Anti-inflammatory effects of triptolide loaded poly(d,l-lactic acid) nanoparticles on adjuvant-induced arthritis in rats

Triptolide (TP), which has potent immunosuppressive effects, anti-inflammatory and severe toxicity on digestive, urogenital, blood circulatory system, was used as a model drug in this study. The aim of this study was to investigate the anti-inflammatory effect of complete Freund's adjuvant-induced arthritis in rats treated with TP-loaded poly(d,l-lactic acid) (PLA) nanoparticles (TP-PLA-NPs) by gavage. TP-PLA-NPs were prepared by the modified spontaneous emulsification solvent diffusion method (modified-SESD). Nanoparticles were shown to be small particle size (149.7 nm), low polydispersity index (0.088), a fine spherical shape with smooth surfaces determined by dynamic light scattering (DLS) and transmission electron microscope (TEM). Encapsulation efficiency and the in vitro release of TP from nanoparticles were measured by the reverse phase high-performance liquid chromatography (RP-HPLC). The in vitro release profile of TP from nanoparticles exhibited a typical biphasic release phenomenon, namely initial burst release and consequently slow release. The potential therapeutic arthritic method of TP-PLA-NPs was established. The results obtained in experiments indicated that TP-PLA-NPs significantly inhibited the adjuvant-induced arthritis, and had preferable anti-inflammatory effect with the long-time administration.