title: Nano-scale surface morphology, wettability and osteoblast adhesion on nitrogen plasma-implanted NiTi shape memory alloy.
abstract: Plasma immersion ion implantation (PIII) is an effective method to increase the corrosion resistance and inhibit nickel release from orthopedic NiTi shape memory alloy. Nitrogen was plasma-implanted into NiTi using different pulsing frequencies to investigate the effects on the nano-scale surface morphology, structure, wettability, as well as biocompatibility. X-ray photoelectron spectroscopy (XPS) results show that the implantation depth of nitrogen increases with higher pulsing frequencies. Atomic force microscopy (AFM) discloses that the nano-scale surface roughness increases and surface features are changed from islands to spiky cones with higher pulsing frequencies. This variation in the nano surface structures leads to different surface free energy (SFE) monitored by contact angle measurements. The adhesion, spreading, and proliferation of osteoblasts on the implanted NiTi surface are assessed by cell culture tests. Our results indicate that the nano-scale surface morphology that is altered by the implantation frequencies impacts the surface free energy and wettability of the NiTi surfaces, and in turn affects the osteoblast adhesion behavior.
authors.affiliation: Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong.
authors.forename: X M
authors.initials: XM
authors.lastname: Liu
authors.forename: S L
authors.initials: SL
authors.lastname: Wu
authors.forename: Paul K
authors.initials: PK
authors.lastname: Chu
authors.forename: C Y
authors.initials: CY
authors.lastname: Chung
authors.forename: C L
authors.initials: CL
authors.lastname: Chu
authors.forename: Y L
authors.initials: YL
authors.lastname: Chan
authors.forename: K O
authors.initials: KO
authors.lastname: Lam
authors.forename: K W K
authors.initials: KW
authors.lastname: Yeung
authors.forename: W W
authors.initials: WW
authors.lastname: Lu
authors.forename: K M C
authors.initials: KM
authors.lastname: Cheung
authors.forename: K D K
authors.initials: KD
authors.lastname: Luk