Surface potential change in bioactive titanium metal during the process of apatite formation in simulated body fluid

Hyun Min Kim, Teruyuki Himeno, Masakazu Kawashita, Ju Hyung Lee, Tadashi Kokubo, Takashi Nakamura

Research output: Contribution to journalArticlepeer-review

162 Citations (Scopus)


Bioactive titanium metal can be prepared by NaOH and heat treatments that present the metal with a graded bioactive surface layer of amorphous sodium titanate. This study used laser electrophoresis together with transmission electron microscopy (TEM) and energy-dispersive X-ray microanalysis (EDX) to relate the surface potential change of the bioactive titanium metal with its surface structural change in simulated body fluid (SBF). The surface potential of the metal was highly negative immediately after immersion in SBF. With increasing soaking time, the surface potential increased, revealing a maximum positive value, and then decreased to a constant negative value. TEM-EDX showed that immediately after immersion in SBF, the metal surface formed Ti-OH groups by exchanging Na+ ions in the surface sodium titanate with H 3O+ ions in the fluid. Thereafter, with increasing soaking time the metal surface formed an amorphous calcium titanate, then an amorphous calcium phosphate, and, finally, apatite with bone-like composition and structure. These results indicate that the process of apatite formation on bioactive titanium metal is initiated by the formation of Ti-OH groups with negative charges that interact with calcium ions with positive charges to form calcium titanate. The calcium titanate gains a positive charge and later interacts with phosphate ions with negative charges, forming amorphous calcium phosphate. The amorphous calcium phosphate eventually transforms and stabilizes into bone-like crystalline apatite with a negative charge.

Original languageEnglish
Pages (from-to)1305-1309
Number of pages5
JournalJournal of Biomedical Materials Research - Part A
Issue number4
Publication statusPublished - 2003 Dec 15
Externally publishedYes


  • Apatite
  • Bioactivity
  • Simulated body fluid (SBF)
  • Titanium metal
  • Zeta potential

ASJC Scopus subject areas

  • Ceramics and Composites
  • Biomaterials
  • Biomedical Engineering
  • Metals and Alloys


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