Flocculation of Cells by Cellulose Nanofibers Modified with Concentrated Polymer Brushes

A new type of three-dimensional cell culture using a cellulose nanofiber modified with a concentrated polymer brush (CNF-CPB) is described from the viewpoint of colloidal flocculation. By varying the CNF-CPB concentrations from 0.005 to 0.5 wt %, we demonstrate that hepatocyte cells self-assemble with the CNF-CPBs and change the floc size and shape (fully filled or hollow) in a concentration-dependent manner. A protein adsorption test indicates that affinity interaction between the proteins (cells) and CPB is critical for cellular flocculation. In addition, gene expression analysis confirms that the cellular flocs using CNF-CPBs enhance cell functions compared to CNFs with semidilute polymer brushes and pristine CNFs.