Reviews & Analysis

A supramolecular complex termed “hemoCD1” was constructed as the aqueous synthetic Hb/Mb model using a 1:1 inclusion complex of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphinatoiron(II) with a per-O-methylated β-cyclodextrin dimer with a pyridine linker. HemoCD1 was used as a selective CO scavenger in vivo due to its extremely high binding affinity to CO. In addition, hemoCD1 was utilized to quantify the accumulation of endogenous and exogenous CO in organs/tissues. Finally, hemoCD1 was employed as an antidote for CO poisoning in animals.

Hydrophobically modified polysaccharides have attracted considerable attention in the biomedical field because of their biocompatibility, biodegradability, and nontoxicity. This article reviews previous studies on micellar structures formed by hydrophobically modified polysaccharides (pullulan and amylose) in aqueous solutions by static and dynamic light scattering, small angle X-ray and neutron scattering, and fluorescence from pyrene solubilized in the polymer solution. Depending on the degree of substitution, the hydrophobically modified polysaccharides exist in aqueous solution as full or loose flower necklaces or as nanogels made up of randomly branched polymers.

TEMPO-catalyzed oxidation enables efficient and position-selective conversion of primary hydroxy groups in water-soluble and -insoluble polysaccharides to sodium carboxylate groups. TEMPO/NaBr/NaClO in water at pH 10 is an advantageous system in terms of the degrees of oxidation and reaction rates. Various new water-soluble TEMPO-oxidized polysaccharides have been prepared by TEMPO-catalyzed oxidation, and they have unique properties and functionalities. When crystalline native cellulose and chitin are oxidized by the TEMPO/NaBr/NaClO system under suitable conditions, the obtained water-insoluble oxidized products can be converted to characteristic nanomaterials by mechanical disintegration in water.

Regenerated fibers of β-1,3-glucan (curdlan) and α-1,3-glucan were fabricated by dry-jet wet spinning, and the fiber properties and structures are summarized in this review. The flexible and water-absorbent curdlan and the stiff and strong α-1,3-glucan would be utilized in different applications from conventional cellulose. As a new type of post-treatment, a two-step stretching method in water was developed for α-1,3-glucan by utilizing its crystal transition. This can be applied to various polysaccharides for future production of high-performance fibers.

Relationship between the primary structures and their properties is recognized as an important research subject for polymer chemists. To make progress in this academic field, innovative synthetic procedures of cyclic polymers are essential. The synthetic strategy has two typical pathways: one is the ring closure of functional linear polymers and the other is ring expansion polymerization using cyclic monomers, an initiator, or a catalyst. This focus review deals with the recent synthetic evolution of cyclic polymers, focusing on our new strategy: ring closing without highly dilute conditions.

“Breath figure formation” during the casting process of polymer solutions under high atmospheric humidity provides honeycomb-patterned polymer films (honeycomb films) with regularly arranged micropores. The development of production technology for large-area honeycomb films is indispensable for their various applications. Manufacturing equipment consisting of three zones (for casting, humidification, and drying of polymer solutions) for successive formation of large-area honeycomb films was newly designed and constructed. By using this equipment, physicochemical experimental parameters, e.g., the surface temperature of polymer solutions, dew point of the humidification zone, humidification time, and interfacial tension between water and the polymer solution, were effectively changed to optimize the density and size of condensed water droplets. Large-area honeycomb films were formed by a roll-to-roll process. Herein, recent developments in biomedical applications of honeycomb films are described.

Our recent progress on the phenylazomethine dendrimers to afford advanced functionalities due to the π-conjugated azomethine structure and electronic state are reviewed. The functions include luminous dendrimers by bismuth assembly, Y-shape recognition using porphyrin core, and atomicity-controlled template of metal salts on imine parts. The precisely controlled template ability developed synthesis of multimetallic subnanoparticles and superatoms that can mimic the properties of elemental atoms.

The recent advances of the novel signal-amplification method, “supramolecular allosteric signal-amplification sensing” (SASS), are shown and summarized in this review. The SASS using polymers, polythiophenes and glucans introduced herein will be expandable to further smart polymeric systems, i.e., dynamic supramolecular assemblies.

Acidic pH is identified for various types of tumors, whereby it can be employed for crafting tumor-targeted nanomaterials. Cationic net charge of the nanomaterials at tumorous pH achieves selective interaction with anionic tissue constituents at tumor sites, for the effective tumor accumulation. However, tumorous pH is ca. 6.5, whereas pH of normal tissues is 7.4, and therefore responsiveness to the small pH window is the key toward the success for tumor delivery. The present manuscript highlights the polymer designs that recognize tumorous pH to make tumor-targeted nanomaterials.

The structural characterization of DDS carriers, including transdermal DDS, is one of the essential factors in the understanding of the biological properties and useful for the development of new carriers. This review introduces a quantitative evaluation of the surface coating on a carrier with the contrast variation technique of SAXS in the first section and the localization determination of drug molecules in liposomes in the second section. The final section describes the microemulsions containing deep eutectic solvents in the inner phase for use in transdermal DDS.

Silk fibroin (SF) is a natural protein polymer material and has been fabricated and studied as a scaffold for tissue engineering and regenerative medicine. To append new functions to SF scaffolds and understand their in vivo behaviors, researchers have addressed modifications of SF scaffolds by using transgenic silkworm and peptide modification technologies. These modified SF scaffolds had on-target functions and showed their potential as a material for tissue engineering applications. This review summarizes the methodologies and characteristics of functionalized SF scaffolds.

Water-gated polymer thin-film transistors (WG-PTFTs) fabricated by a simple procedure can be operated at an ultralow voltage, whereby the WG-PTFTs with molecular recognition units allow chemical sensing. Upon the addition of analytes, the electric double layer capacitance of the WG-PTFTs can be changed by accumulation and desorption of charged species at the interface of the semiconductor and electrolytes. For example, the WG-PTFTs have successfully detected biogenic amines and a herbicide glyphosate. In short, our proposed WG-PTFTs are among the most promising platforms for sensing applications based on π-conjugated polymer materials.

Boronic acids (BA) are known for their ability to reversibly interact with the diol groups, a common motif of biomolecules including sugars, ribose, and catechols. One can tailor BAs to elicit a divergent profile of binding strength and specificity on the basis of stereochemistry and controlled electronic effects. This focus review provides an overview of a phenylboronic acid (PBA)-based, totally synthetic platform for insulin delivery applications developed in our group, with focuses on the development of new PBA derivatives, glucose-responsive gels, and the gel-combined medical devices.

Electrospinning (ES) is a technique that can produce nanofiber mats from arbitrary polymers. We prepared actuators consisting of nanofiber mat electrodes and ionic liquid gel using three methods, and examined the effect of the preparation method on actuator performance. The results showed that actuators with nanofiber mat electrodes spun from the lowest spinning solution concentration showed a larger strain against an applied voltage. Furthermore, we prepared two types of actuators with different fiber directions and examined the effect of nanofiber alignment on actuator performance.

Strategic design and synthesis of semiconducting polymers with intrinsic ductility and/or stretchability are introduced in this review. The best polymer films show high charge mobilities over 1 cm²V⁻¹s⁻¹ even at 100% tensile strain. On the other hand, their mechanical properties remain inadequate, with high elastic moduli over 0.1 GPa. For semiconducting polymers to be promising candidates in applications such as wearable electronics, electronic skins, and bioelectronics, the trade-off relationship between their electronic and mechanical performance must be prevented by further developing and combining versatile and efficient approaches.

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.

Block copolymers are used as nano-tools for delivering hydrophobic drugs. Their formulation requires robust characterization and clarification of the critical quality attributes correlating with the safety and efficacy. Static solution scattering from block copolymers is one such technique. This paper outlines the theoretical background and current models for analyzing this scattering and then presents an overview of our recent studies on block copolymers.

Our recent studies on the development of semiconducting polymers based on three novel π-extended heteropolycyclic aromatic frameworks, using phenanthro[1,2-b:8,7-b’]dithiophene (PDT) as a weak donor and alkoxy-substituted anthra[1,2‑c:5,6‑c’]bis([1,2,5]thiadiazole) (ATz) and vinylene-bridged 5,6-difluorobenzo[c][1,2,5]thiadiazole (FBTzE) as new thiadiazole-based acceptor units are described. Furthermore, their detailed relationships between the thin-film structure and device performance in organic field-effect transistors (OFETs) and organic photovoltaic cells (OPVs) were investigated. These results demonstrated that these novel π-extended heteropolycyclic aromatic frameworks have great potential as building units for high-performance OFETs and OPVs.

Ferroelectric polymers, poly(vinylidene fluoride) (PVDF), and its copolymers have been exploited for various applications, including nonvolatile memories, energy harvesters, and piezoelectric/pyroelectric sensors. To achieve better performance in PVDF-based devices, crystallization manipulation and controllable nanostructure formation are unavoidable and are of crucial importance. For this review, recent exploitation of the control of PVDF ferroelectric polymer crystallization at the nanoscale was specifically examined and summarized to provide insight into the future development of ferroelectric polymer nanomaterials.