Magnesium light weight alloys are currently being studied as implants due to their biodegradability. However, its applications are limited by high rate hydrogen evolution during corrosion. Coating on this substrate is one of the ways to reduce the rate of corrosion and increase the life of this type of implant. Hence, hydroxyapatite (HA) was coated on the substrates by using high velocity oxy- fuel (HVOF) spraying. The main purpose of such coatings is increasing bioactivity as well as corrosion resistance of the Mg alloy. Crystal structure was characterized by X-ray diffraction (XRD). Crystallinity of the coating was about 70% in which HA is dominant phase. The amounts of hydrogen gas released during magnesium corrosion tests in simulated body fluid (SBF) were measured to evaluate the corrosion resistance of the coated samples. This coating could decrease hydrogen evolution from 100 per cm 2 .mL to about 15 per cm 2 .mL after 29h of immersion time.

Previous studies have shown that nanostructured coatings produced by plasma spraying can stimulate cellular activity and promote bone healing. Since then, a number of studies have been conducted to better understand how coating nanotopography can be controlled and how it influences bioactivity and healing. This paper reviews some of the key findings in three areas: the effects of nanotopography on bone cell adhesion, the effects of nanotopography on bone-like apatite formation in simulated body fluid, and how to refine the nanotopography of plasma-sprayed coatings.

This work investigates the effects of cerium oxide (CeO 2 ) coatings on the response of osteoblasts to H 2 O 2 -induced oxidative stress. The results show that the coatings have a protective effect, promoting both osteoblast growth and differentiation. This indicates that the CeO 2 coating reduces the production of reactive oxygen species in H 2 O 2 -treated osteoblasts. These coatings, with their antioxidant properties, appear quite promising for bone regeneration.

This study shows that the osteogenic abilities of calcium silicate based coatings can be improved through nanotopographical surface modifications and the addition of bioactive trace elements. CaSiO 3 powders were deposited on titanium substrates by atmospheric plasma spraying and the topography and composition of the resulting coatings were modified by hydrothermal treatments in deionized water and in aqueous solutions of Sr(NO 3 ) 2 . Bone marrow stem cells were cultured on treated and untreated coatings. The cells spread further on treated surfaces and were found to be relatively larger in size than the cells on untreated surfaces. Calcium silicate coatings treated in the strontium-containing solution showed the best overall improvement in terms of bone cell growth and differentiation.

Nanomodified plasma-sprayed titanium coatings have been shown in various studies to improve the early osseointegration of orthopedic implants, although little attention has been paid to the interactions that occur between coating surfaces and osteoblast cells. The aim of this study is to determine how surface structure influences cytoskeleton distribution and cellular differentiation and to assess the role of topography in regulating osteogenic fate. The results show that synergistic effects are achieved on hierarchically structured surfaces, with better cell spreading on nanotexture and multidimensional cytoskeleton distribution occurring over rough macroporous structure. Evidence of greater cytoskeleton reorganization and higher intracellular tension was also revealed.

This work demonstrates the fabrication of a hydroxyapatite (HA) composite material for potential use in biomedical implant applications. A composite powder is prepared by introducing graphene oxide (GO) and F- ions, which are incorporated in the HA crystal structure via in-situ chemical synthesis. The powder is consolidated through spark plasma sintering, resulting in a biocomposite (GO-FHA) material that is mechanically stronger and more chemically stable after implantation than HA. The addition of GO and partial substitution of F- also promote osteoblast proliferation as in-vitro bioactivity tests show.

This work investigates the biofunctionality and corrosion resistance of titanium (Ti) and Ti/bioglass composite coatings. Commercially pure Ti (CP-Ti) and 45S5 bioglass powders were deposited on CP-Ti plates by air plasma spraying and the coating samples were placed in Hanks’ balanced salt solution for simulated body fluid (SBF) testing. After four weeks of immersion, the coatings were examined by SEM imaging and EDS and XRD analysis. EDS analysis showed that the Ca content on the Ti/bioglass coatings increased from 4 to 16 wt%, while no increase in Ca was observed on the Ti coatings. Hydroxyapatite formation was found on both coatings, although the relative intensity of HA on the XRD spectrum was higher for the Ti/bioglass composite layers. Weight measurements before and after immersion showed that the CP-Ti samples experienced a mass gain and that the Ti/bioglass samples underwent a mass loss likely due to the dissolution of calcium and phosphate.

SiO 2 -TiO 2 coatings were prepared by atmospheric plasma spraying followed by hydrothermal treatment in a solution of hydrogen fluoride. The as-sprayed coatings mainly consisted of rutile and quartz phases, which remained relatively unchanged during etching. All treated coatings have the typical characteristics of plasma-sprayed deposits, exhibiting rough surfaces with many splats. Differences in surface structure can be observed, however, at the nanoscale, depending on treatment conditions. Treatments of 60 min at 100 °C appear to be most beneficial, resulting in nanoporous coatings that are shown to promote cell proliferation and, in past studies, have been found to improve osteoblast adhesion.

In this study, bioactive glass powders were synthesized from four different types of oxides (SiO 2 , P 2 O 5 , CaO and MgO). These oxides were mixed, melted, milled and sieved to produce powders with two chemical compositions of the 31SiO 2 -11P 2 O 5 -(58-x)CaO-xMgO system. The powders were plasma sprayed onto AISI 316L stainless steel and Ti6Al4V titanium alloy substrates using a F4MB Sulzer Metco gun. The physical and mechanical properties of coatings, as well as their bioactivity were evaluated. The bioactivity tests were carried out exposing the surface of coatings to simulated body fluid (SBF) during 1, 9 and 15 days. The thickness and hardness of apatite layer produced on the surface of each coating during bioactivity tests were evaluated. The results indicate that the thickness of apatite layer formed during 15 days in SBF is between 31 and 51 µm and its hardness is between 1.5 and 1.9 GPa according to the chemical composition of feed stock powder used to manufacture the coatings. Additionally, the harness of bioglass coatings decreased around 26% after to expose them to SBF.

This paper presents a summary of some of the research conducted on sponge-like titanium coatings developed for orthopedic use. It assesses the pore structure, adhesion properties, and in-vitro and in-vivo biological characteristics of porous titanium coatings deposited by vacuum plasma spraying on metals, PEEK polymer, and two bioceramics, Mg-toughened ZrO 2 and ZrO 2 -toughened Al 2 O 3 . The plasma sprayed coatings show good flexibility in terms of pore size (100-800 µm), overall porosity (40-70%), and coating thickness (600-1500 µm).

Dicalcium silicate/zirconia composite coating with 70 wt.% zirconia and 30 wt.% dicalcium silicate was prepared by plasma spraying. In vitro behaviors of human osteoblast cells on the coating were studied. As a result of rapid exchange of Ca and H in the culture media and dissolution of the dicalcium silicate component from the coatings, a large amount of Si-OH functional group was produced on the coating. These OH bonds were favorable to the adhesion of proteins and cells attachment and thus, the good cytocompatibility of the coatings. Honeycomb-like Ca-P minerals were formed on the coating surface after only 1 day incubation in the culture media. The deposition rate of the Ca-P minerals was greatly improved by the existence of proteins. It may be attributed to the increased Ca ion concentration in the culture media resulting from the dissolution of dicalcium silicate and the good protein adhesion properties of the coating.

In this study, titania and hydroxyapatite nanopowder mixtures are deposited on medical grade titanium substrates by HVOF spraying. To assess bioperformance, human mesenchymal stem cells (hMSCs) were cultured from 1 to 21 days on the surface of HVOF-sprayed TiO 2 and TiO 2 -HA samples. Plasma sprayed HA and uncoated Ti-6Al-4V substrates were used as controls. The active cultures were evaluated for cell proliferation, cytoskeleton organization, and cell-substrate interaction. The results for HVOF-sprayed TiO 2 -HA nanocomposite coatings show strong evidence of bone growth, proliferation, and attachment with cell-substrate interaction levels superior to those of air plasma sprayed HA coatings. Although there are no clear explanations for this favorable behavior, the topography and chemical composition of the surface of the coating appear to be playing important roles.

In this investigation, bioactive ceramic materials, including dicalcium silicate, titania, and zirconia, were deposited on titanium substrates by plasma spraying in order to determine their effect on the bioactivity of metal implants. Cell-seeding tests show that MG63 osteoblast-like cells grow and proliferate well on each of the coating materials. In the case of Ca 2 SiO 4 , the presence of silicon ions is thought to be the key to this behavior. In regard to TiO 2 and ZrO 2 , the bioactivity is thought to result from the nanostructured surfaces and special surface compositions.

In this study, vacuum plasma spraying was used to apply hydroxyapatite-silver composite coatings on titanium substrates, which were then exposed to E. coli, Pseudomonas aeruginosa , and Staphylococcus aureus . The coatings exhibited excellent antibacterial performance ( K > 95%) against all three strains, attributed to the release of silver ions. Cytotoxicity, hemolysis, and simulated body fluid immersion tests showed that added silver affects neither the biocompatibility nor bioactivity of the hydroxyapatite, one of the most widely used medical implant materials due to its close chemical structure with natural bone.

Yttria-stabilized zirconia coatings were deposited onto a Ti-6Al-4V substrate through a microplasma spray technique and incubated in simulated body fluid (SBF) for different periods of time (3, 7, 14, 28 days). The formation of apatite on the surface was investigated to evaluate the bioactivity of the coatings. Surface morphologies and structural changes in the coatings before and after immersion were analyzed by optical microscopy, scanning electron microscopy, and x-ray diffractometry. The calcium (Ca 2+ ) concentration in the solutions was measured directly after the samples were removed, using an inductively coupled plasma atomic emission spectrometer (ICP). The results showed that yttria-stabilized zirconia coatings can be produced by microplasma spraying and, even though the coatings contain few small unmelted particles, apatite can be formed on the coatings that are soaked in SBF solution. These results indicate that the yttria-stabilized zirconia coatings exhibited definite bioactivity.

Formation of bonelike apatite is an essential prerequisite for implants to make direct bond to living bone. The apatite formation can be assessed in vitro using a simulated body fluid (SBF) that has almost equal compositions of inorganic ions to human blood plasma. In this study, Ti coatings were prepared by vacuum plasma spraying, and then they were treated by NaOH aqueous solution, immersed in distilled water, heated at 600 °C in a furnace. Microstructure and bioactivity of the surface modified Ti coatings were examined by SEM observation and SBF test respectively. The results obtained revealed that a net-like structure comprising of many micropores was present on the surfaces of the treated Ti coatings. After immersed in SBF, apatite layer was formed on their surfaces, suggesting that the surface modification coatings have good bioactivity.

In this work, the plasma sprayed titania coatings were treated by H 2 SO 4 for 24h at room temperature to improve the biological properties. The bioactivity was measured by simulated body fluid soaking test, and the biocompatibility was evaluated by quantifying the grafted collagen amount and in vitro cell culture test. The results showed that titania coatings treated by 0.1M and 1M H 2 SO 4 can induce bone-like apatite formation after immersion in SBF for 28 days, while the titania coating treated by 0.01M H 2 SO 4 can not. H 2 SO 4 treatment can promote the grafting of collagen on titania coatings. The in vitro cell culture test confirmed that collagen improved the cellular adhesion and proliferation on titania surface. In conclusion, a certain concentration of H 2 SO 4 treatment is beneficial in improving the bioactivity and biocompatibility of plasma sprayed titania coatings.

In this work, 30wt% calcium silicate, including wollastonite and dicalcium silicate, were mixed with 70wt% ZrO 2 , respectively. The composite powders were deposited onto Ti-6Al-4V substrates to prepare wollastonite/ZrO 2 and dicalcium silicate/ZrO 2 composite coatings using plasma spraying technology. The bioactivity of coatings was evaluated using simulated body fluid soaking test. After the composite coatings were soaked in simulated body fluid for a certain period, apatite was formed on the surface of the wollastonite/ZrO 2 and dicalcium silicate/ZrO 2 composite coatings. In addition, the ZrO 2 in composite coatings may protect the calcium silicate in the coatings from dissolving in simulated body fluid.

In this paper, nano-structured TiO 2 coatings have been successfully deposited onto titanium alloy substrates by atmospheric plasma spraying technology using optimized plasma parameters. A chemical treatment method was employed to induce bioactivity on the TiO 2 surface. The bioactivity of as-sprayed and chemical treated TiO 2 coatings were evaluated by investigating the formation of apatite on their surface after they were soaked in simulated body fluids (SBF) for a period of time. Microstructure and the phase composition of the as-sprayed coating and apatite were analyzed by Field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy-dispersive X-ray spectrometry (EDS). The results obtained indicate that as-sprayed TiO 2 coating consists of rutile, anatase and suboxide such as Ti 3 O 5 . The surface of nano-TiO 2 coating is covered by nano particles of about 50nm in size. The bonding strength of TiO 2 coating with Ti alloy substrate is as high as 40 MPa. The corrosion resistance performance of nano-coating in SBF is better than that of Ti-6Al-4V alloy. The surface of as-sprayed TiO 2 coating can not induce bone-like apatite formation. Chemical treatment, such as acid and alkali, can improve bioactivity of TiO 2 coating surface.

In this work, a TiO 2 coating with nanostructured surface was obtained through plasma sprayed nano-sized TiO 2 powder. Its bonding strength onto Ti-6Al-4V substrate is high up to 38 MPa. At same time, we have successfully improved the bioactivity of plasma sprayed TiO 2 coating with nanostructured surface using hydrogen ion implantation and UV illumination. Bone-like apatite can form on the surface of the post-treated TiO 2 coatings after they are soaked in simulated body fluid for a period of time. Introduction of surface bioactivity (bone conductivity) to plasma-sprayed TiO 2 coatings which are generally recognized to have excellent biocompatibility and corrosion resistance as well as high bonding to titanium alloys makes them more superior than many current biomedical coatings such as plasma-sprayed hydroxyapatite.