OECT Based Lactate for Real Time Diabetic Wound Monitoring

Diabetic patients have an increasing risk of developing the diabetic foot ulcer (DFU). If left untreated these wounds can lead to foot amputations. Clinical research has shown that real time monitoring of the lactate concentration helps guide therapy and improve patient outcome [1]. Blood tests for measuring lactate levels can provide only the systemic levels. We are developing a non-invasive and low-cost lactate biosensor which can provide the localized wound lactate levels and can provide continuous measurements to monitor the wound health.<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 biosensor because of its good performance for the ion-to-electron transduction 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. The printed gate was first dropped casted with mixed chitosan and LoX. Functionalized sensors were stored under 4 degrees for 24hrs until they were fully dried and then washed with DI water and PBS solution. The device was measured in simulated wound fluid and has the response range from 500uM up to 5mM with a sensitivity of 117 uA/mM. Later, the layer-by-layer strategy was attempted according to the sequence nafion, chitosan and LoX, which exhibited a better range up to 10mM. Modifications to the functionalization method, such as carboxy-functionalized multi-walled carbon nanotubes (MWCNT) mixed with Tetrathiafulvalene (TTF), nafion, L-Lactate oxidase (LoX) and chitosan in acetic acid were dropped casted one after the other will be tried for further improvement. In addition, pH and extra reactions are also taken into consideration to help further correction for the lactate sensor. The results from the developed lactate sensor will be presented.<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>