Introduction:
Mass photometry, a recently-developed technique for measuring the mass of single molecules in solution, has the potential to aid companies utilizing adeno-associated viruses (AAV) for gene therapies. Researchers from the UK Center for Process Innovation (CPI) found that mass photometry performed as well as the gold standard approaches for assessing the number of full/empty viral capsids, which is a critical measure of AAV product quality.
- The presence of empty capsids reduces the amount of therapeutically active product and acts as an impurity in AAV manufacturing. Current gold-standard techniques for assessing empty capsids are nonoptimal.
- Using a combination of droplet digital PCR (ddPCR) and enzyme-linked immunosorbent assay (ELISA) to measure genome and protein capsid titer is accurate but low throughput. Other methods such as analytical ultracentrifugation and UV spectroscopy have their limitations.
- The researchers tested two new techniques, anion-exchange high performance liquid chromatography (AEX-HPLC) and mass photometry, to improve their analytical toolbox. Mass photometry, which relies on light scattered from a single particle to measure its mass, was comparable in accuracy to ddPCR/ELISA with faster run times.
- The team is working on improving their HPLC technique and exploring other methods such as capillary isoelectric focusing (cIEF) and size exclusion chromatography multi-angle light scattering (SEC-MALS) for empty/full capsid analysis.
- Mass photometry could be a valuable tool for companies looking to assess the empty capsid content of their final AAV product.
Conclusion:
Mass photometry has demonstrated its potential in aiding gene therapy companies using adeno-associated viruses. By accurately measuring the mass of single molecules in solution, mass photometry can provide valuable information about the empty capsid content of AAV products, which is crucial for product quality assessment. With faster run times and no need for labeling, this high-throughput technique could be a valuable addition to the analytical toolbox of gene therapy manufacturers.
