Redox-cycling and H2O2 generation by fabricated catecholic films in the absence of enzymes.

Phenolic matrices are ubiquitous in nature (e.g., lignin, melanin, and humics) but remain largely intractable to characterize. We examined an abiotic phenol-polysaccharide matrix fabricated by the anodic grafting of catechol to chitosan films. Previous studies have shown that catechol-modified chitosan films are redox-active and can be repeatedly interconverted between oxidized and reduced states. Here we developed quantitative electrochemical methods to characterize biorelevant redox properties of the catechol-modified chitosan films. Our analysis demonstrates that these films can (i) accept electrons from biological reductants (e.g., ascorbate and nicotinamide adenine dinucleotide phosphate, NADPH) and (ii) donate electrons in a model biological oxidation process. Furthermore, these films can donate electrons to O(2) to generate H(2)O(2). The demonstration that abiotic catechol-chitosan films possess catalytic activities in the absence of enzymes suggests the possibility that phenolic matrices may play an important role in redox cycling and reactive oxygen species (ROS) signaling in biology and the environment.