Melanin as an adsorbent for drug residues

The binding of seven veterinary drugs (clenbuterol, chlorpromazine, diethylstilbestrol, 19-nortestosterone, salbutamol, salicylic acid and trenbolone) to melanin from Sepia officinalis was investigated. Basic and hydrophobic drugs were the most strongly bound. Desorption by ethanol was complete for neutral drugs but only partial for the basic drugs, which suggests that binding of the latter involves an ionic component. A method of synthesizing melanin in an immobilized form (melanin-PS) on the surface of porous silica was developed. When the drug binding properties of melanin-PS were investigated, its capacity to bind the basic drug clenbuterol was found to be higher (5.9 nmol mg-1) than that for the neutral hydrophobic drug 19-nortestosterone (0.56 nmol mg-1); for both drugs the attainment of binding equilibrium with melanin-PS was relatively rapid (< 5 min). By virtue of its binding kinetics, high capacity and mechanical robustness, melanin-PS offers potential for use in chromatography or solid-phase extraction and may additionally enable modelling of drug-melanin interactions.