The influence of surface energy on competitive protein adsorption on oxidized NiTi surfaces

Alexandra Michiardi, Conrado Aparicio, Buddy D. Ratner, Josep A. Planell, Javier Gil

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164 Scopus citations


NiTi shape memory alloy surfaces, untreated, and oxidized by a new oxidation treatment (OT) in order to obtain a Ni-free surface, have been compared in terms of surface energy and protein adsorption behavior. The polar and dispersive components of the surface energy have been determined. A competitive adsorption process between fibronectin and albumin has been carried out by 125I-radiolabeling. Moreover, the adhesion strength between both proteins and NiTi surfaces has been evaluated by performing an elution test. The results show that the OT treatment enhances the hydrophilic character of NiTi surfaces by significantly increasing the polar component of their surface energy. Moreover, the OT treatment increases the amount of fibronectin and albumin adsorbed. It also increases the fibronectin affinity for NiTi surfaces. The elution test results could suggest a conformational change of fibronectin as a function of chemical composition of NiTi material and of surface treatment. Finally, a linear correlation between the amount of adsorbed albumin and the polar component of the surface energy of NiTi surfaces has been demonstrated. This work indicates that the OT treatment has an influence on the surface energy value of NiTi materials, which in turn influences the protein adsorption process.

Original languageEnglish (US)
Pages (from-to)586-594
Number of pages9
Issue number4
StatePublished - Feb 2007

Bibliographical note

Funding Information:
The authors are grateful to Alonso Siendones, who has partly collaborated in the contact angle study. They also want to thank the helpful assistance in the protein adsorption study of Jeanette Stein and Winston Ciridon (University of Washington). The University of Washington Engineered Biomaterials (UWEB) program (NSF (EEC-95, 29161) provided support for parts of this study. Finally, Alexandra Michiardi wants to thank the Catalan government for its financial support through FI00624 grant.


  • Albumin
  • Fibronectin
  • Nickel-titanium alloys
  • Protein adsorption
  • Surface energy


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