pH-Mediated Regulation of Polymer Transport Through SiN Pores

TL;DR

This study investigates how pH levels influence polymer transport through silicon nitride pores, revealing mechanisms for controlled capture and translocation crucial for sequencing applications.

Contribution

It introduces a charge regulation model coupled with transport equations to explain pH-dependent polymer conductivity in SiN pores, including DNA trapping at low pH.

Findings

Non-monotonic pH dependence of avidin conductivity explained by electroosmotic and electrophoretic forces.

DNA is electrostatically trapped at low pH, enhancing capture and translocation.

Model accurately reproduces experimental zeta potential data.

Abstract

We characterize the pH controlled polymer capture and transport thorough silicon nitride (SiN) pores subject to protonation. A charge regulation model able to reproduce the experimental zeta potential of SiN pores is coupled with electrohydrodynamic polymer transport equations. The formalism can quantitatively explain the experimentally observed non-monotonic pH dependence of avidin conductivity in terms of the interplay between the electroosmotic and electrophoretic drag forces on the protein. We also scrutinize the DNA conductivity of SiN pores. We show that in the low pH regime where the amphoteric pore is cationic, DNA-pore attraction acts as an electrostatic trap. This provides a favorable condition for fast polymer capture and extended translocation required for accurate polymer sequencing.