Upcycled coffee waste into nanocellulose-reinforced alginate-carboxymethyl cellulose hydrogels for tunable drug delivery

Abstract

Upcycling agro-waste into active biomaterials provides a sustainable solution to advanced drug delivery systems. Most of the developed carriers exhibited limited stability under physiological conditions, which is necessary for the prolonged release of loaded bioactive molecules. To address these issues, we synthesized cellulose nanocrystal (CNC)-reinforced sodium alginate/carboxymethyl cellulose hydrogel scaffolds for tunable drug release. CNCs were extracted from spent coffee grounds as an eco-friendly source of nanocellulose. The hydrogels were ionically crosslinked with Ca²⁺ ions. The scaffolds exhibited a porous and interconnected morphology. The composite scaffolds exhibited enhanced swelling potential compared to pure polymer scaffolds (593.9 → 805.7 %), indicating superior water absorption and structural integrity. A decrease in thermal stability was observed in composite scaffolds (216 °C) compared to pure polymer scaffolds (228 °C), attributed to the presence of heat-sensitive functional groups. The scaffolds exhibited no adverse effects on 3 T3 cells, showing their cytocompatibility. Sustained drug release was observed in the composite scaffolds (44.74 %) compared with the pure polymer scaffolds (66.58 %) after 15 days at physiological pH, demonstrating their potential as drug carriers for biomedical applications. These results demonstrate the effective valorization of coffee waste into nanocellulose for reinforcing biopolymer-based hydrogels, providing a green, biocompatible platform for drug delivery applications.

Keywords: Biocompatibility; Nanocellulose; Spent coffee grounds; and Drug delivery.