Microrheology of DNA Hydrogels

TL;DR

This study uses diffusing-wave spectroscopy to analyze the viscoelastic properties of DNA hydrogels, revealing a liquid-to-gel transition linked to DNA bond lifetime and percolation, aiding future design of DNA-based materials.

Contribution

First microrheology measurements of DNA hydrogels using DWS, demonstrating the relationship between temperature, DNA bond dynamics, and gel formation.

Findings

Identified the liquid-to-gel transition across melting temperature.

Showed the elastic and loss moduli crossover related to DNA bond lifetime.

Linked percolation threshold to the melting temperature.

Abstract

A key objective in DNA-based material science is understanding and precisely controlling the mechanical properties of DNA hydrogels. We perform microrheology measurements using diffusing-wave spectroscopy (DWS) to investigate the viscoelastic behavior of a hydrogel made of Y-shaped DNA nano-stars over a wide range of frequencies and temperatures. Results show a clear liquid-to-equilibrium-gel transition as the temperature cycles up and down across the melting-temperature region for which the Y-DNA bind to each other. These first measurements reveal the crossover of the elastic G'({\omega}) and loss modulus G'({\omega}) when the DNA-hydrogel formed at low temperatures is heated to a fluid phase of DNA nano-stars well above the melt temperature Tm. We show that the crossover relates to the life-time of the DNA-bond and also that percolation coincides with the systems' Tm. The approach demonstrated here can be easily extended to more complicated DNA hydrogel systems and provides guidance for the future design of such transient, semi-flexible networks that can be adapted to the application of molecular sensing and controlled release.