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.