Phosphorous-containing, amphiphilic ABB′ copolymers as siRNA nanocarriers with enhanced stability, reduced in vitro cytotoxicity, and efficient knockdown ability for the treatment of ocular diseases†

Abstract

An RNA interference (RNAi) strategy using siRNA targeting NF-κB could counteract its harmful effects and provide therapeutic benefits for several ocular pathophysiologies. Rare-earth metal-mediated group-transfer polymerization was employed to synthesize precise AB and ABB′ block copolymers from 2-vinylpyridine and dialkyl vinylphosphonates (DAVP, alkyl = ethyl, allyl) as siRNA nanocarriers. Modifying the allyl group of the vinylphosphonate unit transformed these polymers into cationic, amphiphilic copolymers. All polymers showed maximum siRNA encapsulation at a low N/P ratio of 2. The cationic unit distribution along the PDAVP chain influences the encapsulation capacity and the stability of the polyplexes. A less dense distribution of cationic units led to increased amounts of free siRNA, even at higher N/P ratios, but to a better stability of the polyplexes. Diffused calcein signals observed from cells treated with ABB′/siRNA polyplexes revealed an endosomal escape capability while maintaining excellent in vitro cell viability. Ocular cell lines transfected with these polyplexes demonstrated a superior NF-κB/RelA gene silencing efficiency. This study highlights the potential of phosphorous-containing, amphiphilic polymers as nucleic acid carriers with enhanced stability, excellent cytotoxicity profiles, and efficient knockdown ability.