Abstract: A new analytical system is described which provides total particle count and high-resolution size measurements for biological structures such as virus and protein aggregates. This system builds on the Nanoparticle Tracking and Analysis (NTA) technique for the simultaneous visualization and individual sizing of nanoparticles based on their Brownian motion. Virus production and purification processes rely on overall measurements of concentration such as optical density and infectivity assays which may take days to obtain results. The NTA method provides a total particle concentration result in minutes, providing a clearer picture of how the sample has been attenuated or killed by the purification process. Fluorescence measurements can be used to isolate a sub-population of interest. NTA provides the only alternative for concentration and sizing of polydisperse protein aggregates formed in the submicron range.

Abstract: A novel addition to a technique for the analysis of nanoparticles in a suspension is described. The Nanoparticle Tracking Analysis (NTA) technique sizes individual nanoparticles, based on their Brownian motion. NTA allows nanoparticles to be sized on a particle-byparticle basis, resulting in a higher resolution analysis and therefore a better understanding of polydispersity than ensemble methods (such as dynamic light scattering, DLS) and it also yields directly a count/concentration measurement. Analysis of scattering intensity is a recent development allowing sub-populations of nanoparticles with varying scattering characteristics to be resolved in a complex mixture. Now this technique has been extended to the analysis and differentiation of fluorescently labeled nanoparticles. With the appropriate wavelength lasers and optical filters, the technique has been shown to be able to differentiate between sub-populations in a heterogeneous mixture.