Electrokinetic nanofluidic sensing of DNA nanostar condensate

TL;DR

This study demonstrates a novel electrokinetic nanofluidic method to detect DNA nanostar condensates, revealing their phase transition behavior and binding properties, which could enable new biosensing technologies based on liquid-liquid phase separation.

Contribution

It introduces a new nanofluidic sensing technique for DNA nanostar condensates, linking phase transition detection to electrokinetic measurements and surface interactions.

Findings

Condensate increases nanochannel current and alters electroosmotic flow.

NS condensate binds more strongly to silica walls than individual NS.

Phase transition temperature correlates with salt concentration and matches other methods.

Abstract

We demonstrate electronic sensing of DNA nanostar (NS) condensate. Specifically, we use electrokinetic nanofluidics to observe and interpret how temperature-induced NS condensation affects nanochannel current. The increase in current upon filling a nanochannel with NS condensate indicates that its electrophoretic mobility is about half that of a single NS and its effective ionic strength is $\sim35$% greater than that of 150mM NaCl in phosphate buffer. $\zeta$-potential measurements before and after exposure to NS show that condensate binds the silica walls of a nanochannel more strongly than individual NS do under identical conditions. This binding increases electroosmotic flow, possibly enough to completely balance, or even exceed, the electrophoretic velocity of NS condensate. Although the current through a flat nanochannel is erratic in the presence of NS condensate, tilting the nanochannel to accumulate NS condensate at one entrance (and away from the other) results in a robust electronic signature of the NS phase transition at temperatures $T_c$ = $f$([NaCl]) that agree with those obtained by other methods. Electrokinetic nanofluidic detection and measurement of NS condensate thus provides a foundation for novel biosensing technologies based on liquid-liquid phase separation.