Adaptability and elasticity of the mixed lipid bilayer vesicles containing non-ionic surfactant designed for targeted drug delivery across the skin.

Novel potential carriers for non-invasive drug delivery were prepared from polyoxyethylene(20) oleyl ether (C(18:1)EO(20)) and soybean phosphatidylcholine (SPC) in different relative molar ratios, R(e); this produced stiff SPC liposomes (2r(ves) approximately 120 nm) at one end and much smaller (2r(mic) <or= 15 nm), comparably non-deformable, mixed micelles at the other end of aggregate spectrum. Deformability of the mixed amphiphat vesicles (2r(v) approximately 105 nm) existing in-between increases with R(e) non-linearly, up to a quasi-plateau at R(e) >or= R(e)(sat) = 0.25 in the bilayer. The surfactant-saturated bilayers exhibit bending rigidity of kappa(c) approximately 2.1 k(B)T, as determined with an improved vesicle adaptability assay involving analysis of normalised flux density through a nano-porous barrier as an activated transport process. Pore penetrability vs. driving pressure data measured with the mixed amphiphat vesicles resemble results of computer simulation of deformable vesicles penetrating a constriction [Gompper G, Kroll DM. 1995. Driven transport of fluid vesicles through narrow pores. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics. 52:4198-4208], confirming basic similarity of both processes. The improved assay can reveal partial lipid solubilisation at R(e)>R(e)(sat), which is linearly proportional to R(e) - R(e)(sat). C(18:1)EO(20)-SPC mixed vesicles that can cross narrow pores are arguably suitable for targeted drug delivery across intact skin.