Organic Electrochemical Transistors and Foreign Body Reaction: First Steps Toward Long‐Term Implantable Biosensing

ABSTRACT Organic Electrochemical Transistors (OECT) have been widely used to detect a myriad of analytes and signals, ranging from glucose content in sweat to brain epileptiform activity. Due to their biocompatibility, small footprint, conformability, and high signal amplification, OECTs can not only be used in wearable, but also in implanted sensor systems, providing superior signal quality. However, although there is a risk of triggering the Foreign Body Reaction (FBR) with implantation, FBR impact on OECTs has rarely been discussed. Therefore, here we evaluate the effect of the FBR fibrotic response on OECT performance, i.e. when the OECT is covered by protein layers, in vitro. In more detail, we analyze poly(3,4‐ethylenedioxythiophene):poly (styrene‐sulfonate) (PEDOT:PSS) based OECTs and intentionally cover their channels with protein layers commonly formed during FBR, such as albumin, collagen and fibrinogen. Despite slightly increasing devices' switching time, proteins do not hamper their operation. Further coverage by yeast cells as a proof of concept of wound healing process also did not jeopardize OECT functioning, indicating devices could resist the FBR fibrotic response without anti‐FBR strategies.