Porous Calcium Phosphate Coatings Research Articles

Adhesion and Cohesion of Three-Dimensional Porous Calcium Phosphate Coatings on Titanium Deposited by Ultrasound-Assisted Micro-Arc Oxidation Method

Adhesion and Cohesion of Three-Dimensional Porous Calcium Phosphate Coatings on Titanium Deposited by Ultrasound-Assisted Micro-Arc Oxidation Method

Antibacterial Calcium Phosphate Coatings with Zinc Oxide Nanoparticles

Porous calcium phosphate coatings (C-P) with ZnO nanoparticles were obtained via the micro-arc oxidation method on a titanium substrate. ZnO nanoparticles were added to the C-P coatings to change the zeta potential and improve the coatings’ bioactivity and antibacterial properties. The samples with coatings were studied via scanning electron microscopy (SEM), X-ray diffraction, energy dispersive microanalysis, potentiodynamic polarization, and zeta potential measurement. The coatings modified with ZnO nanoparticles showed improved physical, electrochemical, and electrical properties, compared to the initial unmodified coatings. Modification with ZnO nanoparticles contributed to an increase in zeta potential from −60 mV to −53 mV. Functionalization of the coatings with ZnO nanoparticles allowed us to increase the anticorrosion characteristics by about 30%. The biological studies showed that the coatings had no cytotoxic effect on L929 fibroblast cells. The antibacterial activity of the coating rose by 99% after the addition of ZnO nanoparticles against the bacterium Staphylococcus aureus.

Effect of aluminium oxyhydroxide nanoparticles on the structure and properties of the calcium phosphate coatings

Modification of calcium phosphate (C-P) based biocoatings with aluminum oxyhydroxide AlO(OH) nanoparticles and its effect on their morphology, structure, phase composition, wettability, electrical and biological properties are studied. C-P coatings were formed on the titanium substrate by the microarc oxidation (MAO) method in the acidic electrolyte. Porous calcium-phosphate coatings were functionalized by aluminum oxyhydroxide nanoparticles by hydrolysis reaction in aqueous suspension of AlN nanopowder. The increase ultrasonic dispersion duration of AlN suspension up to 60 min provides more uniform distribution of AlO(OH) on the coating surface. The introduction of positively charged AlO(OH) nanoparticles has been unveiled to increase zeta potential value of the coating surface. The antimicrobial activity of the C-P coating rises by 27% after the introduction of AlO(OH) nanoparticles and the proliferation of L929 cells on the coatings functionalized by the nanoparticles grows by 25%. The results obtained demonstrate the aluminum oxyhydroxide nanoparticles introduction significantly improve the functional properties of the C-P coatings.

Metal Ions Supported Porous Coatings by Using AC Plasma Electrolytic Oxidation Processing.

Coatings enriched with zinc and copper as well as calcium or magnesium, fabricated on titanium substrate by Plasma Electrolytic Oxidation (PEO) under AC conditions (two cathodic voltages, i.e., −35 or −135 V, and anodic voltage of +400 V), were investigated. In all experiments, the electrolytes were based on concentrated orthophosphoric acid (85 wt%) and zinc, copper, calcium and/or magnesium nitrates. It was found that the introduced calcium and magnesium were in the ranges 5.0–5.4 at% and 5.6–6.5 at%, respectively, while the zinc and copper amounts were in the range of 0.3–0.6 at%. Additionally, it was noted that the metals of the block S (Ca and Mg) could be incorporated into the structure about 13 times more than metals of the transition group (Zn and Cu). The incorporated metals (from the electrolyte) into the top-layer of PEO phosphate coatings were on their first (Cu+) or second (Cu2+, Ca2+ and Mg2+) oxidation states. The crystalline phases (TiO and Ti3O) were detected only in coatings fabricated at cathodic voltage of −135 V. It has also been pointed that fabricated porous calcium–phosphate coatings enriched with biocompatible magnesium as well as with antibacterial zinc and copper are dedicated mainly to medical applications. However, their use for other applications (e.g., catalysis and photocatalysis) after additional functionalizations is not excluded.

Effect of the Porosity, Roughness, Wettability, and Charge of Micro-Arc Coatings on the Efficiency of Doxorubicin Delivery and Suppression of Cancer Cells

Porous calcium phosphate coatings were formed by the micro-arc oxidation method on the surface of titanium for the loading and controlled release of the anticancer drug doxorubicin. The coatings’ morphology and microstructure were examined by scanning electron microscopy. The phase composition was determined with the help of X-ray diffraction analysis. Studies of the hydrophilic properties of the coatings and their zeta potential were carried out. Data on the kinetics of doxorubicin adsorption-desorption were obtained. In addition, the effect of calcium phosphate coatings impregnated with doxorubicin on the viability of the Neuro-2a cell line was revealed. The coating formed at low voltages of 200–250 V contained a greater number of branched communicating pores, and therefore they were able to adsorb a greater amount of doxorubicin. The surface charge also contributes to the process of the adsorption-desorption of doxorubicin, but this effect is not fully understood and further studies are required to identify it.

Improving the Degradation Resistance and Surface Biomineralization Ability of Calcium Phosphate Coatings on a Biodegradable Magnesium Alloy via a Sol-Gel Spin Coating Method

Bioactive calcium phosphate (CaP) coatings have been applied on biodegradable magnesium (Mg) and its alloys to provide a suitable degradation rate for orthopedic applications. However, the porous CaP coatings formed in the aqueous solution owns poor degradation resistance and thus short in vivo valid life. This paper reports a sol-gel spin coating method to prepare hydroxyapatite (HA, Ca10(PO4)6(OH)2) and fluorine doping HA sealing coatings on a porous CaP coating. The effects of fluorine content on the degradation and biomineralization behaviors of the composite coatings were studied. It reveals that the homogeneous and stable sol-gel coating, especially the fluorapatite coating could significantly improve the degradation resistance and surface biomineralization ability of the porous CaP coating on the Mg alloy.

Enhanced Bioactivity of Calcium Phosphate Coatings Obtained by a Direct Electrodeposition from Hanks’ Solution on Ti Surface / Zwiekszona Bioaktywnosc Powłok Fosforanowo-Wapniowych Otrzymanych Metoda Bezposredniego Elektroosadzania Na Powierzchni Ti Z Roztworu Hanka

The main requirements for titanium biomaterials are: (a) biocompatibility, (b) resistance to biological corrosion and (c) antisepticity. These requirements may be met by a new generation of titanium biomaterials with a specific surface layer of strictly defined microstructure, chemical and phase composition. Recently, various surface modifications have been applied to form a bioactive layer on Ti surface, which is known to accelerate osseointegration. The purpose of this study was to investigate bioactivity of porous calcium phosphate coatings prepared by a direct electrodeposition on Ti surface from a modified Hanks’ solution. The thick 200 nm coatings, were prepared via cathodic polarization at constant voltage -1.5 V vs. OCP in a Hanks’ solution. In order to evaluate the potential use of the coatings for biomedical applications, the adsorption of bovine serum albumin (BSA), the most abundant protein in blood, and living cells attachment (osteoblasts, U2OS) were studied. The observed differences in living cells attachment suggest a more promising initial cellular response of Ca-P coatings with a pre-adsorbed albumin. The topography and a cross-section view of the Ca-P coatings were characterized using SEM and STEM techniques. The surface analytical techniques (AES, XPS, and FTIR) were used to characterize their chemical composition before and after protein BSA adsorption.

Concurrent elution of calcium phosphate and macromolecules from alginate/chitosan hydrogel coatings

The concurrent release of calcium phosphate and biomacromolecules may improve wound healing responses at the interface with ceramic materials of orthopaedic and dental implants. Hydrogel coatings consisting of a mixture of alginate and chitosan were doped and applied onto solid carriers with the aim of investigating their use as local delivery vehicles. Coatings containing both the model macromolecule FITC-dextran 70 kDa (FD 70) and dispersed calcium phosphate carbonate (CPC) nanoparticles were coated onto a solid, nonporous model substrate to study the concurrent release of FD 70 and calcium and phosphate ions from within the hydrogel. Hydrogel coatings containing only FD 70 were cast onto porous calcium phosphate coatings, similar to hydroxyapatite, to study the release of FD 70 from, and calcium and phosphate ions through, the hydrogel coating. Transmission electron microscopy showed good dispersion of the CPC nanoparticles, and scanning electron microscopy and atomic force microscopy showed that increased CPC loading resulted in an increase in surface roughness but to extents well below those affecting cell responses. The release of FD 70 from CPC-loaded coatings was similar to release from the hydrogel alone, although higher CPC loadings resulted in small changes. The release of FD 70 was better described by double or triple phase zero order release kinetics; this complex time dependence indicates that in addition to outdiffusion, other, time-dependent factors apply, such as swelling of the gel, as expected from the known effects of calcium ions on alginate. Calcium and phosphate ions were also released, with similar release kinetics, through the hydrogel layer from the underlying CaP layer. In either case, release decreased to negligible levels after 3 days, suggesting that the systems of this study are suitable for short-term concurrent release of water-soluble biomacromolecules and calcium and phosphate ions.

Fabrication of Porous Titania and Porous Calcium Phosphate Coatings on Titanium Surface

A network-like porous layer on titanium was prepared by acid-etching with a mixture of CaCl2 and HCl. The pores ranged from 1 to 10!m. The small pores distributed in big pores. In the simulated biological environment, porous octacalcium phosphate (OCP) coatings spontaneously formed on the porous- surfaced titanium. Pre-calcification after acid-etching accelerated OCP precipitation. The OCP coatings had big pores of about 25!m and small pores of 1~3!m, the latter distributed in the former at different depth.

Thermal spraying of biomaterials

Osteoconductive hydroxyapatite coatings for metallic endoprostheses for hip and knee joint replacement provide a state-of-the-art template for enhanced in-growth of bone cells. However, the high temperature of the plasma jet leads to large scale dehydroxylation and decomposition of the starting powder. A model is being developed to explain the formation of chemically and mechanically inhomogeneous porous calcium phosphate coatings deposited by atmospheric plasma spraying onto titanium alloy substrates. In addition the biofunctionality is being discussed of titania bond coats and their influence on the in vivo performance of hydroxyapatite-titania duplex coating systems.