Biodegradable Dextran Nanogels for RNA Interference: Focusing on Endosomal Escape and Intracellular siRNA Delivery

The successful therapeutic application of small interfering RNA (siRNA) largely relies on the development of safe and effective delivery systems that are able to guide the siRNA therapeutics to the cytoplasm of the target cell. In this report, biodegradable cationic dextran nanogels are engineered by inverse emulsion photopolymerization and their potential as siRNA carriers is evaluated. The nanogels are able to entrap siRNA with a high loading capacity, based on electrostatic interaction. Confocal microscopy and flow cytometry analysis reveal that large amounts of siRNA-loaded nanogels can be internalized by HuH-7 human hepatoma cells without significant cytotoxicity. Following their cellular uptake, it is found that the nanogels are mainly trafficked towards the endolysosomes. The influence of two different strategies to enhance endosomal escape on the extent of gene silencing is investigated. It is found that both the application of photochemical internalization (PCI) and the use of an influenza-derived fusogenic peptide (diINF-7) can significantly improve the silencing efficiency of siRNA-loaded nanogels. Furthermore, it is shown that an efficient gene silencing requires the degradation of the nanogels. As the degradation kinetics of the nanogels can easily be tailored, these particles show potential for intracellular controlled release of short interfering RNA.