One-pot approach to form in situ colchicine-containing nano-hydroxyapatite within microemulsion composite system for sustained transdermal delivery

Currently, high protein and fat food in daily diet often causes the prevalence of gout, which is common treated with colchicine as specific medicine. Transdermal delivery with microemulsion is very attractive for topical colchicine delivery due to its permeation enhancement across the skin barrier. However, the lack of controlled drug release ability compromises the performance of microemulsion for transdermal delivery. Herein, a colchicine transdermal delivery vehicle with one-pot approach that synchronously achieved in situ colchicine encapsulation during nano-hydroxyapatite (Hap) formation inside water/lecithin/n-propanol/isopropyl myristate microemulsion as microreactor was proposed. The optimal formulation was determined at the composition proportion (w/w) of 13% lecithin, 26% n-propanol, 53% IPM, and 8% water. This composite formulation not only possessed high transdermal flux and enhanced drug loading efficiency, but also exhibited a tunable sustained-release behaviour. This composite system combined the transdermal permeation advantage of microemulsion and controlled drug release capacity of nano-Hap, implying a promising vehicle for transdermal delivery of colchicine to produce desirable pharmacological effects.