Research Topics

Prediction and control of hydrogel fluidity with DNA

Focusing on the fact that the base sequence greatly influences the stability of the double helix structure formed by DNA, we synthesized a new hydrogel cross-linked by the DNA double helix structure.
When the macroscopic flow time of this gel was examined, it was found that the dissociation time of the DNA double helix structure coincided with the dissociation time in a wide time domain.
Since the stability of the DNA double helix structure can be freely adjusted by designing the base sequence, by synthesizing the gel using this method, a hydrogel with arbitrary fluidity, even under physiological conditions, can be obtained. It is suggested that it can be synthesized.

M. Ohira, T. Katashima, M. Naito, D. Aoki, Y. Yoshikawa, H. Iwase, S. Takata, K. Miyata, U. Chung, T. Sakai, M. Shibayama, X. Li, Star- Polymer–DNA Gels Showing Highly Predictable and Tunable Mechanical Responses. Advanced Materials , 2108818 (2022).

Hiroki Ueda, Team Leader of the Institute of Physical and Chemical Research (Professor, Department of Pharmacology, Graduate School of Medicine, The University of Tokyo), Etsuo Susaki, Visiting Researcher (Associate Professor), etc. We have established "CUBIC-HistoVIsion (CUBIC-HV)", a three-dimensional tissue staining and observation technique for organ and whole body scales.
We measured the brain before and after clearing using small-angle X-ray scattering and found that the brain was an electrolyte gel and that clearing removed lipids.

EA Susaki, C. Shimizu, A. Kuno, K. Tainaka, X. Li, K. Nishi, K. Morishima, H. Ono, KL Ode, Y. Saeki, K. Miyamichi, K. Isa, C. Yokoyama, H. Kitaura, M. Ikemura, T. Ushiku, Y. Shimizu, T. Saito, TC Saido, M. Fukayama, H. Onoe, K. Touhara, T. Isa, A. Kakita, M. Shibayama, HR Ueda, Versatile whole-organ / body staining and imaging based on electrolyte-gel properties of biological tissues. Nature Communications. 11, 1982 (2020).

It was found that it is possible to maintain a uniformly dispersed state even after gelation by densely filling the polymer in the solution. Such a gelling process is called bond percolation and has been considered as a theory for a long time, but it was realized for the first time in a real system.
With such a simple method, we succeeded in synthesizing a gel with extremely high uniformity, which overturns the common sense of soft materials.
This method can be applied to a wide range of polymer species and is expected to have a ripple effect in many fields such as medicine, pharmacy, chemistry, and optics.

X. Li, S. Nakagawa, Y. Tsuji, N. Watanabe, M. Shibayama, Polymer gel with a flexible and highly ordered three-dimensional network synthesized via bond percolation. Science Advances . 5, eaax8647 (2019).
X. Huang, S. Nakagawa, X. Li, M. Shibayama, N. Yoshie, A Simple and Versatile Method for the Construction of Nearly Ideal Polymer Networks. Angewandte Chemie International Edition , 1–8 (2020).

Nafion is a fluorocarbon-based polymer that has been actively used industrially for a long time, but the correlation between its physical properties and its structure is still unclear in many places.
This time, by strictly unifying the sample preparation conditions and performing light scattering, small-angle X-ray scattering, and leo-small-angle neutron scattering over a wide concentration range of 0.5-30 wt%, the universal solution properties of Nafion and nano are performed. The structure was clarified.

CI Gupit, X. Li, R. Maekawa, N. Hasegawa, H. Iwase, S. Takata, M. Shibayama, Nanostructures and Viscosities of Nafion Dispersions in Water / Ethanol from Dilute to Concentrated Regimes. Macromolecules . 53, 1464–1473 (2020).

The criticality just before gelation has attracted the interest of many physicists because of its universality, and much research has been done. Among them, the origin of the slow motion mode proportional to the cube of the scattering vector q remains as an unsolved problem.
In this systematic study, this slow motion mode is completely unrelated to the conventional Zimm mode (one of the internal motions of macromolecules), and is a translational motion of a critical cluster with a power distribution. It was clarified that it was a combination of.

X. Li, T. Noritomi, T. Sakai, EP Gilbert, M. Shibayama, Dynamics of Critical Clusters Synthesized by End-Coupling of Four-Armed Poly (ethylene glycol) s. Macromolecules . 52, 5086–5094 (2019).