Abstract: The device for measuring and displaying the concentration of glucose in the blood comprises a display device (2) into which disposable sensors (1) comprising a biomembrane (9) can be inserted. The display device (2) comprises a built-in computer (3) in whose memory (7) a glucose concentration diagram (5) is stored and which can evaluate the measurement results of the sensors (1). The computer (3) comprises a time measuring device (4) whose zero setting can be correlated in an irreversible manner with the date of manufacture of the disposable sensors (1). Before the device is supplied to the patient, the glucose concentration diagram, which corresponds to the characteristics of the biomembrane (9) of the disposable sensors (1) at the time of manufacture, is irreversibly calibrated. The glucose concentration diagram is automatically and irreversibly corrected, taking into account the time-dependent characteristics of the biomembrane (9) of the disposable sensors (1), by means of the time measuring device (4).

Abstract: An electrochemical sensor is designed for use in detecting a concentration of an analyte in a sample solution. The sensor to have a longer useful lifetime, improved stability and improved response time for single or multiple use applications. In one aspect, some of these goals are achieved by providing the multilayer enzyme electrode membrane having both nonporous and microporous layers. The microporous layer is formed from a polymer binder, a polymer powder, a surfactant and a mineral powder. In another aspect, certain of these goals are achieved by the use of a layer comprised of an enzyme disposed within a polymer matrix. In certain embodiments, the multilayer enzyme electrode membrane includes an outermost layer which is capable of dissolving in the sample solution such that the interface between the multilayer enzyme electrode membrane and the sample solution is continually renewed.

Abstract: A sensor for the amperometric assay of cholesterol is provided which comprises a sensing electrode containing a first redox mediator and a reference electrode in simultaneous contact with a reagent strip containing a second redox mediator. The presence of the second redox mediator greatly amplifies the current flow produced by the presence of cholesterol and produces linear correlation of current flow with concentration over an extended range. The sensing electrode comprises a non-conductive support member having an electrically conductive layer containing the first redox mediator. The reference electrode is typically a Ag/AgCl electrode formed by coating an ink containing Ag/AgCl dispersed in a resin on a non-conductive base.

Abstract: The present invention provides a method of detecting an analyte in a sample the method comprising adding a sample suspected of containing the analyte to a membrane comprising a closely packed array of self-assembling amphiphilic molecules, the membrane including a plurality of ion channels selected from the group consisting of peptides capable of forming helices and aggregates thereof, podands cryptands and coronands, a first receptor moiety reactive with the analyte being attached to the ion channel at an end thereof, the first receptor moiety being such that it normally exists in a first state, but when bound to the analyte exists in a second state, said change of state of the first receptor moiety causing a change in the ability of ions to pass through the ion channel, the first receptor moiety being selected from the group consisting of antigens, peptides, antibodies (e.g.

Abstract: There is disclosed an enzyme electrode, comprising a polyion complex membrane of an immobilized enzyme, formed on an electrode base. According to the enzyme electrode, an enzyme substrate or the like can be quantitatively determined with less hindrance of easily oxidizable coexistent materials, conveniently, exactly, and rapidly.

Abstract: An electrochemical sensor for remote detection, particularly useful for metal contaminants and organic or other compounds. The sensor circumvents technical difficulties that previously prevented in-situ remote operations. The microelectrode, connected to a long communications cable, allows convenient measurements of the element or compound at timed and frequent intervals and instrument/sample distances of ten feet to more than 100 feet. The sensor is useful for both downhole groundwater monitoring and in-situ water (e.g., shipboard seawater) analysis.

Abstract: There is disclosed an apparatus for the determination of a trace amount of an analyte substance or organism. A substrate solution is brought into contact with a small diameter tube which has captured, at least on its inner surface, a trace amount of an analyte substance or organism. The trace amount has the ability to change the pH of the substrate solution.

Abstract: A multi-electrode biosensor for sensing a material present in a sample includes a substrate, a plurality of working electrodes formed on the substrate, a counter electrode formed on the substrate, and a reference electrode formed on the substrate.

Abstract: Protein is two-dimensionally aggregated and fixed to produce a functional thin film. A denatured film of a first protein is formed on the surface of a substrate solution such as an aqueous sugar or salt solution. A solution of a second protein which may be the same as or different from the first protein is then injected below the surface of the substrate solution at a distance sufficient not to disturb the surface. The substrate solution has a higher surface tension and specific gravity than the second protein solution causing the second protein to float between the denatured protein film and the substrate solution surface to form the two-dimensionally aggregated and fixed protein. The denatured film of first protein may be formed by injection of a solution of the first protein below the surface of the substrate solution. The aggregated and fixed protein can be heated and then transferred onto a solid surface such as in the formation of a biosensor.

Abstract: It has been found that imidazole and related buffers enhance the activity of certain preservatives, for example either (1) a mixture of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one or (2) 5-bromo-5-nitro-1,3-dioxane, that are used in clinical diagnostic reagents. It has also been found that these buffers and certain surfactants, such as BRIJ 700 and related hydrophilic surfactants, enhance the precision and accuracy of enzyme biosensors.

Abstract: An electrochemical biosensor able to measure hydrogen peroxide which is stable at temperatures near 37.degree. C. or in excess of 37.degree. C. for sustained periods of time and in biological environments. The electrochemical biosensor contains a thermostable peroxidase, preferably derived from soybean, and is useful in analytical biosensors.

Abstract: A method and apparatus are provided for marking predetermined events with a biosensor. The biosensor includes a sensor for receiving a user sample to be measured and a processor for performing a predefined test sequence for measuring a predefined parameter value. A memory is coupled to said processor for storing predefined parameter data values. A marker member is manually coupled by the user to the processor for selectively marking one of a plurality of predetermined events with a stored predefined parameter data value.

Abstract: Erythrocyte exclusion membranes suited for test strips of electrochemical sensors have a porous matrix and a mobile erythrocyte aggregating agent. The membranes typically comprise a water-insoluble hydrophobic polymer incorporating a hydrophilic polymer and with the erythrocyte aggregating agent. Such membranes can have a pore size which is several times larger than the diameter of erythrocytes, and allow rapid passage of plasma by holding back the erythrocytes as rouleaux at the surface of the membrane. The membranes are preferably made by forming in situ on a test strip using spray casting.

Abstract: A biosensor for rapid quantification of a specific component contained in various biological samples with high accuracy has an electrically insulating base, an electrode system including a working electrode and a counter electrode formed on one face of the insulating base, and a reaction layer formed on the insulating base in close contact with the electrode system. The reaction layer contains at least a hydrophilic polymer, a buffer and an enzyme which is separated from the buffer.

Abstract: A biosensor for measuring gas-phase organic chemicals rapidly and accurately. The biosensor includes a thick film electrochemical device having an insulating substrate, electrodes formed on the substrate, connecting pads for the electrodes and an insulating layer, and a responsive membrane formed on the electrode portion of the electrochemical device. The responsive membrane is provided with a moisture-absorbing gel layer in which an enzyme for reacting with the gas-phase organic chemical is immobilized.

Abstract: The biosensor of this invention includes an electrically insulating substrate; an electrode system formed on the substrate which includes a working electrode and a counter electrode; and a reaction layer formed on the substrate or above the substrate with a space therebetween. The reaction layer includes a pyranose-oxidizing enzyme.

Abstract: The biosensor of this invention can quantify a substrate in a sample liquid by electrochemically measuring the amount of an electron acceptor that has been reduced by electrons generated in a reaction between the substrate and an oxidoreductase. The biosensor has an electrically insulating substrate and an electrode system formed on the substrate including a working electrode, a counter electrode and a third electrode used for detecting a liquid junction. The third electrode can be used merely for detecting a liquid junction, or can be used as both a reference electrode and a liquid junction detecting electrode.

Abstract: A redox electrode for the rapid detection of glucose in aqueous media and a method for its use are provided. The redox electrode comprises an electrically conductive member such as copper, and a redox membrane in direct contact with said electrically conductive member. The redox membrane comprises a polymer matrix such as PVC containing a plasticizer, and a complex of 7,7,8,8-tetracyanoquinodimethane and tetrathiafulvalene with the complex having a burgundy-red coloration and characterized by a broad absorption from about 340 nm to about 550 nm and weaker absorption between about 650 nm to about 800 nm having about six small peaks with an absorption maximum at about 750 nm. Glucose is rapidly assayed by bringing the redox electrode and a reference electrode into simultaneous contact with an aqueous medium containing KCl, phosphate buffer, glucose oxidase, peroxidase, and 3,3',5,5'-tetramethylbenzidine dihydrochloride. The potential of the redox membrane is then monitored until it is stable.

Abstract: The present invention provides an immobilization medium which can immobilize bioreagents to support materials and which dries to a water resistant layer or film. The immobilization medium comprises (i) a liquid or fluid binding reagent and (ii) complexes of a bioreagent immobilized to a solid phase which are evenly dispersed within the binding reagent. The suspension can further include supplemental ingredients evenly dispersed throughout the medium which can provide the medium with electrochemical properties, enhance the stability of the immobilized bioreagent and/or improve the medium's capability of drying to a substantially water resistant or insoluble layer. The immobilization medium provided by the instant invention is in the form of a homogeneous liquid suspension.

Abstract: A method is revealed for the quantitative determination of the proportion of the free form of a thyroid hormone ligand in a sample of a biological fluid in which the ligand is present partly in the free form and also partly in a form in which it is bound to physiological binding proteins. In the first step, a ligand derivative of the thyroid hormone with an immunoglobulin, a labelled specific binder, and a test tube whose walls are coated with an excess of a protein material are provided. In the second step, a sample of the biological fluid containing an unknown amount of the free thyroid hormone ligand, a solution containing a known amount of the ligand derivative, and a solution containing a known, less than stoichiometric amount of the labelled specific binder are added to the test tube to form a liquid reaction mixture.

Abstract: The present invention relates to novel compounds used in an electrode membrane combination. These novel compounds include a linker lipid for use in attaching a membrane including a plurality of ionophores to an electrode and providing a space between the membrane and the electrode, the electrode being either in part or totally made up of the linker lipid. The linker lipid comprises within the same molecule a hydrophobic region capable of spanning the membrane, an attachment group used to attach the molecule to an electrode surface, a hydrophilic region intermediate said hydrophobic region and the attachment group, and a polar head group region attached to the hydrophobic region at a site remote from the hydrophilic region.

Abstract: An electrode strip for use in an electrochemical sensor for measuring a compound in a sample is provided, including an electrode support, a reference or counter electrode disposed on the support, a working electrode spaced from the reference or counter electrode on the support, a covering layer defining an enclosed space over the reference and working electrodes and having an aperture for receiving a sample into the enclosed space, and a plurality of mesh layers interposed in the enclosed space between the covering layer and the support, the covering layer having a sample application aperture spaced from said electrodes and said reference electrode spaced from said working electrode at a position remote from and on the opposite side of said working electrode from said aperture.

Abstract: A regenerable biosensor probe adapted for positioning in a bioreactor comprises a selectively permeable interface membrane, a porous protein-receiving matrix adjacent to the interface membrane, an indicating electrode, an inlet conduit through which fresh protein conjugate may flow to the protein-receiving matrix, and an outlet conduit through which spent protein conjugate may be removed from the protein-receiving matrix. A selectively permeable interface membrane, which may be used in a biosensor system to separate biochemical, optical or other processes from an analyte matrix comprises a supporting mesh, a perfluorosulfonic acid polymer impregnated substrate and a homogenous film of perfluorosulfonic acid polymer.A method of preparing this interface membrane comprises fixing a substrate on to a supporting mesh to form a substrate membrane, casting a perfluorosulfonic and polymer on the substrate membrane and curing the product to so formed.

Abstract: A microbiocidal solution for in vivo and in vitro treatment of microbial infections includes an electrolyzed saline containing regulated amounts of ozone and active chlorine species wherein the ozone content is between about 5 and 100 mg/L and the active chlorine species content of between about 5 and 300 ppm. The active chlorine species comprises free chlorine, hypochlorous acid and the hypochlorite ion as measured by a chlorine selective electrode. The solution is prepared by subjecting a 1% or less saline to electrolysis under conditions sufficient to produce the desired active ingredients. The solution is preferably utilized at an isotonic saline concentration and may be adjusted with hypertonic saline. The solution may be used for the in vitro treatment of infected whole blood, blood cells or plasma to reduce contamination and is effective in treatment of fluids infected with HIV, hepatitis and other viral, bacterial and fungal agents.

Abstract: A protein such as an enzyme of antibody is immobilized by crosslinking crystals of the protein with a multifunctional crosslinking agent. The crosslinked protein crystals may be lyophilized for storage. A preferred protein is an enzyme such as thermolysin, elastase, asparaginase, lysozyme, lipase or urease. Crosslinked enzyme crystals preferably retain at least 91% activity after incubation for three hours in the presence of a concentration of Pronase.TM. that causes the soluble uncrosslinked form of the enzyme to lose at least 94% of its initial activity under the same conditions. A preferred enzyme:Pronase.TM. ratio is 1:40. Enzyme crystals that are crosslinked may be microcrystals having a cross-section of 10.sup.-1 mm or less.

Abstract: A solid state, multi-use electrochemical sensor having an electrically nonconductive substrate, a working electrode, and a semi-permeable membrane covering the working electrode. The working electrode includes an electrically conductive material adhered to a portion of the substrate. A first portion of the conductive material is covered with an electrically insulating dielectric coating, and a second portion of the conductive material is covered with an active layer. The active layer includes a catalytically active quantity of an enzyme carried by platinized carbon powder particles, which are distributed throughout the active layer. A sensor package for incorporating a sensor is provided.

Abstract: The present invention is a novel, ultra-small tip, internal referenced, amperometric microbiosensor that uses an immobilized biological interface to measure the concentration of an analyte in a specimen. It consists of a casing that narrows to an aperture having a diameter at the tip no greater than 4 .mu.m; enclosed within the casing a reference electrode and a working electrode both immersed in electrolyte; within the aperture, an inner polymer film, an immobilized biological interface layer, and an outer specimen-compatible, non-virulent polymer film. Another important feature of the present invention is that the microbiosensor can readily be encased in a durable protective sheath. The microbiosensor is especially useful in situ for specimens that cannot be mixed, such as in situ compounds in unmixed fluid, or semi-solid specimens.

Abstract: An enzyme electrode, specific binding or the like electrochemical assay method capable of performing always stably high detection sensitivity (responsibility) and reappearance even in the case of blood, urine and the like samples that contain interfering substances and also of applying suitably to disposable use, and a novel p-phenylenediamine compound which is used in the assay method.

Abstract: A polymeric membrane electrode gives potentiometric responses to macromolles, such as protamine, in solution or biological specimens. A protamine-responsive membrane includes a lipophilic cation-exchange material for ionic macromolecules in a specially formulated plasticized, polymeric matrix material. Potentiometric response to protamine has been observed in membranes comprising 30-70 wt. % polymeric matrix material, such as polyvinyl chloride; 1-3 wt. % salt of a tetraphenylborate, such as potassium tetrakis(4-chlorophenyl) borate or salt of an organophosph(on)ate, such as calcium bis-[4-(1,1,3,3-tetramethylbutyl)phenyl] phosphate; and 30-70 wt. % of a plasticizer, such as 2-nitrophenyl octyl ether or tris (2-ethylhexyl) phosphate.

Abstract: A method and apparatus provide a system for measuring a measurable component in a sample. A sample is introduced into a chamber. A permeable membrane to the measurable component allows the component to pass into a second chamber. In the second chamber the component is measured directly or reacted in the presence of an enzyme to generate a detectable product detected by a detector therein. The second chamber is then flushed. The second chamber is only of a size sufficient to contain enough liquid to wet the detector therein.

Abstract: A solid shale, multi-use electrochemical sensor having an electrically nonconductive substrate, a working electrode, and a semi-permeable membrane covering the working electrode. The working electrode includes an electrically conductive material adhered to a portion of the substrate. A first portion of the conductive material is covered with an electrically insulating dielectric coating, and a second portion of the conductive material is covered with an active layer. The active layer includes a catalytically active quantity of an enzyme carried by platinized carbon powder particles, which are distributed throughout the active layer. A sensor package for incorporating a sensor is provided.

Abstract: A small diameter flexible electrode designed for subcutaneous in vivo amperometric monitoring of glucose is described. The electrode is designed to allow "one-point" in vivo calibration, i.e., to have zero output current at zero glucose concentration, even in the presence of other electroreactive species of serum or blood. The electrode is preferably three or four-layered, with the layers serially deposited within a recess upon the tip of a polyamide insulated gold wire. A first glucose concentration-to-current transducing layer is overcoated with an electrically insulating and glucose flux limiting layer (second layer) on which, optionally, an immobilized interference-eliminating horseradish peroxidase based film is deposited (third layer). An outer (fourth) layer is biocompatible.

Abstract: A managing method includes steps of selecting a function according to the type of an electrode mounted on the portable blood sugar value-measuring apparatus; executing a process of clocking a predetermined period of time; deciding whether or not the clocking process has been switched over to a different process while the predetermined period of time is being clocked; and reading out data of measured blood sugar values stored in a storing device from a termination point of the first predetermined period of time when the first predetermined period of time has terminated without the switch-over from the first clocking process to the blood sugar value-measuring process being decided in the deciding process.

Abstract: An oxygen electrode comprising a plastic sheet, two or three electrode patterns formed on the plastic sheet, a paraffin layer formed on the peripheral portion of the plastic sheet for delineating a sensitive area, a carrier sheet impregnated with an electrolyte and placed on the central portion or the sensitive area of the plastic sheet, and a gas permeable membrane covering the carrier sheet and the paraffin layer. A biosensor may be also provided by further providing a microorganism or enzyme-immobilized layer on the gas permeable membrane of the above oxygen electrode.

Abstract: A new group of Os(II) and Os(III) compounds useful as redox mediators in electrochemical biosensors. These compounds have 1) low oxidation potential, 2) fast reaction kinetics between the electroactive center of an enzyme and the compound, 3) slow oxidation of osmium by oxygen, and 4) excellent solubility in aqueous medium. These mediators are particularly useful as a component of a reagent used in an electrochemical biosensor, wherein the biosensor is useful for measuring analytes from a biological fluid, such as blood.

Abstract: The biosensor of this invention can quantify a substrate in a sample liquid by electrochemically measuring the amount of an electron acceptor that has been reduced by electrons generated in a reaction between the substrate and an oxidoreductase. The biosensor has an electrically insulating substrate and an electrode system formed on the substrate including a working electrode, a counter electrode and a third electrode used for detecting a liquid junction. The third electrode can be used merely for detecting a liquid junction, or can be used as both a reference electrode and a liquid junction detecting electrode.

Abstract: A seal and wiper assembly covers the opening of a reservoir of buffer solution in a blood glucose level. A monitor. A replaceable test cap is designed for single use. As the test cap is installed, a clock starts to run. After a predetermined time, the clock disables the monitor. As the test cap is removed from the buffer, the assembly wipes the buffer from the glucose sensor.

Abstract: Salicylate hydroxylase isolated from Pseudomonas bacteria can be used to determine the level of salicylate in a body fluid by reacting a sample of the fluid with the enzyme and monitoring the conversion of salicylate to catechol. A method of purifying the enzyme from crude bacterial extract using a salicylate affinity column is also disclosed.

Abstract: A biosensor for quantification of a specific component contained in various biological samples comprises an electrically insulating base plate, an electrode system including a working electrode and a counter electrode which are provided on the electrically insulating base plate, a reaction layer formed on the electrode system including at least an oxido-reductase, and an enclosure member having a hollow space constituting a sample supplying channel on the electrically insulating base plate, wherein substantially the whole of the reaction layer is exposed to the hollow space.

Abstract: The miniaturized oxygen electrode having a small size exceeding the limit of miniaturization of the prior art electrode comprises an insulating substrate 21, 31 and, provided thereon, a pair of electrode patterns 22, 23 each comprising an active section 22A, 23A, a terminal section 22C, 23C for external connection, and a lead wire portion 22B, 23B for the connection thereof, the active sections 22A, 23A being mutually connected through an electrolyte-containing material 24, the electrolyte-containing material 24 being covered with an oxygen-permeable membrane 28, the lead wire portion 22B of at least one 22 of the electrode patterns extending below the active section 23A of at least one of other electrode patterns, 23, with an insulating layer 29 intervening between the lead wire portion 22B and the active section 23A.

Abstract: A biosensor for measuring alcohol concentration includes an insulating substrate and an amperometric device formed on the insulation substrate, having a plurality of conductive lines and connective pads and a plurality of electrodes. An enzyme immobilized layer is formed on one of the plurality of electrodes of the amperometric device and an enzyme paste is printed on the amperometric device. An outer membrane is formed on the substrate having the plurality of electrodes for forming an electrode system and an insulating membrane is formed on the substrate, except on the outer membrane.

Abstract: Sensor devices for examining fluid samples having, between the sample under examination and a detector, a membrane made of polyvinyl chloride in un-plasticized form. This membrane material acts as a barrier to paracetamol and sugars but is permeable to hydrogen peroxide and to oxalate, so these species can be determined after passing through the membrane. When they are not present as such in the sample, they may be formed from analytes which are sought (e.g. by enzymic action, which is especially applicable to the determination of glucose, using an oxidase enzyme). The membranes may be made by solvent casting, conveniently to a thickness of 10 to 40 .mu.m, and used in electrolytic systems with a platinum anode. The membrane material can be formed into multi-layer membranes, which may incorporate layers of material to protect it or modify the permeability, or added materials for example enzymes.

Abstract: A biosensor comprising a substrate material, at least one antibody covalently immobilized on the substrate material, and a pair of metal contact electrodes for measuring the impedance of the biosensor. A process for producing a biosensor in accordance with this invention as well as a process for utilizing the biosensor are also disclosed.

Abstract: The present invention relates to a system for detecting, in a reliable, precise and highly sensitive manner, biochemical agents such as enzymes that catalyze a redox potential change. One electrode is used to measure redox potential changes in an aqueous electrolyte containing the biochemical agents. Another electrode is used to deliver a feedback current to the electrolyte in response to measured Changes in electrolyte redox potential. The amount of feedback current or charge delivered through the electrode to the electrolyte is sufficient in magnitude to maintain a constant redox potential. Quantitation of the amount of feedback current or charge necessary to maintain the constant redox potential may then be used to determine the amount of biochemical agents present. Alternatively, the redox potential need not be kept constant, but instead may be allowed to reach a new steady-state.

Abstract: A biosensor for quantifying a specific compound has a reaction layer containing at least an enzyme, and an electrode system having a working electrode and a counter electrode formed on an insulating base plate; the biosensor detects the specific compound contained in a sample on the basis of an electrochemical response. In quantifying, the working electrode and the counter electrode are short-circuited before the voltage is applied therebetween. The short-circuiting eliminates measuring errors that may occur due to nonuniform dissolution of the reaction layer in a sample, and achieves highly reliable quantification of a specific compound.

Abstract: The present invention relates to a method of determining histamine content as a freshness index of food. An examination liquid is injected in a reaction cell, an amount of dissolved oxygen (DO) is recorded through an oxygen sensor and an amplifier in the recorder. Then, an enzymatic reagent having histamine oxidase activity is injected in the reaction cell, a decrease in the dissolved oxygen is recorded in the recorder, and the histamine concentration is determined on the basis of the decrease by a micro computer.

Abstract: A voltage applying method for a hydrogen type enzyme electrode in a chemical sensor and using a pair of working electrodes, a reference electrode and a counter electrode includes detecting a contact of a test specimen with the enzyme electrode; keeping a potential applied to the working electrodes at a first potential of substantially zero for a first preset time; applying a second potential that is higher than a hydrogen peroxide detect potential to the working electrodes for a second preset time; dropping the second potential to a third potential below zero potential; and sweeping from the first potential to a fourth potential higher than said hydrogen peroxide detect potential at a fixed rate. Other variations of the method are disclosed.

Abstract: An electrochemical sensor cartridge with at least three reservoir cells, the floor of each cell in leakproof contact with the surface of an electrode assembly whose conductivity is affected by the presence of an analyte in that cell.

Abstract: A glucose sensitive FET sensor is provided which includes a substrate, a source electrode formed in the substrate, a drain electrode formed in the substrate, a hydrogen ion sensitive film formed on the substrate to cover the source electrode and the drain electrode, and a thin enzyme immobilized membrane formed on the hydrogen ion sensitive film and containing glucose oxidase and gluconolactonase. Also provided is a method of producing a glucose sensitive FET sensor which includes the steps of preparing an enzyme immobilized membrane as a thin film containing glucose oxidase and gluconolactonase and forming the membrane on a hydrogen ion sensitive film which is formed on a substrate to cover a source electrode and a drain electrode, both of which are formed in the substrate.

Abstract: Oxidoreductases are chemically modified so as to change their net charge at a given pH. Through such modification the adsorption of the enzymes on surfaces, their retention in similarly or oppositely charged polymer membranes and their binding with similarly or oppositely charged macromolecules, particularly redox macromolecules, is controlled. The modified enzymes, of which modified recombinant glucose oxidase is an example, are useful in biosensors, e.g. for glucose; as marker enzymes of antigens or antibodies in immunosensing; and as labels of nucleotide sequences in probes, e.g. for DNA nucleotide sequences.