Research Topics

Prediction and regulation of hydrogel fluidity using DNA sequences

We synthesized a new hydrogel cross-linked by DNA duplexes. DNA sequences can precisely control the mechanical responses of this hydrogel.

The dissociation time of the DNA duplex closely matched the macroscopic flow time of the gel over a broad time range.

Adjusting the base sequence allows for the design of the activation Gibbs energy of the DNA duplex, allowing for the synthesization of a hydrogel with customizable fluidity even under physiological conditions.

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, Professor in the Department of Pharmacology, The University of Tokyo, along with Etsuo Susaki, Associate Professor, have developed a technique called "CUBIC-HistoVIsion (CUBIC-HV)." This innovative method allows for three-dimensional tissue staining and observation of 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).

We designed a new gelation scheme that densely fills the precursor polymers during the gelation process, known as bond percolation in classical percolation theory.
By employing this straightforward method, we successfully synthesized a gel with remarkable uniformity, challenging conventional thinking about soft materials.
This method can be applied to a wide variety of polymers and is expected to have a significant impact on various fields, including 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 widely used in industry for a significant period. Yet, the relationship between its physical properties and structure remains unclear in many areas.
By standardizing sample preparation and conducting light scattering, small-angle X-ray scattering, and small-angle neutron scattering across a concentration range of 0.5-30 wt%, we clarified the universal solution properties of Nafion and nanomaterials.

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 before gelation has drawn significant interest from physicists, sparking extensive research. A key unsolved issue is the origin of the slow-motion mode proportional to the cube of the scattering vector q.
In this systematic study, we found that the slow motion of the clusters did not represent the Zimm mode, which is one of the internal motions of macromolecules. Instead, it reflects a superimposed translational motion of critical clusters with a power distribution.

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).