A reappraisal of Fe(III) adsorption by melanin.

The adsorptive capacity of melanin for Fe(III) was investigated. Iron is involved in promoting the formation of reactive oxygen species which has consequently been associated with Parkinson's disease. Neuromelanin has been suggested to act as an iron scavenger and, therefore, determining the capacity of melanin to adsorb iron is relevant. Although a few reports have quantified the binding capacity, the current research examined the effect of solution pH on adsorption as well as considering physiologically relevant matrices. In addition, desorption is described for the first time. Our results indicated that adsorption over an acidic pH range was relatively constant and was not significantly affected by the presence of protein or lipid. This paper, therefore, goes beyond published reports by investigating a broader range of factors. It also highlights the importance of melanin in the brain through its homeostatic regulation of Fe(III), through the desorption profile of melanin, a novel result.