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In recent years, many different biomedical implants have been created for prolonged usage within the human body. The number of these implants has been steadily expanding. It is a common practice to use metallic bioimplants as substitutes when attempting to replace human body components in an anatomically acceptable manner. But the metallic bioimplant was mostly made biocompatible by putting a biocompatible coating on its surface and then using the right surface modification techniques. This was the primary method by which the biocompatibility of the bioimplant was achieved. Thermal spraying is a method that is frequently employed in surface modification treatments to modify metallic bioimplants. These methods can be found in the medical field. This is due to the adaptability of the thermal spraying method. Because of their capacity to respond and adapt to physiochemical circumstances, coatings that are based on hydroxyapatite (HAp) are the most popular type to be used in thermal spraying. This is due to the fact that HAp is a naturally occurring mineral. On the other hand, the majority of the HAp coatings are unsuccessful as a result of the coating’s weak mechanical qualities and insufficient adhesive strength. Supplying the coating in question with reinforcement in the form of hard particles and doing so in the appropriate proportions makes it feasible to alter the qualities of HAp-based coatings to fulfill a variety of requirements. This can be accomplished by providing the coating with reinforcement. The purpose of this inquiry was to deconstruct and analyze a variety of thermally sprayed (TS) coatings. These coatings were used to adhere HAp-based coatings on bioimplants. In addition, a detailed discussion is offered on how the reinforcements have an effect on the mechanical and biocompatible qualities of the coatings. In addition, we have discussed the difficulties associated with TS HAp coatings and their potential uses in the manufacturing of 3D biomedical implants through the utilization of cold spray (CS). [ABSTRACT FROM AUTHOR]

Calcium strontium phosphate was electro-crystallized on Ti along with hydroxyapatite (HA). Stock solutions of 167 mM CaCl2, 167 mM SrCl2, and 100 mM NH4H2PO4 were initially prepared. Two different electrolyte formulations of equi-amounts of (CaCl2 + SrCl2) and NH4H2PO4 were used. The Ca:Sr ratios were maintained as 9:1 and 3:1, respectively, in these two formulations. Using these solutions, a cathodic deposit was obtained on Ti using ultrasonic agitation of the electrolyte at the current density of 10 mA/cm2 for 60 min. The electrolytes were heated at 50°C. X-ray diffraction (XRD) and field-emission scanning electron microscope (FE-SEM) analysis were utilized to characterize the phase compositions and surface morphology of the coatings. A surface roughness tester, an universal testing machine, and contact angle measurements were used to estimate the coating roughness, pull-off tensile adhesion strength, and wettability, respectively. The coatings were composed of hydroxyapatite (HA) and calcium strontium phosphate. The strontium (Sr) substitution was nearly 0.5% and 1% in the coatings obtained from the 9:1 and 3:1 Ca:Sr ratios, respectively. The coatings contained predominantly spherical crystals and occasional plate-like crystals attached to the substrate. Both the coatings displayed a similar surface roughness of about 450 nm. The coating obtained from the first electrolyte (Ca:Sr = 9:1) had a higher contact angle in simulated body fluid, but a lower pull-off adhesion strength than the coating obtained from the second (Ca:Sr = 3:1) electrolyte. [ABSTRACT FROM AUTHOR]

Biomedical coatings were elaborated by pulsed electrodeposition with hydrogen peroxide (H 2 O 2) into electrolytes on Ti 6 Al 4 V substrates, and the effect of H 2 O 2 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 % H 2 O 2 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 % H 2 O 2 exhibited the highest corrosion resistance, with E corr at −0.189 V/SCE and i corr at −1.11 μA cm−2 [ABSTRACT FROM AUTHOR]

In this study, hydroxyl apatite (HA) as a bio-ceramic is coated on the TiNi shape memory. In this approach, Tri-ethanolamine and butanol were used as suspensions. To set up Electrophoretic Deposition (EPD) process, voltages of 20, 30 and 40 volts were applied on the cathode for 1-5 minutes. The sintering process was done in the Ar atmosphere for two hours at 800°C. SEM and XRD were used to investigate surface morphologies and phases. Obtained results showed that higher electrical currents led to generation of thicker coatings registering 105% and 12.3% improvement for weight and thickness after 6 minutes, respectively. Moreover, Transformation of HA to other calcium phosphate phases doesn’t happen at a sintering temperature of 800°C. Moreover, a uniform, homogeneous and crackles coating can be reached in the voltage of 30 volts at low sintering temperatures. This process can be utilized an alternative technique for bioactive coatings. [ABSTRACT FROM AUTHOR]

The high catalytic activity of arenediazonium, along with the ability of gold ions to form specific bonds with amikacin, has been used in the fabrication of an electrochemical sensor based on a glassy carbon electrode modified with a gold solution and arenediazonium tosylate (Ar/GGCE) for the detection and quantification of amikacin upon its release from implants. Atomic force microscopy, cyclic voltammetry, and square-wave voltammetry were used to demonstrate that the use of a gold solution and arenediazonium tosylate for the surface modification of a glassy carbon electrode significantly enhances the electrode characteristics. The determination of amikacin was achieved using square wave voltammetry, which enabled the detection of amikacin at the Ar/GGCE in the concentration range 0.2–60 μM and ensured a limit of detection of 0.058 μM for amikacin released from implants. [ABSTRACT FROM AUTHOR]

Despite of possessing very high biocompatibility and osteointegrating properties, HAp exhibits poor mechanical strength and cannot be used in high load-bearing areas. To improve the drawbacks of HAp, it can be either doped with polymeric material or can be coated on some substrate having high mechanical strength. Polymeric substances are known for their mechanical strength and non-toxicity. Addition of polymers in the HAp matrix enhances the properties of HAp. Poly methyl methacrylate (PMMA) is used as bone cement and possesses excellent antimicrobial properties. It is doped inside the HAp matrix to modify some of the drawbacks of HAp, such as brittleness, degeneration, the growth and spread of microbes and bacteria over time. α-Al2O3 was chosen because of its chemical inertness, high mechanical strength, resistant to corrosion, wear and tear. The present study focuses on the comparison of doping of PMMA in HAp and PMMA-doped HAp coating on α-Al2O3, which is being studied first time. The changes in the phase, surface morphology, corrosion resistance, optical contact angle and mechanical behaviour of both the coated and doped samples were studied. The hardness of the coated samples and the doped samples was found to be higher than the pure HAp samples. The dielectric properties of both the samples were studied, and it was observed that initially at lower frequency, the impedance of doped samples was lower in comparison to coated samples. Coated samples showed higher contact angle in comparison to doped samples. Clotting behaviour was studied using whole blood clotting method. [ABSTRACT FROM AUTHOR]

Although the hydroxyapatite (HA) coating implant prepared by laser cladding exhibits good biological activity due to its chemical composition similar to biological bone, the original surface roughness of the laser-clad coating is high, which is unfavorable for long-term cell adhesion and proliferation. In order to improve the biological activity of HA coating implants and increase the adhesion and proliferation rate of osteoblasts on their surface, microtextures with different length-diameter ratios and depth gradients were prepared on the HA coating surface by nanosecond laser with reference to the microscopic morphology characteristics of the biological bone surface. By investigating the effects of microtexture aspect ratio and depth gradient on osteoblast adhesion characteristics, it was found that bone-like microtextures better controlled and simulated cell-material surface interactions. The geometric morphology of microtextured bone with a wide front end and narrow rear end and a depth gradient from front to back was an important signal for osteoblast proliferation. When the aspect ratio of bone microtexture was 2.5:1 and the maximum depth gradient was 15.7 μm, osteoblasts within the microtexture showed optimal growth, proliferation, and adhesion. Additionally, due to induction by microtexture contour shape and depth gradient morphology, cell morphology showed varying adhesion morphology from the front to the back of the microtexture. The results demonstrated that HA coatings with bone-like microtextures had superior osteoblast proliferation and adhesion properties compared to the original cladded coating surface, beneficial for enhancing the application of HA-coated bone implants in large segment bone repair. [ABSTRACT FROM AUTHOR]

In this study, hydroxyapatite (HA) incorporated in mesoporous SiO 2 particles (SiO 2 /HA) was initially synthesized using a soft template method. The resulting structure owned a high surface area (796.62 m2 g-1) and a substantial pore volume (0.757 cm3 g-1). The TEM and FESEM images indicated that the synthesized mesoporous particles possessed a spherical morphology, with a diameter of approximately 200 nm, and pores of slit-shape. The mission was to improve the surface characteristics of NiTi implants by composite coatings. This investigation emphasized specifically the impact of different concentrations of mesoporous SiO 2 /HA particles within the electrolyte on the properties of HA/mesoporous composite coatings. The surface characteristics of the coatings were examined using ATR-FTIR, FESEM, EDS, AFM, and hydrophilicity measurements. Furthermore, the osteogenic activity of the coatings was evaluated by culturing the osteosarcoma cell line SAOS-2 on the coated samples. The introduction of mesoporous particles resulted in a decrease in the coatings' surface roughness along with an improvement in their wettability. Moreover, there was an enhancement in the cell viability (99% after 7 days), proliferation, adhesion, and growth of SAOS-2 cells at the optimized concentration of mesoporous SiO 2 /HA particles (1000 mg/L). DAPI images illustrated that the mesoporous particles did not cause any adverse impact on the cellular nuclei. Finally, in the apoptosis test, the composite coating displayed a reduced number of necrotic cells compared to the pure HA coating. [ABSTRACT FROM AUTHOR]

β-TiNb alloys have attracted much attention due to their excellent comprehensive mechanical properties and biocompatibility. However, its high cost and large difference between elastic modulus and human bone will limit its application. In this study, a porous Nb-32.5Ti-xTa alloy coating, approximately 1.3 mm thick, was prepared on the surface of Ti-6Al-4V using laser cladding technology. Subsequently, the properties of the composite coating were characterized. The results show that the addition of Ta and Nb elements contributes to the formation of β phase. The formation of Nb2O5 and Ta2O5 passivation films during electrochemical corrosion significantly enhanced the corrosion resistance of the coating, and the protection rate of Ti32.5Nb20Ta coating was 68.06 %. The cladding coating had better biocompatibility than the substrate. Furthermore, the sample deposited a large amount of hydroxyapatite (HA) in simulated body fluid (SBF), which proved that the coating had good bone formation ability. [ABSTRACT FROM AUTHOR]

Zinc (Zn) distinguishes itself as an excellent candidate for temporary orthopaedic implants due to its advantageous corrosion rate compared to other biodegradable metallic materials like Mg and Fe. The present research involved the fabrication of a porous, corrosion-resistant, and biocompatible plasma electrolytic oxidation (PEO) coating on a Zn–1Mg alloy. Bioactivity was imparted to the PEO coating by incorporating hydroxyapatite (HA) and silver-incorporated hydroxyapatite (SHA) nanoparticles into it by synergising the PEO process with electrophoretic deposition (EPD) in a single step. FESEM and EDS are utilised to confirm the porous PEO oxide layer formation and its sealing by HA and SHA particles in PEO-EPD coating. The coatings' phase composition, surface roughness, scratch resistance, and wettability were evaluated to assess their suitability for temporary implant applications. The coatings' wettability and roughness significantly improved compared to the untreated substrate, rendering it suitable for orthopaedic implant applications. The scratch resistance of the PEO coating was satisfactory and showed additional improvement in the thicker film with lower porosity, achieved through the combined PEO-EPD process. The electrochemical corrosion test in biological media revealed that the PEO coating enhanced the degradation resistance of Zn–1Mg, which was further enhanced by incorporating HA and SHA particles into the PEO coating. The in-vitro bioactivity test in simulated body fluid (SBF) and cytotoxicity test using L929 (Mouse fibroblast) cells proved that adding HA made the fabricated PEO coating biologically more favourable. Furthermore, the SHA-incorporated PEO coating is antibacterial against E. coli bacterial strains, enabling protection against post-implantation infections. • ZnO-HA ceramic composite coating developed on Zn–1Mg by PEO. • ZnO-HA coating showed 3 orders lower i corr compared to bare alloy. • Ceramic-composite coating proved to be bioactive and biocompatible. • Silver-incorporated coating exhibited the bactericidal property. [ABSTRACT FROM AUTHOR]

This study discusses the contribution of Cu2+ and Mg2+, two biologically important ions substituted into the structure of fluorohydroxyapatite. FHA, a partial substitution of fluorine ion in HA has received a great attention because it improves the corrosion resistance of orthopedic implants. Copper, Magnesium and copper-Magnesium doped fluorohydroxyapatite (FHA) coatings were electrochemical deposited on titanium (Ti) using a cyclic voltammetry technique. The coatings properties were identified by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The corrosion behavior of coated and uncoated samples, immersed for 7 days in aerated simulated body fluid (SBF) in a presence of 0.2 g/l human serum albumin (HAS) was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The synergetic effect of albumin and doped elements on the degradation of Ti was studied. As a result of these investigations, it is revealed that: fluoride, copper and magnesium were successfully incorporated into apatite lattice structure. The additions of ions in FHA crystal matrix reduced the crystallite size, increased the crystallinity and changed the structure of F-hydroxyapatite. All the electrochemical techniques employed demonstrated that the coatings that were produced offered superior protection against corrosion for titanium when exposed to artificial body fluids. The nano-Mg-FHA coating improves effective protection to Ti and presents the highest corrosion resistance. The outcomes of this investigation were also compared with already published works to validate the research results. [ABSTRACT FROM AUTHOR]

A major strategy to combat implant-associated infections is to develop implant coatings with intrinsic antibacterial activity. Since hydroxyapatite (HAp) coatings and antibiotic administration are commonly used in clinical settings, developing HAp-coated implants with localized antibiotic-releasing properties has attracted popularity. Considering the antibacterial metal species (Ag, Zn, Cu, etc.) in metal–organic frameworks and their drug delivery capacity, in this study, a gentamicin-loaded zeolitic imidazolate framework-8 nanolayer was deposited on a plasma-sprayed HAp coating (HAp/ZIF-8@Gent), which served as a Gent and Zn2+ reservoir. The investigation on the binding interaction between ZIF-8 and HAp indicated that the growth of ZIF-8 was through a Zn2+ seed layer on the HAp coating via an adsorption–replacement mechanism, instead of simple physical adsorption. The HAp/ZIF-8@Gent coating exhibited a sustained drug-release property, and the cumulative concentration of released Gent reached 239.8 ± 7.1 μg/mL on day 8. Compared to the HAp-Zn and HAp/ZIF-8 coatings, the HAp/ZIF-8@Gent coating exhibited significantly higher antibacterial activity against E. coli. This was ascribed to the combined antibacterial effects of Zn2+ and Gent. The cytocompatibility of the HAp/ZIF-8@Gent coating was confirmed via cell proliferation. Above all, the ZIF-8-modified HAp coating with localized delivery of Gent and Zn2+ possessed excellent antibacterial activity and acceptable cytocompatibility, showing potential in mitigating implant-associated infections. [ABSTRACT FROM AUTHOR]

To effectively combat infectious osteoporosis, Ti‐based implants with enhanced antibacterial and osseointegrative properties are urgently required. Herein, a one‐step method involving Mg thermal‐reduction is employed to modify a hydroxyapatite (HA) array on Ti, which comprises an inner TiO2 layer and an outer nanorod‐like HA layer. This process introduces oxygen vacancies (OVs) into the TiO2 layer and deposits a Mg─O‐contained amorphous nanolayer on each HA nanorod. The introduced OVs enhance reactive oxygen species (ROS) yield by the array during ultrasound treatment via narrowing TiO2 bandgap and improving H2O molecules absorption. The produced ROS, combined with a weak alkaline microenvironment created by the degraded Mg─O nanolayer, endows the array with potent bacterial‐killing and biofilm‐eradicating efficacies within a 5 min ultrasound treatment via the combination of proton‐consumption and cell envelop‐detriment effects. Moreover, due to the alkaline microenvironment and the released Mg2+, the array hinders osteoclastogenesis by activating the inflammation‐related FAK‐PI3K‐AKT signaling pathway in macrophages, as revealed by transcriptomic analysis, resulting in robust osseointegration in rat femoral shaft with concurrent bacterial‐infection and osteoporosis. This work paves a new way for simultaneously endowing a sonosensitive coating on Ti with sonodynamic treatment‐derived high antibacterial ability and alkaline microenvironment‐mediated strong osseointegration for infectious osteoporosis treatment. [ABSTRACT FROM AUTHOR]

Titanium dental implants are one of the best replacements for the natural teeth. It can reduce early failures compared to other implant materials. During mastication, generally, implant loosening occurs between the bone and the implant surface. Therefore, to resolve this issue, surface modification of the implant surface was done which can provide better bonding between the implant and the bone. In this study, we designed five different types of surface texture on the implant and compared them with the solid non-textured implant. In addition to that, we used four different hybrid composite coating materials along with hydroxyapatite, for better osseointegration and bone formation. Thus, we modeled a bony structure like mandible using solid modeling technique. We considered average biting force of 250 N with different bone conditions. After the analysis, it has been observed that 'U' and 'V' shape textures exhibited the optimized textures for dental implant with coating combination of HA1.5TO1.5SR and HA3Sr for weak and very weak bone conditions. The coating for straight and dome shaped textures for strong and very strong bone conditions showed better results, whereas 'U' shaped and dome shaped textures showed better results for normal bone condition. [ABSTRACT FROM AUTHOR]

Orthopedic implants play a crucial role in restoring the function and life quality of the population with musculoskeletal disorders. However, implant failure and lack of integration with the surrounding bone tissue, mainly in patients with low bone quality, remain significant challenges in biomedicine. Porous bioactive coatings have emerged as a promising approach to address these issues. This work aims to explore the feasibility of preparing porous hydroxyapatite coatings by high-velocity oxy-fuel spray (HVOF) and, as a first approach, to evaluate the performance of the porous bioactive coatings obtained in simulated body fluid for a possible application in orthopedic surfaces. This paper discusses the use of polyester as a pore-forming agent and the importance of some relevant factors, such as coating fabrication parameters and post-spraying treatments, for producing porosity in the coatings. The results display the formation of different degrees of porosity ranging from 3.8% to 38% depending on the weight fraction of the pore-forming phase employed to prepare the hydroxyapatite coatings. The coatings were evaluated in Hanks balanced solution at body temperature by employing different electrochemical techniques; interestingly, the results suggest different bioactive responses as a function of porosity. [ABSTRACT FROM AUTHOR]

Production of diamond coatings on titanium substrates has demonstrated as a promising strategy for applications ranging from biosensing to hard tissue engineering. The present study focuses on monitoring the nucleation and growth of bone-like carbonated-hydroxyapatite (C-HA) on polycrystalline diamond (PCD) synthetized on titanium substrate by means of a hot filament chemical vapor deposition (HF-CVD) method. The surface terminations of diamond coatings were selectively modified by oxidative treatments. The process of the C-HA deposition, accomplished by precipitation from simulated body fluid (SBF), was monitored from 3 to 20 days by Raman spectroscopy analysis. The coupling of morphological and structural investigations suggests that the modulation of the PCD surface chemistry enhances the bioactivity of the produced materials, allowing for the formation of continuous C-HA coatings with needle-like texture and chemical composition typical of those of the bone mineral. Specifically, after 20 days of immersion in SBF the calculated carbonate weight percent and the Ca/P ratio are 5.5% and 2.1, respectively. Based on these results, this study brings a novelty in tailoring the CVD-diamond properties for advanced biomedical and technological applications. [ABSTRACT FROM AUTHOR]

In this study, duplex coating process (Boriding + Hydroxyapatite) was applied to 316L stainless steel alloys. Before coating, the substrate materials were shotblasted with 300–500 µm glass beads in a vacuum type shot blast machine. Tribological properties of the alloy with boriding process, its bioactivity and biocompatibility was increased with the hydroxyapatite (HA) coating process. Powder pack boriding technique was used in boriding process and Electrophoretic deposition method (EPD) was used in HA coating process. At the end of the study, the microstructures (SEM), elemental analyzes of the coating surfaces (EDS), Ca/P ratios, coating thicknesses were determined. In addition, the hardness and adhesion qualities of the boride layer were determined. When the results obtained are evaluated, duplex layers were successfully formed for all parameters. [ABSTRACT FROM AUTHOR]

A 100 mT magnetic field was introduced during the plasma spraying of hydroxyapatite (HA) coating on Ti6Al4V substrate. The influence of the magnetic field on the microstructure, bonding strength, and bioactivity of the coating was investigated. Compared with as-sprayed coating, the coating sprayed under a magnetic field showed fewer porosity and microcracks and a significantly decreased absolute value of the residual stress. The bonding strength of the coating sprayed under a magnetic field was approximately 173.6 % greater than as-sprayed coating. With increasing time in simulated body fluid, the width of microcracks on the surface of both coatings first increased and then decreased. The widths of microcracks on the coating sprayed under a magnetic field were much smaller than as-sprayed coating. During spraying process, the magnetic field would enhance the wetting and flowing ability of the HA molten droplets, prolonging their cooling, which affects the microstructure and bioactivity of the coating. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to investigate the effect of electrodeposition parameters (i.e. time and voltage) on the properties of hydroxyapatite (HA) coating fabricated on Ti6Al4V surface. Design/methodology/approach: A full factorial design along with response surface methodology was utilized to evaluate the main effect of independent variables and their relative interactions on response variables. The effect of electrodeposition voltage and deposition time on HA coatings Ca/P molar ratio and the size of deposited HA crystals were examined by structural equation modeling (SEM). The formation of plate-like and needle-like HA crystals was observed for all experiments. Findings: The results obtained showed that the higher electrodeposition voltage leads to lower Ca/P values for HA coatings. This is more significant at lower deposition times, where at a 20-minute deposition time, the voltage increased from 2 to 3 V and the Ca/P decreased from 2.27 to 1.52. Full factorial design results showed that electrodeposition voltage has a more significant effect on the size of the deposited HA crystal. With increasing the voltage from 2 to 3 V at a deposition time of 20 min, the HA crystal size varied from 99 to 36 µm. Originality/value: The investigation delved into the impact of two critical parameters, deposition time and voltage, within the electrodeposition process on two paramount properties of HA coatings. Analyzing the alterations in coating characteristics relative to variations in these process parameters can serve as a foundational guide for subsequent research in the domain of calcium-phosphate deposition for implants. [ABSTRACT FROM AUTHOR]

This work studies the influence of the composition of an acetylene–oxygen explosive O2/C2H2 mixture on the structure and properties of hydroxyapatite coatings obtained by detonation spraying. The molar ratios of O2/C2H2 were 2.61; 3.03 and 3.35; the explosive charge was between 73 and 77%. The results of X-ray phase analysis showed partial conversion of the hydroxyapatite (HA) phase to the tricalcium phosphate (α-TCP) phase and formation of the amorphous phase during detonation sputtering. The formation of a small amount of the α-TCP phase during detonation spraying of HA is obviously due to structural transformations occurring during the heating of the material by detonation products. In addition, very rapid cooling of molten particles leads to the formation of the amorphous phase. The study results of the microstructure of the cross sections of the formed coatings, conducted using scanning electron microscopy, indicate that an increase in the O2/C2H2 ratio leads to increased porosity in the coatings. Additionally, an increase in the explosive charge by 77% results in the appearance of transverse cracks in the coating. [ABSTRACT FROM AUTHOR]

In the last 15 years, the cold spray process has demonstrated a great efficiency for the deposition of metallic powders. In this case, the consolidation of coatings is achieved thanks to the high kinetic energy of unmelted particles exhibiting a ductile behaviour. Cold spray is generally of great interest because properties that are not reachable with classical thermal spray technologies ca be expected thanks to lower involved temperatures (typically below several hundred degrees), such as the conservation of both the characteristics of starting powders and substrate properties after spraying. However, in the case of ceramics, cold spray still remains challenging because of the lack of plastic deformation. Here, in the specific case of hydroxyapatite (HAP) and to overcome this brittleness issue, we investigate the role of an intermediate PolyEtherEtherKetone (PEEK) layer between the substrate and the deposit. In a first time, we highlight how the sublayer properties are different, according to the technology used for the deposition (flame spray or air plasma spray). Especially, the influence of the pore volume fraction in the sublayer, on the mechanisms involved in the deposition of HAP is discussed. Indeed, the porosity can help improving the building-up and consolidation of the HAP coating, especially when the deposition efficiency of the powder is very low. In this case, the sublayer is kept intact, and the rebound of particles are promoted, inducing a complete filling of the PEEK porosity with HAP. As a consequence, a thick and cohesive hybrid coating is created, containing PEEK and HAP. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the surface characteristics of a nanocrystalline hydroxyapatite coating made through atomic layer deposition (ALD-HA) on titanium surfaces and to investigate its effect on blood coagulation and platelet adhesion. Grade 2 square titanium discs (0.7 cm, 1 mm thick) were used (n = 108). Half of the substrates (n = 54) were coated with ALD-HA, and the other half were used as the non-coated control. Surface free energy (SFE), contact angle (CA), surface roughness (Ra), and chemical composition were evaluated. Blood thrombogenic properties were assessed on ALD-HA and non-coated surfaces using the kinetic clotting time method. The platelets' adhesion and morphology were also evaluated. The ALD-HA-coated surfaces demonstrated significantly higher polar SFE (p < 0.001) and lower CA (p < 0.001) values compared to the non-coated surfaces. In addition, the surface roughness was significantly lower for the ALD-HA (p < 0.001) than for the non-coated surfaces. Platelets adhered to both surfaces; however, there was variability in platelet morphologies in different areas with higher platelet density on the ALD-HA surfaces. There was no significant difference in the overall absorbance values of the hemolyzed hemoglobin for both substrates, and the total clotting time was achieved at 60 min. It can be concluded that the ALD-HA coating of titanium can enhance surface wettability, increase surface free energy, and support blood coagulation and platelet adhesion. [ABSTRACT FROM AUTHOR]

Bone replacement is one of the major medical procedures in the oral surgery field due to the progressive ageing population and to illness or trauma in younger age groups. The use of implants without biological activity and effective osseointegration increases the chances of implant failure. This work aims to improve the interaction between implants and bone by using Bioglass 45S5 (BG)/hydroxyapatite (HAp) mixtures, including copper-, zinc-, and cerium-doped BG, as well as co-doping by the mentioned metals, as coatings produced by the CoBlastTM technique. All coatings present a uniform coverage of the Ti-6Al-4V substrate. Furthermore, in vitro testing using human osteosarcoma Saos-2 cells indicated that BG/HAp coatings have no cytotoxic effect, and the used of doping agents did not alter cell adhesion, proliferation, or alkaline phosphatase (ALP) expression when compared to undoped coating. These results demonstrate that BG/HAp by CoBlastTM can be a solution to improve implants' osseointegration. [ABSTRACT FROM AUTHOR]

This study is the second part of a two-part study whereby supersaturated solutions of calcium and phosphate ions generate well-defined hydroxyapatite coatings for orthopaedic implants. An 'ideal' process solution is selected from Part 1, and the detailed characterisation of films produced from this solution is undertaken here in Part 2. Analysis is presented on the hydroxyapatite produced, in both powder form and as a film upon titanium substrates representative of orthopaedic implants. From thermal analysis data, it is shown that there is bound and interstitial water present in the hydroxyapatite. Nuclear magnetic resonance data allow for the distinction between an amorphous and a crystalline component of the material. As hydroxyapatite coatings are generated, their growth mechanism is tracked across repeated process runs. A clear understanding of the growth mechanism is achieved though crystallinity and electron imaging data. Transmission electron imaging data support the proposed crystal growth and deposition mechanism. All of the data conclude that this process has a clear propensity to grow the hydroxyapatite phase of octacalcium phosphate. The investigation of the hydroxyapatite coating and its growth mechanism establish that a stable and reproducible process window has been identified. Precise control is achieved, leading to the successful formation of the desired hydroxyapatite films. [ABSTRACT FROM AUTHOR]

Due to their biodegradable nature and enhanced adhesive strength at the interface, poly– (lactic acid) (PLA) based coatings are frequently used in biomedical alloys. But it is unable to create metal-tissue interaction because of its very hydrophobic surface feature. Researchers are therefore looking at composite coatings that are reinforced with hydroxyapatite (HA). In this study, the effect of halloysite nanotube (HNT) was investigated to hydroxyapatite (HA) reinforced PLA coatings synthesized on Ti–6Al–4V (Ti64) biomedical alloy. Investigations were conducted on the hybrid coatings' characterization such as SEM/EDS, FTIR, contact angle tests, and XRD analyses. Adhesion tests at alloy-coating interface were revealed with ASTM D3359–09 standards. In-vitro electrochemical corrosion tests (ASTM–G59) and immersion tests (ISO-23317) were conducted on coatings for reveal both biodegradability and osteoconductivity behaviours of coatings. SEM morphologies revealed that surfaces have micron-sized pores on both coatings. But HA/HNT reinforced coatings have more homogenous morphology with decreased pore size. The elemental distribution of coatings was confirmed by the EDS analyses. While FTIR research demonstrated a variation in the influence of HNT on the coating of PLA depending on the bond status, XRD results showed that there were no phase changes in the coatings. It was found that coatings with HNT reinforcement, have higher adhesion strength at the substrate-coating interface (1B for HA and 4B for HA/HNT reinforced coatings). Following in-vitro electrochemical corrosion experiments, it was discovered that the corrosion current density (Icorr) value reduced even more with the PLA/HA-HNT coating (1.784, 0.245, and 0.032 µA cm–1) than it did with the PLA/HA coating alone. The results of the impedance spectroscopy (Nyquist curves) confirmed that the coatings' corrosion resistance increased as the Icorr value decreased. Possible corrosion mechanism was discussed with equivalent circuit model which consist two–constant elements. It was found that both coatings exhibited a characteristic that induced calcium phosphates (CaPs) on their surfaces after in-vitro immersion tests. The contact angle tests revealed that the high hydrophobic effects of coatings would have a positive effect on the alloy–tissue interaction in the long term due to the bioactive compounds that they have. The dense and homogeneous CaPs in the PHH coatings increased with HNT reinforcement, leading to more effective interaction with surrounding tissues during in-vitro tests. The findings led to the conclusion that the hybrid coatings produced with the reinforcement of HA/HNT will not readily delaminate during application and will improve the interaction between the alloy and the tissue under prolonged physiological conditions. [ABSTRACT FROM AUTHOR]

Titanium (Ti) exhibits superior biocompatibility and mechanical properties but is bioinert, while hydroxyapatite (HA) possesses excellent osteogenesis and is widely used for the modification of Ti surface coatings. However, the synthesis of homogeneous and stable HA on metallic materials is still a major challenge. In this study, porous titanium dioxide nanotube arrays were prepared on Ti surface by anodic oxidation, loaded with calcium and phosphorus precursors by negative pressure immersion, and HA coating was formed by in situ crystallization of calcium and phosphorus on the surface by hydrothermal heating. Scanning electron microscopy (SEM), X‐ray diffraction (XRD), and bonding strength were conducted to confirm the surface characteristics of each group. The cell proliferation, mineralization degree, and alkaline phosphatase (ALP) activity of MC3T3‐E1 cells on samples were calculated and compared in vitro experiments. Cylindrical samples were implanted into rat femurs to evaluate biocompatibility and osteogenesis in vivo. The results showed that HA crystals successfully synthesized in TiO2 nanotubes, enhancing the bonding strength of HA coating and Ti substrate under negative pressure. Moreover, HA coating on Ti substrate remarkably enhanced cell proliferation and osteogenic differentiation activity in vitro, and improved new bone formation as well as osseointegration in vivo. [ABSTRACT FROM AUTHOR]

The demand for orthopedic implants is increasing, driven by a rising number of young patients seeking an active lifestyle post-surgery. This has led to changes in manufacturing requirements. Joint arthroplasty operations are on the rise globally, and recovery times are being reduced by customized endoprostheses that promote better integration. Implants are primarily made from metals and ceramics such as titanium, hydroxyapatite, zirconium, and tantalum. Manufacturing processes, including additive manufacturing and thermal plasma spraying, continue to evolve. These advancements enable the production of tailored porous implants with uniform surface coatings. Coatings made of biocompatible materials are crucial to prevent degradation and enhance biocompatibility, and their composition, porosity, and roughness are actively explored through biocompatibility testing. This review article focuses on the additive manufacturing of orthopedic implants and thermal plasma spraying of biocompatible coatings, discussing their challenges and benefits based on the authors' experience with selective laser melting and microplasma spraying of metal-ceramic coatings. [ABSTRACT FROM AUTHOR]

In this study, multilayered Cu/HA/ZnS + PEEK coatings were fabricated using hybrid technology on Zr–2.5Nb alloy substrates. The use of electrophoretic deposition (EPD) and heat treatment allowed the 1st base composite ZnS + PEEK layer and the 2nd hydroxyapatite (HA) top layer to be obtained. The EPD kinetics of both layers was studied. Heating at a temperature of 450 °C and slow cooling resulted in densification and sulfonation of PEEK. It also led to an increase in the adhesion of HA particles on the surface of the PEEK + ZnS layer and to the settlement of HA particles deep into the 1st layer. The effect of substrate preparation on the adhesion strength of coatings was investigated. The ZnS + PEEK layer exhibited high adhesion to the chemically treated zirconium alloy. Furthermore, the first layer was characterized by a high scratch resistance. The selective distribution of Cu on the top of the coating was obtained by shadow-masked pulsed laser deposition (PLD). The multilayered coatings exhibited high roughness and mild hydrophobicity. This study showed the possibility of obtaining a multilayered coating system with a controlled distribution of bioactive components (HA) and antimicrobial components (Cu) on its surface using a hybrid method that combined EPD, heat treatment, and PLD. [ABSTRACT FROM AUTHOR]

Ion-substituted calcium phosphate (CP) coatings have been extensively studied as promising materials for biomedical implants due to their ability to enhance biocompatibility, osteoconductivity, and bone formation. This systematic review aims to provide a comprehensive analysis of the current state of the art in ion-doped CP-based coatings for orthopaedic and dental implant applications. Specifically, this review evaluates the effects of ion addition on the physicochemical, mechanical, and biological properties of CP coatings. The review also identifies the contribution and additional effects (in a separate or a synergistic way) of different components used together with ion-doped CP for advanced composite coatings. In the final part, the effects of antibacterial coatings on specific bacteria strains are reported. The present review could be of interest to researchers, clinicians, and industry professionals involved in the development and application of CP coatings for orthopaedic and dental implants. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to determine whether changing the stem coating grants superior outcomes at a minimum follow-up of five years. Methods: Retrospective review of a consecutive series of primary total hip arthroplasties (THAs) operated by direct anterior approach between 01/01/2013 and 31/12/2014. Two stems were compared, which were identical except for their surface coating; "the Original stem" was fully coated with hydroxyapatite (HA), while "the ProxCoat stem" was proximally coated with plasma-sprayed titanium and HA. Matching was performed. Clinical assessment included modified Harris hip score (mHHS), Oxford hip score (OHS), and forgotten joint score (FJS). Radiographic assessment evaluated alignment, subsidence, pedestal formation, heterotopic ossification, radiolucent lines ≥ 2 mm, spot welds, cortical hypertrophy, and osteolysis. Results: 232 hips received the Original stem and 167 the ProxCoat stem, from which respectively five hips (2.2%) and no hips (0%) underwent revision. Matching identified two groups of 91 patients, with comparable patient demographics. At > five years follow-up, there were no differences in OHS (16 ± 6 vs 15 ± 5; p = 0.075) nor FJS (81 ± 26 vs 84 ± 22; p = 0.521), but there were differences in mHHS (89 ± 15 vs 92 ± 12; p = 0.042). There were no differences in alignment, subsidence, pedestal formation, heterotopic ossification, cortical hypertrophy, and osteolysis. There were differences in prevalence of proximal radiolucent lines (12% vs 0%; p < 0.001) and distal spot welds (24% vs 54%; p < 0.001). Conclusion: At a minimum follow-up of five years, this study on matched patients undergoing primary THA found that ProxCoat stems results in significantly fewer radiolucent lines, more spot welds, and less revisions than Original stems, thus suggesting better bone ingrowth. [ABSTRACT FROM AUTHOR]

Metallic bioimplant are widely used now-a-days to replace a part of human body in a physiologically accepted manner. However, the bio-compatibility of the metallic bioimplant was mainly achieved by the incorporation of a bio-compatible coating on its surface through suitable surface modifications techniques. In surface modifications techniques, the thermal spraying is widely used for modification of metallic bioimplant due to its versatile nature. In thermal spraying, the hydroxyapatite (HAp)-based coatings are mainly preferred because this coating responses to physiochemical environment and adapts itself accordingly. But bulk of the HAp coating give out due to less adhesion strength of the HAp coating and its poor mechanical properties. The properties of HAp-based coatings can be designed as per requirements by reinforcing this coating through hard particulates in suitable proportions. In this paper, the various thermal sprayed (TS) coatings used for performing HAp-based coatings on bioimplant were discussed. The influence of reinforcements on the mechanical and bio-compatible properties of the coatings is also discussed in detail. Lastly, the challenges in the TS HAp coatings along-with the future perspective of TS coating in fabricating of 3D biomedical implants by using cold spray (CS) has also been summarized. [ABSTRACT FROM AUTHOR]

Silver has been widely used for surface modification to prevent implant-associated infections. However, the inherent cytotoxicity of silver greatly limited the scope of its clinical applications. The construction of surfaces with both good antibacterial properties and favorable cytocompatibility still remains a challenge. In this study, a structurally homogeneous dopamine–silver (DA/Ag) nanocomposite was fabricated on the implant surface to balance the antibacterial activity and cytocompatibility of the implant. The results show that the DA/Ag nanocomposites prepared under the acidic conditions (pH = 4) on the titanium surface are homogeneous with higher Ag+ content, while an obvious core (AgNPs)–shell (PDA) structure is formed under neutral (pH = 7) and alkaline conditions (pH = 10), and the subsequent heat treatment enhanced the stability of PDA–AgNPs nanocomposite coatings on porous titanium. The antibacterial test, cytotoxicity test, hypodermic implantation and osteogenesis test revealed that the homogeneous PDA–AgNPs nanocomposite coating achieved the balance between the antibacterial ability and cytocompatibility, and had the best outcomes for soft tissue healing and bone formation around the implants. This study provides a facile strategy for preparing silver-loaded surfaces with both good antibacterial effect and favorable cytocompatibility, which is expected to further improve the therapeutic efficacy of silver composite-coated dental implants. [ABSTRACT FROM AUTHOR]

Hydroxyapatite (HA) coatings on metallic implants have been extensively used in orthopedic applications to improve tissue-implant interactions, enhance their biocompatibility, and enhance their functionality. However, the expensive synthetic HA is the most widely used bioceramic for implant coatings, leading to high implants costs. Hence, this research explored the potential of an inexpensive biogenic HA derived from fish scales and FsHA/yttria-stabilized zirconia (YSZ) bioceramic coatings on a Ti–6Al–4V alloy as an alternative to synthetic HA coatings. The FsHA/YSZ powders and the coatings were examined with X-ray diffraction (XRD) and scanning electron microscopy/energy dispersive X-ray (SEM/EDX), and the surface roughness, microhardness, corrosion resistance, bioactivity, and in vitro cytotoxicity of the coatings were also determined. The morphological powder analysis revealed particles with a slightly irregular morphology and a fine spherical morphology, while the coating microstructure analysis revealed a fine lamellar morphology, with partially melted and unmelted FsHA particles, and fine microcracks along with evenly dispersed ZrO2 particles. The surface roughness of the FsHA coating increased by 87.5% compared with the uncoated substrate, and the addition of YSZ significantly reduced this value. A 35.5% increase in hardness was obtained in the FsHA + 20 wt.% YSZ coating, and the FsHA coating showed a 43.2% reduction in the corrosion rate compared with the uncoated substrate; a further 73% reduction was observed with the addition of YSZ. The microstructure of the coatings after 14 days of immersion in simulated body fluid (SBF) revealed enlarged cracks and delaminated segments with well-grown apatite spherulite layers on the whole surface of the coatings, while in vitro cytotoxicity analysis showed a good cell viability of 95% at the highest concentration of the specimen. [ABSTRACT FROM AUTHOR]

Ti6Al4V substrates were electrochemically deposited with nano-crystalline hydroxyapatite (HA) from aqueous electrolytes. Cathodic HA coatings were obtained when the electrolyte was stirred using ultrasonic vibration. Two current densities of 20 mA/cm2 and 50 mA/cm2 were employed. Polarization and electrochemical impedance spectroscopy (EIS) were the techniques used to estimate the corrosion of coatings in simulated body fluid (SBF). The results indicate good corrosion resistance for the coating obtained at 50 mA/cm2 from ultrasonic stirring of the electrolyte. [ABSTRACT FROM AUTHOR]

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 R ct 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. [Display omitted] [ABSTRACT FROM AUTHOR]

• Laser treatment can modulate the morphology, thickness and density of HA coating. • Microstructures and thin oxide layers promote nucleation and deposition of HA. • Adhesion strength of HA coating to Mg alloy substrate is 31.86 ± 1.71 MPa. • Coating effectively reduces the corrosion rate of magnesium alloys to 0.146 mm/y. • Coating with good biological activity can promotes osteoblasts proliferation. 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. [ABSTRACT FROM AUTHOR]

• Hydroxyapatite (HAP) composite paper with biocompatibility and hygroscopicity was prepared. • HAP composite paper has better hygroscopic and triboelectric properties than pure paper, making it more suitable for wearable sensing applications. • The HAP composite paper-based triboelectric nanogenerator can detect and distinguish different joint movements. • Hemostatic and disposable HAP composite paper can be degraded in the natural environment without harm. Wearable triboelectric nanogenerators (TENGs) have attracted considerable attention in the field of self-powered sensors that can be worn on the skin directly without packaging because of their breathability, conformability, and sensitivity to collect biomechanical energy. However, high humidity on the skin can affect the wearable TENG output performance, substantially affecting the sensor performance and stability. When worn for a long time, humidity can even cause skin inflammation. Thus, for a wearable TENG, moisture control and biocompatibility are also key factors that need to be addressed. Herein, we report a hygroscopic and biocompatible paper-based TENG using a hydroxyapatite (HAP) mineral coating to enhance the paper fiber. The mineral coating can maintain the surface of the paper fiber, which will not cause large external deformation of the paper fiber under a force, avoid squeezing out excess water, and keep the friction surface dry, avoiding humidity affecting the output performance. Without interfering with the performance of the TENG, the maximum water absorption of the HAP composite paper is ∼8 μL. The HAP composite paper–based TENG (4 cm2) has an open-circuit voltage and short-circuit current 5.8 times and 4.2 times that of pure paper, respectively, and can obtain 80.4 mW/m2 output and directly light 117 LEDs. At relative humidity values of 25.7 %, 43.1 %, and 58.8 %, the performance retained the peak values of 80.2 %, 68 %, and 63.7 %, respectively. Even at a high relative humidity of 71.7 %, the triboelectric performance of HAP composite paper is retained 59.3 %, and the stability under humidity is better than that of pure paper (45.6 %). In addition, the mineral paper can even work with tissue fluid and output performance decreases by 43.8 %. The mineral-enhanced paper TENG with high power generation performance, hygroscopicity, biocompatibility, and degradability provides a new perspective for disposable wearable sensors, even in medical treatment. [ABSTRACT FROM AUTHOR]

To evaluate the adhesion of mono and duospecies biofilm on a commercially available dental implant surface coated with hydroxyapatite nanoparticles (nanoHA). Titanium discs were divided into two groups: double acid-etched (AE) and AE coated with nanoHA (NanoHA). Surface characteristics evaluated were morphology, topography, and wettability. Mono and duospecies biofilms of Streptococcus sanguinis (S. sanguinis) and Candida albicans (C. albicans) were formed. Discs were exposed to fetal bovine serum (FBS) to form the pellicle. Biofilm was growth in RPMI1640 medium with 10% FBS and 10% BHI medium for 6 h. Microbial viability was evaluated using colony-forming unit and metabolic activity by a colorimetric assay of the tetrazolium salt XTT. Biofilm architecture and organization were evaluated by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). AE surface had more pores, while NanoHA had even nanoHA crystals distribution. Roughness was similar (AE: 0.59 ± 0.07 µm, NanoHA: 0.69 ± 0.18 µm), but wettability was different (AE: Θw= 81.79 ± 8.55°, NanoHA: Θw= 53.26 ± 11.86°; P = 0.01). NanoHA had lower S. sanguinis viability in monospecies biofilm (P = 0.007). Metabolic activity was similar among all biofilms. In SEM both surfaces on C. albicans biofilm show a similar distribution of hyphae in mono and duospecies biofilms. AE surface has more S. sanguinis than the NanoHA surface in the duospecies biofilm. CLSM showed a large proportion of live cells in all groups. The nanoHA surface reduced the adhesion of S. sanguinis biofilm but did not alter the adhesion of C. albicans or the biofilm formed by both species. • Commercially available implant surface with hydroxyapatite nanoparticles reduce the adhesion of Streptococcus sanguinis. • This commercially available surface shows potential in diminishing Streptococcus infections. • A commercially available implant surface coated with hydroxyapatite nanoparticles does not alter C. albicans adhesion. [ABSTRACT FROM AUTHOR]

Impact of sintering temperature and aging time was investigated on purity and phase of hydroxyapatite powders synthesized through sol–gel process. Phase, composition, and morphology of the prepared hydroxyapatite powders were characterized using X‐ray diffraction (XRD), Fourier transform infrared (FT‐IR), and scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS). Plausible mechanism respective to the formation of HAP from the precursors Ca(NO3)2·4H2O and triethyl phosphite (TEP) by sol–gel process was determined from 31P NMR analysis. Further, the development of hydroxyapatite coatings on 316L SS metallic surfaces was done by varying the spin coating parameters such as spin speed, spin time, and sintering atmosphere, and their corrosion resistance behavior in SBF solution was evaluated by electrochemical impedance spectroscopy (EIS) and TAFEL polarization analysis. From the results, we inferred that the HAP coatings deposited on 316L SS surfaces at 3000 rpm/min under nitrogen atmosphere sintering have shown improved corrosion resistivity. The effect of aging time, sintering atmosphere, and spin speed was evaluated in terms of corrosion resistance behavior. [ABSTRACT FROM AUTHOR]

In order to merge high-mechanical properties and suitable bioactivity in a single scaffold, zirconia porous structures are here coated with a hydroxyapatite layer. The digital light processing (DLP) technique is used to fabricate two types of scaffolds: simple lattice structures, with different sizes between struts (750, 900 and 1050 µm), and more complex trabecular ones, these latter designed to better mimic the bone structure. Mechanical tests performed on samples sintered at 1400 °C provided a linear trend with a decrease in the compressive strength by increasing the porosity amount, achieving compressive strengths ranging between 128–177 MPa for lattice scaffolds and 34 MPa for trabecular ones. Scaffolds were successfully coated by dipping the sintered samples in a hydroxyapatite (HA) alcoholic suspension, after optimizing the HA solid loading at 20 wt%. After calcination at 1300 °C, the coating layer, composed of a mixture of HA and β-TCP (β-TriCalcium Phospate) adhered well to the zirconia substrate. The coated samples showed a proper bioactivity, well pronounced after 14 days of immersion into simulated body fluid (SBF), with a more homogeneous apatite layer formation into the trabecular samples compared to the lattice ones. [ABSTRACT FROM AUTHOR]

In current medicine, joint revision surgery plays an important role in the treatment of degenerative joint diseases. Infections of the artificial joints are an iatrogenic, accompanying symptom after joint replacement procedures. A new approach is to functionalize the bioactive coatings of the implants by infiltrating them with anti-inflammatory drugs. This work aims at a one-step approach in manufacturing drug-doped, porous hydroxyapatite coatings by high-velocity suspension flame spraying (HVSFS). Thermal exposure of the temperature-sensitive drugs is critical. Therefore, a new process setup, combining one axial and one radial suspension line, is used for coating deposition. The lower dwell time of the suspension in the flame through radial injection helps in controlling the temperature exposition of the contained drug to the flame. Additionally, the influence of the powder morphology, used as a carrier for the drug in the suspension, is investigated by carrying out spray experiments with suspensions from three different granule types. To analyze the temperature exposition within the coating process, fluoresceine was used as a model drug, as the decomposition of the organic, fluorescing molecules can be easily controlled by fluorescence intensity measurements. It could be shown that the deposition of temperature-sensitive organic molecules is possible without degrading the molecular structure by a modified HVSFS process. This knowledge offers new possibilities in the cost-effective one-step manufacturing of functionalized, anti-inflammatory bioceramic coatings on orthopaedic implants. [ABSTRACT FROM AUTHOR]

An anatase TiO2 coating doped with trace silver and paracetamol components was manufactured via the impregnation method combined with the potentiostatic reduction approach. The surface morphologies, microstructures and components were characterized via many surface analytical technologies. In addition, an electrochemical evaluation approach was developed to assess degradation behaviors of the beneficial chemicals in the phosphate buffer solution (PBS). The results demonstrated that the TiO2 coating was loaded with silver and paracetamol successfully. The Ag-oxy-carbide complex, coming from the reaction of silver ions and with hydroxyl groups in paracetamol, was helpful for the beneficial species sustainedly releasing from the coating during the 18-day immersion and remaining in the coating even after 18-day immersion in the PBS. [ABSTRACT FROM AUTHOR]

With the objective of enhancing the stability of scorodite, its encapsulation with hydroxyapatite (Ca5(PO4)3OH) (HAP) and fluorapatite (Ca5(PO4)3F) (FAP) surface coatings, the two most stable of the calcium phosphates, inert to pH and redox potential variations, are presented in this work. The experimental work includes: (1) determination of the metastable zone for HAP and FAP precipitation, (2) the synthesis of crystalline scorodite under atmospheric conditions using hydrothermal scorodite seed and its characterization, (3) the coating of scorodite with hydroxyapatite and fluorapatite with supersaturation-controlled heterogeneous crystallization, and (4) the long-term stability of the encapsulated scorodite solids. Hydroxyapatite and fluorapatite were prepared with homogeneous precipitation from a metastable solution to which reagents were added at a controlled flow rate. Crystalline scorodite was produced with seeding precipitation and encapsulated with a direct apatite (HAP or FAP) deposition that was controlled by adjusting the pH and reagent addition. The stability tests in oxic and anoxic environments over the pH range of 5–9 showed the release of arsenic from the apatite-coated scorodite to be much lower than from naked scorodite, thereby demonstrating that apatite-based encapsulation of hazardous materials is technically feasible and merits further consideration for development into an arsenic stabilizing technology. [ABSTRACT FROM AUTHOR]

Vascular transplantation is an effective and common treatment for cardiovascular disease (CVD). However, the low biocompatibility of implants is a major problem that hinders its clinical application. Surface modification of implants with extracellular matrix (ECM) coatings is an effective approach to improve the biocompatibility of cardiovascular materials. The complete ECM seems to have better biocompatibility, which may give cardiovascular biomaterials a more functional surface. The use of one or several ECM proteins to construct a surface allows customization of coating composition and structure, possibly resulting in some unique functions. ECM is a complex three-dimensional structure composed of a variety of functional biological macromolecules, and changes in the composition will directly affect the function of the coating. Therefore, understanding the chemical composition of the ECM and its interaction with cells is beneficial to provide new approaches for coating surface modification. This article reviews novel ECM coatings, including coatings composed of intact ECM and biomimetic coatings tailored from several ECM proteins, and introduces new advances in coating fabrication. These ECM coatings are effective in improving the biocompatibility of vascular grafts. [ABSTRACT FROM AUTHOR]

Ceramic coatings have a long history in the orthopaedic field, with plasma sprayed coatings of hydroxyapatite as leading standard in the manufacturing process; however, these coatings can contain secondary phases resulting from the decomposition of hydroxyapatite at high temperatures, which limit the lifetime of implants and their osseointegration. This work aims to produce coatings that can maximize bone osseointegration of metallic implants. In order to preserve the raw characteristics of hydroxyapatite powders that are thermally unstable, coatings were deposited by cold spray onto Ti6Al4V alloy substrates. In contrast with other thermal spray technologies, this process presents the advantage of spraying particles through a supersonic gas jet at a low temperature. On top of hydroxyapatite, carbonated nanocrystalline apatite was synthesized and sprayed. This biomimetic apatite is similar to bone minerals due to the presence of carbonates and its poor crystallinity. FTIR and XRD analyses proved that the biomimetic characteristics and the non-stoichiometric of the apatite were preserved in the cold spray coatings. The cold spray process did not affect the chemistry of the raw material. The adhesion of the coatings as well as their thicknesses were evaluated, showing values comparable to conventional process. Cold spraying appears as a promising method to preserve the characteristics of calcium phosphate ceramics and to produce coatings that offer potentially improved osseointegration. [ABSTRACT FROM AUTHOR]