Arginase-1 responsive lipid nanoparticles for cytosolic TNF-α-siRNA release to alleviate colitis

Efficient cytosolic delivery of small interfering RNA (siRNA) remains a challenge in RNA therapeutics, particularly for oral administration. Identifying new cytosolic stimulus-responsive targets is thus crucial for optimizing siRNA delivery. Given the elevated intracellular arginase-1 (Arg1) levels in inflamed colonic mucosa, we developed lipid nanoparticles (siRNA-LANPs) derived from L-arginine-modified chitosan (ACS) for the cytosolic release of TNF-α-siRNA to treat ulcerative colitis (UC). The siRNA-LANPs exhibited superior Arg1-binding affinity compared to its substrate, L-arginine, enabling rapid Arg1-responsive release. Moreover, we found that siRNA-LANPs maintained nanoparticle stability, and 84.5 % of the loaded siRNA remained intact in simulated digestive fluids over 12 h. Following oral administration, siRNA-LANPs efficiently penetrated the mucus layer and preferentially accumulated in inflamed colonic tissue compared to healthy colon tissue. In DSS-induced colitis mice, siRNA-LANPs significantly reduced disease severity through TNF-α silencing, achieving greater therapeutic efficacy than sulfasalazine (a first-line UC treatment). The siRNA-LANPs exhibited superior TNF-α silencing compared to transfection reagent Lipo3000 and TNF-α biologic agent infliximab. The enhanced performance was attributed to multiple endocytic pathways, improved lysosomal escape capability (29.7 %), and Arg1-mediated cytoplasmic siRNA release. In summary, Arg1 seems to be a promising intracellular target for stimulus-responsive, oral siRNA delivery in UC treatment.