Nanoparticulate DNA scavenger loading methotrexate targets articular inflammation to enhance rheumatoid arthritis treatment.

Abnormal high cell-free DNA (cfDNA) activates toll-like receptor 9 (TLR9) in immune cell's endosome to produce inflammatory cytokines that aggravate rheumatoid arthritis (RA). Previously, we successfully developed cationic nanoparticles (cNPs) relieving symptoms of RA rats by scavenging cfDNA, but the strong positive charges of cNPs may cause systemic toxicity during circulation via intravenous injection. Herein, we design cNP-pp-PEG to shield the nanoparticles with MMP2-sensitive peptide (pp) linked PEG, the cations are exposed only when PEG is removed by MMP2, which is enriched in the inflamed articular cavity. Taking advantage of the self-assembled cNP-pp-PEG, hydrophobic methotrexate (MTX) is loaded into its core through hydrophobicity interaction, obtaining MTX@cNP-pp-PEG. The engineered reagents exhibit lower toxicity, longer retention time and higher accumulation in inflamed joints comparing to its counterpart MTX@cNP-pp due to the hidden cationic charges. Moreover, the anti-inflamed activity of MTX strengthens the therapeutic efficiency of cNPs. The dual roles of cNPs as therapeutic agent and MTX carrier significantly enhance the therapeutic efficacy and extended administration interval to 4 days. This research addresses the issues of targeting inflamed joints, reducing the systemic toxicities of both cNPs and MTX, and extending administration interval, demonstrating an upgraded strategy for DNA scavenger application.