DAISY-NTA for Virus Particle Analysis
DAISY-NTA is perfectly suited to routine analysis of viral particle preparations. A single measurement will quickly tell you the total viral particle count, identify any aggregates, and give further information on virus particle quality. The ability of DAISY-NTA to accurately measure refractive index at the single particle level gives the possibility to distinguish between complete virions and empty capsids. Below you can see an example of DAISY-NTA analysis of adenoviral vector preparations.
Quantification and Characterisation of Adenoviral Preparations
Size and concentration
From a single recording DAISY-NTA provides unprecedented insight into the content of your viral preparations. As with standard NTA, DAISY-NTA accurately reports size and concentration of particles within your samples.
Refractive index reveals more about your viral particles
In addition, DAISY-NTA measures the refractive index of each particle. At the population level this analysis can help to identify subpopulations and contaminants within your sample. When combined with hydrodynamic size measurement, the refractive index becomes extremely powerful in identifying aggregates of particles. Aggregates generally appear larger and with a lower refractive index than the bulk of particles in the sample. The plots above show how you can clearly identify and quantify aggregates based on their size and refractive index in combination. Using both size and refractive index, differences between these viral preparations are revealed that are not apparent when simply analysing size alone.
Polydispersity as a measure of quality in adenoviral preparations
Total particle count is a poor correlate of viral titer. This necessitates time-consuming assays for viral titer such as the plaque formation assay in cell culture. DAISY-NTA reports the polydispersity (size heterogeneity) of your viral preparations using the span statistic. In general, a span value <1 indicates a monodisperse sample. Comparing the span values of these three preparations to a measure of their quality, total particle count divided by pfu titer, shows strong correlation between lower polydispersity and higher quality in the viral preparations.
