Electrodeposited Calcium Phosphate Coatings Research Articles

Mechanical and biological properties of electrodeposited calcium phosphate coatings

Calcium phosphate (CaP) coatings were electrochemically deposited on titanium substrates. By increasing the electrodeposition time (from 1 to 30 min), the coating thickness increases but also the surface morphology of the CaP coatings is greatly affected going from smooth to plate-like, featuring elongated plates, ribbon-like and finally sharp needle structures. Micro-stretch tests reveal that, regardless of the coating morphology and thickness, the electrodeposited CaP coatings have strong adhesion with the titanium substrates and their failure mode is cohesive failure. The effects of different morphologies on cellular behavior such as adhesion, viability, proliferation, and osteogenic gene expression were studied. The surface morphology of CaP coatings has a remarkable effect on cell attachment, proliferation, and viability. A smooth surface results in better adhesion of the cells, whereas the presence of sharp needles and ribbons on rough surfaces restricts cell adhesion and consequently cell proliferation and viability. The improved cell adhesion and viability on the smoother surface can be attributed to the higher contact area between the cell and the coating, while the needle-like morphology inflicts damage to the cells by physically disrupting the cell wall. There is no significant difference in the level of osteoblast gene expression when osteosarcoma cells are cultured on coatings with different morphologies. Our study provides crucial insights into the optimum electrodeposition procedures for CaP coating formation leading to both good cell-material interaction and sufficient mechanical properties. This can be achieved with relatively thin coatings produced by short electrodeposition times.

Design of tailored biodegradable implants: The effect of voltage on electrodeposited calcium phosphate coatings on pure magnesium

AbstractMagnesium, as a biodegradable metal, offers great potential for use as a temporary implant material, which dissolves in the course of bone tissue healing. It can sufficiently support the bone and promote the bone healing process. However, the corrosion resistance of magnesium implants must be enhanced before its application in clinical practice. A promising approach of enhancing the corrosion resistance is deposition of bioactive coating, which can reduce the corrosion rate of the implants and promote bone healing. Therefore, a well‐designed substrate‐coating system allowing a good control of the degradation behavior is highly desirable for tailored implants for specific groups of patients with particular needs. In this contribution, the influence of coating formation conditions on the characteristics of potentiostatically electrodeposited CaP coatings on magnesium substrate was evaluated. Results showed that potential variation led to formation of coatings with the same chemical composition, but very different morphologies. Parameters that mostly influence the coating performance, such as the thickness, uniformity, deposits size, and orientation, varied from produced coating to coating. These characteristics of CaP coatings on magnesium were controlled by coating formation potential, and it was demonstrated that the electrodeposition could be a promising coating technique for production of tailored magnesium‐CaP implants.

Effect of duty cycle on preparation and corrosion behavior of electrodeposited calcium phosphate coatings on AZ91

In present work, calcium phosphate coatings on AZ91 substrate were prepared by pulse electrodeposition at different duty cycle (0.05, 0.10, 0.15, 0.20) in the mixed solution of 0.1M Ca(NO3)2 and 0.06M NH4H2PO4 at 60°C. Phase composition and corrosion behavior of the as-deposited coatings were studied. Results showed that the calcium phosphate coatings had a grass-like structure. As the duty cycle increased, phase composition of the coatings changed from hydroxyapatite (HA) to mixture of HA and dicalcium phosphate dihydrate (DCPD). The adhesion of strength between the coatings and the substrate were higher than 10MPa. Potentiodynamic polarization test and electrochemical impedance spectroscopy test in simulated body fluid (SBF) indicated that the samples deposited with calcium phosphate coatings exhibited better corrosion resistance as compared with the bare AZ91 alloy.

Investigation of duty cycle effect on corrosion properties of electrodeposited calcium phosphate coatings

The bioceramic calcium phosphate (CaP) is frequently used for improving bone fixation in titanium medical implants and thus increasing lifetime of the implant. It is known that the application of CaP coatings on metallic implant devices offers the possibility of combining the strength of the metals and the bioactivity of the ceramic materials. Many different techniques are available for producing CaP coatings. Electrochemical deposition method is widely used because of its ease of operation parameters, low temperature requirement, reproducibility and suitability for coating complex structures. This technique allows obtaining CaP coatings which promote bone in growth during the first healing period leading to permanent fixation. Electrochemical pulse technique is an alternative to calcium phosphate deposition techniques usually employed to cover orthopedic or dental titanium implant surfaces. Additionally, pulse electrodeposition technique can produce more uniform and denser CaP coatings on metallic implants. In this study, CaP based coatings were produced by electrochemical pulse technique on Ti6Al4V substrates. The resulting CaP deposits were investigated by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Corrosion properties of the CaP coatings were also investigated. The results showed that various duty cycle ranges have remarkably effect on morphology, crystallinity and corrosion properties of the produced CaP coatings.

CNTs as ion carriers in formation of calcium phosphate coatings

Surface functionalisation of carbon nanotubes (CNTs) provides possibility of employing them in the biomedical industry as drug/growth factor carriers improving healing of a patient after injury. Carbon nanotubes are also very perspective nanomaterials as reinforcement in composites because of their mechanical properties. In the present work, single wall CNTs (SWCNTs), single wall/double wall (SW/DWCNTs) and multiwall CNTs (MWCNTs) functionalised with –COOH, –OH and –NH2 groups were tested as ion carriers in electrodeposition and as reinforcements in the composite calcium phosphate coatings. In our research, new composite coatings with Ca/P ratios ranging from 1·0 to 1·50 were obtained during electrodeposition in electrolytic solutions containing –COOH functionalised SWCNTs and MWCNTs. Amorphous calcium phosphates were fabricated in electrolytic solutions containing –NH2 functionalised MWCNTs, while no coating was fabricated in electrolytes containing –OH functionalised SW/DWCNTs. The structure and kind of functionalised groups of CNTs had an influence on the type, morphology and thickness of electrodeposited calcium phosphate coatings.

The porosity and roughness of electrodeposited calcium phosphate coatings in simulated body fluid

Calcium phosphate coatings were electrochemically deposited on titanium from the aqueous solution of Ca(NO3)2 and NH4H2PO4 with the current density of 10 mA cm-2 for deposition time of 15 min. The obtained brushite coatings, (CaHPO4?2H2O), were converted to hydroxyapatite (HA) by soaking in simulated body fluid (SBF) for 2, 7 and 14 days. The brushite and hydroxyapatite coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). It was shown that the increase in soaking time increases the porosity, roughness and crystallite domain size of HA coatings and decreases the unit cell parameters and unit cell volume, while does not affect the HA mean pore area. The calcium and phosphorus ions concentrations in SBF were determined by atomic absorption spectroscopy (AAS) and UV-Vis spectroscopy, respectively and the mechanism of HA growth based on dissolution-precipitation was proposed.

Human osteoblast-like cells response to pulsed electrodeposited calcium phosphate coatings

Calcium-deficient hydroxyapatite (Ca-def HAP) coatings are synthesized by pulsed electrodeposition on titanium alloy (Ti6Al4V) substrates. Physico-chemical characterizations of the coating are carried out using Scanning Electron Microscopy (SEM) associated with Energy Dispersive X-ray Spectroscopy (EDXS) for X-ray microanalysis, and Scanning-Transmission Electron Microscopy (STEM) and X-Ray Diffraction (XRD) for structural characterization. Moreover, the biocompatibility properties of the synthesized biomaterial are studied by observing the human osteoblast-like cells’ (MG-63) response, which is investigated using a proliferation study carried out with an MTS test, and a cellular morphology study performed by SEM. The analysis of gene expression is carried out using a Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR). The results indicate that the pulsed electrodeposited Ca-def HAP coating doesn't produce any cytotoxic effect and enhances the gene expression of alkaline phosphatase (ALP) and osteocalcin (OC) which are the two main markers of osteoblast differentiation and bone neoformation.

Morphological modifications of electrodeposited calcium phosphate coatings under amino acids effect

Calcium phosphate coatings are synthesized on titanium alloy (Ti6Al4V) substrates by pulsed electrodeposition. This work aims to observe the morphological modifications of the coating when an amino acid is added to the electrolytic solution used in the process. The effects of two amino acids (glutamic acid and aspartic acid) are studied at a low and a high concentration. The coating morphology is observed at a nanometer scale by field emission gun-scanning electron microscopy (FEG-SEM). The structural characterization of the coating is performed by Fourier transformed infrared spectroscopy (FT-IR), Raman spectroscopy and X-ray diffraction (XRD). Moreover, corrosion measurements of the prosthetic surfaces are carried out by potentiodynamic polarization experiments in a physiological solution named Dulbecco's modified eagle medium (DMEM). The results show that the addition of an amino acid to the electrolytic solution leads to the decrease of the size of the crystallites which compose the prosthetic calcium phosphate coating that becomes denser and less porous than the coatings obtained without amino acid. Consequently, the corrosion behavior of the prosthetic material immersed in DMEM is improved.

In vitro degradation of electrodeposited calcium phosphate coatings by osteoclast-like cells

The aim of this study is to investigate the in vitro degradation of electrolytically deposited calcium phosphate coatings in the presence of osteoclast-like cells. Titanium alloy plates electrolytically coated with calcium phosphate with or without chitosan were incubated with RAW264.7 cells for 14 days. The TRAP activity was measured and the cell attachment and proliferation capacity were analyzed. The calcium ion concentrations in the culture medium before and after incubation were calculated. Both coatings were observed with scanning electron microscopy and characterized through an x-ray diffractometer and Fourier transform infrared spectrum. The RAW264.7 cells differentiated into TRAP-positive osteoclast-like cells on both coatings after 7 days. Although presenting different cell attachment pattern, the RAW264.7 cells demonstrated the similar TRAP activity and proliferation capacity. It was found that the calcium ion concentrations in the medium decreased at the beginning, but increased after 11 and 14 days. The chitosan containing coatings had higher Ca2+ concentration in the medium compared to that without chitosan. Besides, the incubation of coatings with cells induced higher calcium ion concentrations than those without cells at day 11 and day 14. Despite the structural changes of dissolution pits and osteoclastic resorption lacunae present on both coatings, the x-ray diffractometer and Fourier transform infrared spectrum showed few alternations in their chemical compositions. Both electrodeposited calcium phosphate coatings can be resorbed by osteoclast-like RAW264.7 cells and dissolved in the culture medium in vitro. The degradation brings little change to the chemical compositions of both coatings.

In vitro corrosion behavior of electrodeposited calcium phosphate coatings on Ti6Al4V substrates

Calcium phosphate coatings on titanium alloy substrates are synthesized by pulsed electrodeposition and characterized by scanning electron microscopy associated to energy dispersive X-ray spectroscopy and by X-ray diffraction. The corrosion behavior of CaP/Ti6Al4V systems and uncoated Ti6Al4V are investigated using electrochemical methods in three physiological solutions and simulated with an equivalent circuit. The results reveal that the calcium phosphate coatings act as a protective layer especially when electrodeposition is carried out in the presence of hydrogen peroxide into the electrolyte which is used to control the chemical composition of the coatings and which implies a control of the corrosion behavior of the prosthetic material.

Early bone apposition and 1‐year performance of the electrodeposited calcium phosphate coatings: an experimental study in rabbit femora

The aim of this study was to investigate the early bone apposition and 1-year performance of the electrodeposited calcium phosphate coatings with or without chitosan. Seventy-two cylindrical implants with a length of 8 mm and a diameter of 3.3 mm were divided into three groups: electrodeposited calcium phosphate coated without chitosan, with chitosan, and an uncoated control. The implants adopted the special gap design and were inserted into the rabbit femora. After 2, 4, 26, and 52 weeks, the implants were retrieved and analyzed for bone formation, bone-to-implant contact, and coating degradation. It was found that the coatings without chitosan had the highest bone contact at early time (P<0.05). The coatings with chitosan had the least bone formation within gaps after 2, 4, and 26 weeks of implantation (P<0.05). However, no difference was found among the three groups after 52 weeks. Both coatings showed degradation as early as 2 weeks post-implantation. And after 52 weeks, most of the coatings had been degraded. There were no inflammatory reactions and hardly any osteoclasts around the implants and the coatings. The confocal laser scanning microscopy observation further demonstrated the different bone deposition characteristics. With scanning electron microscopy, no coatings could be found on both the implant surface and the bone interface. Bone apposition to both electrodeposited calcium phosphate coatings was different at early time but almost the same after 52 weeks. And both coatings showed early as well as a continued degradation in the rabbit femora. To cite this article: Wang J, Sun C, Wang Y, Wang Y. Early bone apposition and 1-year performance of the electrodeposited calcium phosphate coatings: an experimental study in rabbit femora. Clin.

Effects of pulsed current and H 2O 2 amount on the composition of electrodeposited calcium phosphate coatings

Calcium phosphate coatings on Ti6Al4V substrates were elaborated by pulsed electrodeposition with hydrogen peroxide (H 2O 2) into electrolyte. The surface morphology and the chemical composition of the coatings were characterized by scanning electron microscopy (SEM) associated to Energy Dispersive X-ray Spectroscopy (EDXS) for X-ray microanalysis. The obtained results were systematically confirmed at the nanometre scale analysis using scanning transmission electron microscopy (STEM). Moreover, X-ray diffraction (XRD) was performed in order to identify the coatings phases. The results showed that pulsed electrodeposition without H 2O 2 into electrolyte followed by heat treatment favoured coatings made of two phases which are stoichiometric hydroxyapatite (HAP) and β-tricalcium phosphate (β-TCP). On the other hand the addition of an optimized H 2O 2 amount into electrolyte led to adherent and uniform coatings mainly made of stoichiometric hydroxyapatite (HAP).

Antibacterial Titanium/Calcium Phosphate Implant Surfaces

The antibacterial effects of titanium oxide/calcium phosphate and calcium phos-phate/copper phosphate composite coatings have been investigated. Implant-like rough blasted tita-nium substrates are covered by a native titanium oxide layer. Together with the electrodeposited calcium phosphate layer a clear antibacterial effect has been observed. Electrodeposited calcium phosphate coatings were also dipped in aqueous copper sulphate solutions to convert partly calcium phosphate to copper phosphate. The antibacterial properties of such coatings can be controlled and adjusted to the clinical setting and to specific indications. Patient-tailored antibacterial treatments seem to be possible and may be of special interest for high-risk operations.

Proliferation and Differentiation of MC3T3-E1 Cells on Calcium Phosphate/Chitosan Coatings

The incorporation of chitosan into electro-deposited calcium phosphate (CaP) coatings increases bone marrow stromal cell attachment. We hypothesized that such electrodeposited CaP/chitosan coatings can also enhance the proliferative ability and differentiation potential of osteoblasts. To verify this hypothesis, we cultured osteoblast-like MC3T3-E1 cells on these CaP coatings. It was found that MC3T3-E1 cells cultured on the electrodeposited CaP/chitosan coatings had cell proliferation rates higher than those on the electrodeposited CaP coatings. At the same time, both alkaline phosphatase activity and collagen expression were increased, and both bone sialoprotein and osteocalcin genes were up-regulated when MC3T3-E1 cells were cultured on the electrodeposited CaP/chitosan coatings. Additionally, within the range of selected chitosan concentrations in solution, no significant difference was found between the CaP/chitosan coatings. Our results suggest that the electrodeposited CaP/chitosan coatings are favorable to the proliferation and differentiation of MC3T3-E1 cells, which may endow them with great potential for future applications.

In vitro precipitation of electrodeposited calcium-deficient hydroxyapatite coatings on Ti6Al4V substrate

In this study, electrodeposited calcium phosphate coatings were characterized by X-ray diffraction, using a scanning electron microscope equipped with an EDAX detector, before and after immersion in DMEM (Dulbecco's Modified Eagle Medium). After 1, 7, 14, and 21 days of immersion, the calcium and phosphate contents in solution were measured by inductively coupled plasma atomic emission spectrometry (ICP-AES). The results indicated that precipitation of the coating occurred. Before immersion in DMEM, the electrodeposited coating was a mixed crystalline and amorphous calcium-deficient hydroxyapatite with a Ca/P atomic ratio of about 1.5, but during the immersion period these phases rapidly disappeared and were followed by the precipitation of a crystalline apatite with a Ca/P atomic ratio near 1.65. On the basis of these results, we conclude that an electrodeposited calcium phosphate coating on roughened titanium alloy substrate may act as a precursor for newly precipitated calcium phosphate in in vitro experiments independent of cellular activities.

Behavior of human osteoblast‐like cells in contact with electrodeposited calcium phosphate coatings

Calcium-deficient hydroxyapatite (Ca-def-HAP) thin films were elaborated on Ti6Al4V substrates by electrodeposition. The coatings exhibit two different morphologies and crystallinities. Human osteoblast-like cells (MG-63) were cultured on the surfaces of these materials; the cell content and viability were evaluated up to 28 days. The scanning electron microscopy and biological investigations showed cells with a normal morphology, good proliferation, and viability from 7 to 21 days. But after 28 days, the number of live cells decreases in both cases; however, this decrease is less important in the case of calcium phosphate (CaP) coating surface when compared with the control (cell culture plastic). The cells cultured on Ca-def-HAP coating exhibit more cellular extensions and extracellular matrix. RT-PCR for type I collagen, alkaline phosphatase, and osteocalcin studies were also carried out, and was found that the CaP enhances gene expression of ALP and OC and thus the differentiation of osteoblast-like cells. Moreover, this study shows that the difference in the morphology of CaP coatings has no effect on the biocompatibility.

Characterization of electrodeposited calcium phosphate coatings by complementary scanning electron microscopy and scanning-transmission electron microscopy associated to X-ray microanalysis

Calcium phosphate (CaP) coatings on Ti6Al4V substrate were elaborated by electrodeposition at different current densities (2, 5 and 10 mA/cm 2). The surface morphology and the chemical composition of the coatings were characterized by scanning electron microscopy associated to X-ray microanalysis (SEM-EDXS). However, these CaP coatings are irregular specimens (rough surface, porosity, variable thickness), so the SEM-EDXS analysis becomes limited. Therefore, we carried out an experimental procedure to minimize these effects which is based on global analysis by SEM-EDXS confirmed by a nanometer scale analysis using scanning transmission electron microscopy associated to X-ray microanalysis. Moreover, phase analysis was performed by X-ray diffraction in order to corroborate the chemical characterization and to identify the different calcium phosphate phases as a function of current density. The results showed that at 2 mA/cm 2 current density, the coating is composed of an octacalcium phosphate: Ca 8H 2(PO 4) 6 and its amorphous phase called OCPam. At 5 mA/cm 2, the coating is a mix of calcium deficient hydroxyapatite (Ca-def HAP): Ca 10 − x (HPO 4) x(PO 4) 6 − x (OH) 2 − x with 0 < × ≤ 2 and its amorphous phase called Ca-def HAPam. And, at 10 mA/cm 2, the coating is mainly composed of an amorphous phase of Ca-def HAPam. Furthermore, cathodic reaction mechanisms of electrolytic CaP coatings on Ti6Al4V are proposed to explain the different kinds of calcium phosphate obtained.

Transformation of Electrodeposited Calcium Phosphate Coatings in Simulated Body Fluid and in Culture Medium

The coatings formed on the H2O2-treated titanium substrate by electrodeposition were used in order to evaluate the difference of transformations in the simulated body fluid (SBF) and the culture medium with MG63 cells. A porous hydroxyapatite (HA) coating with relatively low crystallinity and large crystallites was formed on the H2O2-treated titanium substrate by electrodeposition. HA coating transformed for 5 days in the SBF consisted of densely-packed rod-shaped crystallites with various differentiated grains. Octacalcium phosphate (OCP) and HA coating transformed for 5 days in the culture medium consisted of both flake-shaped and rod-shaped crystallites with indistinct grains. MG-63 cells were well attached and proliferated during the transformation into this flaked-shaped OCP. This difference between transformations of the HA coatings in the acellular SBF and in the culture medium with MG63 cells is due to different ion composition in each solution and proteins in culture medium.

Micrometer level structural and chemical evaluation of electrodeposited calcium phosphate coatings on TA6V substrate by STEM-EDXS.

Hydroxyapatite (HA) coatings on titanium alloy substrates Ti6Al4V have been prepared in our laboratory by electrodeposition and hydrothermal synthesis. In this paper, the morphology, crystal size, porosity and Ca/P atomic ratio are investigated using scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), Raman microspectroscopy and X-ray energy dispersive spectroscopy (EDXS). The results obtained show that after being hydrothermally treated and calcined at high temperature, the electrodeposited brushite coating is converted into a stoichiometric hydroxyapatite having a crystal size which changes considerably from the surface to the substrate alloy. In addition, variation of the surface coating porosity as a function of the electrolyte temperature has also been carried out.

Multilayer systems for corrosion protection of stainless steel implants

The influence of vapour deposited TiNbN and/or of electrodeposited calcium phosphate coatings on the anodic dissolution of polished and roughened X5CrNil8.10 stainless steel specimens in 0,9% NaCl solution was investigated. Both coatings are responsible for an increase in the pitting corrosion resistance. The results were compared with those of similarly prepared and coated TiAlV specimens.