzyme, is adapted to oxidize the analyte.

[0095] Embodiment 25 : The method according to any one of the two preceding embodiments, wherein the biorecognition component, specifically the enzyme, is at least one of: glucose oxidase (GOx) and glucose dehydrogenase (GDH).

[0096] Embodiment 26 : The method according to any one of the preceding embodiments, wherein the analyte determinable by the analyte sensor is glucose.

[0097] Embodiment 27 : The method according to any one of the preceding embodiments, wherein the further electrode comprises at least one of: a counter electrode, a reference electrode and a combined counter / reference electrode.

[0098] Embodiment 28 : The method according to the preceding embodiment, wherein the further electrode is or comprises a single combined counter / reference electrode.

[0099] Embodiment 29: The method according to the preceding embodiment, wherein the AgCl- comprising composition is provided in step E) as an AgCl-comprising layer with a thickness in the range of 1 pm to 100 pm, specifically 5 pm to 60 pm, more specifically 15 pm to 25 pm.

[0100] Embodiment 30: The method according to any one of the preceding embodiments, wherein the AgCl-comprising composition comprises AgCl in the form of particles with a particle size in the range of 0.5 pm to 80 pm, specifically 1 pm to 50 pm, more specifically 2 pm to 20 pm.

[0101] Embodiment 31 : The method according to any one of the preceding embodiments, wherein the AgCl-comprising composition comprises a total amount of AgCl in the range of 10 pg to 100 pg, specifically 20 pg to 50 pg, more specifically 25 pg to 35 pg. Embodiment 32 : The method according to any one of the preceding embodiments, wherein the AgCl-comprising composition further comprises at least one of: elemental Ag and at least one binder.

[0102] Embodiment 33 : The method according to the preceding embodiment, wherein a weight per weight ratio of elemental Ag to AgCl in the AgCl-comprising composition may be in the range from 10: 1 to 1 :20, e.g. in the range from 10: 1 to 1 : 10.

[0103] Embodiment 34: The method according to any one of the two preceding embodiments, wherein the binder comprises a non-conductive polymer, particularly a PVC-based polymer and / or a polyurethan-based polymer, specifically a TPU-based polymer.

[0104] Embodiment 35: The method according to any one of the three the preceding embodiments, wherein the AgCl-comprising composition comprises AgCl and the at least one binder in a ratio in the range of 1 TOO to 100: 1, specifically in the range of 1 :50 to 50: 1, more specifically in the range of 1 : 10 to 10: 1.

[0105] Embodiment 36: The method according to any one of the preceding embodiments, wherein both the first conductive layer and the second conductive layer are formed by the same conductive material.

[0106] Embodiment 37: The method according to the preceding embodiment, wherein the conductive material comprises at least one of: carbon, gold, silver, platinum, and copper, e.g. gold- plated copper.

[0107] Embodiment 38 : The method according to any one of the preceding embodiments, wherein the substrate comprises at least one electrically insulating material.

[0108] Embodiment 39: The method according to any one of the preceding embodiments, wherein the first side of the substrate and the second side of the substrate are facing in opposite directions.

[0109] Embodiment 40: An analyte sensor for determining at least one analyte in a bodily fluid, wherein the analyte sensor is obtained by the method according to any one of the preceding embodiments. Embodiment 41 : The analyte sensor according to the preceding embodiment, wherein the analyte sensor comprises: a) the at least one substrate, wherein the substrate comprises the first side and the second side; b) the at least one first conductive layer, wherein the first conductive layer at least partially covers the first side of the substrate; c) the at least one second conductive layer, wherein the second conductive layer at least partially covers at least one of the first side and the second side; d) the at least one working electrode, wherein the working electrode comprises: at least one part of the first conductive layer; and the at least one working electrode material at least partially covering the at least one part of the first conductive layer; e) the at least one further electrode, wherein the further electrode comprises: at least one part of the second conductive layer: the AgCl-comprising composition at least partially covering the at least one part of the second conductive layer; and the protective layer covering the AgCl-comprising composition apart from the at least one interaction area accessible to the bodily fluid.

[0110] Embodiment 42: A system for manufacturing at least one analyte sensor for determining at least one analyte in a bodily fluid, the system being configured for performing the method according to any one of the preceding embodiments referring to a method, the system comprising: i. at least one first application device for applying the at least one first conductive layer at least partially covering the first side of the substrate; ii. an application device for applying the second conductive layer at least partially covering at least one of the first side and the second side; iii. at least one device for providing the at least one working electrode material at least partially covering the first conductive layer; iv. at least one device for providing the at least one AgCl-comprising composition at least partially covering the second conductive layer; v. at least one device for providing the at least one protective layer covering the AgCl-comprising composition apart from the at least one interaction area accessible to the bodily fluid; and vi. at least one exposure device for exposing the AgCl-comprising composition at least partially to ultraviolet light. Short description of the Figures

[0111] Further optional features and embodiments will be disclosed in more detail in the subsequent description of embodiments, preferably in conjunction with the dependent claims. Therein, the respective optional features may be realized in an isolated fashion as well as in any arbitrary feasible combination, as the skilled person will realize. The scope of the invention is not restricted by the preferred embodiments. The embodiments are schematically depicted in the Figures. Therein, identical reference numbers in these Figures refer to identical or functionally comparable elements.

[0112] In the Figures and Tables:

[0113] Figure 1 shows a perspective view of an analyte sensor for determining at least one analyte in a bodily fluid;

[0114] Figure 2 shows a flow chart illustrating a method of manufacturing at least one analyte sensor for determining at least one analyte in a bodily fluid;

[0115] Figure 3 shows a diagram of a voltammetric experiment involving the further electrode of the analyte sensor;

[0116] Figure 4 shows a diagram with representative potentiometric curves;

[0117] Figure 5 shows experimental data illustrating the electrochemical capacity of the further electrode as a function of a duration of the exposition to ultraviolet light; and

[0118] Figure 6 shows experimental data illustrating leached silver as a function of a duration of the exposition to ultraviolet light.

[0119] Table 1 shows experimental data regarding the effect of leaching of Ag+from the further electrode.

[0120] Detailed description of the embodiments Figure 1 shows a perspective view of an analyte sensor 110 obtained by a method of manufacturing at least one analyte sensor 110 for determining at least one analyte in a bodily fluid as described above or as further described herein below. The analyte sensor 110 comprises at least one substrate 112, wherein the substrate 112 comprises a first side 114 and a second side 116. The substrate 112 may specifically comprise at least one insulating material 118, such as polyethylene terephthalate (PET) or polycarbonate (PC). Other electrically insulating materials 118 may also be feasible. The substrate 112 may specifically be a planar substrate 112. As illustrated in Figure 1, the substratel l2 may have an elongated shape, such as a strip shape 120 or a bar shape with the first side 114 and the second side 116 being opposing sides of the strip-shaped substrate 112 facing in opposite directions. Other shapes of the substrate 112 may be feasible, e.g. a rod shape (not shown in the Figures).

[0121] The analyte sensor 110 further comprises at least one first conductive layer 122, wherein the first conductive layer 122 at least partially covers the first side 114 of the substrate 112. The embodiment schematically depicted in Figure 1 shows the first conductive layer 122 covering the first side 114 of the substrate 112 fully. However, other embodiments, wherein the first conductive layer 122 may cover only parts of the first side 114, such as at least one area of the first side 114 are also feasible (not shown). The analyte sensor 110 further comprises at least one second conductive layer 124, wherein the second conductive layer at least partially covers at least one of the first side 114 and the second side 116 of the substrate 112. In the embodiment schematically depicted in Figure 1, the second conductive layer 124 fully covers the second side 116 of the substrate 112. The second conductive layer 124 may alternatively cover only parts of the second side 116, e.g. at least one area of the second side 116 (not shown). In a further embodiment, the second conductive layer 124 may cover parts of the first side 114, such that the first conductive layer 122 and the second conductive layer 124 may both be arranged on the first side 114. In this case, the working electrode 128 and the further electrode 142 may both be arranged and / or positioned on the first side 114 of the substrate 112. As an example, at least one conductor may be arranged on the substrate 112 for each of the working electrode 128 and the further electrode 142, wherein the conductors lead separately to the working electrode 128 and the further electrode 142 (not shown). In said embodiment, the working electrode 128 may be covered and / or masked in step F) such that the AgCl-comprising composition 146 is exposed to the ultraviolet light while the working electrode 128 may be protected against the exposition to ultraviolet light. As an example at least one covering device may be used, e.g. a plain covering device protecting against ultraviolet light. In Figure 1, an embodiment of the analyte sensor 110 is illustrated, wherein the second conductive layer 124 at least partially covers the second side 116 of the substrate 112 and the further electrode 142 is provided on the second side 116 of the substrate 112.

[0122] The first conductive layer 122 and the second conductive layer 124 may each comprise at least one electrically conductive or semiconducting material 126, such as at least one material selected from: conductive carbon, gold, silver, platinum, and copper, e.g. gold-plated copper. In particular, both the first conductive layer 122 and the second conductive layer 124 may comprise or may be formed by the same conductive material 126.

[0123] As illustrated in Figure 1, the analyte sensor 110 further comprises at least one working electrode 128. The working electrode 128 comprises at least one part 130 of the first conductive layer 122 and at least one working electrode material 132 at least partially covering the at least on part of the first conductive layer 122. Thus, the working electrode 128 may specifically comprise a layer setup, as shown in Figure 1. Specifically, a part of the first electrically conductive layer 122, which is not covered by the at least one working electrode material 132, may form at least one electrical lead 134 for electrically contacting the working electrode 128. The electrical lead 134 may also comprise at least one electrical contact pad on the substrate 112 (not shown).

[0124] The working electrode material 132 may be configured for undergoing a detectable chemical reaction with the analyte or in the presence of the analyte, more specifically at least one electrochemical reaction, which is electrically detectable, such as by one or more of a potentiostatic measurement and an amperometric measurement. The working electrode material 132 may e.g. comprise at least one enzyme 136 capable of catalyzing at least one chemical reaction altering the analyte, e.g. a chemical reaction in which the analyte is oxidized and / or reduced. As an example, in case the analyte is glucose or comprises glucose, the enzyme 136 may comprise one or more of glucose oxidase and glucose dehydrogenase. In addition, the working electrode material 132 may comprise one or more additional components, such as mediator compounds configured for electron transfer and the like. The working electrode material 132 may comprise at least one reagent layer 138 comprising at least one biorecognition component 140, particularly the enzyme 136, adapted to interact with the analyte. As illustrated in Figure 1, in the area, in which the reagent layer 138 covers the first conductive layer 122, the first conductive layer 122 and the reagent layer 138 may form the working electrode 128. As depicted in Figure 1, the analyte sensor 110 further comprises at least one further electrode 142. The further electrode 142 comprises at least one part 144 of the second conductive layer 124 and at least one AgCl-comprising composition 146 at least partially covering the at least one part 144 of the second conductive layer 124. The further electrode 142 further comprises at least one protective layer 148 covering the AgCl-comprising composition 146 apart from at least one interaction area 150 accessible to the bodily fluid. Thus, as illustrated in Figure 1, the at least one further electrode 142 may comprise a layer setup comprising the second conductive layer 124, the at least one AgCl-comprising composition 146 and the at least one protective layer 148. Thus, specifically, at least one edge 151 of the further electrode 142 may be uncovered by the protective layer 148, and the uncovered edge 151 may form the at least one interaction area 150 in which the AgCl-comprising composition 146 may get in contact with the bodily fluid. The interaction area 150, specifically the uncovered edge 151, may e.g. be generated by cutting a layer setup comprising the substrate 112, the working electrode 128 and the at least one further electrode 142 by at least one of a mechanical cutting and a laser cutting. The further electrode 142 may specifically comprise two interaction areas 150. As illustrated in Figure 1, the two interaction areas 150 may in particular be parallel and may be facing in opposite directions. As an example, the interaction area 150 may have a surface in the range from 0.01 mm2to 1 mm2, more specific from 0.1 mm2to 0.5 mm2, more specific from 0.2 mm2to 0.4 mm2.

[0125] As also shown in Figure 1, at least one part of the second conductive layer 124 may remain uncovered by the AgCl-comprising composition 146. This at least one part may form or may comprise at least one conductive lead 134, e.g. for electrically contacting the at least one further electrode 142. In particular, the at least one conductive lead 134 may also form one or more electrical contact pads for electrically contacting the at least one further electrode 142 (not shown).

[0126] The further electrode 142 may comprise at least one of: a counter electrode, a reference electrode and a combined counter / reference electrode 152. As illustrated in Figure 1, the further electrode 142 may be or may comprise a combined counter / reference electrode 152 and thus combine several functionalities. The at least one further electrode 142 and the working electrode 128 may form part of an electrochemical circuit, wherein the further electrode 152 in form of the combined counter / reference electrode 152 may provide the reference potential and balance the current flow from the working electrode 128. In particular, the electrochemical detection reaction at the working electrode 128 may be one of two half reactions, wherein the further of the two half-reaction may take place at the further electrode 142, specifically the combined counter / reference electrode 152. As an example, the half reaction taking place at the working electrode 128 may comprise an oxidation of the analyte, specifically glucose, while the half reaction taking place at the combined counter / reference electrode 152 may comprise a reduction, specifically a reduction of Ag+to elemental Ag. The analyte sensor 110 may in particular be used for one or more of a potentiometric or potentiostatic measurement and an amperometric measurement. Thus, the measurement signal of the analyte sensor 110 may comprise one or more of a voltage measurement signal and a current measurement signal. The measurement signal may be used for the determination of the analyte, such as for detecting the concentration of the analyte.

[0127] The analyte sensor 110 specifically may be configured as an in vivo analyte sensor, configured for determining the at least one analyte in the bodily fluid while the bodily fluid is still contained in a body of a user. Thus, the analyte sensor 110 may comprise at least one implantable portion 154 as illustrated in Figure 1 , such that the analyte sensor 110 may at least partially be in contact with the bodily fluid of a user, e.g. via the implantable portion 154. Besides the implantable portion 154, the analyte sensor 110 may optionally comprise at least one further part or component that may remain outside of the body tissue, e.g. a contacting portion having one or more electrical contact pads electrically connected to the working electrode 128 and the further electrode 142, respectively (not shown). The implantable portion 154 arranged within the body tissue and the further part or component arranged outside of the body tissue may be electrically connected and / or connectable.

[0128] Even though not shown in Figure 1, in the portion of the implantable portion 154 of the analyte sensor 110 outside the working electrode 128 and outside the further electrode 142, the first and / or second conductive layers 122, 124 may fully or partially be covered with one or more electrically insulating materials, such as one or more electrically insulating resins or the like, in order to avoid a direct contact between the first and / or second conductive layers 122, 124 and the bodily fluid. Outside the implantable portion 154, the electrically insulating material may fully or partially be removed, in order to provide for contact portions for electrically contacting the working electrode 128 and the further electrode 142. In addition to the one or more electrically insulating materials or covers, one or ore biocompatibility materials may be present.

[0129] The analyte sensor 110 for determining at least one analyte in a bodily fluid is obtained by the method of manufacturing at least one analyte sensor 110 for determining at least one analyte in a bodily fluid, as described above and / or as further described below. The method is illustrated in the flow diagram shown in Figure 2. The method comprises the following method steps, which may specifically be performed in the given order. However, a different order may also be possible. The method may further comprise additional method steps, which are not listed. Further, one or more or even all of the method steps may be performed only once or repeatedly. The method steps may in particularly be performed in manner, wherein two or more steps may fully or at least partially be overlapping in time. As shown in Figure 2, the method comprises the steps of

[0130] A) providing the at least one substrate 112 comprising the first side 114 and the second side 116;

[0131] B) providing, specifically applying, the at least one first conductive layer 122 at least partially covering the first side 114 of the substrate 112;

[0132] C) providing, specifically applying, the at least one second conductive layer 124 at least partially covering at least one of the first side 114 and the second side 116;

[0133] D) providing the at least one working electrode 128 on the first side 114 by providing the at least one working electrode material 132 at least partially covering the first conductive layer 122;

[0134] E) providing the at least one further electrode 142 on at least one of the first side 114 and the second side 116 by providing: the at least one AgCl-comprising composition 146 at least partially covering the second conductive layer 124; and the at least one protective layer 148 covering the AgCl-comprising composition 146 apart from the at least one interaction area 150 accessible to the bodily fluid;

[0135] F) exposing the AgCl-comprising composition 146 at least partially to ultraviolet light.

[0136] In the flow chart of Figure 2, method step A is denoted by reference number 156, method step B is denoted by reference number 158, method step C is denoted by reference number 160, method step D is denoted by reference number 162, method step E is denoted by reference number 164 and method step F is denoted by reference number 166.

[0137] As part of step F) of the method, the AgCl-comprising composition 146 is at least partially exposed to ultraviolet light. Specifically, the interaction area 150, which is comprised by the AgCl-comprising composition 146, may be at least partially exposed to ultraviolet light. As an example, in step F) an artificial ultraviolet light source may be used having a peak wavelength in the range of 200 nm to 400 nm. The ultraviolet light used in step F) may specifically have an intensity in the range of 1 mW / cm2to 200 mW / cm2, specifically 10 mW / cm2to 100 mW / cm2, more specifically 50 mW / cm2to 75 mW / cm2Other conditions of irradiation may be feasible. In particular, the conditions of irradiations may be such that the AgCl-comprising composition 146 exposed to the ultraviolet light receives a predefined radiation dose, specifically a total energy per area.

[0138] Step F) may comprise exposing the AgCl-comprising composition 146 at least partially to the ultraviolet light in a stepwise fashion, wherein each exposition step may comprise exposing the AgCl-comprising composition 146 at least partially to the ultraviolet light for an exposition time in the range from 3 seconds to 2 minute, specifically from 15 seconds to 1 minute, more specifically an exposition time of 30 seconds. Each exposition step may be followed by at least one dissipation step coprising a radiation break in the range from 1 second to 30 seconds, specifically 3 seconds to 10 seconds, more specifically a radiation break of 5 seconds. Thus, the AgCl-comprising composition 146 may be at least partially exposed to the ultraviolet light for a total amount of exposition time in the range from 10 seconds to 1 hour, specifically from 30 seconds to 30 minutes, more specifically from 1 minute to 20 minutes.

[0139] As part of step F), without wishing to be bound by this theory, AgCl may at least partially be photochemically transformed into elemental Ag. Specifically, in step F) elemental Ag may be formed by the ultraviolet light at least partially reducing the AgCl in the interaction area 150, specifically the AgCl at the surface of the interaction area 150. Particularly, the AgCl of the AgCl-comprising composition 146 may be at least partially decomposed, specifically at the surface of the interaction area 150. Thus, as a result of step F), the AgCl comprised by the AgCl- comprising composition 146 may be at least partially covered by elemental Ag. In particular, the AgCl may fully or partially be shielded and / or separated from the bodily fluid by the elemental Ag generated in the photochemical reaction in step F). A direct contact of the bodily fluid with the AgCl and a leaching of Ag+ into the bodily fluid may thus be reduced.

[0140] Table 1 shows experimental data acquired using three analyte sensors 110 obtained by the method of manufacturing at least one analyte sensor 110. The three analyte sensors 110 are exposed to ultraviolet light from an UV LED Array, having a peak wavelength of 365 nm and a FWHM of 6 nm. The UV LEDs are combined to a homogeneous floodlight source. The intensity, specifically the incident irradiation power, is 65 mW / cm2. The three analyte sensors 110 are exposed to the ultraviolet light at a distance of 175 mm from the UV LED Array. The three analyte sensors 110 are exposed to ultraviolet light in a stepwise fashion, wherein 30 seconds of irradiation are followed by a radiation break of 5 seconds for heat dissipation. The three analyte sensors 110, specifically the AgCl-comprising composition 146, are exposed to the ultraviolet light for a total amount of 1 minute, 4 minutes and 16 minutes, respectively, by repeating the above-cited radiation steps of 30 seconds with consecutive radiation breaks twice, eight times and 32 times, respectively. Furthermore, an analyte sensor is used in the experiment that differs from the three analyte sensors 110 only in that it is not exposed to ultraviolet light. Each of the three analyte sensors 110 and the further analyte sensor are immersed in 1 ml of ultrapure water at 37 °C for 24 hours. After 24 hours the analyte sensors 110 and the further analyte sensor are removed and the amount of soluble forms of Ag, specifically Ag+, in the 1 ml eluate is determined using mass spectrometry. For the determination of Ag in the eluate, the eluate is diluted at a ratio of 1 : 10 in 2% HNO3. Standards of 5 pg Ag / L, 10 pg Ag / L and 20 pg Ag / L are used in the process of determining the amount of soluble forms of Ag, as well as an internal standard of 10 pg Rhodium / L.

[0141] Table 1: Experimental data regarding the effect of leaching of Ag+from the further electrode

[0142] Table 1 indicates the mass of Ag in ng determined in the four different eluates corresponding to three analyte sensors 110 exposed to ultraviolet light for 1 minutes, 4 minutes and 16 minutes respectively, and to the analyte sensor that had not been exposed to ultraviolet light. Each value is an average value determined from three measurement values. The three measurement values are generated by measuring three specimen of each type of analytes sensor. As can be seen from the data displayed in Table 1, the amount of soluble forms of Ag that leaches into the ultrapure water surrounding the analyte sensor, is significantly reduced for the analyte sensors 110 that are exposed to ultraviolet light as compared to the analyte sensor not exposed to ultraviolet light. Furthermore, the data in Table 1 indicate that a total exposition time of 16 min has the strongest effect in reducing the leaching of soluble forms of Ag into the surrounding ultrapure water. The experimental data support the notion that step F) of the method of manufacturing at least one analyte sensor 110 may reduce the leaching of soluble forms of Ag, such as Ag+ions, into the bodily fluid thus increasing the biocompatibility of the analyte sensor 110 as well as the reliability, in particular during the time period after sensor insertion, during which adverse body reactions against soluble forms of silver may occur. Figure 3 shows a voltammogram 182. In the corresponding experiment, the voltage between the combined counter / reference electrode 152 and the working electrode 128 is varied, while the current is measured. This experiment may in particular indicate, how much the potential of the further electrode 142, specifically the CERE 152, shifts under the load of a specific current. Herein, a low shift may be desirable since it may corresponds to a more stable reference potential of the CERE 152, which may contribute to an improved sensor performance of the analyte sensor 110. The x-axis of the voltammogram 182 is marked by reference sign 170 and shows the voltage in Volt. The y-axis of the voltammogram 182 is marked by reference sign 172 and shows the current in nanoampere (nA). The curves displayed in Figure 3 correspond to experimental data acquired for analyte sensors 110 obtained by the method of manufacturing an analyte sensor 110, whose AgCl-comprising composition 146 has been exposed to ultraviolet light for 1 minute, 4 minutes and 16 minutes, respectively; as well as for an analyte sensorthat differs from said analyte sensors 110 only in that the AgCl-comprising composition 146 of said analyte sensor has not been exposed to ultraviolet light. In particular, the data corresponding to an analyte sensor 110 with a total exposition time of 1 minute is marked by reference sign 174; the data corresponding to an analyte sensor 110 with a total exposition time of 4 minute is marked by reference sign 176; the data corresponding to an analyte sensor 110 with a total exposition time of 16 minute is marked by reference sign 178; and the data corresponding to an analyte sensor whose AgCl-comprising composition 146 has not been exposed to ultraviolet light is marked by reference sign 180. As can be seen from Figure 3, the reference potential shift under load is smaller for the analyte sensor 110, whose AgCl-comprising composition 146 was subject to ultraviolet light for 16 minutes, than the reference potential shift for the analyte sensor, whose AgCl-comprising composition 146 was not exposed to ultraviolet light. For example, at a current of 20 nA, the potential shift of the CERE 152 that was not exposed to ultraviolet light amounts to about 25 mV as compared to theoretical zero, which is marked by the dotted line. In contrast, the corresponding shift of the CERE 152 that was exposed to ultraviolet light for 16 minutes amounts to less than 10 mV. Both shifts are indicated in Figure 4 by dashed doublesided arrows. Without wishing to be bound by this theory, this surprising effect may be due to the generation of nanoparticles of elemental silver as a result of the exposition to ultraviolet light, which may act as catalytic centers, that may improve the electrochemical performance of the further electrode 142, specifically the CERE 152.

[0143] Figure 4 shows a diagram with a representative potentiometric curve 184 for each of the three analyte sensors 110 having been exposed to ultraviolet light for 1 minute, 4 minutes and 16 minutes, respectively, as well as for an analyte sensor that has not been exposed to ultraviolet light. In particular, the data corresponding to an analyte sensor 110 with a total exposition time of 1 minute is marked by reference sign 174; the data corresponding to an analyte sensor 110 with a total exposition time of 4 minute is marked by reference sign 176; the data corresponding to an analyte sensor 110 with a total exposition time of 16 minute is marked by reference sign 178; and the data corresponding to an analyte sensor whose AgCl-comprising composition 146 has not been exposed to ultraviolet light is marked by reference sign 180. The x-axis of the diagram 183 is marked by reference sign 170 and shows time in hours (h). The y-axis of the diagram 183 is marked by reference sign 172 and shows the potential in millivolts (mV). For the experiment, each CERE 142 is loaded with 5-fold average nominal cathodic current in a suitable electrolyte. The potentials are measured against an external Ag / AgCl 100 mM Cl’ reference electrode. A shift of the potential above 40 mV is considered as a depleted state of the corresponding CERE 142 and the duration of the galvanostatic stripping represents the electrochemical CERE capacity. It can be clearly seen from Figure 4, that longer treatment with ultraviolet light results in shorter operation durations corresponding to a diminished electrochemical CERE capacity. This supports the assumption of AgCl decomposition by UV-irradiation. As illustrated by the data shown in Figure 4, a 16 minutes irradiation results in a reduction of the electrochemical CERE capacity of about 9%. Simultaneously, at least for the first 24 hours, the potential shift under load is smaller, the longer the UV treatment is. This may be a positive effect: the smaller the potential shift from that of the unpolarised CERE 142 is, the better is the electrochemical performance of the CERE 142.

[0144] Figure 5 shows a diagram 183 with experimental data 185 illustrating the CERE electrochemical capacity as a function of the duration of the exposition to ultraviolet light. Correspondingly, the x-axis 170 of the diagram 183 shows the duration of the exposition of the analyte sensor 110 to ultraviolet light in minutes (min). The y-axis 172 of the diagram 183 in Figure 5 shows the duration of operation of the analyte sensor 110 in hours (h). The diagram 183 further shows an exponential decay fitting 186. Considering the fitting 186, e.g. a 10 minutes or a 12 minutes exposition to ultraviolet light may lead to the same amount of decomposed AgCl as an exposition of 16 minutes. The amount of the decomposed AgCl does not seem to change much after 10 minutes of treatment under the given conditions. This may be explained by a decomposition of all of the AgCl at the outer surface of the interaction area 150 and a shadow effect caused by newly formed elemental silver, covering AgCl lying deeper and thus more remote from the interaction area 150. Thus, no further AgCl of the AgCl-comprising composition 146 may be accessed by the UV irradiation and therefore no further AgCl may be decomposed.

[0145] Figure 6 shows a diagram 183 with experimental data 185 illustrating leached silver as a function of the duration of the exposition to ultraviolet light. Correspondingly, the x-axis 170 of the diagram 183 in Figure 6 indicates the duration of the exposition of the analyte sensor 110, specifically the AgCl-comprising composition 146, to ultraviolet light. The duration is given in minutes (min). The y-axis 172 of the diagram 183 shows the leaching of Ag+in nanogram (ng). The diagram 183 further shows an exponential decay fitting 186. Even though, there is seem- ingly no plateau reached at the time point of t=l 6 min in contrast to the CERE electrochemical capacity illustrated in Figure 5, further extrapolation to higher durations of UV treatments results in a YO-value of about 110 ng, which is very close to the value at the time point of t=l 6 min. Herein the YO-value may refer to a value of Ag leaching corresponding to the expected plateau of the fitted curve 186. Thus, the YO-value may correspond to an expected minimal amount of Ag leaching. It can be seen, that after 16 minutes of treatment with ultraviolet light, the quantity of leached silver is reduced by almost a factor of two compared to an analyte sensor whose AgCl-comprising composition is not exposed to ultraviolet light, whereas the amount of decomposed AgCl is about 9% as illustrated by the data shown in Figure 4. This may indicate again, that the AgCl lying at the surface of the interaction area 150 may be the primary source of silver ions, whereas further AgCl particles may initially be densely surrounded by the AgCl- comprising composition 146, specifically by a binder and / or a polymer matrix, comprised by the CERE.

[0146] List of reference numbers analyte sensor substrate first side second side insulating material strip shape first conductive layer second conductive layer electrically conductive or semiconducting material working electrode part of the first conductive layer working electrode material electrical lead enzyme reagent layer biorecognition component further electrode part of the second conductive layer AgCl-comprising composition protective layer interaction area edge combined counter / reference electrode implantable portion method step A method step B method step C method step D method step E method step F x-axis y-axis exposition time of 1 minute exposition time of 4 minute exposition time of 16 minute no exposition to ultraviolet light voltammogram diagram potentiometric curves experimental data exponential decay fitting

Claims

Claims1. A method of manufacturing at least one analyte sensor (110) for determining at least one analyte in a bodily fluid, the method comprising the steps of:A) providing at least one substrate (112) comprising a first side (114) and a second side (H6);B) providing at least one first conductive layer (122) at least partially covering the first side (114) of the substrate (112);C) providing at least one second conductive layer (124) at least partially covering at least one of the first side (114) and the second side (116);D) providing at least one working electrode (128) on the first side (114) by providing at least one working electrode material (132) at least partially covering the first conductive layer (122);E) providing at least one further electrode (142) on at least one of the first side (114) and the second side (116) by providing: at least one AgCl-comprising composition (146) at least partially covering the second conductive layer (124); and at least one protective layer (148) covering the AgCl-comprising composition (146) apart from at least one interaction area (150) accessible to the bodily fluid;F) exposing the AgCl-comprising composition (146) at least partially to ultraviolet light.

2. The method according to the preceding claim, wherein in step F) AgCl is photochemically transformed into elemental Ag.

3. The method according to any one of the preceding claims, wherein in step F) an artificial ultraviolet light source is used, specifically an artificial ultraviolet light source having a peak wavelength in the range of 200 nm to 400 nm.

4. The method according to the any one of the preceding claims, wherein in step F) the AgCl-comprising composition (146), specifically the interaction area (150), is exposed to ultraviolet light having a total intensity of 1 mW / cm2to 200 mW / cm2, specifically 10 mW / cm2to 100 mW / cm2, more specifically 50 mW / cm2to 75 mW / cm2in the spectral range of 200 nm to 400 nm.

5. The method according to any one of the preceding claims, wherein in step F) the AgCl of the AgCl-comprising composition (146) is at least partially decomposed, specifically at a surface of the interaction area (150).

6. The method according to any one of the preceding claims, wherein in step F) the interaction area (150) is at least partially exposed to the ultraviolet light.

7. The method according to any one of the preceding claims, wherein the method comprises forming the at least one analyte sensor (110) by cutting a layer setup comprising the substrate (112), the working electrode (128) and the further electrode (142).

8. The method according to the preceding claim, wherein the interaction area (150) is formed in the cutting process, specifically as a cutting edge of the layer setup.

9. The method according to any one of the preceding claims, wherein step F) comprises exposing the AgCl-comprising composition (146) at least partially to the ultraviolet light in a stepwise fashion, wherein each exposition step comprises exposing the AgCl-comprising composition (146) at least partially to ultraviolet light for an exposition time in the range from 3 seconds to 2 minute, specifically from 15 seconds to 1 minute, more specifically an exposition time of 30 seconds.

10. The method according to the preceding claim, wherein each exposition step is followed by at least one dissipation step, wherein each dissipation step comprises a radiation break in the range from 1 second to 30 seconds, specifically from 3 seconds to 10 seconds, more specifically a radiation break of 5 seconds.

11. The method according to any one of the preceding claims, wherein the working electrode material (132) comprises at least one reagent layer (138) for detecting the analyte, wherein the reagent layer (138) comprises at least one biorecognition component (140), specifically an enzyme (136), adapted to interact with the analyte.

12. The method according to any one of the preceding claims, wherein the further electrode (142) comprises at least one of: a counter electrode, a reference electrode and a combined counter / reference electrode (152).

13. An analyte sensor (110) for determining at least one analyte in a bodily fluid, wherein the analyte sensor (110) is obtained by the method according to any one of the preceding claims.

14. The analyte sensor (110) according to the preceding claim, wherein the analyte sensor (110) comprises: a) the at least one substrate (112), wherein the substrate (112) comprises the first side (114) and the second side (116); b) the at least one first conductive layer (122), wherein the first conductive layer (122) at least partially covers the first side (114) of the substrate (112); c) the at least one second conductive layer (124), wherein the second conductive layer (124) at least partially covers at least one of the first side (114) and the second side (H6); d) the at least one working electrode (128), wherein the working electrode (128) comprises: at least one part of the first conductive layer (122); and- the at least one working electrode material (132) at least partially covering the at least one part of the first conductive layer; e) the at least one further electrode (142), wherein the further electrode (142) comprises: at least one part of the second conductive layer (124);- the AgCl-comprising composition (146) at least partially covering the at least one part of the second conductive layer (124); and- the protective layer (148) covering the AgCl-comprising composition (146) apart from the at least one interaction area (150) accessible to the bodily fluid.

15. A system for manufacturing at least one analyte sensor (110) for determining at least one analyte in a bodily fluid, the system being configured for performing the method according to any one of the preceding claims referring to a method, the system comprising: i. at least one first application device for applying the at least one first conductive layer at least partially covering the first side (114) of the substrate (112); ii. an application device for applying the second conductive layer (124) at least partially covering at least one of the first side (114) and the second side (116); iii. at least one device for providing the at least one working electrode material (132) at least partially covering the first conductive layer; iv. at least one device for providing the at least one AgCl-comprising composition (146) at least partially covering the second conductive layer (124);v. at least one device for providing the at least one protective layer (148) covering the AgCl-comprising composition (146) apart from the at least one interaction area (150) accessible to the bodily fluid; and vi. at least one exposure device for exposing the AgCl-comprising composition (146) at least partially to ultraviolet light.

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