The implementation of lipid nanoparticles (LNPs) has been on the rise since the COVID-19 pandemic. Despite some success, there are translational gaps and challenges in this technology that must be addressed. Zahra Rattray, Senior Lecturer at the University of Strathclyde, pointed to some of these technical challenges and suggested that by maintaining an open dialogue, scientists can begin developing systems and models that can tackle them.
More specifically, the presentation highlighted the use of microfluidics for consistent batch-to-batch production of lipid nanoparticles, while keeping in mind issues like scalability and batch variation.
One case study looked at measuring LNP physicochemical attributes. Using a Zetasizer, the team gathered data on particle size distribution, polydispersity, and encapsulation efficiency. This was complemented with a RiboGreen assay that showed how much oligonucleotide is incorporated into the LNP.
To fully understand the product in depth, Rattray said it is important to understand the formulation in depth. So, she looked at applying a technique called Flow Field-Flow-Fractionation (FFF) which is used for high-resolution separation and analysis of lipid nanoparticles. Unlike traditional methods, this technique can also be integrated with multiple inline detectors to provide in-depth information on concentration and dynamic light scattering (DLS). Rattray mentioned that FFF is routinely complemented with an orthogonal technique called nanoparticle tracking analysis (NTA).
She outlined the value of NTA: “It offers much higher resolution because it tracks individual particles and gives much higher resolution information about particle size distribution and also the concentration of particles. So using NTA, we can actually see if we have one of these processing steps during the manufacturing process, how much do we lose in terms of particle mass, but also how much do we see in terms of aggregation.”
The freeze-thaw stability of LNPs, especially DOTAP LNPs, is relatively poor, meaning many research groups are exploring novel cryoprotectants to stabilise these systems. Using the DLS data, one can observe a loss of stability in the absence of any cryoprotectant.
The Asymmetric Flow Field-Flow Fractionation (AF4) profile was used to analyse the freeze-thaw stability of LNPs across three different batches. The analysis showed that batches 2 and 3 had very similar responses to freeze-thaw cycles and exhibited similar morphologies. Meanwhile, batch 1 displayed a completely different profile which suggests significant batch-to-batch variation.
The LNP protein corona has an impact on immunogenicity, biodistribution and circulation time. For the protein corona LNP traditional recovery techniques lead to loss of LNP structure. Rattray used an AF4 separation technique to investigate SM102 lipid nanoparticles and their interaction with High-Density Lipoprotein (HDL). The morphology of the LNPs changed from spherical to more elongated or oval shapes, indicating that HDL presence alters the confirmation and morphology of the particles.