Hydroxyapatite Coatings Research Articles

Correction: Influence of Plastic Deformation and Hydroxyapatite Coating on Structure, Mechanical, Corrosion, Antibacterial and Cell Viability Properties of Zinc Based Biodegradable Alloys

Correction: Influence of Plastic Deformation and Hydroxyapatite Coating on Structure, Mechanical, Corrosion, Antibacterial and Cell Viability Properties of Zinc Based Biodegradable Alloys

In Vitro Wear of Titanium Reinforced Hydroxyapatite Coatings in Simulated Body Fluid

Abstract Titanium-reinforced hydroxyapatite (Ti-HAP) coatings have been deposited over 254 SMO stainless steel using a low-velocity oxygen fuel technique. FESEM, XRD, Vickers microhardness, and shear strength tests have been performed to characterize the developed coatings. Further, in vitro wear behaviors of the coatings were evaluated using a pin-on-disc wear tester in simulated body fluid. The results reveal that 40Ti-HAP coating possesses superior wear resistance compared to 60Ti-HAP, Ti, and HAP coatings, attributed to higher surface hardness and higher shear strength values. Amongst the tested samples, the friction coefficient was lower for Ti coating, followed by 60Ti-HAP composite coating. The surface roughness was a prominent factor in reducing the friction coefficient of coating samples. Local detachment and brittle fracture were the dominant wear modes in Ti-HAP coating, whereas an additional micro-plowing wear mode was observed in pure hydroxyapatite and titanium coating.

Enhanced mechanical, corrosion, and tribological properties of hydroxyapatite coatings for orthopedic and dental applications

Biomedical coatings were elaborated by pulsed electrodeposition with hydrogen peroxide (H2O2) into electrolytes on Ti6Al4V substrates, and the effect of H2O2 concentration on the electrolyte and the heat treatment was studied. The experimental procedures employed in this study produce a consistent hydroxyapatite coating. This coating is well-suited for use in bio-implants, as it enhances the integration of the implant with surrounding bone tissue and improves the mechanical performance. The coatings' surface morphology and chemical composition were assessed using scanning electron microscopy (SEM) in conjunction with energy-dispersive X-ray spectroscopy (EDXS) for x-ray microanalysis. X-ray diffraction (XRD) was also utilized to identify the phases and composition of the coatings. Nanoindentation and scratch tests were conducted to analyze the nanomechanical properties and adhesion behavior. Potentiodynamic polarization was employed in the Ringer solution to evaluate the corrosion resistance and replicate the conditions of the human body environment. The results of our thorough investigation revealed that employing pulsed electrodeposition with 9 % H2O2 in the electrolyte, combined with subsequent heat treatment, facilitated the creation of coatings comprising two distinct phases: stoichiometric hydroxyapatite (HAP) and β-tricalcium phosphate (β-TCP). Our meticulous research underscores the significance of this process in achieving these specific coating compositions. Under these tests listed above, this composite demonstrated favorable mechanical properties (E = 30.45 GPa and H = 72.2 MPa). It also exhibited superior scratch adhesion and a critical load of 23 MPa and 12 N, respectively. Additionally, an improvement in tribological comportment was observed, and the wear volume decreased from 4.15 106 μm3 to 2.44 106 μm3. The HAP coating heat treated with 9 % H2O2 exhibited the highest corrosion resistance, with Ecorr at −0.189 V/SCE and icorr at −1.11 μA cm−2

Surface characteristics and machining rate of SS 316L coating developed using hydroxyapatite-mixed EDM process

Hydroxyapatite (HA) or bioceramic-based coatings on stainless steel (SS) 316L significantly enhance the biofunctionality of the base material's surface. However, HA's low thermal conductivity and brittleness limit its effectiveness as a coating material. This study investigates HA coating on SS 316L using electric discharge machining (EDM) with varying discharge energies and powder concentrations. Surface morphology, elemental composition, and phase analysis of untreated and coated samples were characterised using field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX), and X-ray diffraction (XRD). The results demonstrate that the HA-assisted EDM process creates a coating comprising biocompatible oxides, phosphates, carbides, and intermetallic compounds. The coating exhibits a thin resolidified layer of 10.74 μm, characterised by redeposited spherical debris, shallow cavities, and a surface texture of 2.688 μm. The layer's hydrophilic nature is confirmed by a minimum contact angle of 47.68°. Taguchi analysis indicates that the machining rate is optimised at an HA powder concentration of 16 g/l, with peak current and HA powder concentration being the most influential parameters affecting resolidified layer thickness, surface texture, and wetting angle. The research intends to motivate SS 316L medical device manufacturers to implement the HA-assisted EDM process for bioimplant's dual machining and coating.

Physico-Chemical Properties of Copper-Doped Hydroxyapatite Coatings Obtained by Vacuum Deposition Technique.

The hydroxyapatite and copper-doped hydroxyapatite coatings (Ca10-xCux(PO4)6(OH)2; xCu = 0, 0.03; HAp and 3CuHAp) were obtained by the vacuum deposition technique. Then, both coatings were analyzed by the X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and water contact angle techniques. Information regarding the in vitro antibacterial activity and biological evaluation were obtained. The XRD studies confirmed that the obtained thin films consist of a single phase associated with hydroxyapatite (HAp). The obtained 2D and 3D SEM images did not show cracks or other types of surface defects. The FTIR studies' results proved the presence of vibrational bands characteristic of the hydroxyapatite structure in the studied coating. Moreover, information regarding the HAp and 3CuHAp surface wettability was obtained by water contact angle measurements. The biocompatibility of the HAp and 3CuHAp coatings was evaluated using the HeLa and MG63 cell lines. The cytotoxicity evaluation of the coatings was performed by assessing the cell viability through the MTT assay after incubation with the HAp and 3CuHAp coatings for 24, 48, and 72 h. The results proved that the 3CuHAp coatings exhibited good biocompatible activity for all the tested intervals. The ability of Pseudomonas aeruginosa 27853 ATCC (P. aeruginosa) cells to adhere to and develop on the surface of the HAp and 3CuHAp coatings was investigated using AFM studies. The AFM studies revealed that the 3CuHAp coatings inhibited the formation of P. aeruginosa biofilms. The AFM data indicated that P. aeruginosa's attachment and development on the 3CuHAp coatings were significantly inhibited within the first 24 h. Both the 2D and 3D topographies showed a rapid decrease in attached bacterial cells over time, with a significant reduction observed after 72 h of exposure. Our studies suggest that 3CuHAp coatings could be suitable candidates for biomedical uses such as the development of new antimicrobial agents.

Early Peri-Implant Bone Healing on Laser-Modified Surfaces with and without Hydroxyapatite Coating: An In Vivo Study.

(1) Objective: The aim of this study was to assess the biological behavior of bone tissue on a machined surface (MS) and modifications made by a laser beam (LS) and by a laser beam incorporated with hydroxyapatite (HA) using a biomimetic method without thermic treatment (LHS). (2) Methods: Scanning electron microscopy coupled with energy-dispersive X-ray spectrometry (SEM/EDX) was performed before and after installation in the rabbit tibiae. A total of 20 Albinus rabbits randomly received 30 implants of 3.75 × 10 mm in the right and left tibias, with two implants on each surface in each tibia. In the animals belonging to the 4-week euthanasia period group, intramuscular application of the fluorochromes calcein and alizarin was performed. In implants placed mesially in the tibiofemoral joint, biomechanical analysis was performed by means of a removal torque (N/cm). The tibias with the implants located distally to the joint were submitted for analysis by confocal laser microscopy (mineral apposition rate) and for histometric analysis by bone contact implant (%BIC) and newly formed bone area (%NBA). (3) Results: The SEM showed differences between the surfaces. The biomechanical analysis revealed significant differences in removal torque values between the MSs and LHSs over a 2-week period. Over a 4-week period, both the LSs and LHSs demonstrated removal torque values statistically higher than the MSs. BIC of the LHS implants were statistically superior to MS at the 2-week period and LHS and LS surfaces were statistically superior to MS at the 4-week period. Statistical analysis of the NBA of the implants showed difference between the LHS and MS in the period of 2 weeks. (4) Conclusions: The modifications of the LSs and LHSs provided important physicochemical modifications that favored the deposition of bone tissue on the surface of the implants.

Microplasma-Sprayed Titanium and Hydroxyapatite Coatings on Ti6Al4V Alloy: in vitro Biocompatibility and Corrosion Resistance

Microplasma-Sprayed Titanium and Hydroxyapatite Coatings on Ti6Al4V Alloy: in vitro Biocompatibility and Corrosion Resistance

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.

Hydroxyapatite Film with Distinctive Roughness for Simulating the Bone Microenvironment and Revealing the Behavior of Metastatic Mammary Cancer.

Breast cancer is a common malignant tumor arising in normal mammary epithelial tissues. Nearly 75% of the patients with advanced mammary cancer develop bone metastases, resulting in secondary tumor growth, osteolytic bone degradation, and poor prognosis. The bone matrix comprises a highly hierarchical architecture and is composed of a nonmineral organic part, a predominantly type-I collagen, and a mineral inorganic part composed of hydroxyapatite (HA) nanocrystals (Ca10(PO4)6(OH)2). Although there has been extensive research indicating that the material properties of bone minerals affect metastatic breast cancer, it remains unclear how the microenvironment of the bone matrix, such as the roughness, which changes as a result of osteolytic bone remodeling, affects this disease. In this study, we created HA coatings in situ on polyelectrolyte multilayers (PEMs) by incubating PEMs in a mixture of phosphate and calcium ions. The HA films with distinctive roughness were successfully collected by controlling the incubation time, which served as the simulated microenvironment of the bone matrix. MDA-MB231 breast cancer cells were cultured on HA films, and an optimal roughness was observed in the adhesion, proliferation, and expression of two cytokines closely related to bone metastasis. This study contributed to the understanding of the effect of the microenvironment of the bone matrix, such as the roughness, on the metastasis behavior of breast cancer.

Fabrication and characterization of hydroxyapatite coatings on anodized magnesium alloys by electrochemical and chemical methods intended for biodegradable implants

The fabrication of hydroxyapatite (HAP)/MgO composite coatings on Mg alloy is crucial for enhancing the corrosion resistance and biocompatibility of biomedical implants. In this study, we aimed to investigate the effects of two different surface modification methods, i.e., electrochemical (electrodeposition, ED) and chemical (solution treatment, ST), on the phase structure, degradation properties, and biocompatibility of the composite coatings in comparison to the anodized coating. The surface morphologies and crystalline structures of the coatings were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Subsequently, the degradation rate of the coatings in simulated body fluid were comprehensively evaluated by using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and scanning electrochemical microscopy (SECM) tests. Additionally, in-vitro cell proliferation assays were employed to quantitatively assess the biocompatibilities of the coatings. The results showed that both ED and ST methods were effective in depositing HAP on anodized Mg alloy, resulting in different surface morphologies with hydroxyapatite layer thicknesses of 2.71 μm and 3.56 μm, respectively. In this way, the HAP-deposited coatings exhibited improved corrosion resistances and biocompatibilities compared with those of the anodized coating. Specifically, the ST-deposited composite film displayed superior degradability and biocompatibility which was attributed to its filiform surface morphology and thicker HAP layer. Overall, the present study demonstrates the potential of HAP/MgO composite coatings for biomedical applications, with implications for the development of advanced implant materials with improved performance and biocompatibility.

Modulating the corrosion performance of magnesium alloys through hydroxyapatite coating

Magnesium and its alloys have attracted attention as medical bone implant materials due to their excellent biocompatibility, bone-like mechanical properties, and degradability. However, the clinical application of magnesium is limited by the fact that it corrodes too quickly in body fluids, leading to premature mechanical failure. Surface hydroxyapatite coatings can significantly reduce the initial corrosion of magnesium alloys, but suffer from the problems of non-dense coatings, many defects and poor adhesion strength to the substrate. In this study, we propose femtosecond laser construction of microemulsion cone structures on the surface of magnesium alloys to significantly enhance the densities and thicknesses of the coatings, as well as to improve the bonding strength of the coatings to the substrate, which ultimately reduces the corrosion rate. The corrosion rate of modified hydroxyapatite coating in simulated body fluid is only 0.146 mm/y, and it has the ability to rapidly induce hydroxyapatite mineralization and promote osteoblast proliferation. Furthermore, the surface morphology, chemical composition, and wettability of the laser-modified Mg alloy were analyzed. It was demonstrated that the microstructure and thin oxide layer formed on the surface of the magnesium alloy could provide more sites for HA nucleation, which promotes the deposition and growth of HA and the existence of a mechanical interlocking effect with the substrate. The application of femtosecond laser surface modification represents a rapid and efficacious approach to enhance the quality of hydroxyapatite coatings. This method has successfully controlled the corrosion rate of magnesium alloys with excellent biocompatibility, thereby overcoming potential obstacles to the use of magnesium alloys in clinical applications.

In vitro Biomineralization Ability of Magnesium-Doped Coral Hydroxyapatite Coating Prepared by Pulsed Laser Deposition

Coral hydroxyapatite (CHA) is a calcium phosphate that has a similar inorganic composition to human bone and the porous structure of coral stone. Due to its interconnected network like pore structure, it can serve as a framework for bone conduction. In this study, CHA films and Mg-CHA films were deposited on titanium and silicon substrates by Pulsed laser deposition, and then the films were heat treated respectively. Studies on the adhesion of the coating showed that the heat-treated Mg-CHA film adhered better to the titanium substrate. The experimental study on biomineralization in vitro showed that a small amount of porous structure appeared in the heat-treated Mg-CHA after immersion in SBF for three days, and the porous structure was visible after immersion for seven days. After 14 days, a new apatite layer formed on the surface. This suggested that magnesium undergoes chemical corrosion in SBF, leading to rapid ion exchange, which results in the formation of porous structures and promotes the development of an apatite-like layer. In summary, the heat-treated Mg-CHA films had superior biomineralization properties.

Hydroxyapatite-whitlockite composite coating as a biomimetic material for bone integration

Mg deficiency contributes to disrupting mineral metabolism and impairing bone growth. Continuous supply of Mg2+ from orthopedic implant has emerged as a therapeutic strategy for fracture healing. However, therapeutic efficiency of Mg2+ is concentration-dependent and the controlled Mg2+ delivery is challenging. Mg whitlockite (WH) is Mg2+ reservoir in bone mineral which manipulates Mg2+ release and enhances mechanical strength of natural bone. In this aspect, WH was incorporated into the hydroxyapatite (HAp) coating to endow the coating with Mg2+-release properties and enhance bonding strength to the metal substrate. The HAp/WH composite coating with 30 wt% WH exhibited a two-fold increase in bonding strength than the HAp coating mainly due to the better thermal adaptation of WH to the Ti substrate. The Mg2+-concentration-dependent osteoblastic behaviors were evaluated by using the WH, annealed-treated WH (WH-800) and HAp/WH composite coatings. Compared to HAp and WH-800 coatings, WH and HAp/WH coatings with higher Mg2+ release (4.1–11.5 mM within 7 days) and more negative zeta potential (−36.5 mV and −27.3 mV) exerted greater effects on fibronectin adsorption and unfolding the exposure of RGD motif which facilitated cytoskeleton spreading and enhanced osteoblastic differentiation and mineralization. Considering the difference in Mg2+ release among the WH-containing coatings, our study suggested that 3–12 mM Mg2+in vitro may be optimized. Taken together, the first-time reported HAp/WH composite coating as a biomimetic material shows promise in enhancing bone integration.

Cathodic Synthesis of Strontium-Substituted Hydroxyapatite Coatings

Cathodic Synthesis of Strontium-Substituted Hydroxyapatite Coatings

Corrosion Resistance of Zinc-Doped Hydroxyapatite Coating on Titanium Substrate using Plasma Electrolytic Oxidation for Biomedical Applications

Corrosion Resistance of Zinc-Doped Hydroxyapatite Coating on Titanium Substrate using Plasma Electrolytic Oxidation for Biomedical Applications

Influence of Plastic Deformation and Hydroxyapatite Coating on Structure, Mechanical, Corrosion, Antibacterial and Cell Viability Properties of Zinc Based Biodegradable Alloys

AbstractZinc (Zn)-based biodegradable alloys have been at the forefront of absorbable biomaterial research in recent years due to their high biocompatibility and corrosion rates. The arc melting process was used to produce the Zn–1Cu–1Ag biodegradable alloy. The influence of different plastic deformation rates on the microstructure of the material was examined after the cold rolling at deformation rates of 47% and 61%. The undeformed and deformed alloys have been hydroxyapatite-coated using the electrophoretic deposition process to improve its surface, corrosion, and bioactivity properties. Optical, XRD, SEM, and EDS examinations were used to analyze the samples’ uncoated, coated, and rolled-unrolled forms. The nucleation of the (Ag, Cu)Zn4 secondary phase was formed during the rolling process. Hardness and compression tests were used to determine the mechanical properties of cast and rolled alloys, and in vitro corrosion tests were carried out in simulated body fluid. Antimicrobial and cell viability tests are executed to demonstrate the biocompatibility of the deformed and HA-coated Zn–1Cu–1Ag alloy. The mechanical properties were improved after the rolling process, with the highest results found in 47% of the rolled samples exhibiting a compressive strength of 412.65 ± 0.5 MPa and 61% of the rolled samples exhibiting a hardness value of 88.1 ± 0.5 HV. The samples that were rolled (61%) and coated with hydroxyapatite (HA) exhibited the highest level of corrosion resistance. The antimicrobial tests revealed that the rolled and HA coated Zn1Cu1Ag groups exhibited greater inhibition rates (47 and 61%) compared to the other groups when tested against E. coli. The HA-coated groups exhibited good cell viability ratios, with the maximum viability seen in the rolled and HA-coated group at 47%. Graphical Abstract

Facile fabrication of linezolid/strontium coated hydroxyapatite/graphene oxide nanocomposite for osteoporotic bone defect

Hydroxyapatite (HAp) coatings currently have limited therapeutic applications because they lack anti-infection, osteoinductivity, and poor mechanical characteristics. On the titanium substrate, electrochemical deposition (ECD) was used to construct the strontium (Sr)-featuring hydroxyapatite (HAp)/graphene oxides (GO)/linezolid (LZ) nanomaterial coated with antibacterial and drug delivery properties. The newly fabricated nanomaterials were confirmed by X-ray diffraction analysis (XRD), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) analysis and morphological features were examined by scanning electron microscope (SEM) analysis. The results reveal multiple nucleation sites for SrHAp/GO/LZ composite coatings due to oxygen-comprising moieties on the 2D surface of GO. It was shown to be favorable for osteoblast proliferation and differentiation. The elastic modulus and hardness of LZ nanocomposite with SrHAp/GO/LZ coatings were increased by 67 % and 121 %, respectively. An initial 5 h burst of LZ release from the SrHAp/GO/LZ coating was followed by 14 h of gradual release, owing to LZ's physical and chemical adsorption. The SrHAp/GO/LZ coating effectively inhibited both S. epidermidis and S. aureus, and the inhibition lasted for three days, as demonstrated by the inhibition zone and colony count assays. When MG-63 cells are coated with SrHAp/GO/LZ composite coating, their adhesion, proliferation, and differentiation greatly improve when coated with pure titanium. A novel surface engineering nanomaterial for treating and preventing osteoporotic bone defects, SrHAp/GO/LZ, was shown to have high mechanical characteristics, superior antibacterial abilities, and osteoinductivity.

Hindrances and solutions on the path towards adjoined barium titanate–hydroxyapatite ceramics with uncompromised piezoelectric and biological responses

The synergistic piezoelectric and osteoconductive properties of barium titanate (BT) and hydroxyapatite (HA) could stir the development of a new generation of synthetic bone graft substitutes, with capability for rapid and safe osseointegration. The research focused on two concurrent approaches for coupling the BT and HA materials: (i) conventional sintering of BT-HA powder mixtures; and (ii) functionalization of pre-sintered BT with HA coatings using magnetron sputtering (MS). Irrespective of the BT/HA ratios ranging from 95/5 to 80/20 wt%, nanocrystalline or highly-crystallized nature of the powders, sub-micron- or micron-sized particle dimensions, and sintering temperature, it was observed that the BT-HA reactivity cannot be prevented above 800 °C. At higher temperatures in the range of 1000–1300 °C, HA undergoes decomposition and extensively reacts with BT, leading to the formation of several secondary phases such as CaTiO3, Ba2Ca(PO4)2, BaCa6(PO4)4O, BaCa(PO3)4, and β-Ca2P2O7. As a consequence, the cytocompatibility assessed in fibroblast and osteoblast cell cultures, as well as the piezoelectric response, were significantly altered.Applying HA coatings by MS to the sintered BT ceramics successfully preserved their piezoelectric properties, while also providing an unaltered cytocompatible and osteogenic-prone surface. The HA coatings were fully crystallized at post-deposition annealing temperatures of 550 and 700 °C, achieving crystalline qualities comparable to HA powders sintered at 1100 and 1200 °C, respectively. No reactivity events between BT and HA were observed. Partial reactivity was only noticeable upon annealing at 1000 °C. Therefore, it is suggested that the HA coating of BT is effective in seamlessly coupling the piezoelectric and osteogenic properties of the two constituents without compromise.

Highly bioactive hydroxyapatite coating made by flame spray technique

This research involves fabrication and characterization of flame sprayed hydroxyapatite (HA) coatings on 316 stainless steel substrates where the desirable structure with high porosity can be obtained. Nano-sized HA powder was synthesized and calcined at 600 °C. The subsequent powder was used as feedstock powder for flame spray technique (FS). In-flight particles of HA were spherical with the range of particle size between 3–37 µm. The average coating thickness was 128 µm and the crystalline phases were a mixture of HA and tricalcium phosphate (TCP). Simulated body fluid (SBF) test showed that HA layer was formed after 7 days. Highly bioactive properties were due to high surface area from rough coating and porous structure, which would be beneficial from the flame spray technique. The coating is promising for applications in biomedical field.

Study of Mg-Rich Sulfato-Calcium Hydroxyapatite Coating on Anodized Ti6Al4V-Alloy for Biomedical Applications

Study of Mg-Rich Sulfato-Calcium Hydroxyapatite Coating on Anodized Ti6Al4V-Alloy for Biomedical Applications