An analyte monitor includes a sensor, a sensor control unit, and a display unit. The sensor has, for example, a substrate, a recessed channel formed in the substrate, and conductive material disposed in the recessed channel to form a working electrode. The sensor control unit typically has a housing adapted for placement on skin and is adapted to receive a portion of an electrochemical sensor. The sensor control unit also includes two or more conductive contacts disposed on the housing and configured for coupling to two or more contact pads on the sensor. A transmitter is disposed in the housing and coupled to the plurality of conductive contacts for transmitting data obtained using the sensor. The display unit has a receiver for receiving data transmitted by the transmitter of the sensor control unit and a display coupled to the receiver for displaying an indication of a level of an analyte. The analyte monitor may also be part of a drug delivery system to alter the level of the analyte based on the data obtained using the sensor.

Analyte Monitoring Device And Methods Of Use

Hydrogels have applications in surgery and drug delivery, but are never considered alongside polymers and composites as materials for mechanical design. This is because synthetic hydrogels are in general very weak. In contrast, many biological gel composites, such as cartilage, are quite strong, and function as tough, shock-absorbing structural solids. The recent development of strong hydrogels suggests that it may be possible to design new families of strong gels that would allow the design of soft biomimetic machines, which have not previously been possible.

Hydrogels for Soft Machines

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.

Subcutaneous glucose electrode

A sensor designed to determine the amount and concentration of analyte in a sample having a volume of less than about 1 μL. The sensor has a working electrode coated with a non-leachable redox mediator. The redox mediator acts as an electron transfer agent between the analyte and the electrode. In addition, a second electron transfer agent, such as an enzyme, can be added to facilitate the electrooxidation or electroreduction of the analyte. The redox mediator is typically a redox compound bound to a polymer. The preferred redox mediators are air-oxidizable. The amount of analyte can be determined by coulometry. One particular coulometric technique includes the measurement of the current between the working electrode and a counter or reference electrode at two or more times. The charge passed by this current to or from the analyte is correlated with the amount of analyte in the sample. Other electrochemical detection methods, such as amperometric, voltammetric, and potentiometric techniques, can also be used. The invention can be used to determine the concentration of a biomolecule, such as glucose or lactate, in a biological fluid, such as blood or serum. An enzyme capable of catalyzing the electrooxidation or electroreduction of the biomolecule is provided as a second electron transfer agent.

Small volume in vitro analyte sensor

An electrochemical analyte sensor formed using conductive traces on a substrate can be used for determining and/or monitoring a level of analyte in in vitro or in vivo analyte-containing fluids. For example, an implantable sensor may be used for the continuous or automatic monitoring of a level of an analyte, such as glucose, lactate, or oxygen, in a patient. The electrochemical analyte sensor includes a substrate and conductive material disposed on the substrate, the conductive material forming a working electrode. In some sensors, the conductive material is disposed in recessed channels formed in a surface of the sensor. An electron transfer agent and/or catalyst may be provided to facilitate the electrolysis of the analyte or of a second compound whose level depends on the level of the analyte. A potential is formed between the working electrode and a reference electrode or counter/reference electrode and the resulting current is a function of the concentration of the analyte in the body fluid.

Electrochemical analyte sensor

: Hydrogen peroxide is efficiently electroreduced at an electrode modified with a hydrophilic, permeable film of horseradish peroxidase (HRP) covalently bound to a 3-dimensional epoxy network having polyvinyl pyridine (PVP)-complexed Os(bpy)2Cl+3/+2 redox centers. The sensitivity of the resulting H202 cathode at O.OV(SCE) is 1Acm(-2)M(-1). Its current increases linearly with H2O2 concentration in the 1x10(-7)M(-)2x10(-4)M range. Related NAD(P)H cathodes are based on stoichiometric homogeneous reduction of 02 to H202 by NADH or NAD(P)H. The reduction involves two known steps. In the first step, NAD(P)H transfers two electrons and a proton to a dissolved quinoid. The quinoids are typically derived of phenazines, however phenothiazine and phenoxazine derivatives are also useful. In the second step, two electrons and a proton are transferred from the reduced quinoid to O2. This reaction produces H202 and the original quinoid. Because the two reactions are quantitative, the sensitivity and the linear range of the resulting NADH and NADPH electrodes are identical with those of the H202 electrode, 1Acm(-2)M(-1) and 1x10(-7)M (-2)2x10(-4)M respectively.

Hydrogen peroxide and .beta.-nicotinamide adenine dinucleotide sensing amperometric electrodes based on electrical connection of horseradish peroxidase redox centers to electrodes through a three-dimensional electron relaying polymer network

: Electrooxidizable ascorbate, urate and acetaminophen, that interfere with amperometric glucose assays are completely and rapidly oxidized by hydrogen peroxide in a multilayer electrode. The multilayer electrode is composed of an immobilized, but not electrically wired , horseradish peroxidase (HRP) film coated onto a film of electrically wired glucose oxidase (GOX). The wired enzyme is connected by a redox epoxy network to a vitreous carbon electrode. The current from the electrooxidizable interferants is decreased by their peroxidase-catalyzed Biosensors; Amperometric; Interferants. preoxidation by a factor of 2500 and the glucose/interferant current ratio is increased 103 fold. Undesired electroreduction of hydrogen peroxide can result when HRP is also wired to the electrode. Such unwanted 'wiring' is prevented by incorporating an electrically insulating barrier layer between the wired GO film and the HRP film. The hydrogen peroxide necessary for elimination of interferants can be added externally, or, when this is not possible, it can be generated in situ by means of a coupled enzyme reaction.

Elimination of electrooxidizable interferant-produced currents in amperometric biosensors

: Proteins and glycoproteins of enzymes behave with respect to electron transport, but not ion transport, as good electrical insulators. We have shown that these insulators can be made sufficiently electron conducting to allow the flow of a current between reaction centers of redox enzymes and electrodes equaling or exceeding the current associated with the turnover of the enzymes. In order for such a current to flow it is necessary to introduce into the enzyme proteins of glycoproteins fast electron relaying centers, so as to reduce the electron transfer distances.

Ruben Maidan

Papers

Hydrogen peroxide and .beta.-nicotinamide adenine dinucleotide sensing amperometric electrodes based on electrical connection of horseradish peroxidase redox centers to electrodes through a three-dimensional electron relaying polymer network

Elimination of electrooxidizable interferant-produced currents in amperometric biosensors

Amperometric biosensors based on three-dimensional hydrogel-forming epoxy networks