Characterization of Soluplus/ASC-DP Nanoparticles Encapsulated with Minoxidil for Skin Targeting

Soluplus (Sol) is an amphiphilic graft copolymer capable of forming self-assembled micelles and L-ascorbyl 2,6-dipalmitate (ASC-DP) aggregates spontaneously to form micelles. Micelles are used as drug carriers and can nanoparticulate drugs that are poorly soluble in water, such as minoxidil. The study aimed to prepare minoxidil-encapsulated nanoparticles using Sol/ASC-DP and evaluate their potential for targeted skin application. Sol/ASC-DP nanoparticles or Sol/ASC-DP with minoxidil were prepared using the hydration method, and physical evaluations were carried out, including assessments of particle size and zeta potential. Particle structure was evaluated by transmission electron microscopy (TEM) and 1H-nuclear magnetic resonance spectra to assess particle stability and perform functional evaluations in skin penetration tests. TEM images showed spherical micelle-like particles of approximately 100 nm for Sol/ASC-DP at a 9:1 ratio and of approximately 80 nm for Sol/ASC-DP with incorporated minoxidil at a 9:1:0.5 ratio. Changes were also observed in the solid state, suggesting a hydrophobic interaction between Sol and ASC-DP. In addition, evaporated microparticles (Sol/ASC-DP/minoxidil = 9/1/0.5) improved the skin permeability of minoxidil. These results suggest that Sol/ASC-DP nanoparticles form a stable new nanoparticle due to hydrophobic interactions, which would improve the skin permeability of minoxidil.