Dynamic reactions of liposomes.

Dynamic chemical reactions at the surface of liposomes are of fundamental interest to the understanding of physiological processes at biological membranes and can be exploited to prepare responsive soft materials. In this paper we describe a covalent yet reversible reaction between liposomes. To this end we explored the reversible thioester exchange reaction of membrane embedded amphiphilic thioesters with dithiols from solution. It was found that thioester exchange leads to the formation of covalent inter-liposomal cross-links and aggregation of liposomes. Liposome aggregation has a characteristic lag phase and the rate of aggregation depends on the concentration of dithiols as well as on the concentration of liposomes in solution. The reversibility of the aggregation could be demonstrated by dissociation of the liposome clusters by the addition of a monothiol. Furthermore we developed a fluorescence anisotropy assay to monitor the thioester exchange reaction on the membrane surface. To the best of our knowledge, the formation of a dynamic covalent network of liposomes is unprecedented.