From Colloids to Hydrogels: Concentration-Dependent Cytocompatibility of Carboxylated Cellulose Nanocrystals Prepared via Deep Eutectic Solvents

Pa) capable of supporting three-dimensional (3D) cell encapsulation. Importantly, cytocompatibility is strongly dependent on material state. In the colloidal regime (<0.4 wt %), CNC-COOH exhibits negligible cytotoxicity toward 3T3-L1 fibroblasts and weak to mild cytotoxic effects toward HT-29 epithelial cells. In contrast, hydrogel networks (2 wt %) promote high cell viability (>85-100%) and enable 3D cellular organization. Protein adsorption appears to be limited at the surface of the CNC-COOH hydrogel, as indicated by BSA studies, suggesting that ionic strength-mediated interactions play an important role in network formation under cell culture conditions. These findings establish direct correlations among sustainable surface modification, concentration-dependent assembly, and biological response, providing design principles for CNC-based nanomaterials in biointerfaces, 3D cell culture, and nanomedicine.