Periodic mesoporous organosilica with Serine-Tryptophan dipeptide framework by encapsulating curcumin to enhance ultraviolet shielding

Plant compound curcumin with strong absorption capabilities in UV range has gained significant attention for its potential application as a natural ultraviolet shielding agent. However, certain challenges such as limited water solubility and photostability sill restrict its usage. Nanoencapsulation as one of the advanced delivery systems is explored to overcome these limitations. In this study, we design a periodic mesoporous organosilica (PMO) material with Serine-Tryptophan dipeptide framework via sol-gel synthesis method to encapsulate curcumin as potential sunscreen. The dipeptide PMO material were prepared by co-condensation of self-designed Serine-Tryptophan dipeptide bilateral organic silane precursor and tetraethyl orthosilicate in the presence of template CTAB under alkali condition. The PMO material before and after encapsulating curcumin were characterized by XRD, FTIR and nitrogen adsorption-desorption analysis, which confirmed the presence and maintenance of the mesoporous structure within the encapsulation system. Adsorption kinetics and isotherms during curcumin encapsulation were well described by the pseudo-second-order model and Freundlich isotherm, respectively, indicating chemisorption-dominated multimolecular layer adsorption process. Besides, the material exhibited comprehensive broad-spectrum photoprotection against UV light with dominant protection in UVA region. After encapsulating curcumin, the sun protection factor (SPF) was significantly enhanced, demonstrating the excellent photo-protective nature of dipeptide PMO material. The critical wavelength (λc) for the material exceeded 370 nm. In a simulated sweat release experiment to evaluate photostability, only 2.6% of curcumin was released after 24 hours, demonstrating exceptional stability. Consequently, our findings suggest that dipeptide can serve as framework building constituents for the development of novel PMO material. Furthermore, the PMO material encapsulating curcumin could provide stable protection, demonstrating its potential as effective UV shielding filter.