Development of biodegradable capsaicin nanoparticles and evaluation of active release from semisolid formulations

Encapsulation of capsaicin was optimized within biodegradable polymeric nanoparticles and their release was evaluated from a semisolid dosage form containing the particles, using Franz diffusion cells. To meet this objective, the nanoparticles were prepared by the emulsion-solvent evaporation method. The influence of various parameters affecting the encapsulation of the active ingredient was investigated, such as the type of organic solvent used, the sonication time applied, the nature of the polymer, the initial mass of capsaicin and the nanoparticles production method. Later, using the selected formulation, the drug release was evaluated in vitro and was compared against the release from a commercial formulation. The highest loading and encapsulation efficiency of the drug (400 μg% and 70.2%, respectively) were obtained using 100 mg of PLA polymer, in a mixture of dichloromethane-acetone (1:1 v/v), with a sonication time of 5 minutes and 4 mg of capsaicin as initial mass. The obtained particles were mono disperse, it had a mean diameter of 249 ± 42 nm, with a polydispersity index of 0.06. The zeta potential was-7.45 mV. Finally, the in vitro release studies from different semisolid formulations of capsaicin showed a capsaicin flux and a release percentage of:0.2646 μg/cm²h^-1 and 57% for the loaded nanoparticles incorporated in a commercial base cream formulation; 0.0634 μg/cm2h-1 and 25% for free capsaicin (commercial formulation); 0.0411 μg/cm²h^-1 and 10% for unloaded nanoparticles incorporated in the commercial formulation,respectively.