Background:In this study, a liposomal gel based on a pH-gradient method was used to increase
the skin-layer retention of monocrotaline (MCT) for topical administration.Methods:Using the Box-Behnken design, different formulations were designed to form liposome suspensions
with optimal encapsulation efficiency (EE%) and stability factor (KE). In order to keep MCT
in liposomes and accumulate in skin slowly and selectively, MCT liposome suspensions were engineered
into gels.Results:A pH-gradient method was used to prepare liposome suspensions. The optimal formulation of
liposome suspensions (encapsulation efficiency: 83.10 ± 0.21%) was as follows: MCT 12 mg, soybean
phosphatidyl choline (sbPC) 200 mg, cholesterol (CH) 41 mg, vitamin E (VE) 5 mg, and citric acid
buffer solution (CBS) 4.0 10 mL (pH 7.0). The final formulation of liposomal gels consisted of 32 mL
liposome suspensions, 4.76 mL deionized water, 0.40 g Carbopol-940, 1.6 g glycerol, 0.04 g
methylparaben, and a suitable amount of triethanolamine for pH value adjustment. The results of in
vitro drug release showed that MCT in liposomal gels could be released in 12 h constantly in physiological
saline as a Ritger-Peppas model. Compared with plain MCT in gel form, liposomal MCT in gel had
higher skin retention in vitro.Conclusion:In this study, liposomal gels were formed for greater skin retention of MCT. It is potentially
beneficial for reducing toxicities of MCT by topical administration with liposomal gel.