Phospholipid-detergent systems: effects of polysorbates on the release of liposomal caffeine

It is well known that surfactants are capable of interacting with phospholipid vesicles leading to different aggregated structures and finally to mixed micellar systems. By means of diffusion experiments with Valia-Chien cells the effect of different vesicular structures (MLV and SUV) and that of three polysorbates on the release of a model drug (caffeine) from various vesicle formulations was studied. Obtained results indicate that a remarkable delayed/sustained caffeine release is obtained only with the MLV preparations and that the presence of increasing surfactant concentrations initially leads to a further decrease of drug delivery rate and then to a faster release that reaches a maximum when only mixed micelles are present. The variation of the observed effects with the different tested surfactants, in relation to their lipophilicity (HLB values), is also discussed. (C) 1998 Elsevier Science S.A. All rights reserved.