Fabrication of Curli-PEDOT:PSS Composites for Bioelectronics

Bioelectronic materials must compatibly interface between electronic and biological systems and like all areas of growing technology, aim to be sustainable and renewable to support a fast- changing world . The conductive polymer, poly(3,4 -ethylenedioxythiophene) polystyrene sulfonate ( PEDOT:PSS) is widely studied for bioelectronic applications because of its high conductivity and ease of processing . When PEDOT:PSS has been combined with biopolymers such as cellulose or proteins such as squid ring teeth proteins , the resulting composite s have exhibited synergistically improved properties compared to each material alone . In this study, we combine PEDOT:PSS with a class of bacterial proteins produced by E. coli called curli fibers to prepare a protein -polymer composite . Curli fibers exhibit stiffness, genetic tunability and resistance to environmental stresses such as heat. They can be produced following a simple and scalable procedure , are biodegradable and biocompatible. These properties make curli fibers excellent candidates for biomaterial applications. A process was created to mix the two components into a uniform composite by testing different mixing strategies and thermal processing, followed by drop -casting into a substrate. The optimal preparation process was identified by v isualizing the drop -cast films using an optical microscope and measuring their conductivity. To confirm the homogeneous distribution of the components, energy dispersive x- ray analysis was performed. We characterized the conductivity and morphology of the composite films with curli fiber content ranging from 0 to 100% (w/w). It was observed that composites containing 60% (w/w) curli fibers and 40 % (w/w) PEDOT:PSS exhibited a unique surface morphology and the highest conductivity at ~ 9 S/cm and. We further investigated the water-stimulated electrical self-healing nature of this composite ratio using microscopy and electrical measurements. We conducted various mechanical tests to investigate the mechan ical tunability of the materials. The composite exhibited fast and high electrical recovery compared with pristine PEDOT:PSS film and a significant increase in conductivity after the addition of water, suggesting a synergistic interaction between PEDOT:PSS and the curli fibers. The addition of curli fibers to the composite lowered the Young’s and Shear moduli of the material. We genetically engineered a fluorescent fusion protein to curli fibers and visualized the fluorescence in curli-PEDOT:PSS films.