Fabrication of Curli Fiber-PEDOT:PSS Biomaterials with Tunable Self-Healing, Mechanical, and Electrical Properties.

ABSTRACT

Poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOTPSS) is a highly conductive, easily processable, self-healing polymer. It has been shown to be useful in bioelectronic applications, for instance, as a biointerfacing layer for studying brain activity, in biosensitive transistors, and in wearable biosensors. A green and biofriendly method for improving the mechanical properties, biocompatibility, and stability of PEDOTPSS involves mixing the polymer with a biopolymer. Via structural changes and interactions with PEDOTPSS, biopolymers have the potential to improve the self-healing ability, flexibility, and electrical conductivity of the composite. In this work, we fabricated novel protein-polymer multifunctional composites by mixing PEDOTPSS with genetically programmable amyloid curli fibers produced byEscherichia coli bacteria. Curli fibers are among the stiffest protein polymers and, once isolated from bacterial biofilms, can form plastic-like thin films that heal with the addition of water. Curli-PEDOTPSS composites containing 60% curli fibers exhibited a conductivity 4.5-fold higher than that of pristine PEDOTPSS. The curli fibers imbued the biocomposites with an immediate water-induced self-healing ability. Further, the addition of curli fibers lowered the Young's and shear moduli of the composites, improving their compatibility for tissue-interfacing applications. Lastly, we showed that genetically engineered fluorescent curli fibers retained their ability to fluoresce within curli-PEDOTPSS composites. Curli fibers thus allow to modulate a range of properties in conductive PEDOTPSS composites, broadening the applications of this polymer in biointerfaces and bioelectronics.