Near-Field Communications sensor for lactate determination in saliva and sweat using organic electrochemical transistors (OECTs)

Abstract

Organic electrochemical transistors (OECTs) are attractive devices for the next generation of biosensors, but their widespread adoption has been limited by the need for expensive and bulky measurement instruments. This work addresses this limitation by presenting a low-cost, low-power readout circuit for biasing and measuring the drain current of OECTs, specifically targeting portable and wearable applications for point-of-care testing (POCT). The proposed system utilizes a modified microcontroller-based potentiostat that is compatible with single positive voltage sources. It also includes Near Field Communication (NFC), which allows data to be retrieved wirelessly using a smartphone. A proof-of-concept lactate sensor is presented, designed for measuring lactate concentration in sweat and saliva. The sensor is based on an OECT with a platinum-coated gate and a Nafion membrane that immobilizes the lactose oxidase enzyme, significantly improving the selectivity of the substance to be measured. Low detection limits of 0.35 mM and 0.0485 mM have been achieved in sweat and saliva, respectively. This research provides a complete, low-cost, and non-invasive solution for OECT-based biosensors.