Aqueous-based Nanoemulsion Containing (-)-α-bisabolol for Topical Treatment of Skin Burns

Background: α-Bisabolol (BIS) is a sesquiterpene extracted from the chamomile flowers, whose use to topically treat burn skin has been reported. High lipophilicity of BIS, however, is a problem for both skin application and washing. Objective: The present study aimed to prepare and characterize a stable and safe aqueous-based nanoemulsion to incorporate BIS and favor skin penetration focusing on skin burns' topical treatment. Method: Oil-in-water nanoemulsions were obtained from a pseudo-ternary phase diagram. The selected nanoemulsion was characterized (droplet size, PDI, and zeta potential), and the stability was assessed for 60 days at 6ºC and room temperature. The irritability of the formulation was determined by HET-CAM. Skin permeation studies were carried out in vitro intact skin, hot wa-ter burn skin, and hot plate burn skin. Results: The nanoemulsion incorporated 1% (w/w) BIS, presented droplets' size of 14.0±0.8 nm (PDI= 0.13±0.02), the zeta potential of +7.5±1.9 mV, and was physically stable over 60 days. The HET-CAM did not show any irritability process provided by the nanoformulation. In the skin permeation experiments, when compared to an oily control solution of BIS, nanoemulsion increased 3.7-fold penetration of the drug in intact skin, likely because the nanoformulation act-ed as an absorption drug enhancer. On a hot water burn skin model, the increase in drug pene-tration was 1.7-fold, and in the hot plate burn skin, it was 2.3-fold. Conclusion: The nanoemulsion seems to be a promising alternative for skin burns' topical treatment using this natural active.