Ionizable Lipid Nanoparticles for mRNA Delivery: Internal Self-Assembled Inverse Mesophase Structure and Endosomal...

Area of Science:

• Nanomedicine and Drug Delivery
• Biophysical Chemistry
• Molecular Pharmaceutics

Background:

• Ionizable lipid nanoparticles (LNPs) are essential for mRNA vaccine efficacy, facilitating mRNA loading, delivery, and release.
• The precise relationship between LNP physicochemical properties, internal nanostructure, and biological function remains poorly understood, hindering rational RNA therapeutic design.
• Key ionizable lipids like ALC-0315 and SM-102 are critical for endosomal escape and mRNA transfection.

Purpose of the Study:

• To establish a clear connection between pH-triggered mesophase transitions of ionizable LNPs and their biological performance.
• To provide mechanistic insight into how internal nanostructure influences mRNA delivery efficiency, endosomal escape, and gene expression.
• To investigate the impact of helper lipids, cholesterol, and protein coronas on LNP behavior and efficacy.

Main Methods:

• Utilized time-resolved synchrotron radiation small-angle X-ray scattering (SAXS) to study the pH-dependent self-assembly and structural transitions of LNPs.
• Investigated LNPs containing COVID-19 vaccine ionizable lipids (ALC-0315, SM-102) with and without nucleic acid cargos (mRNA, polyA, plasmid DNA).
• Correlated LNP mesophase behavior with mRNA transfection efficiency in macrophage cells and analyzed protein corona effects.

Main Results:

• Demonstrated that pH-induced mesophase transitions (non-ordered to inverse micellar, hexagonal, cubic phases) correlate with mRNA transfection efficiency.
• Revealed the influence of helper lipids (monoolein, phytantriol) and cholesterol on LNP physicochemical properties and gene delivery performance.
• Showed that protein coronas can alter LNP internal structure and delivery efficiency, potentially explaining in vitro-in vivo discrepancies.

Conclusions:

• The internal nanostructure and pH-dependent mesophase behavior of LNPs are critical determinants of mRNA delivery efficiency and gene expression.
• Understanding these structure-function relationships enables the rational design of improved mRNA therapeutics.
• Future research should focus on optimizing endosomal escape, exploring non-endocytic uptake, modulating protein coronas, and utilizing AI for formulation design.