Recovery of cellulose from biomass waste for 3D printing of slow-release hydrogel scaffolds

Here, following the waste-to-value principle, cellulose extracted from spent coffee grounds was modified to fabricate cargo-loaded hydrogel scaffolds via 3D printing, thereby enhancing resource utilization efficiency. Initially, FTIR spectroscopy confirmed the removal of non-cellulosic fractions, yielding cellulose over 10 %, which was subsequently converted into carboxymethyl cellulose through the etherification process. Furthermore, the concrete inks prepared from two hydrogel microparticles that were made from recovered carboxymethyl cellulose and their photo-crosslinked hydrogels exhibited distinct property characteristics, establishing a foundation for selecting an appropriate formulation for hydrogel scaffold printing. Notably, the structural parameters of the hydrogel scaffolds significantly influenced cargo release kinetics, with scaffolds printed using 0.3 mm and 0.6 mm nozzles demonstrating marked filling density-dependent release behaviors. The nutrient release duration increased from 0.25 to 9 h to 19 and 26 h as filling density was elevated. However, structural factors of the scaffolds were found to critically influence cargo release kinetics within the hydrodynamic field, as the spatial structure governs the surface area-to-volume ratio, thereby affecting diffusion pathways and release behaviors. Finally, the developed release model was utilized to predict the release kinetics of medicine from the hydrogel scaffold, providing a new perspective on scaffold design and manufacture aimed at optimizing performance and minimizing waste. This work, combining waste re-utilization and loss reduction, presents a promising pathway towards circular economy promotion and carbon emission mitigation to advance sustainable development goals.