Abstract
Background: Polymeric nanoparticles have been explored as efficient tools for siRNA delivery to induce RNAi-mediated gene knockdown. Chemical modifications of polyethylenimines (PEI) enhance nanoparticle efficacy and biocompatibility. Their in vivo use, however, benefits from prior analyses in relevant in vitro 3D conditions. Methods: We utilize a 3D ALI cell culture model for testing the biological activities and toxicities of a set of different PEI-based nanoparticles with different chemical modifications. This also includes a novel, fluoroalkyl-modified PEI. Reporter gene knockdown is directly compared to 2D cell culture. In parallel, biocompatibility is assessed by measuring cell viability and lactate dehydrogenase (LDH) release. Results: Knockdown efficacies in the 3D ALI model are dependent on the chemical modification and complex preparation conditions. Results only correlate in part with gene knockdown in 2D cell culture, identifying nanoparticle penetration and cellular internalization under 3D conditions as important parameters. The 3D ALI cell culture is also suitable for the quantitative determination of nanoparticle effects on cell viability and acute toxicity, with biocompatibility benefitting from PEI modifications. Conclusions: The 3D ALI cell model allows for a more realistic assessment of biological nanoparticle effects. A novel fluoroalkyl-modified PEI is described. Optimal preparations of PEI-based nanoparticles for siRNA delivery and gene knockdown are identified.