Enhanced mRNA and pDNA delivery <i>via</i> PEGylated solid lipid nanoparticles with an optimally balanced ionizable/cationic lipid content

Non-viral gene delivery holds significant promise for the treatment of various diseases. Solid lipid nanoparticles (SLNs) are emerging as promising gene delivery vehicles due to their ease of manufacture and high stability. However, the development of efficient and safe SLNs remains a challenge. This study aims to develop ionizable lipid-incorporated PEGylated SLNs (PEG-iSLNs) for effective mRNA and plasmid DNA (pDNA) delivery. Using a solvent emulsification/evaporation technique, a series of PEG-iSLNs were formulated at various weight ratios of the ionizable lipid ALC-0315 to the cationic lipid DOTMA. PEG-iSLNs formulated at an optimal ALC-0315/DOTMA ratio had superior mRNA transfection potency and membrane fusion activity over those with either ALC-0315 or DOTMA alone. iSLNs and PEG-iSLNs appeared to remain stable during storage at 4 °C over 18 and 12 months, respectively. Bioluminescence imaging study demonstrated the feasibility of the top-performing candidate, PEG-iSLN-3, for <i>in vivo</i> delivery of mRNA <i>via</i> both intramuscular and footpad subcutaneous routes, highlighting its potential as an efficient and nontoxic delivery vehicle for diverse nucleic acid cargoes.