Volume 54 Issue 4, April 2022

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.

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.

The present review focuses on the enzymatic synthesis of unnatural oligosaccharides and polysaccharides linked through strictly controlled α(1→4)-glycosidic linkages by glucan phosphorylase (GP) catalysis. In particular, the recent progress of the enzymatic synthesis of unnatural polysaccharides by GP (isolated from thermophilic bacteria, Aquifex aeolicus VF5)-catalyzed polymerization and related reactions is overviewed. The unnatural substrates have high applicability as practical functional materials in pharmaceutical, medicinal, and biological research fields.

Research advances in the extraction, structural and conformational characteristics, and biological activities (antitumor, anti-inflammation, immunomodulatory, hypoglycemic activity) of β-glucans from three fungi, Auricularia auricula judae, Lentinus edodes and yeast, as typical representatives, were reviewed, as well as the potential mechanism and the structure-function relationship. Additionally, as-fabricated β-glucan-derived nanocomposite biomaterials as carriers for delivering drugs, genes, nanoparticles, and fluorescence probes were addressed.

The self-assembly of carbohydrate-based block copolymer systems has allowed recently the conception of novel glyconanoparticles and high-resolution patterning thin films with sub_10nm resolution (high χ) that has never been attained by petroleum-based copolymers and provides these new nanostructured biomaterials with novel properties such as next generation nanolithography, memory devices, OPV and biosensors. The glyconanoparticles can be designed to meet the targeted applications in terms of size, encapsulation and decoration. The control of the lamellar/cylindrical phases orientation can be achieved using thermal, solvent vapor or microwave annealing processes in thin films.

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.

Polysaccharides and “imogolite” (a natural aluminum silicate nanoclay) were used as building blocks to prepare environmentally benign (organic/inorganic) hybrid materials of natural origin. Cellulose nanocrystals (CNCs), cellulose fibers (CFs), and sacran were employed as polysaccharides. By utilizing oppositely charged organic and inorganic components, polysaccharide/imogolite hybrids were prepared by spin-assisted layer-by-layer assembly and solution blending. The fine dispersion and attractive interactions of imogolite with polysaccharides afforded hybrids with improved physicochemical properties.

Bacterial cellulose (BC) has been utilized as a biopolymer matrix for various applications. The advancement of synthetic biology has brought new approaches for its production and functionalization. In this mini-review, we briefly discuss the conventional methods employed to improve BC production and functionalization as well as their challenges. We summarize the applications of synthetic biology to address the challenges and its use to develop novel hybrid living materials. Finally, we consider the opportunities and future prospects of synthetic biology and engineered biological materials.

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.

Cellulosic bottlebrush regioselectively possessing poly(ethylene glycol) (PEG) and polystyrene (PS) side chains (PEG-PS-cellulose) was synthesized, and its secondary structure in dilute solution was investigated with SAXS and SEC-MALS. The relationship between the cross-sectional mean squared radius of gyration (〈S_c²〉) and molecular weight of PS chain (MW_PS) showed that PEG-PS-cellulose has a core-shell-corona structure in cross section. The dependency of main-chain stiffness (λ⁻¹) on MW_PS was discussed on the basis of the interactions of the PS and PEG side chains as well as the restricted rotation of the cellulosic main chain.

A series of polyacrylamide/polyanionic cellulose/Zr–CP (PAM/PAC/Zr–CP) composite hydrogels were prepared via acrylamide polymerization in aqueous solution of PAC and disodium terephthalate (Na₂BDC), followed by posttreatment in 0.1 M ZrOCl₂ solution. The coordination of Zr(IV) clusters with carboxylates on PAC and BDC²⁻ endows the hydrogels with improved strength and adsorption of methyl orange (MO). Specially, over 5 MPa of compressive strength and 500 mg MO/g Zr of MO-adsorption capacity are attained. This work provides a facile and green approach to synthesize CP-based composite hydrogels with enhanced mechanical and adsorptive properties through strong metal–ligand coordination.

Poly(ether sulfone)-based functional ultrafiltration membranes were developed by employing chitosan (CS) and ammonium chloride (NH₄Cl) as antibacterial agents. A PES membrane was prepared and immersed in CS/NH₄Cl solutions at different NH₄Cl concentrations. The composite membranes show enhancement in the antibiofouling properties, where maximum bacteria-killing ratio (%BKR) values of 99.2 and 83.3% were observed against Staphylococcus aureus and Escherichia coli, respectively. The addition of CS/NH₄Cl not only modified the morphological structure of the PES membrane but also increased its hydrophilicity, porosity, and mechanical strength, suitable for ultrafiltration applications.

A synthetic strategy is developed towards highly amphiphilic cellulose nanocrystals (CNCs) by selectively introducing carboxylic acid groups at the reducing end and –C8 units on the surface. The resulting chloroform soluble CNCs formed an exceptionally stable monolayer at the air/water interface, and resulted in a well-defined LB isotherm, allowing their facile transfer to both hydrophilic and hydrophobic substrates. These monolayers were successfully transferred onto substrates to create monolayer or smooth multilayer films.

Cellulose chains with a reducing-end thiol group are of interest to install a controllable topochemical pattern of site-selective modification into nanocellulose materials. Selection of the polymerizing enzyme (cellodextrin phosphorylase; CdP) was pursued here to enhance the synthetic precision in the preparation of 1-thio-cellulose. The CdP from Clostridium stercorarium (CsCdP) was identified as a practical catalyst for 1-thio-cellulose synthesis in high purity (≥95%) directly from β-1-thio-glucose. The synthesis proceeds without the need of cellobiose phosphorylase (CbP) and minimizes the contamination (plain cellulose; ≤5%) in the product.

The self-assembly of biomolecules is an important strategy for fabricating structurally ordered artificial nanomaterials. In this study, we investigated the cellodextrin phosphorylase-catalyzed synthesis and self-assembled structures of cellulose oligomers in the presence of protein denaturants. The modulation of intermolecular interactions between oligomers by protein denaturants under adequate synthesis conditions resulted in the production of oligomers with greater degrees of polymerization and different crystal structures.

Molecular imprinting of methylene blue (MB), a small cationic dye, was conducted to free-standing films prepared from polyion complexes of chondroitin sulfate and chitosan. Molecular permeability of the MB-imprinted films in phosphate-buffered saline (PBS) was evaluated. MB, orange II and porphyrin derivatives were used as permeants to clarify the effects of charge and size of the permeant on the permeation behaviors. In the case of porphyrin derivatives, the inner voids of the films were not significant for the permeation behavior, but the surface charges of the films were important.

A cell-cultivable gel based on a polysaccharide “sacran” has been developed. Although the conventionally produced sacran gel does not show cell adhesion, it achieved compositing with collagen, which has cell adhesion, and showed its potential as a cell scaffold. The feature of this study is that the gelation of sacran was controlled by the addition of salt, and the composite with collagen was achieved for the first time.

In this study, we examined the efficiency of q1-complex and L-SPG complex in translocation to the cytoplasm. The results showed that the q1 complex can deliver YB-1-AS into the cytoplasm about three times more efficiently than the L-SPG complex.

We developed pDNA/polysaccharide complexes suitable for reverse transfection (RTF) and investigated their transfection mechanisms. The pDNA/chitosan/hyaluronic acid ternary complexes showed excellent transfection efficiency in RTF compared with the conventional forward transfection (FTF). The ternary complexes were taken up via macropinocytosis in RTF. Furthermore, the ternary complexes in RTF were transported to late endosomes via microtubules, and were remarkably accumulated in the nucleus. These results suggest that the cell transfection efficiency of the ternary complexes in RTF was enhanced by their efficient delivery to the nucleus via late endosomes.

Utilizing the emulsion-forming ability of partially deacetylated chitin nanofibers, a composite with polystyrene (PS) was prepared. A partially deacetylated chitin nanofiber aqueous dispersion was added to styrene to obtain an oil in a water-type Pickering emulsion. Using the emulsion, suspension polymerization was performed to obtain PS fine particles covered with chitin nanofibers. This composite could be molded by hot pressing, and the molded product was transparent to some extent. Mechanical properties of PS were greatly improved. When the composite was molded again, the mechanical properties did not decrease.