Nanostructured Lipid Carriers for Sustained Release and Enhanced Delivery of Protocorm Extract.

This study aimed to develop a nanostructured lipid carrier (NLC) system incorporating a catechin-rich extract for topical cosmetic applications and to evaluate its physicochemical properties, release behavior, and skin retention performance. Blank NLCs were prepared using hot emulsification followed by sonication, with glyceryl monostearate, caprylic triglyceride, Poloxamer 188, and Tween 80 as the formulation components. NLCs with varying solid-to-liquid lipid ratios were developed while maintaining a constant total lipid content of 5% /. The formulations were characterized based on their particle size, polydispersity index (PDI), zeta potential, and physical stability, including stability after a heating-cooling cycle test. The effect of ultrasonication duration was also evaluated. The optimized NLC was then loaded with a extract and evaluated for in vitro release and skin retention using catechin as a marker. The NLC with a particle size of 235.5 ± 29.8 nm, a narrow PDI range of 0.382 ± 0.090, and a strong zeta potential of -29.8 ± 0.3 mV was selected for the incorporation of the extract. The extract-loaded NLC exhibited a sustained release over 24 h, significantly different from the extract solution ( < 0.05). Skin retention studies revealed that the NLC achieved approximately twice the catechin retention compared to the solution at the 1 h time point (1.30 ± 0.01% vs. 0.68 ± 0.03% /). The -extract-loaded NLC demonstrated favorable physicochemical properties, sustained release behavior, and enhanced skin retention. These findings support its potential as a promising topical delivery system for antioxidant-rich botanical extracts in cosmetic applications.