Novel purification strategies for lipid nanoparticles building blocks

INTRODUCTION
Lipid Nanoparticles (LNPs) became widely known in the COVID-19 pandemic by playing a major role in the development of SARS-CoV-2 vaccines (1).
Nowadays, LNPs are one of the most commonly used tools for xRNA (2, 3) and xDNA delivery (4). LNPs usually consist of five components, ionizable lipids, phospholipids, cholesterols, pegylated lipids, and the payload, each of them adding unique properties to the structure of the LNP. Therefore, synthetic lipids as well as lipid conjugates have been gaining significant importance in recent years as drug target, therapeutic molecules, and liposomes.

Traditionally such molecules are purified by normal phase chromatography on silica using large volume of toxic solvents, including chlorinated solvents. As CDMO and producer of numerous lipids CordenPharma accepted the challenge of reducing organic solvent usage and developing greener processes. Ways to achieve this goal include aqueous/non-aqueous reversed-phase chromatography (NARP) (5, 6) and super critical fluid chromatography (SFC) that can be considered to supplant organic solvents (7) with more benign alternatives. In SFC, the mobile phase consists of a supercritical fluid like carbon dioxide replacing commonly used organic solvents.
SFC shows several benefits compared to HPLC. The polarity of supercritical carbon dioxide is similar to n-heptane, and it is miscible with most organic solvents, allowing to tune the polarity of the solvent. Due to its low viscosity and high diffusivity chromatographic processes are much faster as in HPLC, reducing run times significantly. Also, in economic regard SFC plays an important role by decreasing solvent costs. CO2 is non-toxic, non-flammable, and readily available, making SFC an environmentally benign alternative to other solvent-based chromatography methods.