Development of an ion sensitive field effect transistor based urea biosensor with solid state reference systems.

Area of Science:

• Biosensor technology
• Field-effect transistor applications
• Enzyme immobilization techniques

Background:

• Ion-sensitive field-effect transistors (ISFETs) are crucial for electrochemical sensing.
• Urease biosensors are vital for urea detection in various applications.
• Miniaturization of biosensors requires integrated reference systems.

Purpose of the Study:

• To investigate ISFET-based urease biosensors with integrated solid-state reference systems.
• To evaluate single-ended and differential readout electronics for miniaturized biosensors.
• To optimize transconductance matching between biosensor and reference field-effect transistors (REFETs).

Main Methods:

• Fabrication of sensing membranes with urease immobilized in a conducting polymer matrix.
• Development of ISFET biosensors coupled with solid-state reference systems.
• Optimization of REFET and enzyme field-effect transistor (EnFET) membranes for transconductance matching using photoresist/Nafion™ ratios.

Main Results:

• Urease activity remained high with responses of 12.9–198.1 mV for urea concentrations of 8–240 mg/dL.
• Demonstrated feasibility of miniaturization for ISFET-based urease biosensors.
• Achieved optimal transconductance matching in differential pairs, enabling a wide dynamic operating range.

Conclusions:

• The developed miniaturized biosensors with differential arrangement achieved urea response curves comparable to conventional large sensors.
• The integration of solid-state reference systems facilitates the miniaturization of ISFET-based urease biosensors.
• Transconductance matching is key for achieving wide dynamic range and reliable performance in differential biosensor systems.