Molecular and histological evidence for the biocompatibility of PEDOT-coated microneedles in human skin

The increasing demand for real-time, continuous health monitoring has driven improvements in wearable and skin-attachable devices, particularly in sensing vital body signs and biomarkers. Research on conducting polymers (CPs) in these devices is also growing due to their low cost, flexibility, and versatile fabrication. However, despite their widespread use and claims of biocompatibility, there are limited studies on the biocompatibility of CPs in human skin, and those that exist have only been conducted using cell cytotoxicity or animal testing, lacking proper and comprehensive assessments. To address this critical gap, this study investigates the biocompatibility of CPs, represented by poly(3,4-ethylenedioxythiophene) (PEDOT), in excised human skin. In addition to the pathological evaluation of skin biopsies, a novel assessment of CP's impact on the expression of stress-related gene markers is reported, providing a comprehensive analysis at both the tissue and molecular levels. PEDOT-coated microneedles were implanted in the skin for transdermal interrogation, and after 24 hours of incubation, the exposed skin was studied using histology and RT-PCR. This paper offers fundamental insights for future CP-engineered devices in skin applications, contributing valuable data to the materials community regarding the true biocompatibility of these widely used materials.