Surfactant-Free, Self-Assembled Nanomicelles-Based Transdermal Hydrogel for Safe and Targeted Delivery of Methotrexate against Rheumatoid Arthritis

Methotrexate (MTX) is the first line agent for therapy against rheumatoid arthritis (RA); however, orally its efficacy is hampered by poor solubility, less permeability, short plasma half-life, and reduced bioavailability. Meanwhile, parenteral formulations are associated with severe adverse effects. In an attempt to improve the efficacy of MTX, we synthesized polycaprolactone-polyethylene glycol-polycaprolactone (PCL-PEG-PCL) triblock copolymer by a ring-opening copolymerization reaction and used it as a carrier for the fabrication of MTX-loaded nanomicelles. Surfactant-free, self-assembled nanomicelles were prepared by nanoprecipitation technique and optimized through central composite design. The optimized nanomicelles exhibited a size distribution of 31 nm and an encapsulation efficiency of 91%. In vitro, the nanomicelles exhibited hemocompatibility, sustained release, and significantly high uptake in lipopolysaccharide activated macrophages. To facilitate application on the skin, optimized nanomicelles were loaded into a Carbopol 934-based hydrogel with eucalyptus oil as a penetration enhancer. Eucalyptus oil significantly improved the permeation of nanomicelles through the skin (p < 0.001). When the hydrogel was applied on the RA mice model, nanomicelles exhibited preferentially highest accumulation in the inflamed joints than other organs. As compared with the free MTX, MTX nanomicelles significantly improved the pharmacokinetic (4.34-fold greater half-life, 3.68-fold higher AUC_0-t, and 3.15-fold higher mean residence time) and pharmacodynamic profile ascertained through low inflammatory cytokines expression, improved oxidation protection, recovered behavioral responses, and radiological analysis. MTX nanomicelles-based hydrogel also significantly reduced the hepatotoxicity and did not activate the immune system. These results suggest that the MTX-loaded nanomicelles-based transdermal hydrogel can prove to be a promising agent against RA.