pH-sensitive nano-polyelectrolyte complexes with arthritic macrophage-targeting delivery of triptolide

Since pro-inflammatory macrophages take on a critical significance in the pathophysiology of rheumatoid arthritis (RA), the therapeutics to affect macrophages may receive distinct anti-RA effects. However, the therapeutic outcomes are still significantly impeded, which is primarily due to the insufficient drug delivery at the arthritic site. In this study, the macrophage-targeting and pH stimuli-responsive nano-polyelectrolyte complexes were designed for the efficient targeted delivery of triptolide (TP/PNPs) on the arthritic site. The anionic and cationic amphiphilic copolymers, i.e., hyaluronic acid-g-vitamin E succinate (HA-VE) and the quaternized poly (β-amino ester) (QPBAE-C₁₈), were prepared and then characterized. The result indicated that TP/PNPs with the uniform particle size of ∼ 175 nm exhibited the high drug loading capacity and storage stability based on the polymeric charge interaction, in which DLC and DEE of TP/PNPs were obtained as 11.27 ± 0.44 % and 95.23 ± 2.34 %, respectively. Mediated by the "ELVIS" effect of NPs, CD44 receptor-mediated macrophage targeting, and pH-sensitive endo/lysosomal escape under the "proton sponge" effect, TP/PNPs exhibited the enhanced cellular internalization and cytotoxicity while mitigating the inflammation of LPS-activated RAW 264.7 cells. Even after 96-hour after administration, PNPs were preferentially accumulated in the inflammatory joints in a long term. It is noteworthy that after treatment for 14 days with 100 μg/kg of TP, TP/PNPs significantly facilitated arthritic symptom remission, protected cartilage, and mitigated inflammation of antigen-induced arthritis (AIA) rats, whereas the systematic side-effects of TP were reduced. In this study, an effective drug delivery strategy was proposed for the treatment of RA.