Sensitive organic electrochemical transistor biosensors: Comparing single and dual gate functionalization and different COOH-functionalized bioreceptor layers

We developed new measurement configurations based on organic electrochemical transistors (OECTs). Three types of COOH-functionalized bioreceptor layers were deposited on indium tin oxide (ITO) electrodes on poly(ethylene terephthalate) (PET) substrates and their performance was tested using single gate functionalization organic electrochemical transistor (S-OECT) and dual gate functionalization organic electrochemical transistor (D-OECT) configurations. The three layers included one p-type semiconductor, one insulator, and one self-assembled layer, and the dual gates were connected in series through buffer solutions, so the solution-electrode interfaces had the opposite polarities. We investigated the sensitivities of these systems using the human IgG antigen-human IgG antibody receptor pair for main experiments, and drifts of antibody-functionalized gates without analytes as control experiments. Drifts without analyte can obscure the real sensitivity. We show that the D-OECT has the capability to cancel the drifts, and is also beneficial for showing the sensitivity more exactly. This configuration has the ability to increase the accuracy of antibody-antigen interaction detection, and further decrease or eliminate the effect of ions in the buffer solution. We also prove that the D-OECT can work well with different bioreceptor materials, which indicates that the system can be further applied to different conditions.