title: In vitro and in vivo biocompatibility and corrosion behaviour of a bioabsorbable magnesium alloy coated with octacalcium phosphate and hydroxyapatite.
abstract: Octacalcium phosphate (OCP) and hydroxyapatite (HAp) coatings were formed on Mg-3 mass% Al-1 mass% Zn (AZ31) magnesium alloy by a single-step chemical solution deposition method. Chemically polished AZ31 (Cpol-AZ31) and HAp- and OCP-coated AZ31 (HAp- and OCP-AZ31) were immersed in a medium for 52 weeks or implanted in transgenic mice for 16 weeks to examine the long-term corrosion behaviour and in situ inflammation behaviour. In the medium, Mg-ion release was restricted for the initial several days and the corrosion rate thereafter was suppressed by approximately one-half with the HAp and OCP coatings. HAp-AZ31 showed a ∼20% lower corrosion rate than OCP-AZ31. Tissues of the transgenic mouse emit fluorescence in proportion to the degree of inflammation in situ. The luminescence intensity level was too low to be a problem regardless of the coatings. A thinner fibrous tissue layer was formed around OCP- and HAp-AZ31 than around Cpol-AZ31, indicating that the HAp and OCP coatings suppressed corrosion and foreign-body reaction in vivo. Visible pits were formed in filiform and round shapes in vitro and in vivo, respectively. Corrosion was observed underneath the coatings, and almost uniform corrosion took place in vitro, while local corrosion was predominant in vivo. These differences in corrosion morphology are attributed to the adhesion of tissues and the lower diffusivity on the surface in vivo than that in vitro. Dissolution behaviour of OCP crystals in vivo was different from that in vitro. It was demonstrated that the HAp and OCP coatings developed have great potential for a biocompatible and corrosion protection coating.
authors.affiliation: Biomaterials Unit, International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, Tsukuba 305-0044, Japan. Electronic address: hiromoto.sachiko@nims.go.jp.
authors.forename: Sachiko
authors.initials: S
authors.lastname: Hiromoto
authors.affiliation: Biomaterials Unit, International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, Tsukuba 305-0044, Japan.
authors.forename: Motoki
authors.initials: M
authors.lastname: Inoue
authors.affiliation: Biomaterials Unit, International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, Tsukuba 305-0044, Japan.
authors.forename: Tetsushi
authors.initials: T
authors.lastname: Taguchi
authors.affiliation: Instrumental Analysis Center, Kitami Institute of Technology, Kitami 090-8507, Japan.
authors.forename: Misao
authors.initials: M
authors.lastname: Yamane
authors.affiliation: Instrumental Analysis Center, Kitami Institute of Technology, Kitami 090-8507, Japan.
authors.forename: Naofumi
authors.initials: N
authors.lastname: Ohtsu
mesh_terms: D020341:Absorbable Implants; D000497:Alloys / Q000009:adverse effects / Q000737:chemistry*; D000818:Animals; D001826:Body Fluids / Q000737:chemistry*; D002130:Calcium Phosphates / Q000009:adverse effects / Q000737:chemistry*; D020099:Coated Materials, Biocompatible / Q000009:adverse effects / Q000138:chemical synthesis*; D003343:Corrosion; D017886:Durapatite / Q000009:adverse effects / Q000737:chemistry*; D008422:Materials Testing; D051379:Mice; D008822:Mice, Transgenic; D013499:Surface Properties; D000267:Tissue Adhesions / Q000209:etiology / Q000473:pathology
chemical_list: D000497:Alloys; D002130:Calcium Phosphates; D020099:Coated Materials, Biocompatible; C586533:Mg-Al-Zn-Mn-Si-Cu alloy; C022045:octacalcium phosphate; D017886:Durapatite
keywords: Biocompatibility; Calcium phosphate coatings; Corrosion; In vivo; Magnesium