The effect of nanoscale surface electrical properties of partially biodegradable PEDOT-co-PDLLA conducting polymers on protein adhesion investigated by atomic force microscopy

This study used atomic force microscopy (AFM) to elucidate the interaction of fibronectin (FN) on a conducting and partially biodegradable copolymer of poly(3,4-ethylenedioxythiophene) and poly(D,L-lactic acid) (PEDOT-co-PDLLA) in three different proportions (1:05, 1:25 and 1:50). The copolymers with higher PEDOT:PDLLA content ratios (1:05 and 1:25) had higher surface roughness, water contact angle, with current and conductivity occurring at discrete large grain structures on the surface. In contrast, the lower PEDOT:PDLLA content ratio (1:50) did not show high conductivity grains but showed homogenous surface conductivity across the entire surface. Using FN-functionalized AFM probes, force measurements showed that the copolymers with higher PEDOT content (1:05 and 1:25) had significantly lower adhesion forces (~0.2-0.3 nN), while the copolymer with the lower content of PEDOT (1:50) had stronger FN interactions with significantly higher adhesion forces of 1 nN. By correlating the spatially distributed electrical surfaces with FN interactions, we observed that the synthesis of 1:50 PEDOT:PDLLA produced more uniformly doped polymer films that facilitated FN adsorption through favorable interactions with accessible sulfate dopants. Importantly, these findings are correlated with previous studies showing increased stem cell migration and differentiation on 1:50 PEDOT:PDLLA surfaces compared with surfaces with 1:05 and 1:25 PEDOT:PDLLA ratios.