Drug accumulation in melanin: an affinity chromatographic study.

The affinity of several drugs to melanin has been indirectly assessed using an affinity chromatographic approach based on immobilized melanin. Plots of the retention of the drugs on the affinity column versus the number of molecules applied were fitted best by nonlinear, exponential curves characteristic for each drug. These curves reflect the complexity of the binding behaviour, consisting of a variety of hydrogen bonding, hydrophobic or ionic interactions as well as cooperative or anti-cooperative interactions between the drug molecules and melanin. The nonlinear fitting procedure was based on a descriptive function and allowed to discriminate the binding behaviour according to parameter estimates which specified the investigated drugs.