Effects of tripolyphosphate on cellular uptake and RNA interference efficiency of chitosan-based nanoparticles in Raw 264.7 macrophages

Tumor necrosis factor-alpha (TNF-alpha) is a major pro-inflammatory cytokine that is mainly secreted by macrophages during inflammation. Here, we synthesized a series of N-(2-hydroxy)propy1-3-trimethyl ammonium chitosan chlorides (HTCCs), and then used a complex coacervation technique or tripolyphosphate (TPP)-assisted ionotropic gelation strategy to complex the HTCCs with INF-alpha siRNA (siTNF) to form nanoparticles (NPs). The resultant NPs had a desirable particle size (210-279 nm), a slightly positive zeta potential (14-22 mV), and negligible cytotoxicity against Raw 264.7 macrophages and colon-26 cells. Subsequent cellular uptake tests demonstrated that the introduction of TPP to the NPs markedly increased their cellular uptake efficiency (to nearly 100%) compared with TPP-free NPs, and yielded a correspondingly higher intracellular concentration of siRNA. Critically, in vitro gene silencing experiments revealed that all of the TPP-containing NPs showed excellent efficiency in inhibiting the mRNA expression level of TNF-alpha (by approximately 85-92%, which was much higher than that obtained using OligofectamineisiTNF complexes). Collectively, these results obviously suggest that our non-toxic TPPcontaining chitosan-based NPs can be exploited as efficient siTNF carriers for the treatment of inflammatory diseases. (C) 2016 Elsevier Inc. All rights reserved.