Stability Criterion for the Assembly of Hybrid Lipid-Polymer-Nucleic Acid Nanoparticles

Abstract

Hybrid lipid-polymer-nucleic acid nanoparticles (LPNPs) provide unique delivery strategies for nonviral gene therapy. Since LPNPs consist of multiple components that can undergo different pairwise interactions between them, LPNPs are difficult to prepare and characterize. Here we demonstrate that the interaction between the polycation (polylysine) and DNA is robust through an innovative implementation of fluorescence cross-correlation spectroscopy, implying that the polycation is not displaced by cationic liposomes in the formation process. Hence, the polycation-DNA cores (polyplexes) and liposome shells must be oppositely charged to associate. Furthermore, we prove that the liposome:polyplex number ratio ({rho}N) is the primary critical parameter to predict stable LPNP formation. We establish that{rho} N [≥] 1 is required to ensure that every polyplex is enveloped by a liposome, avoiding the coexistence of oppositely charged species and thereby inhibiting aggregation. We expect our observations to be valid for the formation of many other LPNPs and composite nanomaterials.