Flow Imaging Microscopy to Monitor Lipid Nanoparticle Aggregation

Flow Imaging Microscopy to Monitor Lipid Nanoparticle Aggregation

Lipid nanoparticles (LNPs) are gaining attention as effective drug delivery vehicles, especially since their successful use in the COVID-19 vaccines. Both Moderna and Pfizer SARS-CoV-2 vaccines depend on LNPs to deliver messenger RNA (mRNA), a delicate nucleic acid molecule, to the cytosol of target cells unharmed.

LNPs are a spherical assembly of lipid and/or lipid-like molecules that encapsulate and protect the therapeutic nucleic acid payload in the patient’s body. Like protein-based biotherapeutics, LNPs are subject to aggregation and other forms of degradation during storage periods and following stresses like freeze-thaw cycles or agitation due to sample (mis)handling.

We performed a study to show how FlowCam 8100 and FlowCam Nano can be applied to analyze aggregation and particle formation in an LNP formulation. The LNP formulations were exposed to one of two accelerated stability conditions (freeze-thaw stress and heat stress) to induce aggregation and degradation. Particle concentrations, sizes, and images of the stressed samples were analyzed using FlowCam 8100 and FlowCam Nano. The results of the study demonstrate the combined benefit of FlowCam instruments in LNP biopharmaceutical formulation monitoring and process improvement strategies.

While the differences in submicron (0.3 µm - 1 µm) particle size between samples were negligible, the subvisible (> 1 µm) particle size distribution generated by heating stress was shifted towards larger particle sizes relative to the distribution for particles generated by freeze-thaw stress. These results suggest that heating stress was more damaging to this LNP formulation than freeze-thaw stress.

FlowCam Nano and 8100 images after heat and freeze-thaw stress study

The figure above shows examples of FlowCam 8100 and FlowCam Nano images obtained from freeze-thaw- and heat-stressed samples. The LNP particles generally exhibited the amorphous shapes that are expected of other types of API particles (e.g. protein aggregates). It is important to highlight the boxed FlowCam Nano images for both stresses. Each of these images appears to contain two or more distinct but attached particles, suggesting that these particles could be dimeric LNP structures. 

FlowCam application note thumbnail - Flow imaging microscopy to monitor lipid nanoparticle aggregation


This observation suggests that FlowCam Nano can be used to monitor LNP aggregation even when only oligomeric LNP aggregates have been generated. Download the application note to read the full study.

Download Application Note


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