Melanin synthesis under oxygen pressure

Melanins are promising materials for organic bioelectronics devices like transistors, sensors and batteries. In this study, the chemical structural changes of melanin synthesized by the auto-oxidation of l-3,4-dihydroxyphenylalanine (l-DOPA) were analyzed for a new synthetic procedure that uses oxygen under pressure (4−8 atm). TEM, dynamic light scattering, Fourier transform IR, NMR and X-ray photoelectron spectroscopy were used to characterize the material. Under oxygen pressure, melanin synthesis is accelerated; the polymer obtained is found to have structural differences, most notably a higher number of carbonyl groups and different surface charges compared to conventional synthetic melanin. As a consequence it has higher homogeneity and is soluble in water. To explain these findings a reaction mechanism is proposed based on current melanogenesis models. © 2016 Society of Chemical Industry.