Adapalene (AD) is an FDA-approved
drug that shows good therapeutic efficacy for the treatment of
acne vulgaris. However, due to its negative charge, AD cannot efficiently penetrate across the also negatively-charged skin membrane. This study is the first to assess the treatment of
acne vulgaris using electrostatically optimized AD
emulsions prepared using anionic AD with methoxy
polyethylene glycol-b-poly(ε-
caprolactone) (MC) as an anionic emulsifier coupled with a newly synthesized MC with different contents of an
amine pendant-group (MC-[NH2]x) as a cationic emulsifier. The AD
emulsion prepared using MC-[NH2]x with high cationic charge potential was significantly stable in the short-term studies compared with anionic MC or no emulsifier. Furthermore, the AD
emulsion prepared with the cationic MC-[NH2]x emulsifier provided a two or three times stronger
therapeutic effect against
acne vulgaris than the AD
emulsion prepared with the anionic MC emulsifier or no emulsifier in an animal study. Additionally, the AD
emulsion with high cationic charge potential exerted a remarkable inhibition of macrophage expression, as confirmed by histological analysis. Therefore, the electrostatic interaction between the negatively-charged skin membrane and the AD
emulsion prepared with the cationic MC-[NH2]x emulsifier provides a promising therapeutic strategy for
acne vulgaris.