Studies on self-organized systems of dialkyldimethylammonium bromide in aqueous solution and at liquid and solid interfaces

Abstract

Intensive investigation of properties of synthetic cationic vesicles of DnDAB, n = 10-18, is of great importance for basic and applied science, because it is a model for biological membrane, and especially for cell transfection in genetherapy. In this project we propose a systematic investigation of physicochemical properties of formation of DnDAB vesicles and interaction with additives, including water soluble polymers (polyethylene glycol, for example), surfactants and inorganic salts. It will be varied the concentration of DnDAB and the relative amount of additive in order to obtain the properties of the vesicles and of the vesicle-additive complexes, such as the hydrodynamic radius, thermal states transitions, and the surface potentials (zeta potentials). The interaction of vesicles with a micelle-forming surfactant will also be monitored by surface tension measurements. The effect of the additives on the organization of DnDAB lipids as monolayer at the surface of the solution and deposition of vesicles on solid substrates, will be investigated by Langmuir-Blodgett (LB) and spectroscopic techniques, respectively. This proposal is based on the comparative investigation of the formation and stability of vesicles in solution and molecular films at the surface that, according to recent (unpublished) results obtained by our research group, D18DAB Langmuir films and vesicles interact together modifying the profile of pressure vs. area isotherm, and D18DAB vesicles adsorb as layer-by-layer (LbL) films on a quartz substrate to form several layers according to absorbance data. The nature of this interaction still remains to be clarified, as well as the verification that this interaction occurs for other lipids of DnDAB series. The emphasis on the study of cationic vesicles made by our group since 1990, recognize the need and importance of this research. (AU)