Transdermal delivery system of nanostructured lipid carriers loaded with Celastrol and Indomethacin: optimization, characterization and efficacy evaluation for rheumatoid arthritis

Co-encapsulation of drugs provides a convenient means for treating different symptoms of a disease. Celastrol (Cel) shows potent anti-arthritic activity and Indomethacin (Indo) is effective in relieving inflammatory pain. Nanostructured lipid carriers loaded with Celastrol and Indomethacin (Cel-Indo-NLCs) were prepared by emulsification evaporation–solidification method, optimized by the Box–Behnken design and characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and powder X-ray diffraction analysis (PXRD). Visualization of transdermal translocation of Cel-Indo-NLCs was achieved by confocal laser scanning microscope (CLSM). Further, Cel-Indo-NLCs were incorporated into Carbopol 940 for transdermal delivery. The in vitro studies were evaluated by using the Franz diffusion cells. Cel-Indo-NLCs depicted small particle size (26.92 ± 0.62 nm) and PDI (0.201 ± 0.01), high entrapment efficiency (96.56 ± 1.41%) and drug load (3.65 ± 0.05%). Moreover, Cel-Indo-NLCs showed prominent effect of decreasing paw oedema, inhibiting inflammation and pain by regulating the levels of IL-1β, TNF-α, β-endorphin and Substance P. After the administration of Cel-Indo-NLCs-gel, no skin irritation was observed in rats. There was no difference of gastrointestinal tract between different groups of rats when they were sacrificed. The histological analysis showed no renal and reproductive toxicity. Therefore, it can be concluded that co-encapsulation strategy based NLCs have the potential to provide safe transdermal delivery and are promising in treatment of pain and inflammation associated with rheumatoid arthritis.