Virus Concentration and Adhesion Measured by Laser Tracking

At present there are few methods available for observing the adhesion of viruses. Also, it is difficult to determine virus concentrations on-line. This paper describes the oNanoSight,o a microscope instrument which counts nanoparticles directly from scattered laser light and then determines their diameter by laser tracking the Brownian movement and applying the Stokes-Einstein theory to the random walk pathways. By applying this instrument to preparations of adenovirus, the concentration of viruses has been measured and compared with polystyrene latex spheres. Then, the instrument has been used to detect aggregates of viruses in the suspension. Taking the number of aggregates as a measure of the interparticle adhesion for equal spheres, the self-adhesion of the virus particles has been estimated as a function of two parameters, the adhesion energy and the range of the interaction. The results showed that the virus adhesion was similar to the self-adhesion of polystyrene.