Reductively Responsive siRNA-Conjugated Hydrogel Nanoparticles for Gene Silencing

Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
Journal of the American Chemical Society (Impact Factor: 12.11). 04/2012; 134(17):7423-30. DOI: 10.1021/ja300174v
Source: PubMed


A critical need still remains for effective delivery of RNA interference (RNAi) therapeutics to target tissues and cells. Self-assembled lipid- and polymer-based systems have been most extensively explored for transfection with small interfering RNA (siRNA) in liver and cancer therapies. Safety and compatibility of materials implemented in delivery systems must be ensured to maximize therapeutic indices. Hydrogel nanoparticles of defined dimensions and compositions, prepared via a particle molding process that is a unique off-shoot of soft lithography known as particle replication in nonwetting templates (PRINT), were explored in these studies as delivery vectors. Initially, siRNA was encapsulated in particles through electrostatic association and physical entrapment. Dose-dependent gene silencing was elicited by PEGylated hydrogels at low siRNA doses without cytotoxicity. To prevent disassociation of cargo from particles after systemic administration or during postfabrication processing for surface functionalization, a polymerizable siRNA pro-drug conjugate with a degradable, disulfide linkage was prepared. Triggered release of siRNA from the pro-drug hydrogels was observed under a reducing environment while cargo retention and integrity were maintained under physiological conditions. Gene silencing efficiency and cytocompatibility were optimized by screening the amine content of the particles. When appropriate control siRNA cargos were loaded into hydrogels, gene knockdown was only encountered for hydrogels containing releasable, target-specific siRNAs, accompanied by minimal cell death. Further investigation into shape, size, and surface decoration of siRNA-conjugated hydrogels should enable efficacious targeted in vivo RNAi therapies.

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    • "In addition, our studies using PEG particles enabled us to broaden our understanding of innate immune activation by particles comprised of a polymer composition that enables wide-ranging chemical modifications for enhanced functionality, such as cell targeting, pH-specific cargo release and siRNA incorporation as previously reported by our group and others [19], [20], [53], [54]. Interestingly, although these PEG particles are not considered biodegradable, they did not induce lung inflammation as seen with other non-degradable particles such as those comprised of polystyrene [46]. "
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