Tailoring Lipid Nanoparticle with Ex Situ Incorporated Conjugated Oligoelectrolyte for Enhanced mRNA Delivery Efficiency

Developing new lipid nanoparticle (LNP) formulations typically involves reconstruction from separate elements followed by rigorous purification steps, contributing to drawn-out drug discovery processes. Membrane-intercalating conjugated oligoelectrolytes (COEs) are water-soluble molecules featuring a conjugated backbone and peripheral ionic groups, specifically designed to spontaneously integrate into lipid bilayers. Herein, an ex situ strategy to "dope" the representative COE-S6 into pre-formed messenger RNA-LNPs (mRNA-LNPs) is presented, exploiting its spontaneous membrane intercalation property through a straightforward add-and-mix procedure. Incorporating 0.2% COE-S6 into mRNA-LNPs relative to lipid content reduced particle size from 84.5 ± 1 to 67.9 ± 0.8 nm, elevated cellular uptake, and improved endosomal escape. These traits culminate in an increase in in cellula transfection from 24.2 ± 1.6% to 98.7 ± 0.6%. When injected intravenously into healthy BALB/c mice, the optimized COE-S6-doped mRNA-LNPs boost in vivo luciferase expression by 1.75-fold. Additionally, COE-S6-doped mRNA-LNPs exhibit fluorogenic properties, enabling intracellular mechanistic studies via confocal microscopy. This simple method enhances the properties of mRNA-LNPs with minimal COE quantities, offering a novel strategy to improve existing LNP formulations and provide optical reporting capabilities, essential for expediting drug discovery and delivery.