PEDOT:PSS - A suitable interface for the enzyme PQQ-GDH on electrodes

The coupling of enzymes to electrodes has emerged as a key research area with applications in sensing, bioenergetics, and bioelectrocatalysis. Here, we present a minimalistic manufacturing strategy of such an enzyme electrode showing that the conducting polymer PEDOT:PSS deposited on gold electrodes serves as an excellent platform for mediator-free, oxygen-independent glucose detection using pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH). Adsorptive immobilisation of PQQ-GDH onto PEDOT:PSS yields significant catalytic currents in the presence of glucose. The glucose concentration dependent analysis results in an apparent K_m-value of 0.16 ± 0.03 mM. The catalytic signal can be tuned by adjusting polymer thickness and enzyme loading, while remaining stable across a pH range of 5.5 to 7.2. A less commonly used, but powerful method - faradaic impedance spectroscopy (f-EIS) - was successfully employed to monitor the enzymatic activity on the polymer layer. These findings support mediator-free bioelectrocatalysis and are consistent with direct electron transfer (DET) of the enzyme at the polymer-modified electrode. Our work opens new possibilities for biosensing applications, including flexible and stretchable field-effect transistor (FET) electronics where PEDOT:PSS is widely used.