Signal amplification in enzyme-based amperometric biosensors

Area of Science:

• Electrochemistry
• Biotechnology
• Materials Science

Background:

• Reagentless biosensors offer advantages in clinical diagnostics.
• Enzyme-based biosensors are crucial for detecting various analytes.
• Current amplification methods are needed to improve biosensor sensitivity.

Purpose of the Study:

• To investigate a unique mode of current amplification in reagentless biosensors.
• To explore the role of enzyme-polymer interfaces in signal enhancement.
• To assess the feasibility of this amplification in clinically relevant enzymes.

Main Methods:

• Enzyme-polymer films (chitosan-based) were prepared with covalently attached enzymes and cofactors.
• Carbon nanotubes were incorporated to enhance conductivity.
• Biosensors were constructed by sandwiching the enzyme-polymer film between an electrode and a Nafion film.
• Amperometric enzyme assays and pH-sensitive iridium oxide films were used for data collection.

Main Results:

• Coating biosensors with Nafion led to a current increase of up to 1000%.
• Signal amplification correlated with the interplay between enzyme activity-pH profiles and Nafion-induced pH changes.
• The observed current increase was attributed to pH-driven enzyme activity enhancement.

Conclusions:

• A novel pH-mediated current amplification mechanism was identified in reagentless biosensors.
• This signal amplification strategy is effective for enzymes like alcohol dehydrogenase and glucose oxidase.
• The method shows promise for improving the performance of various sandwich-type enzyme biosensors.