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

Abstract

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.

Biocatalytic oligomerization-induced self-assembly of crystalline cellulose oligomers into nanoribbon networks assisted by organic solvents

“…For example, the cellulase-catalyzed oligomerization of β-ᴅ-cellobiosyl fluoride monomers [29] and the cellodextrin phosphorylase (CDP)-catalyzed oligomerization of α-ᴅ-glucose 1-phosphate (αG1P) monomers from ᴅ-glucose [30–31] and cellobiose [32–33] primers have been demonstrated, where the synthesized cellulose oligomers (also known as cellodextrin) self-assemble in situ into unique nanostructures. In addition to the plain cellulose oligomer, cellulose oligomer derivatives bearing azido [34], alkyl [35], oligo(ethylene glycol) [36], vinyl [37–38], and amino [39–40] groups at the terminal have been successfully synthesized by using glucose derivatives as primers for the CDP-catalyzed oligomerization. By exploiting those enzyme-catalyzed oligomerization systems, various nanostructures, including nanofibrous assemblies [41], rectangular nanosheet-shaped lamellar crystals [30–31 39,42], distorted nanosheets with a bilayer structure [35], helical nanorods with a bilayer structure [35], and network structures composed of nanoribbon-shaped lamellar crystals [33,42–46] have been successfully constructed by changing the enzymatic reactions, tuning the self-assembly kinetics, introducing terminal functional groups, and using additives.…”

Chemoenzymatic Synthesis of Fluorinated Cellodextrins Identifies a New Allomorph for Cellulose‐Like Materials**

“…As expected, the TEM images of the monofluorinated 2F‐EpC ( 4 ), 3F‐EpC ( 5 ) and 6F‐EpC ( 6 ; Figure S8) show a very similar morphology to EpC ( 8 , Figure 2 A, a). This crystalline sheet‐like morphology is well‐known for enzymatically synthesised cello‐oligosaccharides, [22, 43] including derivatised cellulose, such as acrylated cellulose [26] and cellulose conjugated with oligo(ethylene glycol) [28] . On the other hand, multi‐6F‐EpC ( 7 ) particles formed predominantly into significantly shorter platelets (<100 nm length) (Figure 2 B, a).…”

“…This crystalline sheet-like morphologyi sw ellknown for enzymatically synthesised cello-oligosaccharides, [22,43] including derivatisedc ellulose, such as acrylated cellulose [26] and cellulose conjugated with oligo(ethylene glycol). [28] On the other hand, multi-6F-EpC (7)p articles formed predominantly into significantly shorter platelets( < 100 nm length) ( Figure 2B,a). These differences were furtherconfirmed by AFM imaging using samples prepared by depositing diluted sample suspensions on freshly cleaved mica (Figure2B, ba nd c).…”

“…[13][14][15][16] Specifically in relationt o glucose-based materials, glycoside phosphorylases( GPs) [17][18][19][20][21] have shown substantial potentialf or the synthesis of amyloseand cellulose-like materials. In particular,c ellodextrin phosphorylase (CDP,E C2 .4.1.49) [22][23][24] has emerged as ap owerful tool for the synthesiso fd ifferently functionalised cellulose oligomers, giving rise to av ariety of nanostructures (sheets, [25,26] rods, [27] or ribbons [28] )d epending on the nature of the substrate.…”

Unravelling the Specificity of Laminaribiose Phosphorylase from Paenibacillus sp. YM‐1 towards Donor Substrates Glucose/Mannose 1‐Phosphate by Using X‐ray Crystallography and Saturation Transfer Difference NMR Spectroscopy

“…Substrates for GP‐catalysed glycosylations are more readily available, in comparison to those for GT‐catalysed reactions; this makes GPs attractive biocatalysts for carbohydrate syntheses. The use of GP biocatalysts has been demonstrated in academic research, such as in the synthesis of homogeneous crystalline cellulose, self‐assembled structures of alkylated cellulose, cellulose nanoribbons with primary amino groups, and the formation of oligo(ethylene glycol)‐bearing cellulose hydrogels, and more widely at an industrial scale, such as for the synthesis of 2‐ O ‐(α‐ d ‐glucopyranosyl)‐ sn ‐glycerol, a cosmetic ingredient, by sucrose phosphorylase; kilogram‐scale synthesis of lacto‐ N ‐biose, a prebiotic made with lacto‐ N ‐biose phosphorylase; and the synthesis of disaccharide sweetener kojibiose, produced with a sucrose phosphorylase variant from Bifidobacterium adolescentis …”