BERLIN, Germany—Lutein, a well-known antioxidant and anti-free radical used in cosmetics with potential application, is poorly soluble in water and has a low bioavailability due to its lipophilic molecular structure. Therefore, German researchers prepared a lutein nanosuspension to enhance dissolution velocity and saturation solubility (C(s)), which are major factors determining oral bioavailability and penetration into the skin (Int J Pharm. Aug. 23, 2011).
High pressure homogenization (HPH) was used to prepare lutein nanosuspension. Particle size was determined by photon correlation spectroscopy (PCS) and laser diffractometry (LD). The lowest PCS diameter obtained was about 429 nm, the LD diameter 90 percent of 1.2 μm. The zeta potential was about -40 mV in water and -17 mV in the original dispersion medium. The three-month storage study at different temperatures (4°C, 25°C, 40°C) confirmed physical stability despite the low zeta potential of -17 mV in original surfactant solution.
A pronounced increase in saturation solubility by 26.3 fold was obtained for lutein nanocrystals compared to coarse powder. The lutein nanosuspension that was converted into pellets and filled into hard gelatin capsules for nutraceutical use showed a superior in vitro release (factor of 3-4). Lyophilized nanosuspension was prepared for subsequent incorporation into creams and gels. The lyophilized nanosuspension was very well re-dispersible (435 nm). Using cellulose nitrate membranes as in vitro model, permeation through this barrier was 14 times higher for lutein nanocrystals compared to coarse powder. However, pig ear skin did not allow lutein to permeate, but supported localization of the lutein in the skin where it should act antioxidatively.