Search

A dilute water–polymer mixture exhibits a percolation-induced gel–gel phase separation, resulting in a two gel co-continuous substrate, which is used for adipose tissue development.

Vertically oscillating head motions mimicking mechanical accelerations experienced during light jogging or treadmill running at moderate velocity reduce blood pressure in rats and human adults with hypertension.

A hydrogel made of crosslinked clusters of highly branched polymers that has ultralow swelling pressure and that forms in 10 minutes despite its low polymer content functions as an artificial vitreous body for over one year without inducing adverse effects.

Small molecules that target RNA Polymerase I inhibit ribosome biogenesis to activate p53 through the nucleolar surveillance response pathway. Here, the authors show that p53 induction by ribosome stress is dependent on extracellular glutamine availability.

Biological tissues are extremely water rich but remain mechanically stiff, behaviour that is difficult to recapitulate in synthetic materials. Here the authors design a hydrogel/sponge hybrid material driven by a self-organized network of cyano-p-aramid nanofibres that combines these properties for biofunctional materials.

The elastic properties of Tetra-polyethylene glycol (PEG) gel, four-armed PEG network gel, are studied by simulation for deformation of elastic networks containing defects randomly introduced to the network. This network model well reproduces the experimental results of Tetra-PEG gel. In particular, the stress-strain curve of the gel prepared at chain overlap concentration agrees with that of a regular network without defects. As the defect density increases, the Young’s modulus linearly decreases. The fracture and spatial inhomogeneity of the networks are also investigated by the simulation.

Using more than 100 independent iPSC lines derived from patients with Alzheimer’s disease, the authors discovered loci associated with the neuronal production of amyloid β and confirmed their influence using RNA interference.

This study explores the effects of long-term degradation on the viscoelastic properties of viscoelastic liquids using tetra-armed polyethylene glycol (Tetra-PEG) slimes as model material. It aims to enhance control over the viscoelasticity of biomedical materials, like sodium hyaluronate, by introducing specific cleavage sites into the Tetra-PEG slimes to simulate degradation. The study reveals that despite degradation, the slimes maintain a single relaxation mode, offering a method to design viscoelastic liquids with predictable and controllable degradation for biomedical applications.

The osmotic pressure during the gelation process below the overlapping concentration of prepolymers was investigated using a series of model polymer gels, namely, tetra-polyethylene glycol gels. The osmotic pressure decreased during the gelation reaction and was constant after the sol–gel transition, suggesting that the clusters grow and fill the system, at the sol–gel transition point. This representation of the sol–gel transition at the overlapping condition of the critical clusters corresponds well to the aggregation process prediction.

We fabricated the doubly crosslinked gel by stretching the gel during the gelation using tetra-PEG gels. In this gel, two networks having different reference states coexist with and balance each other, influencing Young’s modulus (E) and permanent set (λs). We tuned the time for the stretching imposition on the gels, which influences the 1st network fraction (g1/g0). λs increased with increasing the 1st network fraction, while E had a maximum value against g1/g0, which were explained by the balance between the strain energies of the first and second networks.

A polymer cross-linking system undergoes a phase transition from liquid to solid at a critical point, which is called the sol-gel transition. We independently tuned the intrinsic parameters governing the sol-gel transition, that is, the connectivity and polymer concentration, using a model gel system (tetra-polyethylene glycol gel), and examined the model predictions. The lattice-based percolation model can be applied only for systems prepared around the overlapping concentration. In the case far below the overlapping concentration, the aggregation model well reproduced the transition behavior.

We investigated the mechanical properties of polymer network formed from the AB-type crosslink-coupling of prepolymers with ‘different size’ but ‘same functionality’ (size-mismatched Tetra-PEG gels). Our experiments revealed that the elastic modulus, the fracture energy and the ultimate elongation ratio of the size-mismatched Tetra-PEG gels had tendencies similar to those of conventional Tetra-PEG gels. From these results, we conclude that the size-mismatched Tetra-PEG gels have the same degree of homogeneity as the conventional Tetra-PEG gels, and the difference in prepolymer size does not affect the homogeneity.

A PEG-based carrier, named PEG slime, enables localized recombinant adeno-associated virus (rAAV) delivery to mouse skin ulcer with limited off target delivery, demonstrating a new method for highly localized gene transduction.

We explored the feasibility of Tetra-PEG gel, a controllable hydrogel, as a new biomaterial to develop a coating agent for post-ESD ulcers. We examined the optimal conditions for hydrogel application and developed a specialized catheter, then investigated its properties. Ultimately, we successfully used the optimized hydrogel and device to cover post-ESD ulcers in the porcine stomach. Further optimization of the hydrogel and ongoing research through animal experiments are expected to deepen our understanding of the material’s effects on ulcer healing and contribute to its clinical applications.

The degree of gel-gel phase separation (GGPS) was compared using multi-arm poly(ethylene glycol) (PEG) hydrogels. GGPS can occur at c < c*, with 8-arm PEG exhibiting a stronger turbidity (D) indicating stronger GGPS compared to 4-arm PEG. This indicates that phase-separated PEG can be obtained at low concentrations simply by increasing the number of branches. Furthermore, phase-separated 8-arm PEG showed higher osteogenic differentiation in vitro.

Artificial nanocelluloses are produced via the self-assembly of low-molecular-weight (LMW) cellulose in vitro and represent an emerging class of nanocelluloses developed over the past decade. Most artificial nanocelluloses reported to date are particulates. We have developed two types of nanostructured macroscopic materials through the self-assembly of LMW cellulose: nanoribbon network hydrogels and nanospiked microfibrous materials. This Focus Review summarizes our work along with related studies on these novel nanostructured cellulose materials.

Tetra-PEG gel has highly suppressed heterogeneity, which is considered inherent to conventional polymer gels. In this review, we show a series of experimental results on Tetra-PEG gels, and discuss the homogeneity. Tetra-PEG gel is useful as a model system for examining the model predicting physical properties of polymer gels.

Dissolved polymers directed molecular crystallization behavior under dilute and crowding conditions. Larger poly(ethylene glycol)s (PEGs) accelerated caffeine crystal formation in the dilute regime of PEG solutions, which was attributed to the depletion attraction that promoted caffeine cluster aggregation into crystal nuclei. In the semidilute regime, the crystal formation rate was insensitive to the molecular weight of PEGs. This observation was consistent with polymer blob properties, which govern depletion attraction and maintain a constant size at a given polymer concentration, irrespective of molecular weight in the semidilute regime.

A degradable cross-linked polybutadiene was synthesized using a peptide-based cross-linker. As a degradable cross-linker, we synthesized poly(L-cysteine) (polyCys) by papain-catalyzed chemoenzymatic polymerization. The thiol-ene reaction between polybutadiene and polyCys was conducted in the presence of a radical initiator, resulting in the formation of an insoluble polybutadiene gel. The successful cross-linking and network formation was confirmed by Raman spectroscopy and viscoelastic analysis. Dynamic viscoelastic measurements of the cross-linked polybutadiene revealed the disappearance of slow relaxation mode. The polyCys-linked polybutadiene underwent degradation through acidic hydrolysis, allowing the recovery of soluble polybutadiene.

This focused review introduces our rheological studies on static and dynamic polymer networks using Tetra gel, host-guest gel, and telechelic associative polymer networks. Although the characteristics of crosslinks strongly influence the rheological properties of polymer networks, the understanding of the molecular origin of these properties remains incomplete owing to structural complexity. Our multiple experimental characterizations, including multiaxial stretching and the combination of dynamic viscoelastic and spectroscopic measurements, will add to the molecular understanding and further provide important information on the design of novel polymer network materials.

Despite the tremendous efforts made in recent decades to remove imperfections from gels, discernible signs of spatial defects have been persistently observed in gels. Researchers believe that gels are inherently heterogeneous. In this focus review, I briefly introduce a recent finding from our research group’s efforts to fabricate polymer gels free of spatial heterogeneities via “bond percolation”. The commonly observed scattering profiles for the spatial defects disappeared in the homogeneous gels. The newly observed scattering profiles are a benchmark for gel structures.