In vitro kinetic release study, antimicrobial activity and in vivo toxicity profile of a kojic acid ester-based nanoemulsion for topical application

Nanoemulsions have emerged as novel vehicles for drug delivery that allow sustained or controlled release for topical application. In this study, kojic acid ester-based nanoemulsion (KAE-NA) was analyzed for in vitro permeation evaluation, kinetic release study, in vitro antimicrobial activity and in vivo toxicity profile on embryonic zebrafish (Danio rerio). Based on KAE-NA in vitro permeation evaluation, the percentage of permeation was significantly improved from 4.94% at 1 h to 59.64% at 8 h of application. The permeation rate of KAE-NA at 8 h was 4659.50 μg cm−2 h−1 (initial concentration, C0 = 2000 μg mL−1) with a permeability coefficient (Kp) value of 0.48 cm h−1. The kinetic release analysis showed the Korsmeyer–Peppas model was the best fitted kinetic model with high linearity [R2 = 0.9964]. Antimicrobial activity of KAE-NA was studied against the skin pathogen bacteria Staphylococcus aureus ATCC 43300. The results indicated that the inhibition zone size of the KAE-NA (8.00 ± 0.0 mm) was slightly bigger than that of its active ingredient, kojic acid ester (6.5 ± 0.0 mm). The toxicity profile of KAE-NA on embryonic zebrafish revealed less toxicity with LC50 (50% lethal concentration) more than 500 μg mL−1. The survival rate of the embryonic zebrafish was more than 80% when treated at doses ranging from 7.81–250 μg mL−1 and showed normal development throughout the experiment without any observed deformation. Hence, KAE-NA proved to be less toxic on the embryonic zebrafish.