Search

[Display omitted] • Rapid coating of orientation-controlled hydroxyapatite layer on human tooth in 30 s. • Rapid protection and repair of tooth surface in dental practice using hydroxyapatite. • Laser-assisted novel crystallization using viscous light-absorber paste. • The method is applicable to all tissues of tooth using medically approved equipment. • Finding of hydroxyapatite nanofibers as the constituent of enamel, like as bone. Functionalization of teeth surfaces has attracted much attention from the perspective of preventive dentistry. Laser irradiation (30 s) of the viscous light-absorber paste coated on the tooth substrate enabled ultrafast coating of orientation-controlled fluoride-substituted hydroxyapatite (HAP) rod layers, 150–500 nm thick, in a calcium phosphate solution. On enamel, the layers perfectly inherited orientations and structures of the crystals in the substrate, exhibiting two types of hierarchies at different scales. One was a submicron-scale hierarchy, in which an approximately 60-nm-wide rod comprised multiple thinner rods, approximately 20-nm wide, oriented along the c -axis. The 20-nm-wide rods exhibited another type of nanoscale hierarchy comprising incompletely assembled nanofibers < 5-nm wide. In dentin and cementum, c -axis-elongated HAP rods grown on the substrates displayed less arrangement in their elongation direction than those grown on enamel. Most rods on dentin were single crystals, unlike those grown on enamel. On the cementum, each polycrystalline rod (100–150 nm wide) comprised multiple single-crystal rods approximately 60-nm wide, forming a sub-micron hierarchy similar to that observed in enamel. The developed method may be useful in dental practice for protecting teeth surfaces and repairing microdefects in enamel, dentin, and cementum. [ABSTRACT FROM AUTHOR]

[Display omitted] • In this research, a PDA-coated Zn/Cu/Ag-doped hydroxyapatite coating was successfully applied to a porous tantalum surface. • Among the evaluated variants, CuHA@PDA exhibited the most exceptional photothermal performance, achieving a photothermal conversion efficiency of 66.83%. • The sterilization rate of AgHA@PDA samples reached ninety-seven percent, and after infrared laser irradiation, it reached 99.52%. • The PDA-coated Zn/Cu/Ag-doped hydroxyapatite on porous tantalum exhibited commendable photothermal and antibacterial properties. Porous tantalum finds valuable application in biomedical materials owing to its exceptional elastic modulus and biological activity. Hydroxyapatite nanopowder shares a chemical and crystal structure akin to natural bone apatite, making it a prevalent choice for bone tissue implants. However, addressing concerns like bacterial infections has led to a pressing need for functional modifications. Employing bactericidal ions like Zn/Cu/Ag, through HA doping, holds potential for spectral sterilization. Building upon this premise, a coating involving PDA enveloping ZnHA/CuHA/AgHA can be skillfully applied onto the surface of porous tantalum. This innovation effectively enhances the photothermal properties, culminating in a synergistic antibacterial outcome. The findings reveal that CuHA@PDA boasts the highest photothermal conversion efficiency at an impressive 66.83%. Meanwhile, ZnHA@PDA and AgHA@PDA samples exhibit commendable photothermal performance, further corroborated by bactericidal efficacy demonstrated in both bacterial and in vitro immersion experiments. These results underscore the wide-ranging prospective applications in the realm of HA functionalization and light-mediated sterilization. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Al 2 O 3 with porous surface structure and hydrophilic surface was fabricated. • Nano-rod-like HA coatings were obtained on Al 2 O 3 via hydrothermal synthesis. • The highest bonding strength of HA coatings on porous Al 2 O 3 is 18.3 ± 2.4 MPa. • HA crystals nucleate on the inwall of pores, epitaxially grow and cover on Al 2 O 3. • HA coated-Al 2 O 3 has excellent biological activity in vitro. Abstract Due to excellent mechanical properties and biocompatibility, A1 2 O 3 is considered as a promising biomaterial for biomedical applications. However, the inherent bio-inertness of A1 2 O 3 have limited its wider application. Although applying bioactive hydroxyapatite (HA) coatings on Al 2 O 3 is an effective method to improve surface bioactivity, the bonding strength between the HA coatings and the flat A1 2 O 3 substrate is low. In this study, Al 2 O 3 with micro-porous surface structure and hydrophilic surface was fabricated by anodic oxidation to improve the bonding strength between HA coatings and Al 2 O 3. Then, strong-bonding HA coatings were prepared on the porous Al 2 O 3 by hydrothermal synthesis. The results reveal the uniformity of pore distribution and the wettability of Al 2 O 3 surface are significantly improved with the increase of current density and oxidation time. When the porous Al 2 O 3 is prepared by anodic oxidation at 7 mA/cm2 for 4 h, the diameter of pores is 4.3–7.1 μm and the porous Al 2 O 3 has a contact angle of 42.2 ± 2.6°. Nano-rod-like HA coatings completely and uniformly cover the surface of Al 2 O 3 by hydrothermal synthesis at 180 °C for 24 h. The thickness of HA coatings is almost 30 ± 1.01 μm without delamination and/or cracking at the interface between HA coatings and Al 2 O 3. The highest bonding strength of HA coatings on porous Al 2 O 3 is 18.3 ± 2.4 MPa, which is higher than that of HA coatings formed on flat Al 2 O 3 by other methods. In addition, simulated body fluid (SBF) immersion tests indicate that HA-coated Al 2 O 3 possesses excellent biological activity in vitro. Hence, Al 2 O 3 with bioactive HA coatings could be a candidate biomaterial for biomedical applications. [ABSTRACT FROM AUTHOR]

Highlights • HVOF coatings had more stable phases, more cracks and less roughness compared to the flame sprayed coating. • The corrosion resistance of the HVOF was higher than flame sprayed coatings. • In the flame sprayed samples, corrosion products formed a protective layer that increased corrosion resistance over time. Abstract Hydroxyapatite coatings are biocompatible, osteoconductive and create a corrosion resistance surface on magnesium-based implants. Thermal decomposition of HA during thermal spraying limits its application. To overcome the challenges associated with thermal decomposition of HA during thermal spraying, high velocity oxygen fuel spraying with a good thermal stability for HA is proposed. In this work, the traditional flame spraying was compared to high velocity oxy-fuel (HVOF) for HA depositions on magnesium alloy substrates. The effect of process on microstructure, morphology, corrosion behavior and cellular response of HA layers were evaluated. X-ray diffraction analysis showed that the amount of secondary phases in the HVOF deposited sample was less than that in the flame sprayed coatings. Elemental weight percentage of calcium in corroded surfaces was 21% and 34.5% for HVOF and flame sprayed coatings, respectively. Contrary to the results of the electrochemical impedance spectroscopy measurements for HVOF coating performed during the early hours of immersion in the simulated body fluid (SBF), flame sprayed coating exhibited lower corrosion rate after 5 h immersion in SBF solution. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Triple-layered HAp/Al 2 O 3 /TiO 2 coatings were synthesized via RF magnetron sputtering method. • Biocompatibility and corrosion resistance features of HAp coatings were studied. • XRD, SEM, XPS, and EIS methods were employed for the characterizations of HAp coatings. • Biocompatibility and corrosion performances before and after immersion in simulated body fluid (SBF) solution were analysed. • Deconvolution of XPS spectra provide us with surface chemical bonding states of triple-layered HAp/Al 2 O 3 /TiO 2 coatings. Abstract Triple-layered RF magnetron sputtered HAp/Al 2 O 3 /TiO 2 coatings synthesized onto Ti-6Al-4V alloys were studied to improve the surface biocompatibility and corrosion resistance features. It was seen that the HAp layers played a substantial role in the biocompatibility, while the intermediate Al 2 O 3 /TiO 2 layers were used to enhance the corrosion behavior of the substrate. XRD results showed an enhanced crystallinity along with the (2 1 1) HAp phase after the simulated body fluid (SBF) immersion experiment. Local electronic and chemical bonding states of atomic phosphorus and calcium phosphate groups in the coatings, before and after immersion process, were confirmed via XPS studies. The electrochemical impedance spectroscopy (EIS) evaluated the corrosion, which indicated a reduction in capacitance values and a significant improvement of the corrosion resistance of such coatings; with improved bio-medical properties of Ti alloys. [ABSTRACT FROM AUTHOR]

A novel family of Hydroxyapatite/Chitosan/Collagen/h-BN biocomposite coatings were successfully produced by electrophoretic deposition (EPD). A new type of polyelectrolyte consisting of water, ethanol and isopropyl alcohol was used for EPD process. Collagen (main ligament of human bone) and h-BN (a promising solid lubricant) has been used as supporting material s for biocomposite coatings. The effect of h-BN concentration in the EPD suspension has been investigated. Crystallographic, morphological, spectroscopical, corrosion protection performance, thermal behaviour, mechanical and tribological, topographical and in-vitro biocompatibility investigations have been carried out by XRD, FE-SEM, FTIR, Tafel extrapolation and EIS, TGA/DSC, nanoindentation and nanoscratch, SPM and 12-weeks of immersion into r-SBF, respectively. Corrosion protection performance and mechanical and tribological properties of the coatings have been improved with increase in h-BN concentration in deposition suspension up to 5 g·L −1 and worsen with further increase. The results are encouraging for in-vivo applications of HA/CTS/COL/h-BN biocomposite coatings. [ABSTRACT FROM AUTHOR]

In the present study, we introduce a newly designed antibacterial hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 , HAp) coating that exploits the contact killing capabilities of ZnO. The HAp coating, incorporating ZnO precipitates on its topmost surface layer, was prepared on a Ti substrate using chemical solution deposition followed by heating at 650 °C. The amount of ZnO precipitates could be controlled by changing the ZnO concentration in the deposition solution; furthermore, the Zn release rate from the surface could be controlled by varying the ZnO amount. The ZnO/HAp coating showed excellent antibacterial efficacy against Escherichia coli and Staphylococcus epidermidis strains; however, no correlation was observed between the degree of efficacy and Zn release rate. The antibacterial efficacy of the ZnO/HAp coating likely originates from the contact killing effect of the ZnO precipitates. In summary, the coatings introduced in this work are promising candidates for the surface modification of Ti implants, with a potential ability to combine the prevention of infectious diseases with osteogenic activity. [ABSTRACT FROM AUTHOR]

A biofilm support with high biocompatibility is needed for bioreactors. A nano-hydroxyapatite (HA) coating on carbon fibers (CFs) was prepared by electrochemical deposition (ECD). The sludge immobilization assays, bacterial cells adhesion assays and Derjaguin–Landau–Verwey–Overbeek (DLVO) theory were used to evaluate the capacity of CF supports to immobilize activated sludge and bacterial cells. The sludge immobilization and bacterial cells adhesion assays illustrated that HA coating could enhance the capacity of CFs to immobilize microorganisms. SEM images showed that HA and bacterial cells formed a dense film on CFs surface. In addition, HA, acting as a glue, could combine CFs with bacterial cells or between cells, which helped CFs capture more bacterial cells. DLVO theory illustrated that CFs with HA coating had a lower total interaction energy than CFs without handling, explaining the higher capacity of CFs with HA coating to immobilize bacterial cells. This result was owning to the less negative zeta potential and higher hydrophilicity of CFs with HA coating, and the hydrophilicity made a greater contribution to the lower total interaction energy. Experiments and theory reveal that HA coating could enhance the biocompatibility of CFs, and CFs with HA coating could be used as an excellent biofilm support for bioreactors. [ABSTRACT FROM AUTHOR]

Ag-Ti nanotube array was prepared by simple anodic oxidation method and uniform hydroxyapatite were electrochemically deposited on the nanotubes, and then characterized by SEM, XRD, XPS and EIS. In order to investigate the influence of Ti 3+ on the electrochemical deposition of hydroxyapatite on the nanotubes, the Ag-Ti nanotube array self-doped with Ti 3+ was prepared by one step reduction method. The experiment results revealed that the Ti 3+ can promote the grow rate of hydroxyapatite coatings on nanotube surface. The hydroxyapatite coated Ag-Ti nanotube arrays with Ti 3+ exhibit excellent stability and higher corrosion resistance. Moreover, the compact and dense hydroxyapatite coating can also prevent the Ag atom erosion from the Ag-Ti nanotube. [ABSTRACT FROM AUTHOR]

Hydroxyapatite (HAp), as an important biomaterial for the regeneration and reconstruction of bone tissue, has attracted more and more attention of researchers and scientists due to its unique structure and compositions. However, the preparation of fluorescent HAp with controllable morphology has achieved only limited success. In this work, we reported a novel strategy to construct the water dispersible fluorescent HAp nanorods via the combination of ligand exchange and metal-free atom transfer radical polymerization (ATRP). The Br-containing fluorescent HAp nanorods with controllable size and morphology were first prepared through hydrothermal treatment. A multifunctional organic molecule (named as PTH-Br) with aggregation-induced emission feature was immobilized on the surface of hydrophobic HAp nanorods through ligand exchange reaction. The PTH-Br could be used as the initiator and catalyst for surface-initiated metal-free ATRP using poly(ethylene glycol) methacrylate as monomer to obtain hydrophilic fluorescent HAp polymer nanoparticles. This strategy successfully endowed HAp nanorods excellent fluorescence properties and favorable water dispersibility but well preserved their regular morphology. Biological assays demonstrated that the HAp-PTH-poly(PEGMA) nanoparticles exhibited good biocompatibility and efficient cell uptake performance. Taken together, we have developed a rather facile strategy based on the surface ligand exchange reaction and metal-free photoATRP to fabricate fluorescent HAp with controllable size and morphology, high water dispersibility and biological properties. These HAp-PTH-poly(PEGMA) nanoparticles should be novel and promising candidates for biomedical applications. [ABSTRACT FROM AUTHOR]

Highly selective adsorbent for dibenzothiophene (DBT) was successfully designed and prepared. Molecularly imprinted polymer (MIP) and magnetic hydroxyapatite (MHAP) were used as building blocks for the novel nanocomposite adsorbent. MIP/MHAP was synthesized by grafting polymerization and surface molecular imprinting using DBT as a template molecule. The microstructure and morphology of the designed nanoadsorbent were examined via FTIR, SEM and VSM. Specific surface area and pore size distribution were determined by Quantachrome Nova 3200S automated gas sorption apparatus. Additionally, static adsorption experiments, isotherms and selective recognition adsorption studies were carried out. Reversed-phase high performance liquid chromatography (RP-HPLC) was used to determine DBT. The experimental data exhibits excellent adsorption capacity for DBT reaches 247 mg/g within 60 min. Competitive adsorption results proved that MIP/MHAP have a greater affinity towards DBT molecules than benzothiophene analogues. Pseudo-second-order model and the Langmuir isotherm were used to describe the adsorption process. [ABSTRACT FROM AUTHOR]

In this study, biocomposites based on porous titanium oxide structures and a calcium phosphate (CaP) or hydroxyapatite (HA) coating are described and prepared. Nanotubes (NTs) with different pore dimensions were processed using anodic oxidation of Ti substrates in a NH 4 F-containing electrolyte solution at anodization voltages of 30 and 60 V with a DC power supply. The external diameters of the nanotubes prepared at 30 V and 60 V were 53 ± 10 and 98 ± 16 nm, respectively. RF-magnetron sputtering of the HA target in a single deposition run was performed to prepare a coating on the surface of TiO 2 NTs prepared at 30 and 60 V. The thickness of the CaP coating deposited on the mirror-polished Si substrate in the same deposition run with TiO 2 NTs was determined by optical ellipsometry (SE) 95 ± 5 nm. Uncoated and CaP-coated NTs were annealed at 500 °C in air. Afterwards, the presence of TiO 2 (anatase) was observed. The scanning electron microscopy (SEM), X-ray diffraction (XRD), photoelectron spectroscopy (XPS) and nanoindentation results revealed the influence that the NT dimensions had on the CaP coating deposition process. The tubular surfaces of the NTs were completely coated with the HA coating when prepared at 30 V, and no homogeneous CaP coating was observed when prepared at 60 V. The XRD patterns show peaks assigned to crystalline HA only for the coated TiO 2 NTs prepared at 30 V. High-resolution XPS spectra show binding energies (BE) of Ca 2p, P 2p and O 1s core-levels corresponding to HA and amorphous calcium phosphate on TiO 2 NTs prepared at 30 V and 60 V, respectively. Fabrication of TiO 2 NTs results in a significant decrease to the elastic modulus and nanohardness compared to the Ti substrate. The porous structure of the NTs causes an increase in the elastic strain to failure of the coating ( H/E ) and the parameter used to describe the resistance of the material to plastic deformation ( H 3 /E 2 ) at the nanoscale level compared to the Ti substrate. Furthermore, only the HA coating on the NTs exhibits a significantly increased H/E ratio and H 3 /E 2 factor compared to the NTs and Ti substrate. Increases in resistance to penetration for the indenter were also observed for HA-coated TiO 2 NTs prepared at 30 V compared to uncoated and CaP-coated NTs prepared at 60 V. [ABSTRACT FROM AUTHOR]

[Display omitted] • Alpha Tocopheryl Phosphate (aTP) is a hydrophilic form of Vitamin E. • aTP was grafted to chemically treated Ti6Al4V both as coating or functionalization. • Protocols for the characterization of aTP grafted samples were developed. • The coating was more effective than functionalization for inhibiting biofilm. • The aTP coating promoted cell adhesion and aTP functionalization is not cytotoxic. Alpha-tocopheryl phosphate (α -TP) is the water-soluble form of the antioxidant and lipophilic molecule alpha-tocopherol. Even if α -TP's antioxidant and antibacterial properties are known, it has never been exploited to prevent implantable materials against bacterial surface contamination, till now. Accordingly, the purpose of this work is to couple a chemically treated Ti6Al4V surface with α -TP conferring a local antibacterial activity preserving orthopaedic and dental prosthetic devices. The grafting of the α -TP molecule is explored both as a thin coating (<0.2 µm thick) and through molecular functionalization. As a result, a homogeneous and continuous coating is obtained by auto-polymerization of the molecule on the treated titanium surface, as shown by reflectance spectroscopy, ζ potential titration curve, and Kelvin Prove assay. The coating exposes the phosphate groups (demonstrated by XPS and FTIR analysis), which give to the surface a hydrophilic (contact angle of 40° with water) and very effective antibacterial behaviour, thus reducing the surface infection from the pathogen Staphylococcus epidermidis of >3 logs (≈ 92%) in comparison to the uncoated controls. Contrarily, the phosphorylated groups were used to create the binding to the surface on the functionalized samples, as shown by the XPS analysis. The functionalized surface results in poor antibacterial properties (≈1 log reduction of viable colonies) and hydrophobic behaviour. Finally, the cytocompatibility evaluation towards human mesenchymal stem cells showed the coating treatment to be more cell's friendly in comparison with the functionalization. [ABSTRACT FROM AUTHOR]

In the last years, chitosan-bioactive glass (BG) composites have been developed and investigated as bioactive coatings for orthopedic applications. The increase of bioactivity occurs due to the stimulation of calcium-phosphate/hydroxyapatite formation on the surface while the coating is degrading. In the present work, protein adsorption and its influence on calcium-phosphate precipitation was studied for the first time on such composite coatings. The experiments involved coating of 316L stainless steel substrates with chitosan (Ch) and chitosan-bioactive glass (Ch-BG) and immersion of the coated samples in two different bovine serum albumin (BSA) containing solutions, namely DI H 2 O (with pH adjusted to about 7.2 with diluted NaOH) and simulated body fluid (SBF). In order to investigate the influence of protein adsorption on calcium-phosphate precipitation, samples were also immersed in DI H 2 O and in SBF without BSA. Samples were analyzed by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Surface analysis revealed that adsorption of BSA takes place on all studied samples and that protein adsorption is influenced by the presence of Ca 2+ and PO 4 3− ions. Bioactivity in the form of hydroxyapatite pre-stage formation is significantly increased on Ch-BG composite coating as compared with bare stainless steel surface. However, calcium-phosphate precipitation in SBF is reduced by the presence of BSA. [ABSTRACT FROM AUTHOR]

A pure hydroxyapatite (HA) target was used to prepare the biocompatible coating of HA on the surface of a polytetrafluorethylene (PTFE) substrate, which was placed on the same substrate holder with technically pure titanium (Ti) in the single deposition runs by radio-frequency (RF) magnetron sputtering. The XPS, XRD and FTIR analyses of the obtained surfaces showed that for all substrates, instead of the HA coating deposition, the coating of a mixture of calcium carbonate and calcium fluoride was grown. According to SEM investigations, the surface of PTFE was etched, and the surface topography of uncoated Ti was preserved after the depositions. The FTIR results reveal no phosphate bonds; only calcium tracks were observed in the EDX-spectra on the surface of the coated PTFE substrates. Phosphate oxide (V), which originated from the target, could be removed using a vacuum pump system, or no phosphate-containing bonds could be formed on the substrate surface because of the severe substrate bombardment process, which prevented the HA coating deposition. The observed results may be connected with the surface re-sputtering effect of the growing film by high-energy negatively charged ions (most probably oxygen or fluorine), which are accelerated in the cathode dark sheath. [ABSTRACT FROM AUTHOR]

We report on the synthesis by Pulsed Laser Deposition of simple and Ti doped hydroxyapatite thin films of biological (ovine dentine) origin. Detailed physical, chemical, mechanical and biological investigations were performed. Morphological examination of films showed a surface composed of spheroidal particulates, of micronic size. Compositional analyses pointed to the presence of typical natural doping elements of bone, along with a slight non-stoichiometry of the deposited films. Structural investigations proved the monophasic hydroxyapatite nature of both simple and Ti doped films. Ti doping of biological hydroxyapatite induced an overall downgrade of the films crystallinity together with an increase of the films roughness. It is to be emphasized that bonding strength values measured at film/Ti substrate interface were superior to the minimum value imposed by International Standards regulating the load-bearing implant coatings. In vitro tests on Ti doped structures, compared to simple ones, revealed excellent biocompatibility in human mesenchymal stem cell cultures, a higher proliferation rate and a good cytocompatibility. The obtained results aim to elucidate the overall positive role of Ti doping on the hydroxyapatite films performance, and demonstrate the possibility to use this novel type of coatings as feasible materials for future implantology applications. [ABSTRACT FROM AUTHOR]

The effect of different side chain groups of bisphosphonates (BPs) on the adsorption on the hydroxyapatite (HAP) is still a controversial issue. In this work, we studied the deposition and adsorption of a set of 26 BPs on the HAP (001) surface by using density functional theory (DFT) in which has been shown that the charge, the length or the presence of different functional groups at R 2 side chain can modulate the adsorption energy of the BP. It was observed that negative charged groups at R 2 enhanced the favourable electrostatic interactions between the BP and the HAP surface, but also that the length of R 2 was important to enable the formation of the favorable electrostatic interactions between the functional group at R 2 and the surface. A crossover study between the HAP/BP model (3D-QSAR/DFT) and the inhibition of the human farnesyl pyrophosphate synthase (FPPS) (3D-QSAR) pointed out that the electrostatic character of the R 2 side chain provokes contrary effects in the inhibition of pathological crystallization and in the bone antiresorptive action of BPs. [ABSTRACT FROM AUTHOR]

The hydrothermally prepared hydroxyapatite (HA) coating on Mg alloys might rapidly degrade due to its brittleness. In this research, the polyelectrolytes, comprising poly (ethylenimine) (PEI), poly (styrene sulfonate) (PSS), poly (acrylic acid) (PAA), and poly (phosphate ammonium) (PPA), were employed to improve the degradation resistance and the mechanical properties of the coatings. The chemical composition and microstructure of the as-synthesized samples were characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM) with affiliated energy-dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). Furthermore, Young's modulus (E), hardness (H), and degradation behavior of various HA coatings were investigated using nanoindentation and electrochemical methods and hydrogen evolution. Additionally, density functional theory (DFT) calculations were performed to explore the role of the polyelectrolytes with different functional groups in the interlocking process. These results demonstrate that the interlocking effect is associated with the anti-shear performance of the branched structure and the interaction forces between the functional groups and the Ca2+ ions. Polyelectrolytes present a promising potential for enhanced degradation and mechanical performance of HA coatings on Mg alloys. [Display omitted] • The corrosion resistance of hydrothermally synthesized hydroxyapatite on Mg alloys can be improved by polyelectrolytes. • It is the compactness of the hydroxyapatite coating rather than the thickness that determines its corrosion resistance. • The corrosion resistance is related to the interaction between the polyelectrolytes' functional groups and calcium ions. • The compactness of hydroxyapatite can be enhanced by branched polyelectrolytes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Coatings on AZ31 were developed • The presence of zinc oxide was confirmed • An action against bacterial colonization was developed A new treatment was developed on AZ31 magnesium alloy to act against infection from its initial contact with a contaminated medium. The treatment was made with a coating of hydroxyapatite (HA), additional magnesium and zinc oxide activated with UV radiation before contact with the bacteria (HAMgZn UV). It was tested against Staphylococcus aureus , which is mainly responsible for early infections related to biomaterials. Because of the concurrent action of the UV effect plus the rapid release of Mg2+ from the coating, it provides an excellent action against bacterial colonization. After five hours of contact, the viability of planktonic and sessile bacteria on HAMgZn UV were reduced up to (99 ± 1)% respect to AZ31. In addition, mature biofilm growth for 24 h on HAMgZn UV decreased (90 ± 2)% respect to biofilm growth on AZ31. The research was performed on progressive coverages of AZ31, including HA, with magnesium (HAMg) or zinc (HAZn) or both (HAMgZn) added. The chemical composition of samples was characterized by XPS and ToF-SIMS, and the release of Mg2+ ions was done by ICP-MS. The presence of zinc as zinc oxide on the HAZn and HAMgZn coatings is confirmed, as well as better availability of magnesium from the HAMg and HAMgZn coatings. [ABSTRACT FROM AUTHOR]

[Display omitted] • Amino-GQDs protected catechol structure and expanded antioxidant capacity of PDA. • The synergistic antioxidant effect was ascribed to increased catechol structure. • GQD/PDA coating with more catechol groups exhibited higher reducibility. • GQD/PDA-HAp coating reduced intracellular ROS and protected osteoblast from H 2 O 2. Oxidative stress is a major pathological feature in patients with metabolic bone diseases and isn't conducive to postoperative osseointegration of implants. Although the free-radical scavenging activities of polydopamine (PDA) have been reported, its antioxidant-active catechol structure is susceptible to oxidation. Here, amino-functionalized graphene quantum dots (GQDs) were introduced into PDA to protect catechol structure from oxidation and expand its free-radical scavenging capacity. Compared to the clinically used hydroxyapatite (HAp) coating and the PDA-HAp coating, the GQD/PDA-HAp coating exhibited higher capacity to scavenge ABTS·+, DPPH and O 2 ·-. The enhanced antioxidant effect of the GQD/PDA-HAp coating was ascribed to the combined effects of the sp2-hybridized carbon in GQDs and more catechol groups in PDA, indicating the synergistic antioxidant relationship between GQDs and PDA. In addition, the amino-functionalized GQDs increased the catechol content and the reducibility of the GQD/PDA coating as confirmed by Folin-Ciocalteu colorimetric assay and mediated electrochemical probing. In vitro studies showed that the GQD/PDA-HAp coating minimized intracellular reactive oxygen species production and protected osteoblast viability against H 2 O 2 -induced oxidative stress. Taken together, introducing amino groups in PDA is an efficient approach to preserve its structural related antioxidant properties which may broaden its application in treating oxidative stress-related diseases. [ABSTRACT FROM AUTHOR]

[Display omitted] • Interconnected graphene nanointerface was designed and fabricated in carbon fiber-epoxy-hydroxyapatite composites. • IGE wrap carbon fiber tightly with a porous and radially aligned structure. • Tensile strength and biotribological properties were improved with the introduction of IGE. Interface is critical for the short-term and long-term performance of carbon fiber-epoxy-hydroxyapatite (CHE) composites for orthopedic implant applications because the stress transfer from the matrix to the fibers is via the interface. Herein, a novel type of interconnected graphene (IGE) nanointerface was fabricated in CHE by chemical vapor deposition method with a porous and radially aligned structure being achieved. Effects of IGE on morphology and microstructure of hydroxyapatite coating, mechanical and biotribological properties of CHE were investigated. The results show that IGE could induce the uniform formation of hydroxyapatite, favor the infiltration of epoxy, and promote the bonding of the fiber/matrix interface and the cohesion strength of epoxy matrix, thus enhancing the mechanical and biotribological properties of CHE. Compared with CHE, the tensile strength of IGE modified CHE increased by 21.9 %, and the wear rate of IGE modified CHE decreased by 93.4 %. This work demonstrated the potential of IGE as an interface for mechanically-strong and wear-resistance CHE. IGE-CHE possessing excellent mechanical and biotribological properties has potential application for bone replacement and bone fracture plate. [ABSTRACT FROM AUTHOR]

This aim of this work is to establish a relationship between the surface morphology and mechanical properties of hydroxyapatite coatings prepared using RF magnetron sputtering at temperatures in the range from 400 to 800 °C. The topography of the samples was scanned using atomic force microscopy, and the obtained 3D maps were analyzed using fractal methods to derive the spatial characteristics of the surfaces. X-ray photoelectron spectroscopy revealed the strong influence of the deposition temperature on the Ca/P ratio in the growing films. The coatings deposited at 600–800 °C exhibited a Ca/P ratio between 1.63 and 1.69, close to the stoichiometric hydroxyapatite (Ca/P = 1.67), which is crucial for proper osseointegration. Fourier-transform infrared spectroscopy showed that the intensity of phosphate absorption bands increased with increasing substrate temperature. Each sample exhibited well defined and sharp hydroxyapatite band at 566 cm −1 , although more pronounced for the coatings deposited above 500 °C. Both the hardness and elastic modulus of the coated samples decrease with increasing deposition temperature. The surface morphology strongly depends on the deposition temperature. The sample deposited at 400 °C exhibits circular cavities dug in an otherwise flat surface. At higher deposition temperatures, these cavities increase in size and start to overlap each other so that at 500 °C the surface is composed of closely packed peaks and ridges. At that point, the characteristics of the surface turns from the dominance of cavities to grains of similar size, and develops in a similar manner at higher temperatures. [ABSTRACT FROM AUTHOR]

To improve the bonding strength of Sr and Na co-substituted hydroxyapatite (SNH) coatings for carbon/carbon composites, carbon/carbon composites are surface modified by micro-oxidation treatment. The micro-oxidation treatment could generate large number of pores containing oxygenic functional groups on the surface of carbon/carbon composites. SNH is nucleated on the inwall of the pores and form a flaky shape coating with 10–50 nm in thickness and 200–900 nm in width. The bonding strength between SNH coating and carbon/carbon composites increases from 4.27 ± 0.26 MPa to 10.57 ± 0.38 MPa after the micro-oxidation treatment. The promotion of bonding strength is mainly attributed to the pinning effect caused by the pores and chemical bonding generated by the oxygenic functional groups. [ABSTRACT FROM AUTHOR]

CaCO 3 particles dispersed in liquid media have proven to be good inductors of hydroxyapatite (HAp) growth. However, the use of CaCO 3 deposited as thin films for this propose is unknown. Here, we report the growth of CaCO 3 continuous films on Langmuir–Blodgett (LB) modified titanium surfaces and its use as HAp growth inductor. The Ti surfaces were modified with two, four, and six layers of dihexadecylphosphate (DHP)-LB films containing Ca 2+ , exposed to CO 2 (g) for 12 h. The modified surfaces were immersed in simulated body fluid (SBF) at 37 °C for 36 h and submitted to bioactivity studies. This procedure originates bioactive coatings composed by non-stoichiometric HAp as evidenced by Fourier-Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and X-ray Photoelectron Spectroscopy (XPS). The presence of the CaCO 3 film as pre-coating diminished the time necessary to growth continuous and homogeneous HAp films using a biomimetic approach. The surface properties of the films regarding their roughness, composition, charge, wettability, and surface free energy ( γ s ) were accessed. The presence of HAp increased the wettability and γ s of the surfaces. The coatings are not toxic for osteoblasts as observed for cell viability assays obtained after 7 and 14 days of culture. Moreover, the CaCO 3 thin films promote the recovery of the osteoblasts viability more than the Ti surfaces themselves. [ABSTRACT FROM AUTHOR]

Hydroxyapatite (HAP) has a much lower dissolution rate and solubility than calcite, especially in an acidic environment, so it has been proposed for the protection of marble against acidic rain corrosion. Promising results were obtained, but further optimization is necessary as the treated layer is often incomplete, cracked and/or porous. In this paper, several parameters were investigated to obtain a coherent, uncracked layer, and to avoid the formation of metastable, soluble phases instead of HAP: the role of the pH of the starting solution; the effect of organic and inorganic additions, and in particular that of ethanol, as it is reported to adsorb on calcite, hence possibly favoring the growth of the HAP layer. Finally, a double application of the treatment was tested. Results were compared to those obtained with ammonium oxalate treatment, widely investigated for marble protection. Results indicate that adding small amounts of ethanol to the formulation remarkably increases the acid resistance of treated samples, and yields better coverage of the surface without crack formation. The effectiveness of the treatment is further enhanced when a second treatment is applied. The efficacy of ethanol-doped DAP mixtures was found to be remarkably higher than that of ammonium oxalate based treatments. [ABSTRACT FROM AUTHOR]

This work elucidated the corrosion resistance and cytocompatibility of electroplated Zn- and Si-containing bioactive calcium silicate/zinc-doped hydroxyapatite (ZnHA/CS) ceramic coatings on commercially pure titanium (CP-Ti). The formation of ZnHA/CS coating was investigated through Fourier transform infrared spectroscopy, X-ray diffraction (XRD), scanning electron microscopy, energy dispersive X-ray and inductively coupled plasma analyses. The XRD image showed that the reaction layer was mainly composed of HA and CaSiO 3 . The fabricated ZnHA/CS coatings presented a porous structure and appropriate thickness for possible applications in orthopaedic surgery. Potentiodynamic polarization tests showed that ZnHA/CS coatings exhibited higher corrosion resistance than CP-Ti. Dissolution tests on the coating also revealed that Si 4+ and Zn 2+ were leached at low levels. Moreover, MC3T3-E1 cells cultured on ZnHA/CS featured improved cell morphology, adhesion, spreading, proliferation and expression of alkaline phosphatase than those cultured on HA. The high cytocompatibility of ZnHA/CS could be mainly attributed to the combination of micro-porous surface effects and ion release (Zn 2+ and Si 4+ ). All these results indicate that ZnHA/CS composite-coated CP-Ti may be a potential material for orthopaedic applications. [ABSTRACT FROM AUTHOR]

Hydroxyapatite (HAP) ceramics belong to a class of calcium phosphate-based materials, which have been widely used as coatings on titanium medical implants in order to improve bone fixation and thus to increase the lifetime of the implant. In this study, HAP coatings were deposited from pure HAP targets on Ti6Al4V substrates using the radio-frequency magnetron sputtering technique at substrate temperatures ranging from 400 to 800 °C. The surface morphology and the crystallographic structure of the films were investigated by atomic force microscopy (AFM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The corrosion resistance of the coatings in saliva solution at 37 °C was evaluated by potentiodynamic polarization. Additionally, the human osteosarcoma cell line (MG-63) was used to test the biocompatibility of the coatings. The results showed that all of the coatings grown uniformly and that the increasing substrate temperature induced an increase in their crystallinity. Corrosion performance of the coatings was improved with the increase of the substrate temperature from 400 °C to 800 °C. Furthermore, all the coatings support the attachment and growth of the osteosarcoma cells with regard to the in vitro test findings. [ABSTRACT FROM AUTHOR]

Titanium-based implants are key weight-bearing materials in biomedical engineering due to their excellent bulk mechanical properties and biocompatibility. Designing tissue-material interfaces of titanium implants is essential for an increase in osteointegration of engineered implant materials. Surface morphology is a crucial determinant in the construction of biocompatible and osteointegrative orthopedic and dental implants. Biomimicry of the structural features of bone, specifically its macro-to-mesoporosity, may enable the bone cells to osteointegrate, attain and maintain a physiological strain level. In this study, the surface chemistry and morphology of commercially pure titanium plates were modified using electrochemistry. Titanium oxide substrates were prepared by dual acid polishing and alkaline anodization using 0.1 M KOH in an electrochemical cell with a stainless steel cathode and an anodic voltage of 40 V at 20 °C for 3 min. FE-SEM characterization revealed macro-mesoporous anodized titania surfaces, which were coated by hydroxyapatite using simulated body fluid and pulsed electrochemical deposition at 80 °C, while unprocessed commercially pure titanium surfaces were used as controls. The calcium phosphate deposit on titania plates was characterized as calcium-deficient carbonated hydroxyapatite using XRD, FTIR and FE-SEM, whereas the deposit on non-porous, non-functionalized titanium surfaces was characterized as carbonated apatite. The adhesion strength of the hydroxyapatite coated titania surfaces was 38 ± 10 MPa, implying that these surfaces may be suitable for biological and chemical functionalization of medical implants to tune bioactivity, including delivering drugs. [ABSTRACT FROM AUTHOR]

Hydroxyapatite (HA) can be coated onto metal implants as a ceramic biocompatible coating to bridge the growth between implants and human tissue. Meanwhile many efforts have been made to improve the mechanical properties of the HA coatings without affecting its bioactivity. In the present study, nanostructure titania (TiO 2 ) was mixed with HA powder and HA–nanostructure TiO 2 composite coatings were produced by gas tunnel type plasma spraying torch under optimized spraying conditions. For this purpose, composition of 10 wt% TiO 2 + 90 wt% HA, 20 wt% TiO 2 + 80 wt% HA and 30 wt% TiO 2 + 70 wt% HA were selected as the feedstock materials. The phase, microstructure and mechanical properties of the coatings were characterized. The obtained results validated that the increase in weight percentage of nanostructure TiO 2 in HA coating significantly increased the microhardness, adhesive strength and wear resistance of the coatings. Analysis of the in vitro bioactivity and cytocompatibility of the coatings were done using conventional simulated body fluid (c-SBF) solution and cultured green fluorescent protein (GFP) labeled marrow stromal cells (MSCs) respectively. The bioactivity results revealed that the composite coating has bio-active surface with good cytocompatibility. [ABSTRACT FROM AUTHOR]

A biocomposite coating containing chitosan, silver, and hydroxyapatite was developed on anodized titanium substrate by electrochemical deposition. Coatings were characterized by field-emission scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and polarisation studies. Results showed that the prepared coatings had compact and dense morphology with a thickness of 6.2 ± 0.7 μm and that silver was evenly distributed. Testing the prepared coatings with Gram-positive and Gram-negative bacterial strains exhibited antibacterial activity because of the synergistic effect of silver and chitosan. The prepared coatings were also found to be nontoxic to MC3T3-E1 cells. These results suggested that chitosan/silver-hydroxyapatite biocomposite coatings can prevent the bacterial infection of implants. [ABSTRACT FROM AUTHOR]

The magnetite-hydroxyapatite (M-HAP) nanocomposites were prepared by a chemical co- precipitation procedure and characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and diffuse reflectance spectra (DRS). The ability of the synthesized catalyst for photocatalytic degradation of Acid Blue 25 (AB25), as an organic dye, under UV irradiation was studied. The catalyst was modified employing transition metals (Mn, Fe, Co, Ni, Cu and Zn) trying to improve the catalytic performance of HAP in absence of UV irradiation and in the presence of hydrogen peroxide i.e. a Fenton like reaction. The best results obtained for Cu and Co modified M-HAPs and the effect of operational parameters such pH, amount of catalyst and hydrogen peroxide concentration was studied. In order to investigate the performance of HAP based photocatalyst in visible light region, M-HAP was modified with silver ions. At the end, Langmuir-Hinshelwood kinetic expression used to evaluate and compare the catalytic systems. The strongest degradation activity was observed for Ag-M-HAP/Vis system because of Ag 3 PO 4 formation. Apparent reaction rate constant ( K app ) by Ag-M-HAP/Vis was 63, 36 and 19 times faster than Cu-M-HAP(II)/H 2 O 2 , Co-M-HAP(II)/H 2 O 2 and M-HAP (I)/UV systems, respectively. [ABSTRACT FROM AUTHOR]

In this work, the Density Functional Theory (DFT) calculations are carried out to find out why a certain amount of fluorine is good for teeth and bones. The geometric and electronic configurations of the pristine hydroxyapatite, fluorapatite, and the doping as well as defect systems are investigated. Their mechanical properties are also estimated and discussed. Regardless of biological and environmental factors, according to our simulations, fluorine can not only restore the mechanical properties of the hydroxyapatite lattice, but also effectively prevent the dissociation of the hydroxyl groups on its surface. Although fluorine cannot directly prevent the calcium loss, it can indirectly slow down this process. This study reveals the microscopic working mechanism of the fluorine atom in hydroxyapatite, and partially answers the basic question mentioned at the beginning from the perspective of quantum chemistry and materials science. [Display omitted] • Ca-vacancy in hydroxyapatite leads to obvious inclination of the adjacent OH-group. • F-dopant cannot enhance the mechanical strength of hydroxyapatite. • F-dopant can fill the OH-vacancy and therefore restore the mechanical strength of hydroxyapatite. • The additional hydrogen bond between F and OH can effectively prevent the further formation of OH-vacancies. [ABSTRACT FROM AUTHOR]

A series of nanostructured low-crystalline hydroxyapatite (HA) coatings averaging 170, 250, and 440 nm in thickness were deposited onto previously etched titanium substrates through radio-frequency (RF) magnetron sputtering. The HA coatings were analyzed using infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning and transmission electron microscopy (SEM and TEM). Cross sections of the thin specimens were prepared by FIB to study the microstructure of the coatings by TEM. The deposition process formed nano-scale grains, generating an amorphous layer at the substrate/coating interface and inducing the growth of a columnar grain structure perpendicular to the substrate surface. A microstructural analysis of the film confirmed that the grain size and crystallinity increased when increasing the deposition time. The nanostructured HA coatings were not cytotoxic, as proven by in vitro assays using primary dental pulp stem cells and mouse fibroblast NCTC clone L929 cells. Low-crystallinity HA coatings with different thicknesses stimulated cells to attach, proliferate and form mineralized nodules on the surface better than uncoated titanium substrates. [ABSTRACT FROM AUTHOR]

Among the various coating techniques, plasma spray coating is an efficient technique to protect the metal surface from the various surface problems like wear and corrosion. The aim of this present work is to design and produce a bilayer coating on the non- toxic commercially pure titanium (denoted as CP-Ti) implant substrate in order to improve the biocompatibility and surface properties. To achieve that, Al 2 O 3 -13 wt%TiO 2 (AT13) and hydroxyapatite (HAP) were coated on CP-Ti implant substrate using plasma spray coating technique. Further, the coated substrates were subjected to various characterization techniques. The crystallite size of coated HAP and its morphological studies were carried out using X-ray diffractometer (XRD) and scanning electron microscopy (SEM) respectively. The wear test on the bilayer (AT13/HAP) coated CP-Ti implant surface was conducted using ball-on-disc tester under SBF environment at 37 °C, in order to determine the wear rate and the coefficient of friction. The adhesion strength of the bilayer coated surface was evaluated by micro scratch tester under the ramp load conditions with load range of 14–20 N. The above said studies were repeated on the single layer coated HAP and AT13 implant surfaces. The results reveal that the bilayer (AT13/HAP) coated CP-Ti surface has the improved wear rate, coefficient of friction in compared to single layer coated HAP and AT13 surfaces. [ABSTRACT FROM AUTHOR]

45 wt%-Hydroxyaptite/polyetheretherketone (HA/PEEK) coating materials modified by silane coupling agent (KH560) on PEEK substrate were successfully fabricated by solution casting method and characterized by Fourier transform infrared spectroscopy (FTIR), X-Ray Diffraction (XRD) , scanning electron microscopy (SEM), and tensile testing. The modified HA fillers were obtained to be uniformly distributed in the HA/PEEK coating, which has better properties of tensile strength and fracture toughness than those of the unmodified specimen. A good bonding between the composite coating and the PEEK substrate was achieved by solution casting method, resulting in integral-fracture without falling apart or delaminating during tensile loading. The modified specimens dipped into simulated body fluid (SBF) were characterized by SEM, XRD and FTIR, indicating that the bioactivity of the dipped materials was demonstrated more apparent with extending the dipping time. Therefore, the coating materials may become the substitutes for the hard tissues of the human body in the future, which could realize the balance between the mechanical properties and the bioactivity by modifying the structural design of the coating. [ABSTRACT FROM AUTHOR]

Hydroxyapatite doped with Ag + ions (AgHAp) was synthesized via electrochemical deposition method on anodized titanium. The samples were characterized via X-ray diffraction, Fourier transform infrared spectrum analysis, X-Ray photoelectron spectroscopy and scanning electron microscopy to investigate the phase formation and microstructure of the samples. Highly ordered TiO 2 nanotubes with a diameter of 100 nm were successfully synthesized, and the AgHAp coating was deposited on the TiO 2 nanotubes, which has a thickness of about 17.7 ± 1.5 μm. Moreover, silver was uniformly-distributed on the nanotubes. Bioactivity and electrochemical studies were performed for the AgHAp-coated TiO 2 in a simulated body fluid, where significant good bioactivity and corrosion resistance were exhibited. The antibacterial and osteoblast cell adhesion tests in vitro revealed that the AgHAp coating with 2.03 wt% silver had significant antibacterial and osteogenic properties. Thus, the AgHAp coating was regarded as a promising candidate for coating orthopedic implants. [ABSTRACT FROM AUTHOR]

A carbon/SiC nanowire/Na-doped carbonated hydroxyapatite multilayer coating (CSH coating) was prepared on carbon/carbon composites using a combination method of magnetron sputter ion plating, chemical vapor deposition and ultrasound-assisted electrochemical deposition procedure. The morphology, microstructure and chemical composition of the coating were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The results showed that the CSH coating was consisted of three components: carbon layer, SiC nanowires and Na-doped carbonated hydroxyapatite. The carbon layer provided a dense and uniform surface structure for the growth of SiC nanowires. The SiC nanowires exhibited a porous structure, favoring the infiltration of Na-doped carbonated hydroxyapatite crystals. The Na-doped carbonated hydroxyapatite could infiltrate into the pores of SiC nanowires and finally cover the SiC nanowires entirely with a needle shape. The osteoblast-like MG63 cells were employed to assess the in vitro biocompatibility of the CSH coating. The MG63 cells favorably spread and grew well across the CSH coating surface with plenty of filopods and microvilli, exhibiting excellent cell activity. Moreover, the CSH coating elicited higher cell proliferation as compared to bare carbon/carbon composites. In conclusion, the CSH offers great potential as a coating material for future medical application in hard tissue replacement. [ABSTRACT FROM AUTHOR]

Highlights: [•] We found that different anodization time of titanium significantly effects on nanotube length which further impacts adhesion strength of hydroxyapatite coating layers. [•] Adhesion strength of Hydroxyapatite (HA) coated on titanium dioxide nanotubes is better than that of HA coated on titanium plate. [•] Hydroxyapatite coated on titanium dioxide nanotubes showed higher cell density and better spreading of MC3T3-E1 cells (bone-forming cells) than that coated on titanium plate surface. [ABSTRACT FROM AUTHOR]

Highlights: [•] Two surface treatments were compared to improve bioactivity of sprayed coatings. [•] As-sprayed and alkaline- and collagen-treated samples were analysed. [•] Collagen treated samples showed the best biological behaviour. [•] Alkaline treated samples showed an intermediate bioactivity. [•] Collagen can be successfully bonded to hydroxyapatite–TiO2 coatings. [ABSTRACT FROM AUTHOR]

Highlights: [•] Pulsed laser deposition was applied to coat titanium for biomedical applications. [•] Iron-substituted hydroxyapatite (Fe-HAp) was used as coating material. [•] Properties of deposited films were characterized by complementary techniques. [•] Compact, hard, nanostructured, 1.5μm thick Fe-HAp (0.28wt.% Fe) films were prepared. [ABSTRACT FROM AUTHOR]

Highlights: [•] Microstructure evolution of Ca-def HA coating was systematically investigated. [•] Poor crystalline Ca-def HA has been formed at the deposition time of 5min. [•] Reasons for direct formation of Ca-def HA coating on Mg–Zn–Ca alloy are discussed. [ABSTRACT FROM AUTHOR]

Highlights: [•] It is the first time that magnesium-substituted hydroxyapatite coating was successfully deposited on anodic TiO2 nanotubes by electrochemical deposition. [•] The bond strength between the MgHAp coatings and the substrate was improved by anodization pretreatment. [•] The bioactivity and corrosion resistance of the HAp coatings was enhanced with Mg2+ incorporation in SBF. [•] The MgHAp coatings showed good biocompatibility and no adverse effect in cell culture tests. [Copyright &y& Elsevier]

Highlights: [•] Lower and higher applied load shows two distinct trends concerning microhardness (dense area). [•] Coatings are brittle near the two interface positions. [•] Coatings are found more brittle near the two interfaces mostly for high loads, e.g. 300 and 500gf. [•] Indent roughness increases as the applied load increases. [•] Combined microhardness decreases with increase of porous area percentage microhardness. [ABSTRACT FROM AUTHOR]

Highlights: [•] HA nanoparticles were deposited on TiO2 nanotubular surface by EPD. [•] Nanotubular TiO2 structure enhances HA coating adhesion formed by EPD process. [•] Vacuum sintered coatings offered enhanced corrosion protection. [•] HA particles over TiO2 nanotubes decrease corrosion protection compared to their absence. [ABSTRACT FROM AUTHOR]

Highlights: [•] The incorporation of SWNTs into the HA coating leaded to the formation of homogeneous and crack-free composite coatings. [•] The highest bonding strength was detected for the SWNTs/HA-0.5 composite coating (25.70MPa). [•] The SWNTs/HA composite coatings induced better cell proliferation, cell viability and ALP activity compared to pure HA coating and pure Ti. [•] The results suggested that SWNTs/HA-0.5 and SWNTs/HA-1.0 composite coating prepared in this work is acceptable in terms of mechanical property and in-vitro bioactivity. [ABSTRACT FROM AUTHOR]

Highlights: [•] The morphology of HA particles is influenced by the intensity and direction of magnetic field. [•] The static magnetic field can accelerate the nucleation rate of HA crystals. [•] The adhesiveness of needle-like particles is stronger than the particles of other forms. [Copyright &y& Elsevier]

Highlights: [•] CF/HA coatings were formed on C/C by combination of slurry procedure and UECD. [•] CF provided abundant pores for the infiltration of HA crystals. [•] CF/HA coatings showed better cytocompatibility than the bared C/C. [Copyright &y& Elsevier]

Highlights: [•] 316L SS was surface treated by high energy low current DC electron beam (HELCDEB). [•] Successful electrodeposition of strontium hydroxyapatite on HELCDEB treated 316L SS. [•] SEM morphology exhibits microflower structured strontium hydroxyapatite coating. [•] As-formed coating on HELCDEB treated 316L SS possesses maximum corrosion resistance. [Copyright &y& Elsevier]

Highlights: [•] Nano-hydroxyapatite (n-HAp) particles synthesized using a sol–gel process. [•] Stable suspension of n-HAp powders was prepared in methanol medium. [•] Fluoride and MAO pre-treatments were applied on AZ91 samples as intermediate layers. [•] Electrophoretic deposition process was used for coating n-HAp particles. [•] The MAO/n-HAp/AZ91 system is highly prone to be utilized as bio-absorbable implants. [ABSTRACT FROM AUTHOR]

Highlights: [•] Coating of hydroxyapatite on Ti alloy surface using different doses of H2O2. [•] Coating of hydroxyapatite on Ti alloy surface using different doses of NH4OH. [•] Establishing correlations between potential and time with addition of H2O2 and NH4OH. [ABSTRACT FROM AUTHOR]