Bioinspired Artificial Melanosomes As Colorimetric Indicators of Oxygen Exposure.

Many industries require irreversibly responsive materials for use as sensors or detectors of environmental exposure. We describe the synthesis and fabrication of a nontoxic surface coating that reports oxygen exposure of the substrate material through irreversible formation of colored spots. The coating consists of a selectively permeable rubber film that contains the colorless organic precursors to darkly pigmented synthetic melanin. Melanin synthesis within the film is triggered by exposure to molecular oxygen. The selectively permeable rubber film regulates the rate of oxygen diffusion, enabling independent control of the sensitivity and response time of the artificial melanosome, while preventing leaching of melanin or its precursors.