Galactosylated trimethyl chitosan-cysteine nanoparticles loaded with Map4k4 siRNA for targeting activated macrophages.

Galactosylated trimethyl chitosan-cysteine (GTC) nanoparticles (NPs) were developed for oral delivery of a mitogen-activated protein kinase kinase kinase kinase 4 (Map4k4) siRNA (siMap4k4) to the activated macrophages for treatment of dextran sulfate sodium (DSS)-induced ulcerative colitis (UC). siRNA loaded GTC NPs were prepared based on ionic gelation of GTC with anionic crosslinkers (tripolyphosphate (TPP) or hyaluronic acid (HA)). The types of crosslinkers involved in GTC NPs significantly affected their physicochemical characteristics. GTC/TPP NPs with smaller particle size and lower zeta potential possessed superior structural stability in gastrointestinal environment compared to GTC/HA NPs. Cellular uptake of GTC/TPP NPs in activated macrophages was significantly enhanced compared to trimethyl chitosan-cysteine (TC)/TPP NPs owing to galactose receptor-mediated endocytosis. The in vitro and in vivo gene knockdown measurement showed that siMap4k4 loaded GTC/TPP NPs effectively inhibited TNF-α production, which remarkably outperformed siMap4k4 loaded TC/TPP NPs. Compared to TC/TPP NPs, GTC/TPP NPs more efficiently promoted the distribution of siRNA in ulcerative colon following oral administration. Daily oral administration of GTC/TPP NPs containing siMap4k4 significantly improved DSS-induced body weight loss, colon length shortening, and increase of myeloperoxidase activity. This study would provide an effective approach for oral siRNA delivery in the treatment of inflammatory bowel diseases.