Polyhydroxamic microcapsules prepared from proteins: a novel type of chelating microcapsules.

Microcapsules were prepared from three proteins, namely human serum albumin (HSA), bovine fibrinogen and ovalbumin, by an interfacial crosslinking process using terephthaloylchloride. They were further treated with alkaline hydroxylamine in order to disrupt ester and anhydride bonds in the walls. All microcapsules survived the treatment. They exhibited a significant increase in size and became sensitive to trypsin. The hydroxylamine treatment also resulted in attachment of hydroxamic groups to the membrane, making the microcapsules capable of iron binding. These properties were evaluated after soaking microcapsules in a 140 mumol/l ferric solution and determination of iron in the supernantant. Lower amounts of iron were found to be complexed by HSA microcapsules (mean value: 29.3 mumol iron/g microcapsule dry weight) as compared with fibrinogen and ovalbumin microcapsules (43.7 and 44.9 mumol/g, respectively). Microcapsule chelating properties were further improved by esterification of the free carboxyl groups of the membrane with benzyl alcohol or ethanol using a carbodiimide, prior to the hydroxylamine treatment. Comparable values of iron binding were obtained from esterified and hydroxylamine-treated batches prepared from the three proteins (about 50 mumol iron/g).