N‐acetylglucosamine microemulsions: Assessment of skin penetration, cytotoxicity, and anti‐melanogenesis

Abstract Background N ‐acetylglucosamine (NAG) is an amino sugar which can reduce melanin production. NAG has previously been formulated for topical use in many nanocarrier systems, excluding microemulsions (MEs). In this study, NAG was prepared in the form of MEs and assessed in terms of skin permeability, cytotoxicity, and effectiveness for cosmetic applications. Aims To investigate the skin penetration, cytotoxicity, and anti‐melanogenesis of N ‐acetylglucosamine loaded microemulsions (NAG‐MEs). Methods Two NAG‐MEs (NME1 and NME2) were prepared. The in vitro penetration study of NAG‐MEs was evaluated by modified Franz diffusion cells using full‐thickness porcine ear skin as the membrane. The optimized formula was then selected for further assessment of cytotoxicity and efficiency. In vitro cytotoxicity was examined using human keratinocytes (HaCaT cells) and B16 melanoma cells. Anti‐melanogenic activity was investigated by determination of melanin production of B16 melanoma cells. Results The cumulative amounts of NAG from NME1 and NME2 in the receptor fluid at 24 hours were 1010.46 ± 31.63 and 1260.99 ± 100.19 µg/cm 2 and those accumulated in the skin membrane were 155.59 ± 19.19 and 181.11 ± 20.38 µg/cm 2 , respectively. NME2 and its blank counterpart (Blank‐ME2) showed no adverse effects on the viability of both HaCaT and B16 melanoma cells. The anti‐melanogenic activity data showed that the NME2 treated B16 cells exhibited a significant melanin reduction. Conclusions NAG‐MEs could allow NAG penetrate through and accumulate in full‐thickness porcine ear skin. NME2 was safe for both normal human keratinocytes and melanoma cells. It also showed effectiveness on anti‐melanogenic activity in B16 melanoma cells.