Microrheology of DNA hydrogels

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Cao, Tianyang 
Stoev, Iliya 
Zupkauskas, Mykolas 

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 nanostars 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. Our measurements reveal a crossover between the elastic G'(ω) and loss modulus G"(ω) around the melting temperature Tm of the DNA building blocks, which coincides with the systems percolation transition. This transition can be easily shifted in temperature by changing the DNA-bond length between the Y-shapes. Employing also bulk rheology, we further demonstrate that by reducing the flexibility between the Y-shaped DNA bonds we can go from a semi-flexible transient network to a more energy-driven hydrogel with higher elasticity while keeping the microstructure the same. This level of control in mechanical properties will facilitate the design of more sensitive molecular sensing tools and controlled release systems.

DNA hydrogels, self-assembly, microrheology
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Proceedings of the National Academy of Sciences of the United States of America
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National Academy of Sciences
European Commission Horizon 2020 (H2020) Marie Sk?odowska-Curie actions (642774)
EPSRC (1503622)
EPSRC (1494719)
Z. X. receives financial supports from National University of Defense Technology Scholarship at Cambridge, and NanoDTC Associate Programme. E. E. and A. C. acknowledge support from the ETN-COLLDENSE (H2020- MCSA-ITN-2014, grant no. 642774). E. E. and T. W. thank the Winton Program for Sustainable Physics. T. C. and D. L. thank the National Basic Research Program of China (973 program, No. 2013CB932803), the National Natural Science Foundation of China (No. 21534007), and the Beijing Municipal Science & Technology Commission for financial supports. I. S. and R. L. acknowledge support from EPSRC, No. RG90425 and 135307. M. Z. is funded by a joint EPSRC and Unilever CASE award RG748000.