preparation of stable plurilamellar liposomes dispersed in two soluble types of collagens and the effect of collagens on the release rate of entrapped sodium chromate

combination formulations of liposomes with collagen have been previously introduced as a means of obtaining more stable and less permeable liposomes. in this study, the effect of aqueous solutions of the collagen products collapur? (col) and collapuron-dak? (cold) from henkle co., on the release rate of sodium chromate (chr) as a water-soluble model drug from stable plurilamellar vesicles (splvs) was evaluated. results showed that dispersing splvs in diluted solutions (10%) of the collagens, increased the release rate from liposomes at 32°c. it is speculated that after binding to the hydrophilic surface of liposomes, the structure of the collagen changes and the hydrophobic portions become more exposed. this is likely to cause a penetration of these portions into the bilayer structure (which is fluid at this temperature), thus causing an expansion in the membrane and an increase in permeability. in higher concentrations (30% and 50%), this increasing effect is not observed, which is suggested to be due to the aggregation of collagen fibrils and the resultant higher viscosity. it is concluded that these collagens in optimum concentrations, which seems to be above 30%, could find a good place in the preparation of topical liposomes, due to their flexible effects on the release rate of liposomes, as well as the dermatological effects of collagen itself.