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.

*Yang JHC, Teii K, Chang C, Matsumoto S, Rafailovich M. Adv. Funct. Mater. 2021; 31:2005066