Resveratrol nanosuspensions for dermal application--production, characterization, and physical stability.

Nanosuspensions of the anti-oxidant resveratrol (5%) were produced for dermal application. Production was performed by high pressure homogenization, applying 1.500 bar up to 30 cycles. Four nanosuspensions were investigated using the stabilizers Tween 80, Poloxamer 188, Plantacare 2000 and Inutec SP1, 1% and 2% respectively. The nanosuspensions were characterized regarding size (photon correlation spectroscopy, laser diffraction), zeta potential and crystallinity. Nanocrystal sizes were about 150 nm (Poloxamer, Plantacare) and about 200 nm (Tween, Inutec); no amorphous fraction could be detected in the nanocrystals. In a short-term stability study (30 days, room temperature), the nanosuspensions with 2% stabilizer proved to be either less stable or at least had no stability advantage over the 1% formulations. All formulations with 1% stabilizer were stable in the short-term study, Plantacare and Inutec showing best stabilization. The stabilization is attributed solely or mainly to steric stabilization, because the measured zeta potentials in the original dispersion media were close to zero (-1 to -5 mV, Tween, Poloxamer, Plantacare) or around -20 mV (Inutec).