One-Step Assembly of TiO₂-Liposomes Based on Interfacial Sol-Gel Process within Lipid Bilayer

There is a growing interest in the use of hybrid liposomes for various biochemical and biomedical applications. In this study, we report the first preparation and characterization of a class of TiO₂-reinforced liposomes by a one-step assembly approach. The amphiphilic natural structure of lipids is exploited to localize a hydrophobic molecule, namely, precursor tetrabutyl titanate (TBOT), in the mid-plane of the liposomal bilayer assemblies in the aqueous phase. In situ TiO₂ nanoshell formation is driven by subsequent interfacial hydrolysis of TBOT and the ensuing condensation within the hydrophobic interstices of the lipid bilayer. The core-shell structure, like cell and wall, is demonstrated by means of scanning electron microscopy and transmission electron microscopy images, and the formation of the TiO₂ shell is confirmed using energy-dispersive X-ray spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. To study the structural evolution of the hybrid liposomes during titania formation, fluorescence probe technique and surface pressure versus molecular area (π- A) isotherms are designed. The results demonstrate that the incorporation of TBOT into the mid-membrane of the lipid and titania in the core of the membrane strengthened the assembly of the lipid bilayer. We further demonstrate that titania shell improved the stability and release property of liposomes. We expect that the reported new TiO₂-coated liposomes by co-assembly will be valuable in designing hybrid liposomes, exhibiting integrative capacity for drug encapsulation, compartment reaction, and photocatalysis.