Doped Hydroxyapatite Coatings Research Articles

Investigation of the structural properties of Si4+-doped HAP coatings on Ti-6Al-4V substrate as a corrosion barrier in biomedical media

The coatings of co-substituted bioactives play an important role in stimulating biological and physical properties for biomedical applications. Hydroxyapatite (HAP), a mineral compound possessing a hexagonal structure, exhibits high thermodynamic stability under typical physiological conditions. In this experimental study, Si4+-doped HAP coatings with varying concentrations (2.5 %, 5 %, and 10 % wt) were prepared on a Ti-6Al-4V substrate using the spin-coating technique and extreme centrifugal force (2500 rpm). The coated samples were characterized by XRD, FTIR, AFM, FESEM, and EDS techniques. The presence of cracks and voids in the HAP coatings detrimentally affected the performance of the implants. Tetraethyl orthosilicate (TEOS) was used in the coatings to mitigate the cracks and voids. Polarization and EIS studies in the simulated body fluid (SBF) were used to assess the corrosion resistance of the coatings. The decrease in current density and the improved resistance to corrosion observed in the coated samples, as compared to the uncoated Ti-6Al-4V, demonstrate the corrosion-inhibiting effects of anodizing. The integration of Si4+ ions in the structure of HAP caused the size of nanoparticles to decrease from 16.23 nm to 11.67 nm, and the surface roughness of the produced coatings exhibited a decrease from 29.18 to 5.65 nm. In the Nyquist plots, the 5 % Si4+-doped HAP coating displayed the highest Rct value of 17.99 MΩ.cm2 compared to the bare Ti-6Al-4V with a resistance of 0.13 MΩ.cm2. The 5 % Si4+-doped HAP coating was chosen as the optimal sample based on the study results. The results of this work show that surface modification with Si4+-doped HAP coatings is a promising approach for improving the functionality of the Ti-6Al-4 V alloy for biomedical applications.

Influence of deposition temperature on the structure and functional properties of Mg doped hydroxyapatite coatings deposited on manufactured AZ31B alloy substrates by RF magnetron sputtering

In this paper, we study the effect of deposition temperature on the structural and nanomechanical properties on the degradation and bioactivity behaviour of Mg doped hydroxyapatite (HAP) deposited on AZ31B alloy substrates extracted by parts manufactured according to the prostheses production route. The coatings were prepared by RF (Radio Frequency) magnetron sputtering technique at room temperature (RT) and 200 °C, respectively. By adding Mg into the HAP matrix, the hardness and elastic modulus values of the coatings have significantly improved as compared to the bare HAP, the highest H3/E2 ratio of 0.022 being obtained for the HAP + Mg at 200 °C. XRD analysis showed the presence of an α-Mg hexagonal structure for the uncoated AZ31B alloy, while the GIXRD patterns revealed the presence of HAP and Mg in the coated samples. The crystallinity degree of HAP is not changed by Mg addition, while the apatite structure was preserved for all investigated coatings. All investigated samples exhibited typical IR bands of phosphate, carbonate, and hydroxyl functional groups, confirming the formation of apatite phases. By increasing the deposition temperature from room temperature up to 200 °C, the electrochemical behaviour of the coatings, in simulated body fluid and Dulbecco's Modified Eagle Medium, is improved obtaining more electropositive values for corrosion potential, smaller current densities, and higher polarization resistance. The coatings deposited at 200 °C showed the best electrochemical behaviour. Also, by increasing the deposition temperature and incorporating Mg into HAP matrix, the hardness and elastic modulus are increased by more than two-fold, as compared to pure HAP. Furthermore, all coatings deposited on AZ31B alloys are suited for further coating with a mussel-derived surface-binding peptides, but the coatings deposited at 200 °C led to the most regular peptide distribution on the surface. Overall, the results indicated that the biodegradation of HAP + Mg based coatings and the AZ31B alloys can be controlled according to the current clinical needs within implantology field.

Rare transition metal doped hydroxyapatite coating prepared via microwave irradiation improved corrosion resistance, biocompatibility and anti-biofilm property of titanium alloy

Here, we synthesized niobium doped hydroxyapatite (Nb-HAP) coatings on grade-5 titanium (Ti6Al4V) alloy sheets via microwave irradiation for the improvement of its biocompatibility and corrosion resistance with excellent antibiofilm function. The functionalized coated sample confirmed the presence of calcium deficient hydroxyapatite (HAP) containing niobium (Nb). The coating was observed to be denser, thicker and crystalline after doping. The average roughness of the surface was enhanced and became more hydrophilic with the functionalization of Nb. Moreover, the doping was found to have greatly improved the corrosion resistance of the substrates. The apatite layer on the Ti alloy surface revealed to adsorb more protein and enhanced the cell survival by more than 30 %. The presence of Nb in the coating ensured anti-biofilm property against both gram -ve and gram +ve bacteria strains. An improved hemocompatibility towards goat erythrocytes and cytocompatibility towards human keratinocyte cells were also evident in the post coating state. Hence, the microwave-assisted preparation of Nb doped HAP coating not only could improve the physical traits of the substrate, but could enhance the biocompatibility of bone implant as well. Furthermore, the microwave irradiation techniques used here might make the process faster and economical for efficient bioactive HAP coating deposition on Ti alloy. • Microwave assisted niobium doped HAP coating was deposited on Ti alloy sheet. • The doping improved crystallinity and hydrophilicity of the coated surface. • Reinforcement of niobium improved the corrosion resistance of the metal alloy. • The coatings were noncytotoxic, hemocompatible and resistant to bacterial growth.

Effects of silver/selenium/chitosan doped hydroxyapatite coatings on REX-734 alloy: Morphology, antibacterial activity, and cell viability

The goal of this study was to improve the antibacterial activity and cell viability of the Rex-734 alloy in biomedical applications. Various biocomposite coatings, such as single-layer hydroxyapatite (HAp), HAp/silver(Ag), and HAp/selenium(Se)/chitosan(Chit), were applied to Rex-734 alloy at various film thicknesses. The surface coatings were characterized by scanning electron microscopy, SEM, EDX, XRD and coating thickness and hardness of surface coatings were measured. The in vitro antibacterial activities of the coated and uncoated substrates were tested against Esherichia coli JM 103 and Staphylococcus aureus ATCC29293. In vitro cell–material interactions using Saos-2 osteoblast cells were characterized by the 3-(4,5-dimethylthiazol2-yl)− 2,5-diphenyltetrazolium bromide (MTT) assay for cell viability. The post-coating sintering parameters were shown to have a significant effect on the surface morphology. When compared to single HAp and HAp/Ag coatings, Se and Chit additions to HAp powders revealed good crack-free coating surfaces. Crack-free coating morphologies were achieved with a sintering speed of 3 °C/min. While single-HA coatings had an antimicrobial efficiency of 83% against E. coli, this value increased to 94% with Ag additive and to 85% with Se additive. Similarly, Ag and Se additives improved HAp's antimicrobial efficiency against Staphylococcus aureus. Cell viability decreased in the HAp/Ag coating at 86.5% and 90.93%, but increased significantly (p < 0.05) in the HA/Se-Chit coating at 137,43% and 158.23% at the end of the first and seventh days of incubation, respectively. The addition of Ag/Se/Chit to HAp increased the viability of the Rex-734 cells. Furthermore, it was revealed that the HAp-doped Se/Chit duplex biocomposite coating groups increased bone cell viability at much higher rates than the single-layer HAp coatings.

In vivo osteogenesis of plasma sprayed ternary-ion doped hydroxyapatite coatings on Ti6Al4V for orthopaedic applications

Plasma-sprayed hydroxyapatite (HAp) coated metallic implants for orthopaedic and dental application have some inherent shortcomings like brittleness, low fracture toughness, poor tensile strength, slow osseointegration rate and poor antimicrobial properties. To mitigate these shortcomings, we have envisaged and developed specific compositions of Sr, Zn, Ag and F multi-ion doped HAp earlier employing Taguchi statistical principle. The aim of the present investigation is to study the feasibility of plasma spray-coated metallic implants focusing specifically on two specific compositions {based on Sr–Zn–F-HAp – (D1HAp-Ti) and Sr–Zn–Ag-HAp (D2HAp-Ti)} as envisaged earlier. Performance of the above compositions was studied and compared with no coating and pure HAp coated implants. The comprehensive study included detailed material development and characterization up to in vivo pre-clinical trial. Finally, free-flowing granules (75–104 μm) of multi-ion doped HAp were used for plasma spray coating on Ti6Al4V substrate and analyzed the effect of multi-ion doping on HAp. Interestingly, XRD showed presence of HAp as main phase in all cases except undoped HAp coating where secondary phases like α-TCP and β-TCP could also be traced. FTIR study confirmed basic functional groups of HAp for all cases. Scratch adhesion of coating as well as microhardness was found to be increased substantially by multi-ion doping The result from corrosion resistance and SBF immersion test clearly exhibited multi-ion doped HAp coated implant’s superior property co over undoped HAp coating. In vivo implantation of these implants in animal femur defect model and follow up investigation up to 2 months with micro-CT, histology, radiology and fluorochrome labelling showed enhanced osseointegration of multi-ion doped samples as compared to bare, and control samples. . Hence, a multi-ion doped HAp coated titanium substrate can be used as a promising implant coating material for orthopaedic applications.

Effects of Silver/Selenium/Chitosan Doped Hydroxyapatite Coatings on Rex-734 Alloy: Morphology, Antibacterial Activity, and Cell Viability

Effects of Silver/Selenium/Chitosan Doped Hydroxyapatite Coatings on Rex-734 Alloy: Morphology, Antibacterial Activity, and Cell Viability

Rare Transition Metal Doped Hydroxyapatite Coating Prepared Via Microwave Irradiation Improved Corrosion Resistance, Biocompatibility and Anti-Biofilm Property of Titanium Alloy

Rare Transition Metal Doped Hydroxyapatite Coating Prepared Via Microwave Irradiation Improved Corrosion Resistance, Biocompatibility and Anti-Biofilm Property of Titanium Alloy

Biocompatibility and Antibiofilm Properties of Samarium Doped Hydroxyapatite Coatings: An In Vitro Study

The implant-related infection as a consequence of bacterial adherence and biofilm formation remains one of the main causes of implant failure. Grace to recent advances in materials science, their great mechanical properties and their biocompatibility (both in vitro and in vivo), antibacterial coatings have gradually become a primary component of the global strategy for preventing microbial colonization. In the present work, novel antibacterial coatings containing hydroxyapatite nanoparticles doped with two different concentrations of samarium (5SmHAp and 10SmHAp) were obtained on Si substrates using the dip coating method. The morphology and physicochemical properties of these modified surfaces were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). In addition, their antimicrobial effects and biocompatibility were assessed. The results showed a continuous and homogeneous layer, uniformly deposited, with no cracks or impurities. 5SmHAp and 10SmHAp surfaces exhibited significant antibiofilm activity and good biocompatibility without inducing cytotoxic effects in human gingival fibroblasts. All these findings indicate that samarium doped hydroxyapatite coatings could be great candidates for the development of new antimicrobial strategies.

Multi-metal ions doped hydroxyapatite coatings via electrochemical methods for antibacterial and osteogenesis

The Hydroxyapatite (HA) coating on the surface of titanium (Ti) with good bioactivity for osseointegration ability, however, the lack of antibacterial properties. In this study, the pulse electrochemical method was used to oxidize and polymerize pyrrole (Py) into polypyrrole (PPy) in situ, and PPy was used as the regulator of HA nanoparticles (HA-NPs) and metal particles to construct uniform PPy@HA/ZnO-Cu, PPy@HA/ZnO-Ag, PPy@HA/Ag-Cu, and PPy@HA/ZnO-Ag-Cu nanocomposite coatings on the Ti substrate. The antibacterial rates of four groups of composite coatings against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) were all 100%. The PPy@HA/ZnO-Ag composite coating could promote the growth and proliferation of Vascular Endothelial Cells (VECs) and Bone Marrow Mesenchymal Stem Cells (BMSCs). Therefore, the PPy@HA/ZnO-Ag composite coating has the best osteoinductive ability among all the groups, excellent antibacterial property, angiogenic and osteogenic capability, which can be used as an ideal implant coating.

Antimicrobial Properties of Samarium Doped Hydroxyapatite Suspensions and Coatings

Post-implant infections are a major health problem, and it is well-known that treating them with conventional drugs is accompanied by many disadvantages. The development of new biomaterials with enhanced antimicrobial properties are of major interest for the scientific world. The aim of this study was to synthesize and characterize hydroxyapatite doped with Samarium (Ca10−xSmx(PO4)6(OH)2, xSm = 0.05, 5Sm-HAp) suspensions, pellets and coatings. The 5Sm-HAp coatings on Si substrates were obtained by rf magnetron sputtering technique. The different techniques such as ultrasound measurements, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Glow Discharge Optical Emission Spectroscopy (GDOES), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were used to examine the obtained coatings. The results showed that the doped Sm ions entered the structure of hydroxyapatite successfully and Sm ions was uniformly doped onto the surface of the support. The depth profile curves of Ca, P, O, H, Ce and Si elements exhibit their presence from a surface to substrate interface as function of sputtering time. XPS analysis indicated as calcium-phosphate structures enriched in Sm3+ ions. Furthermore, the antimicrobial properties of the 5Sm-HAp suspensions, targets and coatings were assessed against Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923 and Candida albicans ATCC 10231. The results of the antimicrobial assays highlighted that that the samples presented a strong antimicrobial activity against the tested microbial strains. The results showed that the coatings after 48 h of incubation inhibited the growth of all tested microbial strains under the value of 0.6 Log CFU/mL. This study shows that the 5Sm-HAp samples are good candidates for the development of new antimicrobial agents.

Hydroxyapatite – barium/strontium titanate composite coatings for better mechanical, corrosion and biological performance

The effect of piezoalectricity from piezoelectric materials promotes the growth of bone. However, the material should be subjected to stress before it can produce an electric charge that promotes repair of bones and reconstruction of it conducive to healing of fracture. This mainly includes the coatings, hardness, tribometer and biological tests on the composite material. Initially the widely used stainless steel metal of 316L grade is selected and then it was cut into small samples of specific dimensions 10 mm × 10 mm × 4.5 mm and 20 mm × 10 mm × 4.5 mm. Then BaTiO3 (Barium titanate) doped hydroxyapatite (HA) and SrTiO3 (Strontium titanate) doped HA powders were coated on the stainless steel samples by Plasma Spray Technique. X Ray Diffraction was done to characterise the material. Vickers hardness test was performed to check the hardness of various coated samples. Then tribology was performed using linear reciprocating test to examine the wear resistance of the coated sample. The effect of piezoelectricity of BaTiO3 and SrTiO3 promoted the growth of osteoblasts and interaction with HA, which was better than the piezoelectric effect of HA alone. The result show that BaTiO3 doped hydroxyapatite and SrTiO3 doped hydroxyapatite coatings could enhance the bio mineralization (calcium precipitation) process.

Physico-Chemical Properties and In Vitro Antifungal Evaluation of Samarium Doped Hydroxyapatite Coatings

Hydroxyapatite (HAp) and samarium doped hydroxyapatite, Ca10−xSmx(PO4)6(OH)2, xSm = 0.05, (5SmHAp), coatings were prepared by sol-gel process using the dip coating method. The stability of 5SmHAp suspension was evaluated by ultrasound measurements. Fourier transform infrared spectroscopy (FTIR) was used to examine the optical characteristics of HAp and 5SmHAp nanoparticles in suspension and coatings. The FTIR analysis revealed the presence of the functional groups specific to the structure of hydroxyapatite in the 5SmHAp suspensions and coatings. The morphology of 5SmHAp nanoparticles in suspension was evaluated by transmission electron microscopy (TEM). Moreover, scanning electron microscope (SEM) was used to evaluate the morphology of nanoparticle in suspension and the morphology of the surface on the coating. The SEM and TEM studies on 5SmHAp nanoparticles in suspension showed that our samples consist of nanometric particles with elongated morphology. The SEM micrographs of HAp and 5SmHAp coatings pointed out that the coatings are continuous and homogeneous. The surface morphology of the 5SmHAp coatings was also assessed by Atomic Force Microscopy (AFM) studies. The AFM results emphasized that the coatings presented the morphology of a uniformly deposited layer with no cracks and fissures. The crystal structure of 5SmHAp coating was characterized by X-ray diffraction (XRD). The surface composition of 5SmHAp coating was analyzed by X-ray photoelectron spectroscopy (XPS). The XRD and XPS analysis shown that the Sm3+ ions have been incorporated into the 5SmHAp synthesized material. The antifungal properties of the 5SmHAp suspensions and coatings were studied using Candida albicans ATCC 10231 (C. albicans) fungal strains. The quantitative results of the antifungal assay showed that colony forming unity development was inhibited from the early phase of adherence in the case of both suspensions and coatings. Furthermore, the adhesion, cell proliferation and biofilm formation of the C. albicans were also investigated by AFM, SEM and Confocal Laser Scanning Microscopy (CLSM) techniques. The results highlighted that the C. albicans adhesion and cell development was inhibited by the 5SmHAp coatings. Moreover, the data also revealed that the 5SmHAp coatings were effective in stopping the biofilm formation on their surface. The toxicity of the 5SmHap was also investigated in vitro using HeLa cell line.

Production, Characterization and Surface Properties of Sr Doped Hydroxyapatite Coating on Magnesium Alloy by Hydrothermal Method

In this study, the surface of AZ91D magnesium alloy was coated with undoped and at different ratios strontium doped hydroxyapatite. Coatings were carried out at 180 °C in 3 hours. The surface roughness of the coated samples was determined and the microstructure of the phases forming on the coated surfaces were examined by scanning electron microscopy (SEM). The chemical composition of the phases formed on the coated surfaces was determined by energy dispersed X-ray spectroscopy (EDS). The phases formed on the surfaces were characterized by X-Ray diffraction (XRD) and Fourier transform infrared spectrometry (FT-IR). The AZ91D magnesium alloy was coated successfully with undoped and strontium doped hydroxyapatite by hydrothermal method. The highest surface roughness value was measured as Ra = 8.255 µm in 15% strontium doped sample. It was determined that the (Ca + Sr) / P ratios of the coatings were higher than the stoichiometric ratio of hydroxyapatite, 1.67. It was determined that the closest coating to the stoichiometric ratio was 10% Sr doped coating.

Obtaining and Characterizing Thin Layers of Magnesium Doped Hydroxyapatite by Dip Coating Procedure

A simple dip coating procedure was used to prepare the magnesium doped hydroxyapatite coatings. An adapted co-precipitation method was used in order to obtain a Ca25−xMgx(PO4)6(OH)2, 25MgHAp (xMg = 0.25) suspension for preparing the coatings. The stabilities of 25MgHAp suspensions were evaluated using ultrasound measurements, zeta potential (ZP), and dynamic light scattering (DLS). Using transmission electron microscopy (TEM) and scanning electron microscopy (SEM) information at nanometric resolution regarding the shape and distribution of the 25MgHAp particles in suspension was obtained. The surfaces of obtained layers were evaluated using SEM and atomic force microscopy (AFM) analysis. The antimicrobial evaluation of 25MgHAp suspensions and coatings on various bacterial strains and fungus were realized. The present study presents important results regarding the physico-chemical and antimicrobial studies of the magnesium doped hydroxyapatite suspensions, as well as the coatings. The studies have shown that magnesium doped hydroxyapatite suspensions prepared with xMg = 0.25 presented a good stability and relevant antimicrobial properties. The coatings made using 25MgHAp suspension were homogeneous and showed remarkable antimicrobial properties. Also, it was observed that the layer realized has antimicrobial properties very close to those of the suspension. Both samples of the 25MgHAp suspensions and coatings have very good biocompatible properties.

Magnesium and fluoride doped hydroxyapatite coatings grown by pulsed laser deposition for promoting titanium implant cytocompatibility

Magnesium (Mg) and fluoride (F) ions hold promising perspective for bone tissue regeneration by stimulating osteoblast cells proliferation and differentiation. Inspired by bone structure, Mg/F doped hydroxyapatite (HA) coatings with rapid surface apatite deposition ability and robust cytocompatibility will be an ideal bioactive coating for the surface functionalization of titanium implants. In this study, F doped HA (F-HA) coating, Mg doped HA (Mg-HA) coating and two superimposed double (Mg-F-HA) coatings were fabricated on titanium substrate by using pulsed laser deposition. In vitro bioactivity studies showed that three coatings exhibited different microstructure after soaking for 7 days: rice-like nano-porous structure (F-HA coating), 3D porous network structure (Mg-HA coating) and an ordered linear structure similar to cancellous bone (Mg-F-HA coating). For Mg-F-HA coating, it can better promote the transformation from apatite-like to HA phase due to the synergistic effect of Mg and F. Cell viability studies indicate that Mg/F doped HA coating can hold a good biocompatibility without cytotoxicity and improve the interfacial bioactivity of titanium substrate, specifically, both on regulation of biodegradation rate and good cellular proliferation. In summary, Mg/F doped HA structure yields a sustained bioactive coating for surface modification of titanium implant for rapid cell proliferation.

Effects of Aloe Vera Gel Extract in Doped Hydroxyapatite-Coated Titanium Implants on in Vivo and in Vitro Biological Properties.

Hydroxyapatite-coated titanium alloys have been a popular choice as bone implants for load-bearing applications for the compositional similarity of hydroxyapatite to natural bone. The limited osteoinductive properties exhibited by the hydroxyapatite (HA) coatings have led to the incorporation of growth factor or dopants for improved osseointegration. This study aims to investigate the effects of a naturally occurring aloe vera gel extract, acemannan, in doped hydroxyapatite coatings on the in vitro osteoblast cell viability and in vivo new bone formationin a rat distal femur model. Silver oxide and silica-doped hydroxyapatite coatings were developed by the induction plasma spray coating method on Ti alloys to introduce antibacterial properties along with induction of angiogenic properties, respectively. The doped coating was further consecutively dip coated with acemannan to analyze its effects on the in vivo early stage osseointegration and chitosan to control the burst release of the acemannan from the calcium phosphate matrix. The results show controlled release of acemannan from the chitosan coatings, with enhanced osteoblast cell viability by the incorporation of acemannan in vitro. Improved osseointegration with a seamless implant interface and improved new bone formation was noted by the acemannan and chitosan coating in vivo, 5 weeks after implantation. Our results demonstrate the efficacy of a combination of natural medicine and naturally occurring polymer in a doped hydroxyapatite-coated titanium implant on the bone tissue regeneration for load-bearing orthopedic applications.

Enhanced osteogenic protein expression on human osteoblast-osteoclast co-culture system using doped hydroxyapatite plasma coatings for orthopedic and dental applications

For decades, research has been attributed to the monoculture of either mesenchymal stem cells (MSCs) or monocytes to differentiate into osteoblasts (OBs) and osteoclasts (OCs) respectively, however, this is far from being realistic. For improved research in the field of biomaterials, the balance between OBs and OCs needs to be investigated simultaneously on in vitro models for a better understanding and prediction of the bone remodeling process in vivo. The study aims to investigate the effects of Mg+2 and Sr+2 dopant in hydroxyapatite coating on the simultaneous differentiation of human MSCs and Tamm Horsfall Protein 1 (THP-1) monocytes into OBs and OCs respectively. We hypothesize that a cultivation regime can be established to show simultaneous proliferation and differentiation of the MSCs and monocytes into OBs and OCs. Also, the presence of Sr+2 and Mg+2 will induce faster bone remodeling and demonstrate enhanced osteogenic properties. Doped hydroxyapatite coatings were fabricated on CpTi substrates using plasma spray coating technique and the influence of dopants on the in vitro OB−OC co-culture was studied by specific marker genes, namely OPG, RANKL, RUNX2, and ACP5. Comparison amongst the expressions of genes reveals the differentiation of the primary cells as early as 5-day time-point. Downregulation of RUNX2 and ACP5 in the doped HA coated samples at 15-day time-point are a proof of the effective role of the dopants in the enhancement of bone remodeling. This study shows the possibility of simultaneous culturing of human OB and OC precursors and demonstrates the efficacy of dopants in the pace change of bone remodeling for bone tissue engineering applications.

In vitro evaluation of Ag doped hydroxyapatite coatings in acellular media

The goal of the present contribution is to show what is the effect of Ag addition on in vitro bioactivity and degradation characteristics of hydroxyapatite (HAP) in simulated body fluid (SBF), Dulbecco's Modified Eagle's medium (DMEM) and phosphate buffer solution (PBS) over a period of immersion at 37 ± 0.5 °C ranged from 1 to 21 days. Also, the corrosion investigations in all three media were carried out at 37 ± 0.5 °C. The results showed that the coatings behaviour is modulated with respect to the testing media and indicated that the Ag addition into hydroxyapatite has enhanced the general behaviour of HAP by either preventing and/or reducing dissolution of the HAP in SBF and DMEM solutions, while in PBS media the Ag addition contributed to a very slow degradation of hydroxyapatite. Thus, it can be said that the Ag addition into HAP enhances the overall chemical stability and behaviour in acellular media.

In Vitro Characterizations of Si4+ and Zn2+ Doped Plasma Sprayed Hydroxyapatite Coatings Using Osteoblast and Osteoclast Coculture.

Osteoporosis is one of the most commonly identified bone disorders, which leads to an enhanced risk of bone fracture, especially for the older population. Hydroxyapatite (HA) coated titanium (Ti)alloys have been used widespread for load bearing applications like hip or knee replacements owing to their compositional similarity to natural bone; however, incorporation of osteoinductivity is still a challenge. The objective of this study is to evaluate the effects of SiO2 and ZnO as dopants in HA coated Ti alloys on cellular osteoporotic conditions mimicked by an in vitroosteoblast and osteoclast coculture model. HA, Si-HA, and Zn-HA coatings showed adhesive bond strengths of 25.7 ± 1.9 MPa, 23.8 ± 2.3 MPa, and 22.9 ± 3.5 MPa, respectively. To study the effects of doped HA coatings on the simulated osteoporotic cellular condition, human mesenchymal stem cells (hMSCs) and monocytes (THP-1) were seeded simultaneously in a ratio of 1:4, respectively. Gene expressions studies were carried out with marker genes showing that the presence of the dopants in the HA coating enhanced osteoblast proliferation along with diminishing cell growth of osteoclasts. This study demonstrates the promising effects of SiO2 and ZnO in plasma sprayed HA coatings on alleviating osteoporosis cellular conditions, which can potentially be used for load-bearing implants in aging patients whose bone resorption is more dominant than bone formation.

Laser synthesis of iron nanoparticle for Fe doped hydroxyapatite coatings

Abstract Thin films of iron doped hydroxyapatite have been prepared by nanosecond Pulsed Laser Deposition (PLD). The composite target used for the deposition has been obtained by mixing commercial hydroxyapatite powder with iron-based nanoparticles produced by femtosecond laser ablation in liquid (LAL) (4% of iron nanoparticles). In fact, LAL technique allows to obtain metallic nanostructures without any toxic chemicals and reagents, with a green approach that is crucial for application in biological and medical technologies. Films have been prepared with substrate temperature growing from room temperature (RT) to 500 °C. The effect of deposition temperature on morphology, composition and structural properties of coatings has been investigated. Films deposited at higher temperature result dense and crystalline, they present microscale and nanoscale structures, an average surface roughness of 0.3 μm and magnetic properties suitable for biomedical applications.