Electrochemical Analyte Detection Apparatus and Method

Abstract

A method and apparatus for electrochemical detection of analyte in a sample makes use of a binding interaction and relies on the discovery that asymmetric distribution of a redox enzyme between two electrodes that occurs when a redox enzyme-containing reagent is immobilized at the surface of one electrode can be detected as a chemical potential gradient arising from an asymmetry, in the distribution of oxidized or reduced redox substrate. This chemical potential gradient can be detected potentiometrically by observing the potential difference between the electrodes in an open circuit, or amperometrically by observing the current flow between the electrodes when the circuit is closed. In both cases, the observation of asymmetry can be done without the application of an external potential or current to the electrodes.

Description

[0001]This application claims the benefit of U.S. Provisional Application No. 60 / 952,099 filed Jul. 26, 2007, which application is incorporated herein by reference for all purposes.BACKGROUND OF THE INVENTION[0002]This application relates to an apparatus and method for electrochemical detection of an analyte in a sample. The invention utilizes a specific binding relationship between the analyte and at least one reagent provided in the apparatus as a means for detecting the analyte.[0003]Analysis methods in which specific binding between an analyte and a reagent forms the basis for the assay are known. For example, in enzyme-linked immunoassay (EIA or ELISA) procedures, a sandwich is formed between an immobilized antibody and a mobile enzyme-antibody reagent when analyte is present through the interaction of the analyte with the antibody components. This results in the immobilization of the enzyme. The subsequent detection of immobilized enzyme is therefore indicative the presence of...

AI Technical Summary

Benefits of technology

[0065]The present invention provides the ability to perform binding assays for the detection of analyte with electrochemical detection, without the need to apply an external potential or current, and without the need for washing steps commonly employed in sandwich immunoassay procedures. Because of this, the apparatus used to perform the assay can be much simpler, easy to use, and less expensive. In addition, the device components in an electrochemical assay are more robust than those used for example in optical measurements, facilitating the manufacture of the low cost reusable meter for use with disposable test devices.

[0066]The present invention can make use of small samples of blood, tears, saliva, or sweat, with minimal invasiveness to the subject. (samples of less than 10 ul, preferably less than 1 ul are particularly desirable for blood tests). Further, the present invention can provide for very rapid test times. Common immunoassay procedures take up to an hour or more. The small volume of the test devices of the invention and the sensitivity of the test to small differences in the distribution of the enzyme means that shorter times (for example less the 30 minutes, more preferably less than 10 minutes, and most preferably less than 1 minute) are accessible depending on the concentration of analyte to be measured and the binding kinetics of the analyte with the binding elements of the mobile and immobilized reagents.

[0067]Depending on the nature of the sample and the redox substrate, it may be possible to use materials from the sample as part of the reaction system. For example, endogenous glucose can be used as a component of the redox substrate in a glucose oxidase-based system when the sample is a blood sample.

[0068]In the following examples, the utility and operability of the invention are demonstrated using a model system in which enzyme is coated onto the surface of one of two electrodes in an electrode pair. This model does not require the capture of the enzyme, and therefore is useful for modeling the after-capture behavior with a limited number of variables, although it does not provide a full picture of the binding kinetics of an actual test system. Capture of enzyme using reagents in other enzyme sandwich, competition and displacement assays and the like is well known.

Problems solved by technology

This results in the immobilization of the enzyme.

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