Quantifying Heterogeneous AAV Capsid Loading Using Mass Photometry

Adeno-associated viruses (AAVs) are used in gene therapies to deliver genetic material to cells. Quantifying the proportions of heterogeneously filled AAV capsids is a critical step in AAV therapy characterization. Mass photometry, a technique that measures the mass of individual particles, can identify and quantify different populations of AAV capsids with varied loading in a sample. The SamuxMP mass photometer, which was designed for AAV characterization, has been used to distinguish and measure heterogeneously filled AAVs. It requires minimal sample volumes and concentrations, making it ideal for AAV sample evaluation. Tests have confirmed that the SamuxMP can consistently differentiate and quantify populations of heterogeneously filled capsids in an AAV sample, with results aligning well with those from the more labor-intensive analytical ultracentrifugation (AUC).