Optimization of synthesis conditions for Calophyllum inophyllum L.-loaded solid lipid nanoparticles☆

Background: This study aimed to optimize the synthesis conditions for solid lipid nanoparticles (SLNs) loaded with Calophyllum inophyllum L. (tamanu) oil, a natural extract known for its anti-inflammatory, antimicrobial, and wound-healing properties. Methods: SLNs were prepared using a hot homogenization–ultrasonication–cold homogenization method, and various formulation parameters were systematically evaluated, including the type and concentration of solid lipids, hydrophilic–lipophilic balance (HLB) of surfactants, sonication power, and homogenization speeds. Results: Among the tested lipids, Naterol® SE produced stable SLNs and was selected for further optimization. Response Surface Methodology (RSM) with a Central Composite Design (CCD) was applied to model the effects of four key factors—HLB value, sonication power, hot homogenization speed, and cold homogenization speed—on particle size and polydispersity index (PDI). The optimized formulation achieved a mean particle size of 148.7 ± 1.39 nm and a PDI of 0.30, with spherical morphology confirmed by SEM and good physical stability under different storage conditions. Objectives: These findings demonstrate that the optimized tamanu oil-solid lipid nanoparticles (TO-SLNs) possess favorable physicochemical characteristics, offering strong potential as a topical nanocarrier system for skin repair and regeneration applications.