Synergizing Carbon: Eumelanin/Graphene-Like Hybrid as Promising Candidate for Applications in Bioelectronics and Nanomedicine

Eumelanins, the black insoluble photoprotective biopolymers of human skin and eyes, have recently emerged as a promising resource for bioinspired and biocompatible functional materials. The reason for this is rooted in their unique properties including semiconductor-like behavior, broad band absorption, permanent paramagnetism, efficient non-radiative UV-dissipation. Organic (bio)electronics appears the first target for a competitive exploitation of eumelanins in material science, nonetheless the low conductivity of these pigments is limiting the implementation of eumelanin based devices. We recently designed and produced a novel organic/organic hybrid material by integration of conductive graphene-like (GL) layers within eumelanin pigment. GL layers were obtained by a two-step oxidation/reduction of carbon black. The stability of GL over a wide pH range and the self-assembling tendency place this material in a leading position for the fabrication of hybrid materials in aqueous media. The hybrid was obtained inducing the polymerization of eumelanin precursors (5,6-dihydroxyindole, DHI and 5,6-dihydroxyindole-2 carboxylic acid, DHICA) in presence of GL layers. The new material was structurally and electrically characterized. This material featured promising biocompatibility and reversible hydration-dependent conductivity. These results may open new perspectives in the design of a nature-inspired biocompatible interfaces and their implementation in bioelectronics and nanomedicine.