Water Lubricating and Biocompatible Films of Bacterial Cellulose Nanofibers Surface-Modified with Densely Grafted, Concentrated Polymer Brushes

Here, an articular cartilage-inspired system was developed using a densely grafted, concentrated polymer brush (CPB) for lubrication and bioinertness and a cellulose nanofiber (CNF) network for mechanical reinforcement. Hydrophilic poly[poly(ethylene glycol) methyl ether methacrylate] chains were grafted onto the CNF surface of the bacterial cellulose network using the surface-initiated atom transfer radical polymerization. The obtained composite films of the modified CNFs, swollen in water, exhibited a mechanical strength of 270 MPa in Young's modulus, fracture strength of 9.3 MPa, frictional properties in the order of 10(-3) for the coefficient of friction, and low adhesion of L929 fibroblasts and human umbilical vein endothelial cells. These properties were comparable to those of articular cartilages without the need for electrostatic interactions. The two latter properties were successfully improved by the modification with the hydrophilic CPB. Thus, the CPB was successfully applied without damaging the distinguishing characteristics of the CNF as a filler.