Direction Dependence of Resistive-Pulse Amplitude in Conically Shaped Mesopores

Abstract

Conically shaped pores such as glass pipets as well as asymmetric pores in polymers became an important analytics tool used for the detection of molecules, viruses, and particles. Electrokinetic or pressure driven passage of single particles through a single pore causes a transient change of the transmembrane current, called a resistive-pulse, whose amplitude is the measure of the particle volume. The shape of the pulse reflects the pore topography, and in a conical pore, resistive pulses have a shape of a tick point. Passage of particles in both directions was reported to produce pulses of the same amplitude and shapes that are mirror images of each other. In this manuscript we identify conditions at which the amplitude of resistive-pulses in a conical mesopore is direction dependent. Neutral particles entering the pore from the larger entrance of a conical pore, called the base, block the current to a larger extent than the particles traveling in the opposite direction. Negatively charged particles on the other hand size larger when being transported in the direction from tip to base. The findings are explained via voltage-regulated ionic concentrations in the pore such that for one voltage polarity a weak depletion zone is formed, which increases the current blockage caused by a particle. For the opposite polarity, an enhancement of ionic concentrations was predicted. The findings reported here are of crucial importance for the resistive-pulse technique, which relates the current blockage with the size of the passing object.

Direction- and Salt-Dependent Ionic Current Signatures for DNA Sensing with Asymmetric Nanopores

“…When the concentration of LiCl decreased to 20 mM, as shown in Fig. 1 C, the current change for backward translocation turned to a sole increase, as previously observed for conical pores at low salt concentrations (34).…”

“…Furthermore the flow is asymmetric with respect to voltage reversal with significantly larger flow rates measured at positive voltages. We note that for conical nanopores with larger diameters of around 50 nm, forward translocations are sometimes observed at low salt concentrations (34).…”

A tunable nanopore sensor for the detection of metal ions using translocation velocity and biphasic pulses

“…48 The resistive pulse magnitude is also a function of nanoparticle charge. 28,48 To summarise the expected results based upon theory, at negative potentials, a negatively charged particle passing through a negatively charged pore will generate a conductive pulse before the resistive pulse, Figure 1e. A positively charged particle, under the same conditions will only generate a resistive pulse but with a greater magnitude compared to the resistive pulse generated from the negatively charged particle of the same size.…”

Fabrication of a single sub-micron pore spanning a single crystal (100) diamond membrane and impact on particle translocation

“…A previous study of particle transport through conical, charged polyethylene terephthalate pores of a similar size to those employed here, attributed a directional dependence on the peak current, to voltage-regulated ionic concentrations within the pore. [70] In particular, for a negatively charged pore and negatively charge particle, a greater blocking peak current is observed when the particle travels from the tip to base.…”