The influence of polymeric properties on chitosan/siRNA nanoparticle formulation and gene silencing

We have previously introduced the use of the biomaterial chitosan to form chitosan/siRNA nanoparticles for gene silencing protocols. This present study shows that the physicochemical properties (size, zeta potential, morphology and complex stability) and in vitro gene silencing of chitosan/siRNA nanoparticles are strongly dependent on chitosan molecular weight (M,,) and degree of deacetylation (1313). High M-w and DD chitosan resulted in the formation of discrete stable nanoparticles similar to 200 nm in size. Chitosan/siRNA formulations (N:P 50) prepared with low M-w (similar to 10 kDa) showed almost no knockdown of endogenous enhanced green fluorescent protein (EGFP) in H1299 human lung carcinoma cells, whereas those prepared from higher M-w (64.8-170kDa) and DD (similar to 80%) showed greater gene silencing ranging between 45% and 65%. The highest gene silencing efficiency (80%) was achieved using chitosan/siRNA nanoparticles at N:P 150 using higher M,, (114 and 170 kDa) and DD (84%) that correlated with formation of stable nanoparticles of similar to 200 nm. In conclusion, this work confirms the application of chitosan as a non-viral carrier for siRNA and the importance of polymeric properties for the optimisation of gene silencing using chitosan/siRNA nanoparticles. (c) 2006 Elsevier Ltd. All rights reserved.