Particle Deformation and Concentration Polarization in Electroosmotic Transport of Hydrogels through Pores

Abstract

In this article, we report detection of deformable, hydrogel particles by the resistive-pulse technique using single pores in a polymer film. The hydrogels pass through the pores by electroosmosis and cause formation of a characteristic shape of resistive pulses indicating the particles underwent dehydration and deformation. These effects were explained via a non-homogeneous pressure distribution along the pore axis modeled by the coupled Poisson-Nernst-Planck and Navier-Stokes equations. The local pressure drops are induced by the electroosmotic fluid flow. Our experiments also revealed the importance of concentration polarization in the detection of hydrogels. Due to the negative charges as well as branched, low-density structure of the hydrogel particles, the concentration of ions in the particles is significantly higher than in the bulk. As a result, when an electric field is applied across the membrane, a depletion zone can be created in the vicinity of the particle observed as a transient drop of the current. Our experiments using pores with openings between 200 and 1600 nm indicated the concentration polarization dominated the hydrogels' detection of pores wider than 450 nm. The results are of importance for all studies that involve transport of molecules, particles, and cells through pores with charged walls. The developed inhomogeneous pressure distribution can potentially influence the shape of the transported species. The concentration polarization changes the interpretation of the resistive pulses; the observed current change does not necessarily reflect only the particle size but also the size of the depletion zone that is formed in the particle vicinity.

Use of solid-state nanopores for sensing co-translocational deformation of nano-liposomes

“…If the shape and the excluded volume of the translocating analyte are constant then ΔI ∝ V applied and in that case ΔI should scale up with the increasing transmembrane voltage. 18,37 In order to validate our hypothesis, we performed translocation experiments with polystyrene nanoparticles. In order to rule out the possibility that the non-existent change in ΔI values was (Fig.…”

“…The magnitude and duration of the resistive spikes (or current blockades) can be used to make inferences about the translocating particles. 37 They attributed hydrogel deformation to concentration polarization due to the electric field inside the nanopore and the non-homogeneous pressure distribution along the pore axis. Moreover, hundreds of nanoparticles can be driven through the pore making nanopore sensing an attractive technique for high throughput characterization of nanoparticles.…”

“…[34][35][36][37] Although, conical glass nanopores and track-etch PET pores are easy to fabricate, their long pore lengths result in lower sensing resolution compared to the thin silicon nitride nanopores. [34][35][36][37] Although, conical glass nanopores and track-etch PET pores are easy to fabricate, their long pore lengths result in lower sensing resolution compared to the thin silicon nitride nanopores.…”

Counting and Sizing of Single Vesicles/Liposomes by Electrochemical Events

“…In 1953, Wallace H. Coulter [27] invented the Coulter counter technique, achieving the detection of certain micron-sized entities (e. g., cells and bacteria). In addition to the developments in nanometre-scale fabrication technology, various biological, solidstate nanopore and/or nanochannel resistive-pulse sensors have emerged and grown to be a powerful and influential technique for single-entity analysis both in fundamental studies and in practical applications, [14,[30][31][32] achieving the successful detection of hard particles, [33,34] emulsions, [35] microgels [36][37][38] and biological entities. In addition to the developments in nanometre-scale fabrication technology, various biological, solidstate nanopore and/or nanochannel resistive-pulse sensors have emerged and grown to be a powerful and influential technique for single-entity analysis both in fundamental studies and in practical applications, [14,[30][31][32] achieving the successful detection of hard particles, [33,34] emulsions, [35] microgels [36][37][38] and biological entities.…”

Tunable Resistive Pulse Sensing: Potential Applications in Nanomedicine

“…TRPS was able to monitor the size changes that took place over time. Resistive pulse sensing has also been employed to study hydrogels, another class of drug delivery nanoformulation [68].…”