Nanoscale Bioreceptor Layers Comprising Carboxylated Polythiophene for Organic Electrochemical Transistor-Based Biosensors

We investigated the carboxylated conjugated polymer poly 3-(3-carboxypropyl)thiophene-2,5-diyl as a nanosized (200–350 nm) biomolecule receptor layer on the channel of organic electrochemical transistor (OECT) devices. Myelin basic protein, SARS-CoV-2 spike glycoprotein S1, and their antibodies (10 nm size scale) were alternately used in the attached molecule form as receptors and analytes. Sub-ng detection in buffer was observed, and response to S1 was also obtained in clinical serum. Changes in threshold voltage and current output from OECT transfer curves and measurements of open circuit potential between receptor layers and a reference electrode provided complementary responses and insight into the response mechanisms, guiding further development of electrochemical field-effect and voltammetric protein sensors based on polymeric active layers with nanoscale functionality.