Electrodeposited Calcium Phosphate Research Articles

Improved corrosion resistance and biocompatibility of magnesium implants by cathode-deposited polypyrrole/dicalcium phosphate dihydrate composite coating

As a new-generation of concerned biomedical metal implants, magnesium (Mg) alloy has the degradability, biocompatibility and mechanical properties close to human bones that inert metals do not have. However, the side effects caused by rapid degradation become the biggest obstacle restricting its practical application. Here, we report that the preparation of polypyrrole/calcium phosphate (PPy/CaP) composite coating on Mg alloy by the application of the cathode deposition twice in a row, which delayed the corrosion of Mg alloy and reduced its corrosion current density, the biocompatibility was also greatly improved. This method is simple to operate, and could get a tightly bonded PPy coating on active metals without passivation treatments. It also avoids the substrate exposure due to the high solubility of the single electrodeposited calcium phosphate coating, and finds the future direction for application of electrodeposited modified Mg alloy.

Preparation and anticorrosion properties of electrodeposited calcium phosphate (CaP) coatings on Mg–Zn–Ca metallic glass

In order to improve the corrosion resistance and bioactivity of Mg–Zn–Ca metallic glass, a series of calcium phosphate (CaP) coatings were synthesized on Mg66Zn30Ca4 metallic glass via the electrodeposition method in this paper. As compared with the Mg-based metallic glass, the electrodeposited CaP coatings show considerable improvement in corrosion resistance and bioactivity. Based on the experimental results, the formation and anti-corrosion mechanisms of CaP coatings were proposed, suggesting that electrodeposited CaP coating can promote the precipitation of calcium phosphate and thereby induce the mineralization process. By constructing the predominance area diagram, the relationship between the composition of the CaP solution and the precipitation process of calcium phosphate (CaHPO4·2H2O, Ca5(PO4)3OH) at 25 °C was accurately described. These results provide insights into the electrodeposition process of CaP type coatings.

Electrodeposition of Calcium Phosphate Coatings on Metallic Substrates for Bone Implant Applications: A Review

This review summaries more than three decades of scientific knowledge on electrodeposition of calcium phosphate coatings. This low-temperature process aims to make the surface of metallic bone implants bioactive within a physiological environment. The first part of the review describes the reaction mechanisms that lead to the synthesis of a bioactive coating. Electrodeposition occurs in three consecutive steps that involve electrochemical reactions, pH modification, and precipitation of the calcium phosphate coating. However, the process also produces undesired dihydrogen bubbles during the deposition because of the reduction of water, the solvent of the electrolyte solution. To prevent the production of large amounts of dihydrogen bubbles, the current density value is limited during deposition. To circumvent this issue, the use of pulsed current has been proposed in recent years to replace the traditional direct current. Thanks to breaking times, dihydrogen bubbles can regularly escape from the surface of the implant, and the deposition of the calcium phosphate coating is less disturbed by the accumulation of bubbles. In addition, the pulsed current has a positive impact on the chemical composition, morphology, roughness, and mechanical properties of the electrodeposited calcium phosphate coating. Finally, the review describes one of the most interesting properties of electrodeposition, i.e., the possibility of adding ionic substituents to the calcium phosphate crystal lattice to improve the biological performance of the bone implant. Several cations and anions are reviewed from the scientific literature with a description of their biological impact on the physiological environment.

Effect of Growing Conditions and Post Treatments on Calcium Phosphate Films Obtained by Electrode Position

The effect of growing conditions and post treatments in electrodeposited calcium phosphate films on 316 L stainless steel is presented. The concentration and pH of electrolyte solution and the potential values for the electrodeposition process were determined based on a study of cyclic voltammetry curves. The electrolyte concentration was fixed at 0.025 M ((NH4) H2PO4) and 0.042 M (Ca(NO3)2.4H2O), choosing a pH = 5 as the better condition for the films deposition. In addition, the electrolyte temperature was varied between room temperature and 60°C to determine the influence of this parameter on the deposited films. Films were characterized using Fourier Transform Infrared Spectroscopy, X-ray diffraction and Scanning electron microscopy equipped with energy dispersive spectroscopy. The as deposited films at -1.2 V and -1.7 V exhibit the dicalcium phosphate dihydrate phase (Brushite) while thermal post treatment favor the formation of octacalcium phosphate in amorphous phase, and basic treatment tend to produce the Hydroxyapatite phase. The suggested mechanism for the HAp phase formation, after the basic treatment, consists in providing the necessary OH- groups to complete the synthesis process.

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.

Atomically resolved calcium phosphate coating on a gold substrate.

Some articles have revealed that the electrodeposition of calcium phosphate (CaP) coatings entails a precursor phase, similarly to biomineralization in vivo. The chemical composition of the initial layer and its thickness are, however, still arguable, to the best of our knowledge. Moreover, while CaP and electrodeposition of metal coatings have been studied utilizing atom-probe tomography (APT), the electrodeposition of CaP ceramics has not been heretofore studied. Herein, we present an investigation of the CaP deposition on a gold substrate. Using APT and transmission electron microscopy (TEM) it is found that a mixture of phases, which could serve as transient precursor phases to hydroxyapatite (HAp), can be detected. The thickness of these phases is tens of nanometers, and they consist of amorphous CaP (ACP), dibasic calcium phosphate dihydrate (DCPD), and octacalcium phosphate (OCP). This demonstrates the value of using atomic-resolved characterization techniques for identifying the precursor phases. It also indicates that the kinetics of their transformation into the more stable HAp is not too fast to enable their observation. The coating gradually displays higher Ca/P atomic ratios, a porous nature, and concomitantly a change in its density.

Structural and morphological study of electrodeposited calcium phosphate materials submitted to thermal treatment

The effect of thermal treatments on electrodeposited calcium phosphate materials (CaP) is investigated. For this purpose, several temperatures up to 1000°C are applied to powders obtained by scratching the synthesized coatings from their metallic substrate. The goal is to assess the structural and the morphological modifications of the powders that are known to strongly influence the in vivo bioactivity of the CaP materials.The morphology of the CaP materials is made of needles at room temperature that agglomerate to form rounded particles when the treatment temperature exceeds 800°C. Simultaneously, the crystallinity increases with the treatment temperature until reaching a fully crystalline biphasic structure at 1000°C. This biphasic structure consists in 80% Hydroxyapatite (HAP) and 20% β-tricalcium phosphate (β-TCP).

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.

Enhancement of adhesion bonding between titanium metal and electrodeposited calcium phosphate

A novel hydroxyapatite/rutile coating was prepared on a titanium substrate. Initially, an amorphous calcium phosphate coating layer was electrochemically deposited on a Ti substrate. The surface morphology, chemical composition and phase identification of the coatings were investigated by the X-ray diffraction and scanning electron microscopy associated with an energy dispersive spectrometer. Annealing at 700°C for 3 hrs. transforms the amorphous calcium phosphate layer into well-crystallized hydroxyapatite (HAP) and the Ti metal surface into rutile. The developed HAP/rutile composite surface layer became denser and better adhering with the substrate than the initially formed amorphous calcium phosphate. The adhesion bond strength and the hardness of the coating were extremely raised by thermal annealing.

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.

Electro-deposited calcium phosphate compounds on graphene sheets: Blossoming flowers

A facile electro-deposition method for the preparation of calcium phosphate – graphene composite (CPG) is proposed and investigated in this paper. Flowerlike calcium phosphate (CaP) compounds grow on graphene sheets during the aqueous electro-deposition. The electro-deposited composite is then investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). To better unveil the structure of CPG, graphene sheets are loaded on the carbon film on copper grid for electrodeposition and following SEM, energy dispersive spectrum (EDS) and, particularly, transmission electron microscopy (TEM) test. The results show that the growth process of CPG resembles blossoming flowers, every petal of which is composed of several thin sheets, and the growth exhibits time dependent morphology development which indicates the high controllability of this preparation method. Furthermore, this method can be utilized in wider applications to prepare CPG coatings on many other materials, such as Mg alloys, a potential candidate for biodegradable materials.

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).