Morphological Characterization of Self-Amplifying mRNA Lipid Nanoparticles

Area of Science:

• Biotechnology
• Nanomedicine
• Vaccine Development

Background:

• Messenger RNA (mRNA) technology offers rapid vaccine development for pandemics and endemic diseases.
• Lipid nanoparticles (LNPs) are essential vehicles for delivering mRNA into cells.
• Self-amplifying mRNA (SAM) platforms enhance antigen expression using lower doses than conventional mRNA.

Purpose of the Study:

• To characterize the morphology of LNPs containing self-amplifying mRNA (SAM LNPs).
• To investigate the structural changes of SAM upon encapsulation within LNPs.
• To elucidate the internal structure and component distribution within SAM LNPs.

Main Methods:

• Small-angle neutron scattering (SANS) and small-angle X-ray scattering (SAXS) were employed.
• A capped cylinder core-shell model with two interior compartments was utilized.
• Comparative analysis of free SAM and encapsulated SAM within LNPs was performed.

Main Results:

• SAM undergoes conformational changes, becoming more compact when encapsulated in LNPs.
• A distinct "bleb" morphology, featuring lipid-rich and RNA-rich cores within a lipid shell, was observed in SAM LNPs.
• SANS and SAXS data confirmed a prevalent two-core compartment structure with heterogeneous component distribution.

Conclusions:

• Bleb two-compartment structures are a representative morphology in SAM LNPs.
• Understanding SAM LNP morphology is critical for rational design and optimization of mRNA delivery systems.
• Further research is needed to explore the role of different morphologies and their formation mechanisms in SAM LNP function.