Luteolin (3',4',5,7-tetrahydroxyflavone), a type of flavonoid found in medicinal herbs and vegetables, has been of great interest due to its antioxidative, anti-inflammatory, and anticarcinogenic effects. Despite these beneficial biological properties, the ease with which luteolin forms molecular crystals in conventional aqueous formulations has hampered much wider applications. In this study, we introduce an oil-in-water (O/W) nanoemulsion vehicle system for enhanced follicular delivery of luteolin. The luteolin-loaded nanoemulsion, which had an average hydrodynamic size of approximately 290 nm, was produced by the assembly of poly(ethylene oxide)-block-poly(ε-caprolactone) and lecithin at the O/W interface. The luteolin-loaded nanoemulsion showed outstanding stability against drop coalescence and aggregation. This was confirmed from the slight drop size increase after repeated freeze-thaw cycling and long-term storage. Moreover, in vivo hair growth evaluation demonstrated that the luteolin-loaded nanoemulsions fabricated in this study possessed the hair growth-promotion activity, which is comparable with the case of using a luteolin solution in an organic solvent.
Keywords: amphiphilic block copolymer; follicular delivery; hair growth; luteolin; nanoemulsion.