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Physics Seminar

Microrheology of DNA hydrogels

Speaker: Prof. Erika Eiser (Cambridge University)
Date: Wednesday 10 April 2019
Time: 15:00
Venue: Queens Buildings N/3.28

The specificity of DNA-hybridization allows us to form multi-valent nanostars similar to molecules with a given valency. However, different to regular molecules we can assign to each arm in the DNA-nanostar a given binding strength by varying the length and sequence of the single-stranded DNA terminating the arms. Such specificity has been used to self-assemble short DNA oligomers into 2D and 3D origamis with prescribed nanostructures. Here I will introduce Y-shaped DNA nanostars that can self-assemble into a continuous, viscoelastic hydrogel. Using Diffusing-Wave Spectroscopy (DWS) and dynamic light scattering (DLS), we were able to monitor the change of the viscoelastic modulus G*(w) of our solution of Y-shaped DNA nanostars from a completely fluid to predominantly elastic system over a wide range of frequencies and function of temperature [1-3]. Our micro-rheological measurements reveal that these hydrogels behave like transient networks made of flexible polymers, when building in some flexible linkers. But differently to most (bio)polymeric networks we can form and melt our DNA hysdrogels reversibly by cooling or heating the systems. Moreover, by changing the strength of the sticky overhangs of the Y-shapes we can control the temperature at which the liquid to gel transitions occurs. Finally, our measurements allow us to associate the melting temperature at which this transition occurs as the system’s percolation transition.

[1] Z. Xing et al. ‘Microrheology of DNA hydrogels’, PNAS 115, no. 32 (2018) [2] I. Stoev et al. ‘Single-Beam Optical Tweezers for the Passive Microrheology of Complex Fluids’ SPIE proceedings, paper 10723-91 (2018) [3] Z. Xing et al. 'Structural and linear elastic properties of DNA hydrogels by coarse-grained simulation’, Macromolecules, in print.