What electrolyte can be used for TRPS measurements?

An electrolyte is used to suspend the sample and calibration particles. The same electrolyte is also used to clean the fluid cell and nanopore in between sample and calibration measurements.

When selecting an electrolyte, the user should consider how their particles may behave in this electrolyte, particularly if the chosen electrolyte differs from that used in alternative sample measurements and analyses. For example, some particles will aggregate more readily in higher salt concentrations. Check with Izon (support@izon.com) if you intend to use a non-standard electrolyte as certain chemicals may cause damage to the fluid cell and/or nanopores.

Izon recommends using an electrolyte with a molarity >0.01 M. Typically, an electrolyte with a salt concentration of ~0.1 M (e.g. PBS) is used. Alternative electrolytes such as TRIS, KCl and HEPES are also routinely used for TRPS measurements. Operating with an electrolyte <0.01 M will result in a very small current and associated blockade magnitudes and potentially, particles will go undetected.

For human plasma and cell culture media, Izon regularly uses a PBS based electrolyte with a salt concentration of 0.137 M. For NP1000s and above, this electrolyte is typically diluted to 1/10th strength as the particles are large enough that the reduction in signal to noise from the lower ionic strength is mitigated. While an electrolyte with a salt concentration of 0.137 M is suitable for the measurement of particles <100 nm, if your particles of interest have a small blockade size of <0.1 nA at the minimum stretch of an NP100 nanopore, then using 2x PBS or equivalent can improve the signal to noise ratio of your blockades.

Surfactants can improve wetting of the nanopore and reduce particle aggregation. If the Izon reagent kit is being used to prepare your PBS electrolyte, 600 µL of the Izon wetting solution concentrate is added as the surfactant to improve the performance of the electrolyte.