Cationic block copolymer nanoparticles with tunable DNA affinity for treating rheumatoid arthritis

A high concentration of cell-free DNA (cfDNA) in joints is considered a disease causative agent of rheumatoid arthritis (RA) and cfDNA scavenging has been regarded as an efficient therapeutic avenue. Cationic polymers can hamper progression of joint inflammation in a rat model of RA by scavenging cfDNA; however, they may cause systemic toxicity due to the strong positive charges. To reduce the toxicity, herein a library of cationic nanoparticles (cNPs) of block copolymer micelles is developed and the effects of structure and surface composition on cNP efficacy to bind nucleic acids, toxicity, and therapeutic activity on a collagen induced arthritis (CIA) rat model of RA are assessed. The library includes cNPs with a homoshell from poly(lactic-co-glycolic acid)-block-poly(2-(dimethylamino)ethyl methacrylate) (PLGA-b-PDMA) block copolymers and cNPs with a mixed shell of poly(ethylene glycol) (PEG) and PDMA by coself-assembling PLGA-b-PDMA and PLGA-b-PEG block copolymers. Relatively to the homoshell cNPs, introduction of PEG segments translates into a lower DNA binding efficacy while preserving ability to hamper joint inflammation. Moreover, they show a greater accumulation and longer retention at the inflamed joints, allowing a lower administration frequency. In conclusion, this work shows that the therapeutic index of cationic materials can be tuned by introducing surface neutral moieties.