Highly Conductive Melanin-like Polymer Composites for Nonenzymatic Glucose Biosensors with a Wide Detection Range

Melanin is a natural biopolymer with a conjugated backbone that supposedly provides conductive pathways. However, few studies have synthesized electrically conductive melanin-like polymers (eMLPs) so far. In this study, highly electrically conductive melanin-like polymers (eMLPs) were electrochemically synthesized with tunable morphologies. After a bare gold electrode was coated with eMLP, the electrochemical performances were dramatically improved by a 2-order of magnitude decrease in impedance and up to a 60-fold increase in charge storage capacity. The morphology of the eMLP could be modulated by the ratios of carboxylic acid-bearing poly(l-3,4-dihydroxyphenylalanine) nanoparticles (PLDA NPs) to dopamine without compromising the electrochemical properties. Unlike conventionally insulating polydopamine, eMLP was demonstrated in glucose detection to be a nonenzymatic biosensor with high sensitivity (752.5 μA mM-1 cm-2), a low limit of detection (23 μM), a wide linear range up to 70 mM, and physiological selectivity. This eMLP composite with superior electrochemical performances can be utilized in a wide range of bioelectronics applications from in situ biosensors to implantable bionic interfaces.