Jingyi Chen, Juan Zhang, Jian Wu, Ling Zhang, Li Chen, Jingyang Li, Li Zhang; Preparation of Capsaicin Loaded PLGA Microspheres for Injection: Optimization, Characterization, In Vitro and In Vivo Study; Advanced Nano-Bio-Materials and Devices; 2017:1(2):99-114

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The purpose of this study was to prepare and to characterize a new formulation of injectable capsaicin loaded poly (D,L-lactic-co-glycolic acid) (PLGA) microspheres (CAP-MS). The emulsion solvent evaporation process based on O/W emulsion was applied to prepared the CAP-MS with optimization of formulation using uniform design with three factors and six levels. The optimized formulation was then evaluated in terms of size, encapsulation efficiencies, drug loading, in vitro release profile, distribution and pharmacokinetics. According to the mathematic models, the optimal prescription and preparation technology can be conducted at the concentration of PLGA of 2%, the rotation speed of 1000 rpm and the mass ratio (CAP/PLGA) 1:2. The optimized CAP-MS resulted in spherical shapes and possessed a smooth surface. Average diameter, encapsulation efficiency and drug loading were turned out to be 4.73μm, 82.82% and 27.60%, respectively. In vitro release study represented a low initial burst release of approximately 21.26% within the first 24 h followed by a prolonged release up to 12 days and the release kinetics fitted well to the Higuchi model. In vivo results demonstrated that the drug suspension released rapidly after subcutaneous injection, the accumulate drug release was more than 97% after 12 hours, while the drug loaded microspheres release profile showed a large initial burst effect (59%), and then released slowly, nearly 100% of capsaicin released at the end of 20 days. These results indicate the PLGA microspheres is a promising system that could be exploited as a delivery system for capsaicin with high drug loading capacity and sustained drug release.