Membrane stabilization and transformation in organoclay-vesicle hybrid constructs

We describe the preparation, characterization and properties of a novel inorganic-organic hybrid construct based on the incarceration of individual unilamellar vesicles of 1,2-dimyristoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (DMPG) within an ultrathin shell of polycationic organoclay oligomers. Unlike uncoated vesicles, the organoclay-vesicle nanocomposites show no temperature-dependent changes in size, and exhibit a 12 °C increase in the bilayer melting transition temperature (T_m) due to charge neutralization at the membrane surface. Vesicles coated below T_m, show minimal reversibility in the transition from the L_β to L_α state, whilst constructs produced in the bilayer fluid state demonstrate full reversibility for samples prepared with ultrathin organoclay shells. Release studies indicate that the organoclay-vesicle membranes show a similar permeability to entrapped ibuprofen as uncoated vesicles, suggesting that the constructs could be functionally effective under adverse conditions.