An Adaptive Real-Time 3D Single Particle Tracking Method for Monitoring Viral First Contacts

Here, an adaptive real-time 3D single particle tracking method is proposed, which is capable of capturing heterogeneous dynamics. Using a real-time measurement of a rapidly diffusing particle's positional variance, the 3D precision adaptive real-time tracking (3D-PART) microscope adjusts active-feedback parameters to trade tracking speed for precision on demand. This technique is demonstrated first on immobilized fluorescent nanoparticles, with a greater than twofold increase in the lateral localization precision (approximate to 25 to approximate to 11 nm at 1 ms sampling) as well as a smaller increase in the axial localization precision (approximate to 68 to approximate to 45 nm). 3D-PART also shows a marked increase in the precision when tracking freely diffusing particles, with lateral precision increasing from approximate to 100 to approximate to 70 nm for particles diffusing at 4 mu m(2) s(-1), although with a sacrifice in the axial precision (approximate to 250 to approximate to 350 nm). This adaptive microscope is then applied to monitoring the viral first contacts of virus-like particles to the surface of live cells, allowing direct and continuous measurement of the viral particle at initial contact with the cell surface.