Leucine-tryptophan dipeptide organo-bridged mesoporous silica for naringin encapsulation and strengthening UVB protection

An organo-bridged mesoporous silica with the framework of biomolecule Leucine-Tryptophan dipeptide (Leu-Trp-OBMS) is first constructed through soft-templating sol-gel method. • The dipeptide framework facilitated high naringenin loading through synergistic π-π stacking and hydrogen bonding, conforming to pseudo-second-order kinetics and the Freundlich isotherm. • The optimized 15%-Leu-Trp-OBMS-NAR composite with high SPF values demonstrated excellent UVB shielding performance. • The composite exhibited remarkable retention stability, with less than 3.4% of the loaded naringenin being released in simulated sweat within a 24 h period. The utilization of natural plant polyphenols, such as naringin, as sunscreen agents is hindered by their intrinsic instability. In this research, we devised a novel ultraviolet protection system through the encapsulation of naringin with high capacity (about up to 94.55 mg/g) within a dipeptide organo-bridged mesoporous silica (OBMS), which achieved outstanding UVB protection. A leucine-tryptophan dipeptide-based bridged organosilane precursor (Leu-Trp-BOSP) was synthesized and co-condensed with tetraethyl orthosilicate (TEOS) (5%-20% molar percentage of the precursor) under alkaline conditions, employing cetyltrimethylammonium bromide (CTAB) as a template. The resultant materials (x-Leu-Trp-OBMS) were characterized by XRD, FTIR, SEM, TEM, TG analysis and nitrogen adsorption-desorption analysis, which verified a well-defined mesoporous structure with type IV isotherms. The adsorption of naringin adhered to the pseudo-second-order kinetic model and the Freundlich isotherm, suggesting a multilayer chemisorption process predominantly dominated by cooperative π-π stacking and hydrogen bonding interactions between the tryptophan indole rings, dipeptide amide groups and the aromatic flavonoid core. The optimal formulation (15%-Leu-Trp-OBMS-NAR) attained a sun protection factor (SPF) of 4.45. In simulated sweat release tests, less than 3.4% of the loaded naringin was released over 24 h, demonstrating outstanding retention stability. These results indicate that dipeptide OBMS can serve as an effective scaffold for stabilizing naringin, presenting a promising platform for long-lasting sunscreen formulations. Download: Download high-res image (308KB) Download: Download full-size image