Multifunctional folate receptor-targeting and pH-responsive nanocarriers loaded with methotrexate for treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by progressive cartilage and bone destruction. Activated macrophages that overexpress folic acid (FA) receptors play an important role in RA, due to their abundance in inflamed synovial membrane and joints. In an effort to deliver drugs to the inflamed tissues, multifunctional FA receptor-targeting and pH-responsive nanocarriers were developed. They were composed of lipids, polyethylene glycol (PEG)–poly(lactic-co-glycolic acid) (PLGA) forming a hydrophilic shell, FA around the hydrophilic shell as a targeting ligand, and poly(cyclohexane-1,4-diylacetone dimethylene ketal) (PCADK) and PLGA as a hydrophobic core. PCADK also acts as a pH-responsive material. Methotrexate (Mtx) was encapsulated in the nanoparticles, which exhibited pH-responsive release in vitro. Cellular uptake and cytotoxicity experiments revealed that FA-PEG-PLGA/PCADK–lipid nanoparticles loaded with Mtx (FA-PPLNPs) exhibited superior cellular uptake and higher cytotoxicity to activated macrophages than PPLNPs/Mtx. The therapeutic effect of FA-PPLNPs/Mtx in RA was confirmed in an adjuvant-induced arthritis rat model. These results suggest that the multifunctional folate receptor-targeting and pH-responsive nanocarriers are promising for the treatment of RA.