Colloidal stability of nanocellulose hydrogels in physiological and cell culture environments

Nanocellulose is a promising alternative to animal-derived matrices for tissue engineering, yet its colloidal stability and rheological performance are heavily influenced by the ions and proteins in physiological environments. Here, we systematically investigated the colloidal stability and interfacial behavior of native (nCNF) and anionic (aCNF) cellulose nanofibrils in physiologically relevant media using rheology, zeta potential, static multiple light scattering (SMLS), and multi-parameter surface plasmon resonance (MP-SPR). Increasing ionic strength compressed the electrical double layer, promoting fibril aggregation and the formation of kinetically arrested, volume-spanning networks. At 0.5 wt% CNF, physiological media increased the storage modulus from 10 Pa in water to 170 Pa in DMEM for nCNF and from 40 Pa to 235 Pa for aCNF. Despite macroscopic stability at high ionic strength, SMLS revealed colloidal instability associated with fibril aggregation, while addition of fetal bovine serum reduced phase separation through protein adsorption onto fibril surfaces. MP-SPR measurements showed substantial protein adsorption, with human serum albumin adsorption reaching 717 ng.cm^-2 on nCNF and 611 ng.cm^-2 on aCNF at 54 mg.mL^-1. This study is strictly physicochemical and does not include biological or cellular responses. These detailed insights on nanocellulose network formation and stability contribute its future optimization for biomedical applications.