LAUSR

Cubic boron nitride (c‐BN) has an ultrahardness and a large bandgap energy like diamond. In the last 30 years, most of the attention has been directed towards the mechanical and electronic applications of c‐BN, while its biological potential has been overlooked. The authors report in vitro biocompatibility of high‐quality c‐BN films prepared by plasma‐enhanced chemical vapor deposition using the chemistry of fluorine. c‐BN films become superhydrophilic when chemical‐treated in hydrogen and nitrogen plasmas with or without the impact of low‐energy ions due to a marked increase in polar part of the surface free energy by removal of the fluorine atoms terminating c‐BN surfaces. Satisfactory proliferation and differentiation of osteoblastic cells comparable with a control sample and a superhydrophilic nanocrystalline diamond film, and the formation of mineral deposits by biomineralization are confirmed on the superhydrophilic c‐BN films with negative values of zeta potential. The results demonstrate a high potential of c‐BN as a noncytotoxic ultrahard coating material for biological and biomedical applications.