Cpc200

Carboxylated polystyrene particles, denoted as CPC200, with a mean nominal diameter of 210 nm and stock concentration of 1 × 10¹² particles/mL, were purchased from Bangs Laboratories, USA and used as a calibrant for zeta potential analysis, as well as the sample particles. CPC200s were vortexed for 30 s followed by a 2 min sonication to ensure monodispersity prior to any TRPS analysis or sample incubation.

TRPS was performed using the qNano system (IZON Sciences, New Zealand) with the IZON Control Suite software (V3.1.2.53). NP100, NP200 or NP300 elastomeric tuneable nanopores were used, suitable for analysing beads between 85 and 600 nm (as stated by the manufacturer). Carboxylated polystyrene beads, denoted as CPC200 (Bangs Laboratories, USA), with a mean nominal diameter of 210 nm and stock concentration of 1 × 10¹² particles/ml, were used as a concentration calibrant at 2 × 10⁹/ml. Prior to use, the beads were vortexed for 30 s and sonicated for 1 min to ensure mono-dispersity. An appropriate stretch and a voltage was applied throughout so that the blockades of CPC200s in PBS were at least 0.5 nA above the background noise. The qNano was operated as previously described [38 (link)]. Briefly, the lower fluid cell was filled with 75 μl of PBS, ensuring no air bubbles are present and the upper fluid cell contained 40 μl of sample. After each measurement, the sample was removed from the upper fluid cell and replaced with PBS. This was repeated several times, applying varying amounts of pressure and vacuum, until visible blockades were observed.