Quality by design optimization of microemulsions for topical delivery of <i>Passiflora setacea</i> seed oil

<i>Passiflora setacea</i> seed oil is a natural source of bioactive unsaturated fatty acids, notably linoleic acid (ω-6) and oleic acid (ω-9), with promising antioxidant and anti-inflammatory potential for dermatological applications. However, its direct use is limited by poor physicochemical and organoleptic properties. This study aimed to develop and optimize a topical microemulsion (ME) system incorporating <i>P. setacea</i> seed oil using quality by design principles to address formulation challenges. The oil was extracted via Soxhlet and characterized by gas chromatography-mass spectrometry and thermal analysis. A full factorial design, followed by a Box-Behnken design, was employed to optimize the formulation based on critical quality attributes and the defined quality target product profile. The optimized ME presented a hydrodynamic diameter of approximately 22 nm and polydispersity index below 0.2 and remained stable for 60 days. The ME was gelled with sodium carboxymethyl cellulose, while vitamin E and Liquid Germall^® Plus were incorporated as antioxidant and preservative agents, respectively, yielding the final topical gel formulation. Cytocompatibility assays demonstrated high cell viability for ME at concentrations below 2 mg/mL in RAW 264.7 macrophages and 0.5 mg/mL in human umbilical vein endothelial cells. Overall, this work presents a promising nanotechnology-based topical delivery platform for <i>P. setacea</i> seed oil, employing quality by design principles to ensure formulation performance, stability, and skin cell compatibility.