Electrophoretic deposition of nanostructured hydroxyapatite coating on AZ91 magnesium alloy implants with different surface treatments
Graphical abstract
Introduction
Metallic biomaterials compose major quota of orthopedic implants, nowadays. Prolonged therapy and possible release of undesirable ions of conventional implants such as stainless steels and cobalt–chromium alloys in body environment has demanded new bio-degradable/bio-absorbable materials [1]. In this developing field of healthcare materials, magnesium alloys are posed as potential bio-degradable/bio-absorbable metallic implants. Although, an injured tissue can consume Mg alloys implants during the healing period, the implants suffer from high corrosion rate (i.e. high mass loss and abundant rate of hydrogen evolution) in body environment [2]. Therefore, further treatments should be fulfilled to increase the corrosion resistance of Mg alloys, and consequently improve the hurt bone response to Mg alloys during post implantation [3]. Producing protective bioceramics coatings on Mg alloys would enhance their biocompatibility and decelerate their degradation rate in physiological environments.
Hydroxyapatite (HAp-Ca10(PO4)6OH2) is the main inorganic component of bones, which its application as a coating provides advantages intimately attributed to its nanoscale structure [4], [5]. Moreover, former investigations revealed that the nano-sized HAp can promote mechanical properties, bone cell adhesion and proliferation within the injured area in comparison with the micro-sized HAp [3]. Thus, it seems that applying the nanostructured HAp (n-HAp) on Mg alloys give rise to a good bioactivity and superior corrosion resistance. Many methods are utilized to coat bioceramics on metallic substrates. Among these, electrophoretic deposition (EPD) seems to be more suitable to produce a homogeneous and dense ceramic, polymer and composite coatings for biomedical applications [6]. In EPD technique, direct current (DC) is applied to suspended powder particles in a liquid medium to charge the particles and deposit them onto a conductive substrate of opposite charge [7]. Farrokhi-Rad and Ghorbani applied EPD technique to coat TiO2 nanoparticles on the 304 stainless steel and studied the electrophoretic mobility of titania nanoparticles in different suspension mediums [8]. Mehdipour et al. deposited a kind of bioactive glass-contained Mg on 316L stainless steel via EPD to improve the bioactivity of the substrate [9]. Besides, the biocompatibility of Mg-based alloy surfaces could be improved via controlling their degradation rate utilizing fluoride conversion coating and surface modification through micro arc oxidation (MAO) procedure [10], [11]. Fluoride conversion coatings are MgF2 layers produced by treating Mg substrate in hydrofluoric acid (HF) [12]. Moreover, MAO technique is able to create a thick and stable porous ceramic coating on Mg alloys [3]. The aim of this study was introduction of fluoride conversion coating and MAO-produced layer as intermediate layers for n-HAp coating; also their effect on bio-corrosion behavior of these coating systems was investigated.
Section snippets
Substrate surface preparation
AZ91 magnesium alloy with chemical composition (wt.%) of 8.63% Al, 0.59% Zn, 0.17% Mn, <0.05% Fe, <0.05% Cu and balance Mg was used as substrate. The as-cast AZ91 alloy was heat-treated according to ASTM B661. AZ91 alloy samples were cut into dimensions of 20 mm × 10 mm × 2 mm. The surface roughness of both sides of the specimens was adjusted at Ra = 0.20 ± 0.03 μm, using successive finer silicon carbide abrasive paper up to grit # 600. Then, the specimens were ultrasonically cleaned (WUC-D10H, Wisd
Zeta potential/conductivity measurements
The movement of ceramic particles in a suspension fluid is defined as the electrophoretic mobility (μ) of the charged particles in a suspension [7]. This parameter is supported by the pH, ionic strength and the viscosity of a suspension [17]. The electrophoretic mobility (μ) is defined as Eq. (2) [17].where ζ, ɛ, η are the zeta potential, dielectric constant, and viscosity of the medium, respectively [17]. As the methanol is chosen as a suspension medium for n-HAp deposition, ɛ and η
Conclusion
The present literature introduced the MgF2 and MAO coatings as the inter-layers between AZ91 alloy substrate and n-HAp bioceramic top-coat. Presence of several ions within the coat layer provides promising agents necessary for enhancing the bone-forming ability of implant materials. Higher corrosion resistance of the MAO/n-HAp coated sample led to the tailored degradation kinetics of AZ91 alloy substrate as biodegradable implants. Moreover, its rough surface also plays an effective role in the
Acknowledgement
The authors are grateful for support of this research by Biomaterials Research Group of Isfahan University of Technology.
References (52)
- et al.
Preparation and in vitro degradation of the composite coating with high adhesion strength on biodegradable Mg–Zn–Ca alloy
Mater. Charact.
(2011) - et al.
Biocompatibility and biodegradability of Mg–Sr alloys: the formation of Sr-substituted hydroxyapatite
Acta Biomater.
(2013) - et al.
Fabrication and characterization of rod-like nano-hydroxyapatite on MAO coating supported on Mg–Zn–Ca alloy
Appl. Surf. Sci.
(2011) - et al.
Biocomposites of nanohydroxyapatite with collagen and poly(vinyl alcohol)
Colloids Surf., B
(2006) - et al.
Characterization of electrophoretic chitosan coatings on stainless steel
Mater. Lett.
(2012) - et al.
A review on fundamentals and applications of electrophoretic deposition (EPD)
Prog. Mater. Sci.
(2007) - et al.
Electrophoretic deposition of bioactive glass coating on 316L stainless steel and electrochemical behavior study
Appl. Surf. Sci.
(2012) - et al.
Characterization and corrosion studies of fluoride conversion coating on degradable Mg implants
Surf. Coat. Technol.
(2007) - et al.
A review of the biological response to ionic dissolution products from bioactive glasses and glass-ceramics
Biomaterials
(2011) - et al.
Evaluation and characterization of nanostructure hydroxyapatite powder prepared by simple sol–gel method
Mater. Lett.
(2007)
A simple route to hydroxyapatite nanofibers
Mater. Lett.
Bioactive glass nanoparticles with negative zeta potential
Ceram. Int.
Thick hydroxyapatite coatings by electrophoretic deposition
Mater. Lett.
Design of bioactive bone substitutes based on biomineralization process
Mater. Sci. Eng., C
How useful is SBF in predicting in vivo bone bioactivity?
Biomaterials
Can bioactivity be tested in vitro with SBF solution?
Biomaterials
Preparation and characterization of sol–gel bioactive glass coating for improvement of biocompatibility of human body implant
Mater. Sci. Eng. A
Corrosion behaviour of niobium in phosphate buffered saline solutions with different concentrations of bovine serum albumin
Corros. Sci.
In vitro corrosion behavior of bioceramic, metallic, and bioceramic-metallic coated stainless steel dental implants
Dental Mater.
Electrophoretic deposition of hydroxyapatite coatings on titanium from dimethylformamide suspensions
Surf. Coat. Technol.
Electrophoretic deposition of porous hydroxyapatite scaffold
Biomaterials
Growth characteristics and corrosion resistance of micro-arc oxidation coating on pure magnesium for biomedical applications
Corros. Sci.
Preparation and bioactivity evaluation of bone-like hydroxyapatite nanopowder
J. Mater. Process. Technol.
FTIR, XRD, SEM and solid state NMR investigations of carbonate-containing hydroxyapatite nano-particles synthesized by hydroxide-gel technique
J. Phys. Chem. Solids
Chemical surface alteration of biodegradable magnesium exposed to corrosion media
Acta Biomater.
Synthesis and characterization of bioactive forsterite nanopowder
Ceram. Int.
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