Cellulose nanofibrils (CNFs) in the form of hydrogels stand out as a platform biomaterial in bioink formulation for 3D printing because of their low cytotoxicity and structural similarity to extracellular matrices. In the present study, 3D scaffolds were successfully printed with low-concentration inks formulated by 1 w/v % 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized CNF with less than 1 w/v % gelatin methacrylate (GelMA). Quartz crystal microbalance with dissipation monitoring (QCM-D) measurements showed strong interaction between the two biopolymers. The UV cross-linking ability of GelMA (≤1 w/v %) was enhanced in the presence of TEMPO-oxidized CNFs. Multiple factors including strong physical interaction between CNF and GelMA, in situ cross-linking of CNF by Ca²⁺, and UV cross-linking of GelMA enabled successful 3D printing of low-concentration inks of CNF/GelMA into scaffolds possessing good structural stability. The mechanical strength of the scaffolds was tuned in the range of 2.5 to 5 kPa. The cell culture with 3T3 fibroblasts revealed noncytotoxic and biocompatible features for the formulated inks and printed scaffolds. More importantly, the incorporated GelMA in the CNF hydrogel promoted the proliferation of fibroblasts. The developed low-concentration CNF/GelMA formulations with a facile yet effective approach to fabricate scaffolds showed great potential in 3D printing for wound healing application.

Wood-derived biopolymers have attracted great attention over the past few decades due to their abundant and versatile properties. The well-separated three main components, i.e., cellulose, hemicelluloses, and lignin, are considered significant candidates for replacing and improving on oil-based chemicals and materials. The production of nanocellulose from wood pulp opens an opportunity for novel material development and applications in nanotechnology. Currently, increased research efforts are focused on developing 3D printing techniques for wood-derived biopolymers for use in emerging application areas, including as biomaterials for various biomedical applications and as novel composite materials for electronics and energy devices. This Review highlights recent work on emerging applications of wood-derived biopolymers and their advanced composites with a specific focus on customized pharmaceutical products and advanced functional biomedical devices prepared via three-dimensional printing. Specifically, various biofabrication strategies in which woody biopolymers are used to fabricate customized drug delivery devices, cartilage implants, tissue engineering scaffolds and items for other biomedical applications are discussed.

Cellulose nanocrystals (CNCs) as a renewable and biodegradable nanomaterial have wide application value. In this work, CNCs were extracted from bleached chemical pulp using two stages of isolation (i.e. formic acid (FA) hydrolysis and 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO) mediated oxidation) under mild conditions. In the first stage, FA was used to remove hemicellulose, swell cellulose fibers, and release CNCs. The FA could be readily recovered and reused. In the second stage, the CNCs isolated by FA were further modified by TEMPO-mediated oxidation to increase the surface charge of CNCs. It was found that the modified CNCs with more ordered crystal structure and higher surface charge had better redispersibility and higher viscosity in aqueous phase. Therefore, the modified CNCs could be more effective when used as rheology modifier in the fields of water based coating, paint, food etc.