Cationic Silyl-lipids for Enhanced Delivery of Anti-viral RNA Therapeutics

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PROJECT ABSTRACT Liposomes, including nucleic acid complexed lipid nanoparticles (LNPs) have shown success in drug delivery and formulation of sensitive RNA-based therapeutics, including the recent example of the mRNA Sar-COV-2 vaccine. The goal of this proposal is to synthesize and evaluate novel silyl-containing lipid structures to access innovative cationic lipid structures representing new chemical space for biomedical research. Three classes of cationic silyl-lipids will be synthesized in modular fashion to access structural and conformational cationic lipid analogs that have implications in the phase transition temperature and the fluidity of the bilayer, influencing the stability, toxicity, and fusogenicity of silyl- LNPs. This proposal is organized into three specific aims: 1) Synthesis of novel silyl-containing lipids as diverse cationic lipid vectors using catalytic hydrosilylation methods, particularly focusing on the modular incorporation of a silyldimethyl group as a bioisostere of a cis carbon–carbon double bond of known unsaturated cationic lipid vectors, as well as other silyl groups with relevant properties to modulate the branching and chain length of the resulting lipid. Target molecules include silyl analogs of DOTMA, DOTAP and DOSPA. 2) Evaluate biophysical properties of liposome formation and silyl-LNP formulation through established characterization techniques including measurements of zeta potential, transmission electron microscopy and small-angle X-ray scattering. The RNA/silyl-LNP complex will be characterized using HPLC to quantify RNA encapsulation. 3) Perform in cellulo studies to provide a comparative study on transfection efficacy of siRNA and cytotoxicity of silyl-lipid LNPs with commercially available liposome RNA delivery systems. Overall, our studies aim to demonstrate the potential of cationic silyl-lipids as novel structures for LNP formulation with the long-term goal to develop novel delivery systems and improve transfection efficacy of anti-viral RNA therapeutics.