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

Background/Objectives: This study aimed to develop a nanostructured lipid carrier (NLC) system incorporating a catechin-rich Vanda coerulea extract for topical cosmetic applications and to evaluate its physicochemical properties, release behavior, and skin retention performance. Methods: 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% w/w. 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 V. coerulea extract and evaluated for in vitro release and skin retention using catechin as a marker. Results: 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 V. coerulea extract. The extract-loaded NLC exhibited a sustained release over 24 h, significantly different from the V. coerulea extract solution (p < 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% w/w). Conclusions: The V. coerulea-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.