Tricalcium Phosphate Coatings Research Articles

New strontium-based coatings show activity against pathogenic bacteria in spine infection.

Infections of implants and prostheses represent relevant complications associated with the implantation of biomedical devices in spine surgery. Indeed, due to the length of the surgical procedures and the need to implant invasive devices, infections have high incidence, interfere with osseointegration, and are becoming increasingly difficult to threat with common therapies due to the acquisition of antibiotic resistance genes by pathogenic bacteria. The application of metal-substituted tricalcium phosphate coatings onto the biomedical devices is a promising strategy to simultaneously prevent bacterial infections and promote osseointegration/osseoinduction. Strontium-substituted tricalcium phosphate (Sr-TCP) is known to be an encouraging formulation with osseoinductive properties, but its antimicrobial potential is still unexplored. To this end, novel Sr-TCP coatings were manufactured by Ionized Jet Deposition technology and characterized for their physiochemical and morphological properties, cytotoxicity, and bioactivity against Escherichia coli ATCC 8739 and Staphylococcus aureus ATCC 6538P human pathogenic strains. The coatings are nanostructured, as they are composed by aggregates with diameters from 90nm up to 1μm, and their morphology depends significantly on the deposition time. The Sr-TCP coatings did not exhibit any cytotoxic effects on human cell lines and provided an inhibitory effect on the planktonic growth of E. coli and S. aureus strains after 8h of incubation. Furthermore, bacterial adhesion (after 4h of exposure) and biofilm formation (after 24h of cell growth) were significantly reduced when the strains were cultured on Sr-TCP compared to tricalcium phosphate only coatings. On Sr-TCP coatings, E. coli and S. aureus cells lost their organization in a biofilm-like structure and showed morphological alterations due to the toxic effect of the metal. These results demonstrate the stability and anti-adhesion/antibiofilm properties of IJD-manufactured Sr-TCP coatings, which represent potential candidates for future applications to prevent prostheses infections and to promote osteointegration/osteoinduction.

Heat treatment of plasma sprayed tricalcium phosphate coatings deposited on substrate Ti-6Al-4V ELI

Heat treatment of plasma sprayed tricalcium phosphate coatings deposited on substrate Ti-6Al-4V ELI

Double Substituted with Manganese and Strontium Tricalcium Phosphate Coatings on Zinc-Lithium Biodegradable Alloys for Biomedical Implant Applications

To address the clinical needs for biodegradable implant materials, in this work, zinc-lithium (Zn-Li) biodegradable alloy was coated with double-doped manganese and strontium resorbable tricalcium phosphate (Mn,Sr-TCP). The Pulsed Laser Deposition method was applied for coating preparation. For coating characterization, Fourier Transform Infrared Spectroscopy, X-ray Diffraction, Scanning Electron Microscopy coupled with Energy Dispersive X-ray, and X-ray Photoelectron Spectroscopy were used. The microbiology experiments were performed, testing the inhibition of growth of Gram-positive (Staphylococcus aureus, Enterococcus faecalis) and Gram-negative (Salmonella typhimurium, Escherichia coli) bacteria strains and Candida albicans fungus. The obtained results evidenced about 10% of inhibition of all four bacteria strains by the Mn,Sr-TCP-coated Zn-Li samples, exerting the most pronounced effect on C. albicans fungus (about 50% of inhibition of growth). The prepared coatings can be useful for improving the degradation behavior and biological characteristics of Zn-Li alloys.

Hydroxyapatite Growth on Poly(Dimethylsiloxane-Block-ε-Caprolactone)/Tricalcium Phosphate Coatings Obtained by Electrophoretic Deposition

For the first time, composite coatings based on poly(dimethylsiloxane-block-ε-caprolactone) copolymer and tricalcium phosphate were obtained on stainless steel plates by using the electrophoretic deposition technique. The effect of different deposition times on the final characteristics of the resulting coatings was also studied. Block copolymers were obtained through a combination of anionic and ring-opening polymerization, with good homogeneity and chemical composition (Ð < 1.3 and wPCL = 0.39). The composites obtained at different electrophoretic deposition times revealed a linear dependence between the deposited weight and time during assays. When immersing in simulated body fluid, a higher amount of residual solids ( ∼ 20 %) were observed by thermogravimetric analysis after 7 days of immersion. Scanning electron microscopy micrographs revealed a porous microstructure over the metallic substrate and the absence of micro-cracks, and X-ray diffraction patterns exhibited diffraction peaks associated with a hydroxyapatite layer. Finally, energy-dispersive X-ray analysis revealed values of the Ca/P ratio between 1.40 and 1.50 in samples, which are closer to the stoichiometric hydroxyapatite values reported in hard tissues. The results obtained in this article confirm the usefulness of poly(dimethylsiloxane-block-ε-caprolactone) copolymer and cheaper tricalcium phosphate as precursors of compact and homogenous coatings obtained by electrophoretic deposition, which yields useful substrates for hydroxyapatite growth.

Plasma-Sprayed Manganese-Containing Tricalcium Phosphate Coatings on Titanium

Plasma-Sprayed Manganese-Containing Tricalcium Phosphate Coatings on Titanium

In Vitro Properties of Manganese-Substituted Tricalcium Phosphate Coatings for Titanium Biomedical Implants Deposited by Arc Plasma.

Bioactive manganese (Mn)-doped ceramic coatings for intraosseous titanium (Ti) implants are developed. Arc plasma deposition procedure is used for coatings preparation. X-ray Diffraction, Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy, and Electron Paramagnetic Resonance (EPR) methods are applied for coatings characterization. The coatings are homogeneous, composed of the main phase α-tricalcium phosphate (α-TCP) (about 67%) and the minor phase hydroxyapatite (about 33%), and the Mn content is 2.3 wt%. EPR spectroscopy demonstrates that the Mn ions are incorporated in the TCP structure and are present in the coating in Mn2+ and Mn3+ oxidation states, being aggregated in clusters. The wetting contact angle of the deposited coatings is suitable for cells’ adhesion and proliferation. In vitro soaking in physiological solution for 90 days leads to a drastic change in phase composition; the transformation into calcium carbonate and octacalcium phosphate takes place, and no more Mn is present. The absence of antibacterial activity against Escherichia coli, Enterococcus faecalis, and Pseudomonas aeruginosa bacteria strains is observed. A study of the metabolic activity of mouse fibroblasts of the NCTC L929 cell line on the coatings using the MTT (dye compound 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) test demonstrates that there is no toxic effect on the cell culture. Moreover, the coating material supports the adhesion and proliferation of the cells. A good adhesion, spreading, and proliferative activity of the human tooth postnatal dental pulp stem cells (DPSC) is demonstrated. The developed coatings are promising for implant application in orthopedics and dentistry.

Iron Ion‐Doped Tricalcium Phosphate Coatings Improve the Properties of Biodegradable Magnesium Alloys for Biomedical Implant Application

AbstractIron‐substituted tricalcium phosphate (Fe‐TCP) (about 1 wt%) coatings are deposited on biodegradable Mg‐Ca alloys to improve their corrosion resistance. Pulsed laser deposition technique is used for coating preparation. The 2 µm thick coatings are uniformly deposited. (Ca+Fe)/P ratio for the Fe‐TCP coatings is close to the stoichiometric value. Coated and uncoated Mg‐Ca alloys are subjected to electrochemical tests to investigate the influence of the coatings on their corrosion resistance in simulated body fluid (SBF). Tafel curves corresponding to coated and uncoated Mg‐Ca alloy samples in SBF show that the most electropositive corrosion potential is reached for the Fe‐TCP‐coated Mg‐Ca deposited at 300 °C. From the obtained and calculated values of the electrochemical parameters it follows that this sample possesses the best characteristics: it has the smallest porosity and the highest protective efficiency in SBF. Equine adipose tissue‐derived mesenchymal stem cells are used for 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide test and osteogenic differentiation study. Microbiology tests are performed with Escherichia coli (E. coli) (Gram−) and Staphylococcus aureus (Gram+) bacteria strains. The Fe‐TCP‐coated Mg‐Ca deposited at 300 °C is characterized by the best cytocompatibility and good ability to inhibit the growth of E. coli and is recommended for biomedical implant applications.

“Titanium–Silver-Substituted Calcium Phosphates” Plasma Coatings: Properties, Comparison, and Prospects of Application

The structure of the silver-substituted hydroxyapatite and tricalcium phosphate powders is confirmed by the methods of X-ray phase diffraction analysis and IR spectroscopy. Silver-substituted hydroxyapatite coatings consist of large particles of round shape and the presence of nanoparticles is also detected. The silver-substituted tricalcium phosphate coatings are formed by fine particles and nanoparticles are detected on the entire surface of the coating. Both types of coatings exhibit hydrophilic properties. The adhesion of silver-substituted tricalcium phosphate coatings is almost twice higher than the adhesion of silver-substituted hydroxyapatite powder coating. The obtained coatings are of interest as antimicrobial coatings for intraosseous dental and orthopaedic endoprostheses.

Deposition of hydroxyapatite and tricalcium phosphate coatings by suspension plasma spraying: Effects of torch speed

This research focuses on the deposition of hydroxyapatite (HA) and tricalcium phosphate (TCP) coatings produced by suspension plasma spraying (SPS) using in-house liquid feedstock suspensions. The work studied the effects of torch speed on the thickness, microstructure, and crystalline composition of the coatings. SPS allowed the deposition of HA and TCP coatings with thickness between 28 and 90 μm. The coatings presented lamellar microstructure with complex porosity between the splats. Micropores ranging from 0.2 to 6 μm and close mesopores, from 8 to 45 μm, had a spherical morphology and were homogenously distributed within the coatings. Water evaporation during SPS allowed the retention of pure and crystalline HA coatings. In contrast, the presence of water molecules led to the formation of HA as a secondary phase in the TCP coatings, which formed α-TCP as the major component due to the high temperature reached by the powder during deposition.

Electrochemical corrosion behavior of silver doped tricalcium phosphate coatings on magnesium for biomedical application

Abstract This paper investigates the growth, characterization and electrochemical corrosion properties of tricalcium phosphate (TCP) doped with 0 wt%, 1 wt%, 5 wt% and 10 wt% of silver coatings deposited on magnesium substrate using pulsed laser deposition (PLD). The phase and morphological properties of the coatings were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM) respectively. The SEM images showed that increasing the percentage of Ag dopant reduces the size of droplets formed during the deposition process. The corrosion protection behavior of the coated samples was evaluated using potentiodynamic polarization (PD) and electrochemical impedance spectroscopy (EIS). The corrosion test was performed in Hanks' Balanced Salt Solution and 0.9 wt% saline solution using three electrode electrochemical cell. The results showed that TCP coated magnesium exhibits a much superior stability and lower corrosion rate compared to bare Mg. It was observed that increasing the mass of the Ag dopant increases the corrosion protection, but 10% Ag doping in TCP reduces the corrosion protection behavior. In conclusion, we have developed TCP and TCP doped with 1%, 5% and 10% Ag coating with tunable corrosion protection efficiency.

Biomimetic Coating of Modified Titanium Surfaces with Hydroxyapatite Using Simulated Body Fluid

This study investigated the viability of coating commercially pure titanium (CPTi) surfaces, modified via sandblasting and acid etching, with hydroxyapatite (HA)/tricalcium phosphate coatings using a simulated body fluid (SBF) solution. The samples were immersed in SBF from 3 to 7 days. The morphology and the chemistry of the HA/tricalcium phosphate coating were then analysed. Prior to immersion in SBF, the samples were sandblasted and acid etched to mimic the morphology and roughness of commercially available dental implants. The SBF aided in the formation of crystalline HA/tricalcium phosphate coatings on all the samples. The coatings were uniform and had roughness values higher than the underlying substrate. The highest roughness values for the coatings on the surfaces were obtained at 7 days of immersion in SBF with averageSavalues of 2.9 ± 0.2 µm. The presence of HA/tricalcium phosphate on the surfaces was confirmed by the Scanning Electron Microscope (SEM), Energy Dispersive Spectrometer (EDS), the X-Ray Diffraction (XRD), and the Fourier Transform Infrared Spectrometer (FTIR) analysis. This study shows that it is possible to obtain an adequate and uniform hydroxyapatite coating on pure titanium substrates in a shorter period of time with characteristics that favour the ultimate goal of implants therapy, that is, osseointegration.

An in vivo evaluation of the biocompatibility of anodic plasma chemical (APC) treatment of titanium with calcium phosphate

Implant loosening is an unresolved complication associated with prosthetics. Previous studies report improved osseointegration with hydroxyapatite (HA) or tri-calcium phosphate coatings. Unfortunately, the brittleness and low strength of these coatings in adhesion to the implant or internal cohesion is problematic, restricting their use. Anodic plasma-chemical (APC) treatment, an advanced anodisation method, allows for porous oxide layer formation with incorporation of calcium and phosphate directly into the oxide. This produces superior adhesive strength than a conventional coating of calcium phosphate offering potential for long-term osseointegration. Although the cytocompatibility of several APC treatments have been previously shown, this study was the first to investigate the biocompatibility and osteoconductivity of APC surfaces in vivo when compared with standard HA coated and noncoated commercially pure titanium implant cortical screws. Sample screws were implanted in female Swiss alpine sheep for 12 weeks. Bone remodelling in situ, differences in bone apposition resulting in cortical thickening as well as peak removal torque measurements were assessed. We found no significant differences between the tested coatings and no delamination was observed with any of the APC-treated surfaces. The results suggest that APC-treated samples have similar biological performance to HA-coated screws. In our opinion, APC treatment, which also has superior binding strength to the base metal compared with standard HA coatings as well as similar biocompatibility as shown here, holds great potential for biomedical applications. Now that the in vivo biocompatibility has been proven, the work is being extended to more challenging in vivo models.

Dissolution control and cellular responses of calcium phosphate coatings on zirconia porous scaffold.

Different types of calcium phosphates [hydroxyapatite (HA), fluorapatite (FA), tricalcium phosphate (TCP), and their composites (HA + FA, HA + TCP)] were coated on a zirconia (ZrO(2)) porous scaffold using a powder slurry method. The ZrO(2) porous scaffold was intended for a load-bearing implant, and the apatite layers were coated to improve osteoconductivity. The insertion of an FA intermediate layer between the coating layer and ZrO(2) scaffold effectively suppressed the reaction between the calcium phosphate and ZrO(2) and maintained the coating layer at the initial powder composition. The obtained coating layer, of a thickness of approximately 30 microm, was relatively microporous and firmly adherent to the ZrO(2) scaffold. Dissolution tests in physiological solution showed typical differences depending on the coating layers, with the dissolution rate increasing in the order TCP > HA + TCP > HA > HA + FA > FA. This result suggests the functional coating of the calcium phosphates in view of tailoring the solubility. Osteoblast-like cells, MG63 and HOS, responded similarly in terms of cell growth, morphology, and proliferation rate regardless of the coating types, indicating favorable and comparable cell viability. However, the alkaline phosphatase (ALP) activity of the cells on the pure HA and HA composite coatings (HA + FA and HA + TCP) expressed at higher levels compared to those on pure FA and pure TCP coatings for both MG63 and HOS cells, suggesting a selective cell activity depending on the coating types. All the calcium phosphate-coated-ZrO(2) scaffolds showed higher ALP levels compared to pure ZrO(2) scaffold.

Fibroblast and osteoblast adhesion and morphology on calcium phosphate surfaces.

Implant loosening in bone fixation is an unresolved complication associated with internal fixation. It is generally accepted that this problem can be overcome by modifying the implant/bone interface for improved osseointegration. This is achieved, in part, by hydroxyapatite (HA) or tricalcium phosphate coatings. Unfortunately, the benefits of these coatings are constrained by not only the generally low strength of their adhesion to the implant surface but also the limited cohesion within their layers. Anodic Plasma-chemical treatment (APC) has been developed to incorporate electrolytes and produce coatings with various microtopographies and strong adhesion to implants. In this in vitro study fibroblast and osteoblast morphologies and adhesion to various substrates were evaluated using qualitative and quantitative methods. The substrates were Thermanox plastic and commercially pure titanium. The latter were surface-treated using several different methods: conventional anodisation, plasma spraying of HA and anodic plasma-chemical (APC) treatment in an electrolyte solution containing either calcium and phosphate (APC-CaP) or phosphoric acid (APC-P). Both osteoblasts and fibroblasts showed extensive cell spreading, total cell area and greatest amount of adhesion, with defined adhesion patterns on the Thermanox plastic, anodised titanium, and the two APC-CaP substrates. With fibroblasts, almost no cell spreading and very low adhesion, was observed in cells cultured on the APC-P and HA surfaces. The extent of cell spreading correlated with the area of focal adhesions as assessed by the amount of vinculin labelling. The Thermanox plastic, anodised titanium, and the two APC-CaP substrates were the most cytocompatible substrates with regard to this in vitro evaluation.