Effective Diameters of Virus-Like Particles Measured by Resistive-Pulse Sensing on In-Plane Nanopore Devices

We are developing in-plane nanofluidic devices with multiple pores in series for resistive-pulse measurements of nanoscale particles. Here, we report an approach to calculate the effective diameters of the T = 3 and T = 4 capsids of hepatitis B virus (HBV) capsids from resistive-pulse measurements without using a particle calibration standard and by approximating the noncylindrical cross section of the in-plane nanopore with an equivalent diameter. Because HBV capsids resemble porous protein shells, the capsids displace less electrolyte during translocation and have current pulses with smaller amplitudes than solid particles with similar diameters. To determine an effective volume and, subsequently, an effective diameter for the HBV capsids, we measured the relative pulse amplitudes, nanopore and nanochannel dimensions, device resistance, and electrolyte resistivity. When pore dimensions are precisely measured, effective diameters of the T = 3 and T = 4 HBV capsids were calculated without a calibration standard to be 25.2 ± 0.3 and 28.1 ± 0.3 nm, respectively. If pore dimensions are not completely characterized, one of the capsids can be used as a calibration standard to determine the effective diameter of the other capsid. The effective diameters of the T = 3 and T = 4 capsids were 25.1 ± 0.1 and 28.0 ± 0.2 nm, respectively, when measured across nanopores with equivalent diameters from 68 to 105 nm. Accurate determination of the effective diameters for the T = 3 and T = 4 capsids makes them attractive as calibration standards for resistive-pulse sensing because of their narrow size distributions.