Investigating PEG-lipid alternatives for Lipid Nanoparticles to address the PEG dilemma

Student’s name: Fernanda Siordia Home Institution: Southwestern College NNCI Site: SDNI @ UC San Diego REU Principal Investigator: Dr. Ester Kwon – Department of Bioengineering, UC San Diego REU Mentor: Yazmin Hernandez- Department of Bioengineering, UC San Diego Abstract: Lipid nanoparticles (LNPs) are the most clinically advanced platform for gene delivery, with notable FDA-approved examples including the Onpattro siRNA liver formulation and COVID-19 mRNA vaccines. LNPs consist of an ionizable cationic lipid, a helper lipid, cholesterol, and a poly (ethylene glycol) (PEG) lipid. Ionizable lipids protect the RNA cargo and assist in cytosolic transport, while cholesterol and PEG prevent aggregation and extend the circulation half-life. Helper lipids, typically phospholipids, enhance stability and RNA encapsulation. Currently, FDA-approved lipid nanoparticles (LNPs) administered systemically are primarily used for liver-targeted therapies. This is because LNPs naturally adsorb apolipoprotein (ApoE). Increasing PEG-lipid length and concentration can improve accumulation in non-liver organs. However, this creates a “PEG dilemma”; as the steric barrier also hinders membrane fusion between LNPs and the endosomal membrane, affecting cargo release. The goal of this study is to evaluate PEG-lipid alternatives including poly(sarcosines), poly(sorbates), and poloxamers to maintain stability and enhance mRNA delivery efficiency. The project involves synthesizing LNPs with these alternatives and screening formulations for size, zeta potential, mRNA encapsulation, serum stability, and protein corona formation. Top-performing formulations will be tested for cellular activity to assess endosomal escape efficiency.