# Current enhancement in solid-state nanopores depends on three-dimensional DNA structure

## TL;DR

This study investigates how three-dimensional DNA structures influence ionic current changes during nanopore translocation, revealing structure-dependent crossover concentrations and effects of neutral polymers on ion transport.

## Contribution

It demonstrates that DNA nanostructure complexity affects ionic current behavior and introduces methods to control translocation conditions for improved nanopore sensing.

## Key findings

- Crossover ionic concentration is lower for bundled DNA nanostructures.
- Neutral polymers reduce electroosmotic flow, enabling large DNA translocation at low salt.
- DNA structure influences counterion mobility and ion transport in nanopores.

## Abstract

The translocation of double-stranded DNA through a solid-state nanopore may either decrease or increase the ionic current depending on the ionic concentration of the surrounding solution. Below a certain crossover ionic concentration, the current change inverts from a current blockade to current enhancement. In this paper, we show that the crossover concentration for bundled DNA nanostructures composed of multiple connected DNA double-helices is lower than that of double-stranded DNA. Our measurements suggest that counterion mobility in the vicinity of DNA is reduced depending on the three-dimensional structure of the molecule. We further demonstrate that introducing neutral polymers such as polyethylene glycol into the measurement solution reduces electroosmotic outflow from the nanopore, allowing translocation of large DNA structures at low salt concentrations. Our experiments contribute to an improved understanding of ion transport in confined DNA environments, which is critical for the development of nanopore sensing techniques as well as synthetic membrane channels. Our salt-dependent measurements of model DNA nanostructures will guide the development of computational models of DNA translocation through nanopores.