Surface mechanical properties, corrosion resistance, and cytocompatibility of nitrogen plasma-implanted nickel–titanium alloys: A comparative study with commonly used medical grade materials

  1. K.W.K. Yeung1,
  2. R.W.Y. Poon2,
  3. P.K. Chu1,*,
  4. C.Y. Chung2,
  5. X.Y. Liu2,
  6. W.W. Lu1,
  7. D. Chan3,
  8. S.C.W. Chan1,
  9. K.D.K. Luk1,
  10. K.M.C. Cheung1,*

Article first published online: 12 FEB 2007

DOI: 10.1002/jbm.a.31154

Issue

Journal of Biomedical Materials Research Part A

Journal of Biomedical Materials Research Part A

Volume 82A, Issue 2, pages 403–414, August 2007

Additional Information

How to Cite

Yeung, K.W.K., Poon, R.W.Y., Chu, P.K., Chung, C.Y., Liu, X.Y., Lu, W.W., Chan, D., Chan, S.C.W., Luk, K.D.K. and Cheung, K.M.C. (2007), Surface mechanical properties, corrosion resistance, and cytocompatibility of nitrogen plasma-implanted nickel–titanium alloys: A comparative study with commonly used medical grade materials. J. Biomed. Mater. Res., 82A: 403–414. doi: 10.1002/jbm.a.31154

Author Information

  1. 1

    Division of Spine Surgery, Department of Orthopaedics and Traumatology, Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong

  2. 2

    Department of Physics and Materials Science, City University of Hong Kong, Kowloon, Hong Kong

  3. 3

    Department of Biochemistry, Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong

*Division of Spine Surgery, Department of Orthopaedics and Traumatology, Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong

Publication History

  1. Issue published online: 14 JUN 2007
  2. Article first published online: 12 FEB 2007
  3. Manuscript Accepted: 17 OCT 2006
  4. Manuscript Revised: 8 SEP 2006
  5. Manuscript Received: 10 JAN 2006

Funded by

  • Hong Kong Research Grants Council (RGC). Grant Numbers: HKU 7283/00M, CityU 1/04C
  • City University of Hong Kong. Grant Number: 9667002
  • Scoliosis Research Society. Grant Number: 9667002
  • Hong Kong Innovation Technology. Grant Number: GHP 019/05

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Keywords:

  • cell viability;
  • osteoblast;
  • surface treatment;
  • stainless steel;
  • titanium;
  • nickel–titanium alloy

Abstract

Stainless steel and titanium alloys are the most common metallic orthopedic materials. Recently, nickel–titanium (NiTi) shape memory alloys have attracted much attention due to their shape memory effect and super-elasticity. However, this alloy consists of equal amounts of nickel and titanium, and nickel is a well known sensitizer to cause allergy or other deleterious effects in living tissues. Nickel ion leaching is correspondingly worse if the surface corrosion resistance deteriorates. We have therefore modified the NiTi surface by nitrogen plasma immersion ion implantation (PIII). The surface chemistry and corrosion resistance of the implanted samples were studied and compared with those of the untreated NiTi alloys, stainless steel, and Ti-6Al-4V alloy serving as controls. Immersion tests were carried out to investigate the extent of nickel leaching under simulated human body conditions and cytocompatibility tests were conducted using enhanced green fluorescent protein mice osteoblasts. The X-ray photoelectron spectroscopy results reveal that a thin titanium nitride (TiN) layer with higher hardness is formed on the surface after nitrogen PIII. The corrosion resistance of the implanted sample is also superior to that of the untreated NiTi and stainless steel and comparable to that of titanium alloy. The release of nickel ions is significantly reduced compared with the untreated NiTi. The sample with surface TiN exhibits the highest amount of cell proliferation whereas stainless steel fares the worst. Compared with coatings, the plasma-implanted structure does not delaminate as easily and nitrogen PIII is a viable way to improve the properties of NiTi orthopedic implants. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007

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