Photochemically Inert Broad-Spectrum Sunscreen by Metal-Phenolic Network Coatings of Titanium Oxide Nanoparticles

Titanium dioxide (TiO2) nanoparticles are extensively used as a sunscreen filter due to their long-active ultraviolet (UV)-blocking performance. However, their practical use is being challenged by high photochemical activities and limited absorption spectrum. Current solutions include the coating of TiO2 with synthetic polymers and formulating a sunscreen product with additional organic UV filters. Unfortunately, these approaches are no longer considered effective because of recent environmental and public health issues. Herein, TiO2-metal-phenolic network hybrid nanoparticles (TiO2-MPN NPs) are developed as the sole active ingredient for sunscreen products through photochemical suppression and absorption spectrum widening. The MPNs are generated by the complexation of tannic acid with multivalent metal ions, forming a robust coating shell. The TiO2-MPN hybridization extends the absorption region to the high-energy-visible (HEV) light range via a new ligand-to-metal charge transfer photoexcitation pathway, boosting both the sun protection factor and ultraviolet-A protection factor about 4-fold. The TiO2-MPN NPs suppressed the photoinduced reactive oxygen species by 99.9% for 6 h under simulated solar irradiation. Accordingly, they substantially alleviated UV- and HEV-induced cytotoxicity of fibroblasts. This work outlines a new tactic for the eco-friendly and biocompatible design of sunscreen agents by selectively inhibiting the photocatalytic activities of semiconductor nanoparticles while broadening their optical spectrum

Highly Robust Multilamellar Lipid Vesicles Generated through Intervesicular Self-Assembly Mediated by Hydrolyzed Collagen Peptides

Despite the well-known advantages of lipid vesicles for drug and gene delivery, structural instability limits their practical applications and requires strictly regulated conditions for transport and storage. Chemical crosslinking and in situ polymerization have been suggested to increase the membrane rigidity and dispersion stability of lipid vesicles. However, such chemically modified lipids sacrifice the dynamic nature of lipid vesicles and obfuscate their in vivo metabolic fates. Here, we present highly robust multilamellar lipid vesicles through the self-assembly of preformed, cationic large unilamellar vesicles (LUVs) with hydrolyzed collagen peptides (HCPs). The cationic LUVs undergo vesicle-to-vesicle attachment and structural reorganization through polyionic complexation with HCPs, resulting in the formation of multilamellar collagen-lipid vesicles (MCLVs). The resulting MCLVs exhibit excellent structural stability against variations in pH and ionic strength and the addition of surfactants. Particularly, the MCLVs maintain their structural stability against repeated freeze–thaw stresses, proving the unprecedented stabilization effect of biological macromolecules on lipid lamellar structures. This work provides a practically attractive technique for the simple and quick fabrication of structurally robust lipid nanovesicles without covalent crosslinkers, organic solvents, and specialized instruments