Formulation and in-vitro characterization of Capsaicin loaded ethosomes

The ability of ethosomes to entrap capsaicin was evaluated using four methods of preparation that are; hot method, cold method, classic method and injection method. The ethosomes were prepared, optimized and characterized with the aim to identify a technique best suitable for their formulation. Vesicle shape, size and entrapment efficiency was determined by scanning electron microscopy, dynamic light scattering and ultracentrifugation techniques, respectively. Vesicle sizes varied from an average of 15nm - 400nm depending on the concentrations of phospholipid, ethanol and method of preparation. The formulations demonstrated entrapment efficiency of 29-81% with maximum entrapment obtained in formulations prepared with hot method having high concentration of ethanol. The homogeneity index was measured with Zetasizer that showed formulation prepared with hot method to be more uniform in size distribution having PDI 0.162 while injection method of preparation yielded a moderately broad polydispersity of vesicles (0.276). Physical stability assessment done by storing the selected formulation samples at 4°C and 25°C indicated the refrigerator temperature to be the best for retention of drug in ethosomal vesicles. All formulations kept in refrigerator adequately retained capsaicin during the two months of stability studies while those at ambient temperature noticeably showed leaked drug from vesicles. FTIR analysis showed capsaicin and phospholipid to be compatible with each other with no sign of interaction. DSC studies evidently showed lowering of transition temperature of phospholipid from 327.13°C to 111.63°C in ethosomal formulation due to the presence of ethanol. It was concluded that capsaicin ethosomes can be successfully prepared to employ four different methods and their characterization parameters indicate hot method to be effective for preparation of nano-sized uniform, homogeneous and stable capsaicin ethosomes.