Lipid Nanoparticle Buffer Exchange for Stable Nucleic Acid Delivery

The patent changes the chemical structure parameter of the lipid from quaternary ammonium (permanent positive charge) to tertiary ammonium (pH-dependent charge). This parameter change allows the lipid to be positively charged at acidic pH for nucleic acid binding, then become neutral at physiological pH to reduce cytotoxicity, while maintaining delivery capability.

The patent performs preliminary action by optimizing the buffer composition during the nanoparticle formation process. Specifically, using citrate buffer at controlled pH during mixing and then adjusting to Tris buffer at pH 7.4 stabilizes the nanoparticle structure in advance, preventing aggregation and degradation during storage while maintaining the low cytotoxicity of tertiary ammonium lipids.

The patent extracts the harmful acidic buffer components from the final nanoparticle formulation through a buffer exchange process. By removing the citrate buffer used during formation and replacing it with Tris buffer, the destabilizing agents are taken out, leaving behind stable nanoparticles suitable for long-term storage.

The patent uses a simple buffer exchange approach instead of complex cryopreservation or lyophilization processes. The Tris buffer acts as a simple, effective stabilizing medium that maintains nanoparticle stability without requiring additional cryoprotectants, freezing equipment, or complex drying/reconstitution procedures, thereby maintaining process simplicity.