Enzyme Electrode Impedance Biosensor for Diffusion-Independent Quantification

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Solution Overview

Problem

Conventional biosensors using direct electron transfer-type enzyme electrodes face challenges in measurement accuracy due to substrate diffusion effects, particularly in amperometric measurements.

Innovation Solution

The method involves using a biosensor with an enzyme electrode and a counter electrode, applying AC voltage with varying frequencies and a DC bias higher than the oxidation-reduction potential, to measure impedance and quantify substances like glucose based on charge transfer resistance, independent of mass transfer limitations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If amperometric measurement is used in direct electron transfer-type biosensors, then electron transfer between enzyme and electrode is achieved, but measurement accuracy deteriorates due to substrate diffusion effects

Engineering Contradiction:

Improvemeasurement accuracyVSAvoidsubstrate diffusion effect

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent changes the measurement parameter from current (amperometric) to impedance (electrochemical impedance spectroscopy). By measuring impedance instead of current, the system eliminates the harmful effect of substrate diffusion on measurement accuracy while maintaining direct electron transfer between the enzyme and electrode.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the amperometric measurement mechanism with an electrochemical impedance spectroscopy mechanism. This substitution changes the fundamental measurement approach from detecting current flow to detecting impedance characteristics, thereby eliminating diffusion-related measurement errors.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If conventional biosensor measurement methods are used, then substrate concentration can be detected, but measurement stability deteriorates due to mass transfer limitations

Engineering Contradiction:

Improvemeasurement stabilityVSAvoidmass transfer limitation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the measurement parameter from current to impedance, which fundamentally alters what is being measured. Impedance measurement reflects the electron transfer kinetics at the electrode interface without being influenced by mass transfer limitations, thereby improving measurement stability and reliability.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If impedance measurement with AC voltage is applied to enzyme electrode, then quantification accuracy improves by eliminating diffusion effects, but device complexity increases due to additional measurement circuitry

Engineering Contradiction:

Improvequantification accuracyVSAvoidmeasurement circuit complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent makes the biosensor system multi-functional by integrating both amperometric and electrochemical impedance spectroscopy measurement capabilities. This allows the same enzyme electrode to be used for different measurement modes, improving quantification accuracy while avoiding the need for separate dedicated devices for each measurement type.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enables accurate quantification of substances by correlating impedance values with concentration, reducing the impact of diffusion and other mass transfer-related factors, thus providing stable and precise measurement results.

Implementation Method 1

electrons generated by an enzyme reaction are directly transferred to the electrode without involvement of an oxidation-reduction substance such as an electron transfer mediator, thereby achieving electron transfer between the enzyme and the electrode

Methodology Applied

Scientific EffectDirect electron transfer: Conduction (electrical)

Implementation Method 2

enzymatic catalytic reaction current caused by oxidation-reduction reaction using an electron transfer mediator

Methodology Applied

Scientific EffectOxidation-reduction reaction: Redox Reactions

Implementation Method 3

when sine waves having varying frequencies are applied together with an overvoltage (direct current (DC) bias) higher than the oxidation-reduction potential of the electron transfer subunit or the artificial electron acceptor, the resulting impedance value such as charge transfer resistance correlates with the concentration of the substance in the sample

Methodology Applied

Scientific EffectElectrochemical impedance: Electrical Impedance Tomography

Data Source

PatentEP3447483B1Novel biosensing technology based on enzymatic electrochemical impedance measurement

Publication Date: 2022.01.12 ARKRAY INC

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AI summary

A method for quantifying a substance, which method includes the steps of: introducing a sample containing a measurement target substance to a biosensor (B) comprising an enzyme electrode (12) comprising an electrode (12a) and an oxidoreductase (12b) placed on the electrode in a state where direct electron transfer with the electrode occurs, and a counter electrode (13); applying an AC voltage to the enzyme electrode to carry out impedance measurement; and calculating the concentration of the substance based on an index obtained by the impedance measurement.