A Preliminary Study On The Preparation Of Liposomal Capsaicin And Its Percutaneous Permeability In Scar And Inhibiting Action On Hypertrophic Scarring

Objective To prepare liposomal capsaicin and to investigate its promoting effects on percutaneous permeation of capsaicin through scar and prevention of hypertrophic scarring of rabbit ear model so as to provide a theoretical basis for clinical application.Methods 1. The liposomal capsaicin (0.075% W/V) was prepared with thin-film dispersion combined with microfluidic technique. The encapsulation rate, average diameter and zeta-potential were assayed with supercentrifugation, HPLC analysis and PCS, respectively to show the qualities of liposomal capsaicin. 2. Permeability of liposomal capsaicin through human hypertrophic scar in vitro and hypertrophic scar model of rabbit ears in vivo were performed with commercial capsaicin ointment as control to investigate the enhancement of skin permeation of liposomal capsaicin. 3.The effect of preventing hypertrophic scarring was evaluated with HE and VG staining and immunohistochemical assay of substance P.Results 1. 0.075%(W/V)liposomal capsaicin has been prepared successfully with 48.2% encapsulation rate,154 nm average diameter and -27.5 mV zeta-potential. No obvious changes were found in the external character and the three qualitative parameters of liposomal capsaicin under airproof condition for nine days and under airproof freezing condition for ten months.2.①The in vitro diffusion experiment lasted for 12 hours. Deposition amount of capsaicin through human scars was markedly higher in liposomal capsaicin group than that in commercial capsaicin ointment group (12.33±3.2 vs 3.59±2.02 μg·㎝-2, P < 0.01). ②The in vivo diffusion experiment on rabbit ear scar model also lasted 12 hours. Deposition amount of capsaicin through rabbit ear scars was markedly higher in liposomal capsaicin group than that in commercial capsaicin ointment group (40.03±3.2 vs 9.01±2.02 μg·㎝-2, P < 0.01). 3.After application on rabbit ear scar model ,on gross examination ,the thickness of the scars was much thinner in liposomal group than that in commercial capsaicin ointment group .In histological examination ,the thin dermis in rabbit ear scars with lesser amount of fibroblasts and well-arranged collagen were found in liposomal capsaicin group ,but much thicker dermis with a great deal of fibroblasts and disordered collagen ,even with collagen nodules in commercial capsaicin ointment group . The relative hypertrophic indices (HI) in liposomal capsaicin group and commercial capsaicin ointment group were 3.26±1.04 and 4.15±0.81 respectively with significant difference (p<0.01). Mastocyte count of rabbit ear scars in liposomal capsaicin group and commercial capsaicin ointment group were 5.7±0.3/HP and 11.2±0.7/HP respectively with significant difference (P < 0.01). The SP expression in dermis of rabbit ear scars in commercial capsaicin ointment group was significantly higher than that in liposomal capsaicin group with significant difference(P<0.05). Conclusion 1.The liposomal technique can encapsulate capsaicin with a good stability in the duration observed. 2.The permeability through scar is better with liposomal capsaicin than that with commercial capsaicin ointment both in vitro and in vivo. 3.Upon pharmacodynamical results, liposomal capsaicin has a good penetrating ability into scar and may more satisfactorily inhibit hypertrophic scarring.