PNIPAM/PEDOT:PSS Hydrogels for Multifunctional Organic Electrochemical Transistors

The development of multifunctional organic materials represents a vibrant area of research, with applications spanning from biosensing to drug delivery. This study shows the development of a multifunctional bioelectronic device suitable for prolonged temperature monitoring and drug delivery applications. The device relies on a conducting and thermo-responsive hydrogel made of poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate) (PEDOT:PSS) and poly(N-isopropylacrylamide) (PNIPAM). This multifunctional hydrogel is 4D printable by Digital Light Processing (DLP) method and exhibits optimal biocompatibility. The hydrogel features a low critical solution temperature (LCST) ≈35 °C, above which its resistance changes dramatically due to the shrinkage it undergoes with temperature. The integration of PNIPAM/PEDOT hydrogel into an organic electrochemical transistor (OECT) as the gate electrode allows to generate a miniaturized bioelectronic device with a reversible response to temperature variations between 25 to 45 °C, along with high sensitivity of 0.05 °C⁻¹. Furthermore, the PNIPAM/PEDOT hydrogel demonstrates its utility in drug delivery, achieving an Insulin-FITC release rate of 82 ± 4% at 37 °C, mimicking human body conditions. The hydrogel's functionality to store and release the insulin does not compromise its thermo-responsivity and the overall performance of the OECT. This multifunctional OECT opens new avenues for the development of customizable and personalized sensing and drug-delivery systems.