Systematic Evaluation of Protein-Based Nanoparticles for Stable Delivery of Small Interfering RNA

Developing a delivery vehicle to protect siRNA from degradation is a significant challenge. To solve this challenge, researchers attempted to use protein-based nanoparticles to deliver siRNA with limited to moderate success. However, a systematic investigation of comparing the ability of different protein-based nanoparticles as vehicles to deliver siRNA stably within cells is still unavailable. Therefore, in this study we synthesized a library of both non-targeted (proteinsiRNA) nanoparticles (NPs) and targeted (antibody conjugated protein-siRNA) NPs and evaluated ability to stably deliver siRNA in to cells to silence the gene of interest. We investigated nanoparticles of casein, bovine serum albumin, and gelatin for the delivery of siRNA. We synthesized and characterized a total of 12 nanoconjugates; in these conjugates, we either encapsulated, electrostatically attached, or covalently conjugated siRNA. We evaluated the efficiency of attaching siRNA to nanoconjugates, stability, and cellular delivery. The ability of siRNA to silence the protein of interest in cancer cells was also investigated. Among non-targeted conjugates, BSA matrix imparted relatively high stability to siRNA when encapsulated. Among targeted nanoconjugates, gelatin nanoparticles rendered high stability to siRNA upon covalent conjugation to the surface. On comparing with both targeted and non-targeted NPs for release of siRNA within cells, antibody-gelatin-siRNA conjugate exhibited high release and functional activity (down-regulation of target protein levels) within the cells as confirmed by both fluorescence imaging and Western blotting. In summary, our investigations show that targeted gelatin nanoparticles and non-targeted BSA nanoparticles possess high stability and excellent gene suppression capabilities and warrants further studies. We can extend the results from this study to develop stable siRNA delivery vehicles to specifically silence the protein of interest.