Polystyrene Beads as a Model System for Virus Particles Reveal Pore Substructure as they Translocate

Our research focuses on the extension of the resistive-pulse or Coulter counter technique to detect and analyze virus particles. Using polystyrene spheres as a model system, we show that particles can be distinguished not only by their size, but also by their charge, as they translocate through track-etched polyethylene terephthalate (PET) pores. In addition, we discovered that as a polystyrene sphere translocates, it reveals variations in the pore structure along its length as a series of peaks and valleys in the measured ionic current. This sequence of peaks and valleys is unique to a particular pore, but for that pore, we observed the same sequence for thousands of particle translocations, even particles of different size or with different charge. Also, particles translocating in the reverse direction through the pore give the reverse sequence of peaks and valleys in the ionic current.We analyzed this data to extract information about the particle velocity as it passes through the pore and examined how this effect could enhance virus sensing capabilities. For example, due to the unique pattern of peaks and valleys, it is possible to unambiguously detect when two particles are in the pore at the same time. In addition, we expect that this characteristic pattern will be modulated by the particle geometry. Therefore, it will likely be possible to distinguish between particles of the same size but different shapes. After these model system studies, we plan to test our system with actual virus particles.