Uncovering the Critical Physiochemical Factors behind Polyelectrolyte Complexation with RNA

Polyelectrolyte complexes (PECs) are membranelles materials formed from oppositely charged polymers that phase separate from solution. PEC micelles (PCMs) are a class of self-assembled nanoparticles that contain a non-charged polymer component limiting polyelectrolyte complexation to the nanoscale. PCMs show significant promise for nucleic acid (NA) delivery due to their hydrated nature and programmable features. NAs, due to their dense negative charges, are not only sequestered but play an active role in assembly and thus strongly influence the physical properties of polyelectrolyte assemblies. Despite their like charges, DNA and RNA show vast differences in PCM assembly. Specifically, double-stranded (ds) RNA fails to assemble PCMs under the same conditions as dsDNA, which poses an enormous limitation for delivery of short-interfering RNA, which is predominately double-stranded and holds unique advantages for gene targeting and silencing. Through systemic studies of polyelectrolyte properties and assembly mechanisms, and utilizing a combination of small angle x-ray scattering, microscopy, and all-atom molecular dynamic simulations, we are uncovering the molecular forces behind RNA complexation. These studies expand our understanding of biomaterial self-assembly and will direct the design of future NA delivery systems.