Lactate Biosensor Based on Aerosol Jet Printed Organic Electrochemical Transistors (OECTs) for Real Time Monitoring

Diabetic patients have an increasing risk of developing the foot ulcers. Diabetic foot ulcer (DFU), as one of the complications for diabetics, has bothered people for many years. Clinical research has shown that real time monitoring of the lactate concentration helps guide therapy and improve patient outcome [1]. To reduce blood tests for lactate level measurements, non-invasive and low-cost reliable biosensors need to be developed for monitoring.<br/><br/>In this research, we developed a 3D-printed lactate sensor on top of the flexible Kapton substrate. Organic electrochemical transistors (OECTs) are chosen for the biosensors because of its good performance under aqueous environments and signal amplification. Sensors are fabricated using Optomec Aerosol Jet 5X printer with Au as the source and drain electrode, Pt as the gate, poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonate (PEDOT:PSS) as the channel and polyimide as the insulator layer. Layer by layer strategy is applied for functionalization, tetrathiafulvalene (TTF), chitosan, lactate oxidase (LoX) and bovine serum albumin (BSA) are drop-casted on top of the gate area and then both channel and gate are covered by gelatin to further improve the repeatability of the lactate sensor. Functionalized sensors can be stored in 1X PBS solution for over one month without any deterioration in their sensitivity. The device was measured in both PBS and artificial sweat buffer for comparison and obtained a broad sensitivity range between 10uM up to at least 50mM, which is far beyond the desired range. Blood lactate meter was using as the reference to calibrate the lactate sensor. The printed lactate sensor includes the ZIF connector which can be inserted onto a PCB board and will be used for further diabetic model test.<br/><br/><i>[1] Jia W, Bandodkar AJ, Valdés-Ramírez G, et al. Electrochemical tattoo biosensors for real-time noninvasive lactate monitoring in human perspiration. Analytical Chemistry. 85(14):6553-6560. doi:10.1021/ac401573r</i>