Microfluidic-Based Holonomic Constraints of siRNA in the Kernel of Lipid/Polymer Hybrid Nanoassemblies for Improving Stable and Safe In Vivo Delivery

A safe and efficient delivery system is critical for clinical application of siRNA. However, the conventional electrostatic interaction-based siRNA nanoplexes with bulk mixing preparation were always unsatisfactory for its stability and safety. In this study, the new core–shell lipid/PCL-PEI/siRNA nanoparticles (LPS NPs) endowing holonomic constraint of siRNA in the inner core were prepared by microfluidic technology. On the microfluidic chip, siRNAs were completely compressed into the inner hydrophilic core of reverse PCL-PEI micelles at a low N/P ratio of 5, followed by coating a neutral lipid membrane to form core–shell nanoparticles, which had a uniform size (120.2 ± 1.4 nm) and a negative charge (−8.8 ± 1.6 mV). Compared to bulk mixing-based LMS NPs, the lower usage of cationic PCL-PEI materials and stronger protection of siRNA in serum were found in the microfluidic-based LPS NPs. Furthermore, it was demonstrated that the LPS NPs exhibited significant downregulation of EGFR mRNA and protein expression level both in vitro and in vivo, and showed significant inhibition of tumor growth following systemic administration along with no obvious systemic toxicity. These findings demonstrated that the microfluidic-based lipid/polymer hybrid nanoassemblies would offer a promising siRNA delivery system for clinical application.