A new imaging technique demonstrates the highly convoluted and frenetic activity of a virus-like particle as it works to detect and enter a cell.
The video shows a tiny ball as it zips around in a rapid and erratic manner until it encounters a cell. It then bounces and skids along the surface, and either lifts off again, or insidiously slips into the cell's interior. While seemingly chaotic, it's a strategy that gets the job done.
The "virus" is actually a minuscule polystyrene ball studded with protein segments known as Tat peptides, which are derived from HIV-1 and helps the particle find the cell. The ball was equipped with quantum dots (or semiconductor bits) that emit light, allowing the camera to find and track it.
Unlike other visualizations, like a T7 virus trying to infect a cell, the movement of the virus-like particle and the highly detailed contours of the cell were actually recorded by cameras using a technique called called laser scanning microscopy. One camera was fixed on the particle, while a second camera focused on the cell. The resulting real-time, multi-resolution, 3D visualization is an amalgam of the two. Prior to this technique, only micron microscopy could yield such exquisite detail — but that only produced two-dimensional images, and it killed the cell.
"Following the motion of the particle allowed us to trace very fine structures with a precision of about 10 nanometers, which typically is only available with an electron microscope," noted researchers Kevin Welsher in a statement. A nanometer is one billionth of a meter and roughly 1000 times smaller than the width of a human hair. By measuring changes in the speed of the particle, researchers can infer the viscosity of the extracellular environment just above the cell surface.
Research like this could eventually help researchers prevent infections from happening. It could also assist in the development of medical nanotechnology and microscopic machines.
Read the entire study at Nature Nanotechnology: "Multi-resolution 3D visualization of the early stages of cellular uptake of peptide-coated nanoparticles."