pH‐Triggered Aggregation of Polylysine Nanoparticles Enhances TNF‐α siRNA Delivery for Rheumatoid Arthritis Therapy

Abstract The inefficient lysosomal escape of small interfering RNA (siRNA) from immune cells remains a major barrier to therapeutic efficacy. To address this challenge, an innovative pH‐triggered aggregation nanoplatform for enhanced siRNA delivery is developed. By using adamantane (Ad)‐modified hyperbranched poly‐L‐lysine (HBPL‐Ad) as a backbone, this nanoplatform incorporated acetalated β‐cyclodextrin (β‐ACD) as a pH‐sensitive “gatekeeper”, together with siRNA to prepare physiologically stable aggregated nanoparticles (ANPs). Triggered by the acidic lysosomal microenvironment, the β‐ACD hydrolysis exposed β‐CD cavities to enable strong host‐guest (β‐CD/Ad) binding. This binding caused nanoparticle aggregation and subsequent mild lysosomal membrane permeabilization (LMP), facilitating efficient siRNA escape independent of the proton sponge effect. The ANPs demonstrated superior cellular uptake and significantly enhanced TNF‐α silencing across macrophages, dendritic cells, and Jurkat immune cells in vitro. Intraperitoneal administration of ANPs loaded with TNF‐α siRNA in a collagen‐induced arthritis (CIA) model achieved 93% mRNA reduction and 95% protein reduction in joint TNF‐α levels, significantly outperforming Lipo2000 (56% mRNA and 60% protein reduction), effectively attenuating synovitis and cartilage erosion without detectable systemic toxicity. This work establishes pH‐triggered programmable aggregation as a potent and transformative strategy for overcoming immune cell delivery barriers, offering a promising clinically viable platform for RNAi‐based immunotherapy.