Embedding calix[4]resorcinarenes in liposomes: Experimental and computational investigation of the effect of resorcinarene inclusion on liposome properties and stability.

Two calix[4]resorcinarenes, which differ in the length of the alkyl chain on the methylene bridge between the aromatic rings, have been embedded in unilamellar liposomes prepared from 1-palmitoyl-2-oleoyl-sn-glycerol-3-phosphocholine in three host/guest ratios, following two different procedures. The effect of the insertion of the guests has been evaluated through the measurements of the viscosity and the kinetic stability of the liposomal systems by means of the fluorescent probes pyrene and 5(6)-carboxyfluorescein. The presence of the guests reduces the viscosity of the liposomes, suggesting a modification of the bilayer structure. However, this does not affect liposome stability. A calix[4]resorcinarene cavitand with a more rigid conformation compared to the parent resorcinarene, has been also synthetized and embedded in liposomes. The free energy of the insertion of the substrates in the lipid bilayer has been evaluated through Molecular Dynamics simulations.