Cellulose nanofibers/lignin particles/tragacanth gum nanocomposite hydrogels for biomedical applications

The plethora of environmental concerns faced today is demanding the development of new biodegradable materials from renewable resources. In this regard, natural polymers are promising resources for the design of new materials owing to their ecologically correct and renewable nature. Cellulose is an abundant, biodegradable, non-toxic, and low-cost biopolymer, already widely used to produce bio-based materials. Cellulose fibers when disintegrated result in cellulose nanofibrils (CNF) that have water-binding capacity and produce stable hydrogels1. Lignin is also a bio-renewable polymer that has attracted interest in recent years for its antimicrobial, antioxidant, and UV-shielding properties conferred by the presence of aromatic compounds in its structure2. Lignin can be converted into hydrophilic spherical nanoparticles (LNP) with well-defined surface structure. This is an approach to overcome lignin heterogeneity and low solubility in water and explore new applications. Gum tragacanth (TG) is a highly branched polysaccharide extracted as a dry exudation from the stems and branches of Astragalus gummifer trees. It is also environmentally friendly, biocompatible, and has good rheological properties3, however, the potential applications of TG have not been fully investigated. All these characteristics make CNF, LNP, and TG attractive for material design, applicable in a variety of technological fields, for instance, biomedical materials as drug carriers, wound dressings, and tissue engineering scaffolding. These polymers have a wide range of functionalities in their chemical structures such as hydroxyl and carboxyl groups and great potential to produce hydrogels with high water retention capacity4,5. Hydrogels can be engineered in tunable microstructure, and consequently tunable mechanical properties and degradation rate to mimic the tissue environment. Hydrogel scaffolds can promote the regulation of cellular functions, therefore, improving tissue growth. In this study, CNF, LNP, and TG were used to prepare multicomponent hydrogels for 3D printing scaffolds with biocompatible properties for biomedical application. The results of our work showed that the rheological behavior was improved with the addition of TG to the hydrogel composition. A similar result was observed for the scaffold's swelling capacity and degradation rate, the properties were improved with the increase of the TG content in the hydrogels. The values of Young's compressive modules for hydrogels made it possible to classify them as soft gels at the level between skin and muscle tissues. The combination of properties of these materials makes plant-based hydrogels attractive to design materials with the potential to improve patients' lives through regenerative medicine.