In vitro transdermal drug delivery of astaxanthin emulsion: influence of emulsion droplet size

Astaxanthin is a naturally occurring carotenoid that basically can be found in algae, yeast and marine animals such as salmon, trout and shrimp. It is a red fat­ soluble compound with low oral bioavailability due to its lipophilic characteristic. Astaxanthin has been reported by various researchers as an antioxidant, anti­ inflarnmation, anti-diabetic, anti-cancer and provide cardiovascular health. However, most of the scientific literature only focused on oral bioavailability by explaining in detail gastric dissolution with very limited information on transdermal delivery. This study demonstrate transdermal in vitro permeability of nanoemulsion and evaluate its effect with the reduction of droplet size. In this regard, astaxanthin permeability was evaluated by Franz diffusion cell with a Male Sprague-Dawley rat skin membrane sandwiched between the donor and receptor compartments. The result showed that the amount of astaxanthin permeable from oil formulation after 48 hours (197.67±1.77 µg/ml) was quite low as compared to microemulsion (212.11±2.50 µg/ml) and nanoemulsion (223.22±0.95 µg/ml). This study proved that globules size reduction improved astaxanthin permeability. Nano-sized emulsion showed a 25% increase in astaxanthin permeable value as compared to oil formulation and 11 % increase as compared to micro-sized emulsion. Additionally, the micro-sized emulsion showed a 12% increase with the amount of astaxanthin permeable as compared to oil formulation.