Electroconductive Nanocellulose, a Versatile Hydrogel Platform: From Preparation to Biomedical Engineering Applications

Nanocelluloses have garnered significant attention recently in the attempt to create sustainable, improved functional materials. Nanocellulose possesses wide varieties, including rod-shaped crystalline cellulose nanocrystals and elongated cellulose nanofibers, also known as microfibrillated cellulose. In recent times, nanocellulose has sparked research into a wide range of biomedical applications, which vary from developing 3D printed hydrogel to preparing structures with tunable characteristics. Owing to its multifunctional properties, different categories of nanocellulose, such as cellulose nanocrystals, cellulose nanofibers, and bacterial nanocellulose, as well as their unique properties are discussed here. Here, different methods of nanocellulose-based hydrogel preparation are covered, which include 3D printing and crosslinking methods. Subsequently, advanced nanocellulose-hydrogels addressing conductivity, shape memory, adhesion, and structural color are highlighted. Finally, the application of nanocellulose-based hydrogel in biomedical applications is explored here. In summary, numerous perspectives on novel approaches based on nanocellulose-based research are presented here.

Covalent Tethering of Temperature Responsive pNIPAm onto TEMPO-Oxidized Cellulose Nanofibrils via Three-Component Passerini Reaction

A critical challenge in the application of functional cellulose fibrils is to perform efficient surface modification without disrupting the original properties. Three-component Passerini reaction (Passerini 3-CR) is regarded as an effective functionalization approach which can be carried out under mild and fast reaction condition. In this study, we investigated the application of Passerini 3-CR for the synthesis of thermoresponsive cellulose fibrils by covalently tethering poly(N-isopropylacrylamide) in aqueous condition at ambient temperature. The three components, a TEMPO-oxidized cellulose nanofiber bearing carboxylic acid moieties (TOCN-COOH), a functionalized polymer with aldehyde group (pNIPAm-COH) and a cyclohexyl isocyanide, were reacted in one pot resulting in 36% of grafting efficiency within 30 min. The chemical coupling was evidenced by improved aqueous dispersibility, which was further confirmed by FT-IR, TGA, UV-vis, and turbidity study. It was observed that the grafting efficiency is strongly dependent on the chain length of the polymer. Furthermore, AFM and X-ray diffraction measurements affirmed the suitability of the proposed method for chemical modification of cellulose nanofibers without significantly compromising the original morphology and structural integrity.

Temperature-responsive fibres of cellulose-based copolymers

Novel temperature-responsive fibers electrospun from a click-assembled copolymer of cellulose acetate grafted with oligo(ethyleneglycol) methylether methacrylate random blocks.

Sustainable terpene-based polyamides via anionic polymerization of a pinene-derived lactam

A sustainable lactam, which is derived from the renewable terpene β-pinene, is converted to polyamides with prosperous thermal properties via a convenient anionic ring-opening polymerization (ROP).

Aminomaleimide fluorophores: a simple functional group with bright, solvent dependent emission

Amino-substituted maleimides form a new class of highly emissive compounds, with large Stokes shifts (>100 nm) and high quantum yields (up to ∼60%).

Amino-substituted maleimides form a new class of highly emissive compounds, with large Stokes shifts (>100 nm) and high quantum yields (up to ∼60%). Emission is responsive to the maleimide's environment with both a red-shift, and quenching, observed in protic polar solvents. Aminomaleimides are easily functionalised, providing a versatile fluorescent probe.

Fluorescent Covalently Cross-Linked Cellulose Networks via Light-Induced Ligation

A facile light-induced procedure for the covalent cross-linking of cellulose at ambient conditions employing the nitrile imine mediated tetrazole-ene cycloaddition (NITEC) reaction is presented. Cellulose-tetrazoles with 2 degrees of substitution (0.14 and 0.23) were synthesized in a solution-based transesterification procedure in an ionic liquid. Two bismaleimides with either a trioxatridecane or a dithiodipropionyl backbone were used as cross-linkers to form fluorescent, covalently cross-linked cellulose networks and films, which were characterized by UV/vis spectroscopy, fluorescence spectroscopy, DSC, and TGA. The films showed a broad emission band from 500-700 nm and were thermally stable up to 200 °C. Using the bismaleimide with a disulfide moiety as the cross-linker, reductive degradation of the films can be induced. Finally, cellulose-tetrazole was cross-linked in a spatially resolved fashion, providing a strategy for the shaping of films based on renewable resources.