Self-Assembly of Cellulose Oligomers into Nanoribbon Network Structures Based on Kinetic Control of Enzymatic Oligomerization

The ability to chemically synthesize desired molecules followed by their in situ self-assembly in reaction solution has attracted much attention as a simple and environmentally friendly method to produce self-assembled nanostructures. In this study, α-d-glucose 1-phosphate monomers and cellobiose primers were subjected to cellodextrin phosphorylase-catalyzed reverse phosphorolysis reactions in aqueous solution in order to synthesize cellulose oligomers, which were then in situ self-assembled into crystalline nanoribbon network structures. The average degree-of-polymerization (DP) values of the cellulose oligomers were estimated to be approximately 7–8 with a certain degree of DP distribution. The cellulose oligomers crystallized with the cellulose II allomorph appeared to align perpendicularly to the base plane of the nanoribbons in an antiparallel manner. Detailed analyses of reaction time dependence suggested that the production of nanoribbon network structures was kinetically controlled by the amount of water-insoluble cellulose oligomers produced

Multidimensional Self-Assembled Structures of Alkylated Cellulose Oligomers Synthesized via in Vitro Enzymatic Reactions

The self-assembly of biomolecules into highly ordered nano-to-macroscale structures is essential in the construction of biological tissues and organs. A variety of biomolecular assemblies composed of nucleic acids, peptides, and lipids have been used as molecular building units for self-assembled materials. However, crystalline polysaccharides have rarely been utilized in self-assembled materials. In this study, we describe multidimensional self-assembled structures of alkylated cellulose oligomers synthesized via in vitro enzymatic reactions. We found that the alkyl chain length drastically affected the assembled morphologies and allomorphs of cellulose moieties. The modulation of the intermolecular interactions of cellulose oligomers by alkyl substituents was highly effective at controlling their assembly into multidimensional structures. This study proposes a new potential of crystalline oligosaccharides for structural components of molecular assemblies with controlled morphologies and crystal structures

Enzymatic synthesis and protein adsorption properties of crystalline nanoribbons composed of cellulose oligomer derivatives with primary amino groups

<p>The <i>in vitro</i> enzymatic synthesis of cellulose and its derivatives has attracted growing interest for fabricating novel cellulose-based supramolecular assemblies with unique physicochemical and functional properties. However, their potential biomedical applications have not been sufficiently demonstrated despite their useful features of designable structures and tailor-made surface functionalities. Herein, we demonstrated the production of crystalline nanoribbons composed of cellulose oligomer derivatives with primary amino groups via cellodextrin phosphorylase-catalyzed single-step reactions using α-d-glucose l-phosphate monomers and 2-aminoethyl-β-d-glucoside primers. Then, the fundamental properties of protein adsorption onto the surface-aminated nanoribbons were systematically investigated. It was found that the primary amino groups on the nanoribbon surfaces effectively attracted negatively charged proteins but not positively charged ones. Furthermore, it was demonstrated that the nanoribbons did not show apparent cytotoxicity against cultured cells. Taken together, our findings open a new avenue for the facile production of cellulose-based supramolecular assemblies with tailor-made functionality for future biomedical applications.</p

Enzyme-Catalyzed Bottom-Up Synthesis of Mechanically and Physicochemically Stable Cellulose Hydrogels for Spatial Immobilization of Functional Colloidal Particles

The dispersion stabilization of colloidal particles and subsequent construction of functional materials are of great interest in areas ranging from colloid chemistry to materials science. A promising strategy is the spatial immobilization of colloidal particles within gel scaffolds. However, conventional gels readily deform and even collapse when changes in environmental conditions occur. Herein, we describe the enzyme-catalyzed bottom-up synthesis of mechanically and physicochemically stable nanoribbon network hydrogels composed of crystalline cellulose oligomers in which cellulose nanocrystals (CNCs) as model colloidal particles are immobilized spatially. The stiffness of the hydrogels increased with the amount of CNCs incorporated. Filling the void space of the hydrogels with hydrophobic polymers resulted in polymer nanocomposites with excellent mechanical properties. The nanoribbon networks will be useful for demonstrating the potential functions of colloidal particles

Hydrolytic Activities of Crystalline Cellulose Nanofibers

Cellulose is commonly believed to be inactive to organic substances; this inertness is an essential requirement for raw materials in industrial products. Here we demonstrate the contradictory but promising properties, which are the hydrolytic activities of crystalline cellulose nanofibers for the ester, monophosphate, and even amide bonds of small organic substrates under extremely mild conditions (neutral pH, moderate temperature, and atmospheric pressure). The hydrolytic activities were significantly extended to decompose the coat proteins of model viruses, followed by a drastic decrease in their infection capabilities to the host cells

Enzyme-Catalyzed Bottom-Up Synthesis of Mechanically and Physicochemically Stable Cellulose Hydrogels for Spatial Immobilization of Functional Colloidal Particles

The dispersion stabilization of colloidal particles and subsequent construction of functional materials are of great interest in areas ranging from colloid chemistry to materials science. A promising strategy is the spatial immobilization of colloidal particles within gel scaffolds. However, conventional gels readily deform and even collapse when changes in environmental conditions occur. Herein, we describe the enzyme-catalyzed bottom-up synthesis of mechanically and physicochemically stable nanoribbon network hydrogels composed of crystalline cellulose oligomers in which cellulose nanocrystals (CNCs) as model colloidal particles are immobilized spatially. The stiffness of the hydrogels increased with the amount of CNCs incorporated. Filling the void space of the hydrogels with hydrophobic polymers resulted in polymer nanocomposites with excellent mechanical properties. The nanoribbon networks will be useful for demonstrating the potential functions of colloidal particles

Enzymatic Synthesis of Oligo(ethylene glycol)-Bearing Cellulose Oligomers for in Situ Formation of Hydrogels with Crystalline Nanoribbon Network Structures

Enzymatic synthesis of cellulose and its derivatives has gained considerable attention for use in the production of artificial crystalline nanocelluloses with unique structural and functional properties. However, the poor colloidal stability of the nanocelluloses during enzymatic synthesis in aqueous solutions limits their crystallization-based self-assembly to greater architectures. In this study, oligo­(ethylene glycol) (OEG)-bearing cellulose oligomers with different OEG chain lengths were systematically synthesized via cellodextrin phosphorylase-catalyzed oligomerization of α-d-glucose l-phosphate monomers against OEG-bearing β-d-glucose primers. The products were self-assembled into extremely well-grown crystalline nanoribbon network structures with the cellulose II allomorph, potentially due to OEG-derived colloidal stability of the nanoribbon’s precursors, followed by the in situ formation of physically cross-linked hydrogels. The monomer conversions, average degree of polymerization, and morphologies of the nanoribbons changed significantly, depending on the OEG chain length. Taken together, our findings open a new avenue for the enzymatic reaction-based facile production of novel cellulosic soft materials with regular nanostructures

Enzyme-Catalyzed Bottom-Up Synthesis of Mechanically and Physicochemically Stable Cellulose Hydrogels for Spatial Immobilization of Functional Colloidal Particles

The dispersion stabilization of colloidal particles and subsequent construction of functional materials are of great interest in areas ranging from colloid chemistry to materials science. A promising strategy is the spatial immobilization of colloidal particles within gel scaffolds. However, conventional gels readily deform and even collapse when changes in environmental conditions occur. Herein, we describe the enzyme-catalyzed bottom-up synthesis of mechanically and physicochemically stable nanoribbon network hydrogels composed of crystalline cellulose oligomers in which cellulose nanocrystals (CNCs) as model colloidal particles are immobilized spatially. The stiffness of the hydrogels increased with the amount of CNCs incorporated. Filling the void space of the hydrogels with hydrophobic polymers resulted in polymer nanocomposites with excellent mechanical properties. The nanoribbon networks will be useful for demonstrating the potential functions of colloidal particles

Cellodextrin Phosphorylase-Catalyzed Single-Process Production and Superior Mechanical Properties of Organic–Inorganic Hybrid Hydrogels Composed of Surface-Carboxylated Synthetic Nanocelluloses and Hydroxyapatite

Artificial organic–inorganic hybrid materials produced through mineralization in/on biomolecular assemblies under aqueous-based mild conditions have attracted much attention due to the sustainability derived from environmentally friendly and low-energy production processes and excellent mechanical properties resulting from their highly organized structures. In this study, organic–inorganic hybrid hydrogels composed of crystalline nanoribbon assemblies of terminally carboxylated cellulose oligomers and hydroxyapatite (HAp) were produced via cellodextrin phosphorylase-catalyzed syntheses of the oligomers and in situ HAp mineralization achieved by combining phosphate ions kinetically fed by the enzyme reaction with coexisting calcium ions. Chemical structure characterizations revealed successful syntheses of the oligomers from the appropriate substrates (namely, monomers and primers). Crystallographic characterizations revealed that the cellulose moieties crystallized as the cellulose II allomorph, thereby leading to an antiparallel molecular arrangement in the assemblies, and that the calcium phosphate produced was assignable to HAp. Microscopic observations revealed the production of surface-carboxylated nanoribbon assemblies of the oligomers onto which HAp granules were hybridized, while the hybrid structure was not observed for nanoribbon assemblies of plain cellulose oligomers even after HAp mineralization. Mechanical property characterizations revealed that the stiffness (namely, Young’s modulus) of the hybrid hydrogel was significantly greater than it was without surface carboxylation of nanoribbon assemblies or HAp hybridization, suggesting that HAp hybridization to surface-carboxylated nanoribbon assemblies is essential for improving the mechanical properties of cellulose oligomer hydrogels. Our findings open a new avenue for production of synthetic nanocellulose–inorganic hybrid materials with advanced functions

A Bottom-Up Synthesis of Vinyl-Cellulose Nanosheets and Their Nanocomposite Hydrogels with Enhanced Strength

Extracted nanocellulose from natural resources commonly requires modification before it is used as an effective nanofiller. In the present study, through an enzymatic polymerization of α-d-glucose 1-phosphate from the primer 2-(glucosyloxy)­ethyl methacrylate (GEMA), a novel type of two-dimensional methacrylate-containing cellulose nanosheets (CNS) with a thickness of about 6 nm, named as GEMA-CNS, was directly synthesized under a mild condition by a “bottom-up” method. The structure and morphology of GEMA-CNS were characterized by ¹H-nuclear magnetic resonance (NMR), matrix-assisted laser desorption/ionization time-of-flight mass spectra (MALDI-TOF MS), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and atomic force microscopy (AFM). Afterward, the obtained GEMA-CNS was covalently incorporated into poly­(ethylene glycol) matrix through thiol–ene Michael addition, fabricating a series of GEMA-CNS-based nanocomposite hydrogels. The addition of GEMA-CNS effectively improved the mechanical strength and altered the internal network structures of hydrogels; additionally, the swelling/biodegradation behaviors of gels in phosphate buffer saline (pH 7.4) at 37 °C were affected to some degree. This species of property-tunable hydrogels with GEMA-CNS dosage demonstrates potential applications in tissue engineering. The current presentation opens a new road for direct enzymatic preparation of reactive nanocellulose and its novel applications in nanocomposite materials