Np100 nanopores

Tunable resistive pulse sensing was used to characterize coated SPIONs based on their size and concentration. By tuning the parameters of voltage, stretch and pressure, the nanoparticles, which were suspended in an electrolyte (0.22 µm filtered PBS), were directed through nanopores. When a nanoparticle passed through the nanopore, it caused a transient blockade that was then detected by the Izon Control Suite software (Ver. 3.4.2.51). Size was measured by the blockade magnitude, and the concentration was measured by the blockade frequency. The blockade magnitude and frequency were then converted into their corresponding physical properties by calibration employing calibration particles of known size and concentration.
The coated SPIONs suspensions were diluted to 0.025 mg Fe/mL with PBS. Then, NPs were measured using NP100 nanopores (Izon Science, New Zealand). The measurements were then calibrated with calibration particles CPC 100 (100 nm mean diameter) (Izon Science, New Zealand). Final concentration was then expressed as the number of particles per mL.

Isolated small EVs were characterized by their size, concentration and stability (zeta potential) using a tunable resistive pulse sensing (TRPS) technique from qNano (Izon Science, Christchurch, New Zealand). The analysis was performed using NP100 nanopores, capable of detecting particles within the size range of 50–300 nm (as stated by the manufacturer, Izon Science), and compared to the calibration beads CPC100 (mode diameter, 100 nm). Prior to the analyses, sEV samples were diluted 1:1 in 2x PBS supplemented with 0.1% Tween 20, as recommended by the manufacturer. Measurements were made with 44.29 mm of appropriate stretch and 0.44-volt (V) potential applied on the pores, with at least 500 particles being detected. Each measurement was run with a baseline current of 100 nanoamperes (nA) ± 10 nA. All samples were vortexed for 30 s and sonicated for 2 min prior to analysis.
The charges were quantified by a four-calibration point using CPC100 as described [57 (link),58 (link),59 (link)].