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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]

Insufficient mechanical properties of hydroxyapatite-based composites prompted the search for new and effective solutions for dental applications. To improve the mechanical properties without losing the remineralization potential, the use of hybrid fillers was proposed. The first of them was based on the formation of hydroxyapatite (HA) layer on the surface of SYLOID®244 silica. The second of the investigated fillers was created by simultaneous synthesis of nanoparticles from precursors of HA and silica. The obtained fillers were extensively characterized by spectral methods including X-ray Diffractometry (XRD), Fourier-Transform Infrared Spectroscopy (FT-IR), and X-ray fluorescence (XRF), as well as by Scanning Electron Microscopy (SEM)/Energy Dispersive Spectroscopy (EDS). Tests using probiotic microorganisms were an important part of the analysis, indicating that there was no potential interaction of the materials with microflora. The tests of degree of conversion, depth of cure, opacity, sorption, solubility, flexural and compressive strength, and the remineralizing potential also showed that the composites with nano-sized silica/HA showed better mechanical properties than the composites with HA alone or commercial silica and at the same time the remineralization remained at the desired level. Thus, the proposed composite has a high application potential in the creation of implants and dental materials. [ABSTRACT FROM AUTHOR]

Oral biofilms are highly structured bacterial colonies embedded in a highly hydrated extracellular polymeric substances (EPS) matrix. This study aimed to investigate the characteristics of oral biofilm at different stages of maturation. Oral multispecies biofilms were grown anaerobically from plaque bacteria on collagen coated hydroxyapatite discs in brain heart infusion broth for one and three weeks. The volume of live bacteria and EPS matrix of the biofilms were determined by using corresponding fluorescent probes and confocal laser scanning microscopy. Atomic force microscopy (AFM) was used to quantitatively probe and correlate cell surface adhesion force of biofilms. The surface roughness was quantified in terms of the root mean square average of the height deviations. Adhesion was measured from force–distance data for the retraction of the cell from the surface. The volume of live bacteria and EPS of 3-week-old biofilms was higher than 1-week-old biofilms. The surface roughness value in 1-week-old biofilms was significantly higher than that in 3-week-old biofilms. AFM force–distance curve results showed that the adhesion force at the cell–cell interface was significantly more at-tractive than those at bacterial cells surface of both stages biofilms. Adhesion forces between the AFM tip and the surface of bacterial cell were fairly constant, whereas the cell–cell interface experienced greater adhesion forces in the biofilm's development. As oral biofilms become mature, EPS volume and cell–cell adhesion forces increase while the surface roughness decreases. [ABSTRACT FROM AUTHOR]

Low-modulus β-type Ti-45Nb alloy is a promising implant material due to its good mechanical biocompatibility, non-toxicity, and outstanding corrosion resistance. Its excellent chemical stability brings new challenges to chemical surface modification treatments, which are indispensable for both osteogenesis and antibacterial performance. Coatings containing metal ions as anti-microbial agents can be an effective way to reduce implant-associated infections caused by bacterial biofilm. Gallium ion (Ga3+) has the potential to reduce bacterial viability and biofilm formation on implant surfaces. In this study, a novel two-step process has been proposed for Ga3+ incorporation in hydroxyapatite (HAP) to develop bioactive and antibacterial surfaces on Ti-45Nb alloy. For the generation of bioactive surface states, HAP electrodeposition was conducted, followed by wet chemical immersion treatments in gallium nitrate (1 mM). Different buffers such as phosphate, sodium bicarbonate, ammonium acetate, and citrate were added to the solution to maintain a pH value in the range of 6.5–6.9. Coating morphology and HAP phases were retained after treatment with gallium nitrate, and Ga3+ ion presence on the surface up to 1 wt.% was confirmed. Combining Ga and HAP shows great promise to enable the local delivery of Ga3+ ions and consequent antibacterial protection during bone regeneration, without using growth factors or antibiotics. [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]

In this study, the effects of substrate temperature and ablation wavelength/mechanism on the structural, mechanical, and bioactivity properties of hydroxyapatite (HA) coatings were investigated. HA coatings were deposited on both Si(100) and Ti6Al4V surfaces. Substrate temperature varied from room temperature to 800 °C. Depositions were performed in Ar/H2O and vacuum environments. X-ray diffraction, scanning electron microscopy, and atomic force microscopy techniques were used to analyze structural and morphological variations. The adherence of coatings to the substrates was assessed by the pull-out method. The obtained data indicated that with the temperature increase, the coatings steadily crystallized. However, temperatures above 700 °C adversely affected protein adsorption and adhesion properties. Similar trends were confirmed via pull-out testing, protein adsorption, and cell proliferation tests. The ablation mechanism was also proven to play an important role in the deposition process. Overall, this study provides further evidence that crystallinity is a vital factor in the functionality of the coatings and depends on the deposition conditions. However, all measurements directly indicated that beyond 700 °C, the morpho-structural, mechanical, and bioactivity properties degrade. [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]

This study introduces and explores the use of supersaturated solutions of calcium and phosphate ions to generate well-defined hydroxyapatite coatings for orthopaedic implants. The deposition of hydroxyapatite is conducted via several solutions of metastable precursors that precipitate insoluble hydroxyapatite minerals at a substrate–solution interface. Solutions of this nature are intrinsically unstable, but this paper outlines process windows in terms of time, temperature, concentration and pH in which coating deposition is controlled via the stop/go reaction. To understand the kinetics of the deposition process, comparisons based on ionic strength, particle size, electron imaging, elemental analyses and mass of the formed coating for various deposition solutions are carried out. This comprehensive dataset enables the measurement of deposition kinetics and identification of an optimum solution and its reaction mechanism. This study has established stable and reproducible process windows, which are precisely controlled, leading to the successful formation of desired hydroxyapatite films. The data demonstrate that this process is a promising and highly repeatable method for forming hydroxyapatites with desirable thickness, morphology and chemical composition at low temperatures and low capital cost compared to the existing techniques. [ABSTRACT FROM AUTHOR]

The treatment of critical-size bone defects remains a complicated clinical challenge. Recently, bone tissue engineering has emerged as a potential therapeutic approach for defect repair. This study examined the biocompatibility and repair efficacy of hydroxyapatite-mineralized bionic polylactic acid (PLA) scaffolds, which were prepared through a combination of 3D printing technology, plasma modification, collagen coating, and hydroxyapatite mineralization coating techniques. Physicochemical analysis, mechanical testing, and in vitro and animal experiments were conducted to elucidate the impact of structural design and microenvironment on osteogenesis. Results indicated that the PLA scaffold exhibited a porosity of 84.1% and a pore size of 350 μm, and its macrostructure was maintained following functionalization modification. The functionalized scaffold demonstrated favorable hydrophilicity and biocompatibility and promoted cell adhesion, proliferation, and the expression of osteogenic genes such as ALP, OPN, Col-1, OCN, and RUNX2. Moreover, the scaffold was able to effectively repair critical-size bone defects in the rabbit radius, suggesting a novel strategy for the treatment of critical-size bone defects. [ABSTRACT FROM AUTHOR]

• The widespread use of Mg alloys as biodegradable implant materials is limited due to their rapid degradation rate. • HAp-containing PEO-coatings have attracted much attention for biomedical applications over the past decade. • The application of an HAp-containing coating can help minimize the rate of deterioration of Mg alloys, increase their biological activity, and facilitate bone formation. • HAp-containing coating reduces the rate of corrosion of Mg alloys, allowing for controlled degradation. Mg and its alloys have been introduced as promising biodegradable materials for biomedical implant applications due to their excellent biocompatibility, mechanical behavior, and biodegradability. However, their susceptibility to rapid corrosion within the body poses a significant challenge and restricts their applications. To overcome this issue, various surface modification techniques have been developed to enhance the corrosion resistance and bioactivity of Mg-based implants. PEO is a potent technique for producing an oxide film on a surface that significantly minimizes the tendency to corrode. However, the inevitable defects due to discharges and poor biological activity during the coating process remain a concern. Therefore, adding suitable particles during the coating process is a suitable solution. Hydroxyapatite (HAp) has attracted much attention in the development of biomedical applications in the scientific community. HAp shows excellent biocompatibility due to its similarity in chemical composition to the mineral portion of bone. Therefore, its combination with Mg-based implants through PEO has shown significant improvements in their corrosion resistance and bioactivity. This review paper provides a comprehensive overview of the recent advances in the preparation, characterization, corrosion behavior and bioactivity applications of HAp particles on Mg-based implants by PEO. [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]

The objective of this study is to investigate the efficiency of two processes for the amoxicillin removal through static (batch) adsorption and photocatalytic degradation onto the prepared samples. Three solid materials as photocatalyst and/or adsorbent were synthesized viz. nanotitanium dioxide (NT) prepared by the sol–gel method, scallop shells-based nanohydroxyapatite (NP), and nanotitanium dioxide/nanohydroxyapatite composite (NTP). The physicochemical and morphological properties of the prepared samples were tested by TGA, XRD, DRS, ATR-FTIR, nitrogen adsorption/desorption isotherm, zeta potential, SEM, and TEM. The major operational conditions were optimized for catalyst or adsorbent mass, pH, shaking time, initial amoxicillin (AMX) concentration, power of UV lamp, and temperature. The results illuminated that NTP achieved the highest adsorption capacity (88.46 mg/g) at 20 ℃ and AMX adsorption onto all the solid materials was well applied by Langmuir, Temkin, pseudo-second order, and Elovich models. The maximum desorption percent (98%) was attained by acetone. The degradation percent of AMX reached 85.3 and 99.5% for NT and NTP, respectively, using 0.9 g/L of catalyst dosage through 90 min. AMX photodegradation onto the catalysts' surface was well fitted by Langmuir–Hinshelwood, Arrhenius, and Eyring–Polanyi models with endothermic, physical, and nonspontaneous nature of photocatalysis process. NTP acts as a promising adsorbent and photocatalyst for the antibiotics' removal in wastewater. [ABSTRACT FROM AUTHOR]

Introduction: Despite the increasing use of cementless stems in total hip arthroplasty, the cemented stem has played a valuable role in the armamentarium of orthopedic surgeons. This study aims to compare two types of Libra® stems SERF, one cemented (Libra® C) and the other cementless hydroxyapatite coated (Libra® HA) that were conducted to analyze the medium-term outcome regarding their behavior and longevity. Methods: This is a retrospective study for patients who received primary total hip arthroplasty with Dual Mobility (DM) articulation in the period between January 2014 to January 2020 with a minimum of two years follow-up. Two-hundred hips have been identified in 196 patients. One hundred forty-three Libra® cementless versus fifty-seven Libra cemented stems were implanted and the outcome of these stems is reported. All procedures were performed through the posterior approach and cemented stems were selected for elderly patients with wide medullary canals Dorr Type C. The indications for the index procedure were fractures, avascular necrosis, rheumatoid, and osteoarthritis. One hundred thirty-nine cementless DM cups were used while sixty-one hips had cemented Novae stick cups. Radiological evaluation for cup and stem positions, cement mantle, and radiolucent lines was performed, besides clinical function using the Harris Hip Score. Results: The average age of patients was 60 ± 14.8. At the latest review, none of the cemented stems was revised or awaiting revision. One cementless stem was revised because of cortical perforation. Five intraoperative fractures were observed in the cementless group, but none of them needed revision or affected the stem stability. Readmission to theatre occurred in four patients to evacuate hematoma in two, a reduction of dislocation in one, and grafting bone lysis in one. Conclusion: Cemented stems have an important role in osteoporotic patients with wide medullary canals with excellent outcomes and minimal risk of fracture. Level of evidence: Level IV. [ABSTRACT FROM AUTHOR]

Titanium (Ti) and Ti-based alloys are commonly used in dental implants, and surface modifications of dental implants are important for achieving osseointegration (i.e., direct connection between the implant surface and bone). This study investigated the effect of an eco-friendly etching solution—a hydrogen peroxide–sodium bicarbonate mixture—on the surface properties and contact angles of osteoblast adhesion and proliferation on Ti surfaces. Disk-shaped Ti specimens were prepared using different surface treatments (machining, sandblasting, and sandblasting/acid-etching), and they were immersed in the etching solution and ultrasonically cleaned. Surface characterization was performed using scanning electron microscopy, digital microscopy, contact angle analysis, and X-ray photoelectron spectroscopy. MG-63 osteoblasts were cultured on the specimens, and their adhesion to the specimen surface and proliferation were examined using staining and the MTT assay, respectively. Additional etching with the etching solution caused the formation of nano/micro hierarchical structures, increased surface roughness, and enhanced hydrophilicity. Osteoblast adhesion and proliferation were found to improve on the modified surfaces. The eco-friendly etching method has the potential to enhance the biological properties of Ti implant surfaces and thereby improve dental implant performance. [ABSTRACT FROM AUTHOR]

Using NiTi alloys with shape memory for long-term medical implants requires modification of their surface due to the possible occurrence of corrosion. Hence, the surface of the staples used to join fractured bone within the craniofacial region was modified by applying a titanium oxy-nitrogen layer and a hydroxyapatite coating. Surface-modified clamps were tested in vivo using New Zealand white rabbits. After determining the mechanical characteristics of the bone and considering the initial state and surface modification, the diameter of the wire (used to make the clamps with the appropriate compression force) was selected. Implantation was performed on two groups of rabbits: experimental and control. In the experimental group, an intentionally induced bone fracture was treated in one tibia. On the second tibia, two additional clamps were applied to increase the possibility of a negative impact of the NiTi alloy on a living organism. After 6 weeks of application, a proper joining of the broken bone fragments was stated. Whereas after twelve weeks, no negative impact of the clamp material on a living organism, i.e., a rabbit, was found. Hence, the clamp with the modified surface can connect bone fragments in humans as well as small and medium-sized animals, with an extended range of use up to 12 weeks. [ABSTRACT FROM AUTHOR]

The aim of the present paper was to evaluate the effect of hydroxyapatite coatings on the two types of Mg–Zn–Ag alloys as a possible solution to control magnesium alloy degradation. The coatings were prepared by the radio frequency magnetron sputtering method at a deposition temperature of 300 °C. To perform this evaluation, the coated alloys were immersed in a simulated body fluid solution at body temperature (37 ± 0.5 °C) to determine the corrosion resistance through electrochemical and immersion tests. Moreover, the investigation also consisted of the evaluation of microchemical, mechanical, and morphological properties. The deposition temperature of 300 °C was enough to obtain a crystalline hydroxyapatite structure with a Ca/P ratio close to the stochiometric one. The adhesion of coatings was not influenced by the nature of Mg–Zn–Ag alloys, so similar values for both coated alloys were found. The results showed that the coating was homogonous deposited on the Mg–Zn–Ag alloys and the corrosion resistance of uncoated magnesium alloys was improved. [ABSTRACT FROM AUTHOR]

Biological hydroxyapatite (HA) coatings have been used to repair damaged bone exhibiting fluorosis. However, they are often inappropriate and have some undesirable effects. Consequently, modified HA coatings with functional elements have become popular. In the present work, selenium-doped HA (Se-HA) powders were first synthesized by chemical coprecipitation. A Se-HA nanostructure coating was then fabricated on the surface of a titanium (Ti) substrate by suspension plasma spraying. Energy-dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy, and x-ray powder diffraction demonstrated the homogeneous presence of Se within a Se-HA coating made from the appropriately doped powder. The Se was incorporated into the HA lattice by replacing some of the phosphate groups with selenite groups. The chemical stability of the coating was assessed by immersing samples in a citric acid-modified phosphate-buffered saline solution. The solubility of the Se-HA coating increased slightly owing to the introduction of Se. According to electrochemical tests, the dense Se-HA coating provided the Ti substrate with a reliable biocorrosion barrier. The in vitro bioactivity of the coating was characterized by immersing the samples in simulated body fluid for various times. The results suggested that the Se-HA coating had similar bone-like apatite formation capability to that of a conventional HA coating. Compared with the HA coating, the Se-HA coating effectively promoted the adhesion, proliferation, and differentiation of osteoblasts in the presence of fluoride ions. These results suggest that Se-HA coatings have some potential for improving bone regeneration in fluorosis patients. [ABSTRACT FROM AUTHOR]

Osseointegration plays the most important role in the success of an implant. One of the applications of hydroxyapatite (HAp) is as a coating for metallic implants due to its bioactive nature, which improves osteoconduction. The purpose of this research was to assess the in vitro behavior of HAp undoped and doped with Ag and/or Sr obtained by galvanostatic pulsed electrochemical deposition. The coatings were investigated in terms of chemical bonds, contact angle and surface free energy, electrochemical behavior, in vitro biomineralization in acellular media (SBF and PBS), and biocompatibility with preosteoblasts cells (MC3T3-E1 cell line). The obtained results highlighted the beneficial impact of Ag and/or Sr on the HAp. The FTIR spectra confirmed the presence of hydroxyapatite within all coatings, while in terms of wettability, the contact angle and surface free energy investigations showed that all surfaces were hydrophilic. The in vitro behavior of MC3T3-E1 indicated that the presence of Sr in the HAp coatings as a unique doping agent or in combination with Ag elicited improved cytocompatibility in terms of cell proliferation and osteogenic differentiation. Therefore, the composite HAp-based coatings showed promising potential for bone regeneration applications. [ABSTRACT FROM AUTHOR]

Recently, superhydrophobic magnesium (Mg)-based implants are attracting extensive interest due to their superior corrosion resistance and specific anti-bacterial adhesion characteristics. Nevertheless, the superhydrophobic surface is not conducive to cell adhesion and proliferation, which limits the application of superhydrophobic medical Mg alloys. Herein, the superhydrophobic composite coating of hydroxyapatite (HA)/bismuth sulfide (Bi 2 S 3)/lauric acid (LA) was prepared on AZ31B Mg alloys via hydrothermal and impregnation methods, and the water contact angle of the composite coating was up to 156°, endowing Mg alloys with excellent corrosion resistance and antibacterial properties. Furthermore, the surface of the superhydrophobic coating can be transformed to hydrophilicity upon 808 nm near-infrared (NIR) light irradiation, due to the photothermal effect of Bi 2 S 3 that led to the phase transition of the lauric acid on the surface of the composite coating. After 5 min NIR light irradiation, the contact angle decreased from 156° to 60.6°, and the electrochemical tests showed that the superhydrophobic composite coating with wettability-transformable could provide effective protection for Mg alloy substrate. The antibacterial efficiency of the coated Mg alloy reached 99.9% against Staphylococcus aureus and 95.8% against Escherichia coli , respectively. Meanwhile, the superhydrophobic composite coating with wettability-transformable had good biocompatibility with over 81.2% cell viability on MC3T3-E1 cells and good early cell growth and adhesion. This work provides a strategy for preparing wettability-transformable superhydrophobic hydroxyapatite coatings on Mg-based implants with dual-function of antibacterial ability and osteogenic activity. [ABSTRACT FROM AUTHOR]

In the case of orthopedic and dental interventions, local antibiotic therapy reduces significantly the risk associated with the intervention. The aim of this study was the preparation and characterization of pure hydroxyapatite (HA), Si- and Mg-doped HA, which ensures the sustained release of doxycycline, and the investigation of the parameters, which were crucial for the drug release. The carriers were synthesized using the precipitation method. In order to achieve different morphologies, traditional drying and spray drying methods were used: Si-doped HA was prepared using two different sources of Si, Na 2 SiO 3 and Ludox AS-40, while (Mg(NO 3) 2)*6H 2 O was used for substitution with Mg. The carriers were characterized by XRD, SEM, EDX and TG/DTA methods, and the ion incorporation was also confirmed by lattice parameters calculations. Doxy was bound on the carriers by physical adsorption, the adsorption capacity increased proportionally by increasing the concentration of the initial Doxy solutions (10, 15, 20, 25 g/L). The investigated systems showed different releases with the change of the dissolution medium (in the case of HA microspheres, the release in PBS was twice as high as in SBF), chemical composition and morphology of the carriers. The retard effect of the carriers was improved by the spherical morphology, and the reduced release by ion substitution in both SBF and PBS increased as follows: HA < HASi1

With the increasing incidences of orbital wall injuries, effective reconstruction materials and techniques are imperative for optimal clinical outcomes. In this literature review, we delve into the efficacy and potential advantages of using titanium implants coated with nanostructured hydroxyapatite for the reconstruction of the orbital wall. Titanium implants, recognized for their durability and mechanical strength, when combined with the osteoconductive properties of hydroxyapatite, present a potentially synergistic solution. The purpose of this review was to critically analyze the recent literature and present the state of the art in orbital wall reconstruction using titanium implants coated with nanostructured hydroxyapatite. This review offers clinicians detailed insight into the benefits and potential drawbacks of using titanium implants coated with nanostructured hydroxyapatite for orbital wall reconstruction. The highlighted results advocate for its benefits in terms of osseointegration and provide a novel strategy for orbital reconstruction, though further studies are essential to establish long-term efficacy and address concerns.

This document discusses the use of hydroxyapatite (HA) coatings for orthopedic and dental implants. HA is a bioceramic material that enhances fixation and osseointegration at the implant-tissue interface. The document highlights the advantages of using biodegradable implants, such as eliminating the need for a secondary surgical intervention. It also explores the use of synthetic and biological-derived HA, with the latter showing enhanced mechanical performance and bioactivity. Various techniques for coating implants with HA are discussed, including plasma spray, pulsed laser deposition, and biomimetic coating. The document concludes by emphasizing the focus on the synthesis and characterization of HA-based coatings for applications in bone repair, tissue engineering, and dental implants. [Extracted from the article]

3D printed porous titanium cage is believed with physiology mechanical properties and biocompatibility for orthopedic usage. Typical split cage design with a grafting window and infilled bone graft has raised a lot of questions. In this research, a modified hydrothermal approach, employing chelated calcium to enhance the medium stability and increase the generated amount, is proposed to construct bioactive hydroxyapatite coating inside the porous structure of 3D printed porous titanium cage. The in vitro and transcriptomic results indicated the hydroxyapatite enhanced the cells physical sensing system, therefore enhanced the osteogenesis inside titanium/hydroxyapatite cage. The in vivo goat spinal fusion experiment indicated the integrative titanium/hydroxyapatite cage, compared with typical split cage/graft cage, showed better bone tissue ingrowth and spinal fusion ability. This research provides a promising hydroxyapatite coating strategy for complex porous structure and revealed the potential advantage of integrative titanium/hydroxyapatite intervertebral cage design.

Self-healing and autologous bone graft of calvaraial defects can be challenging. Therefore, the fabrication of scaffolds for its rapid and effective repair is a promising field of research. This paper provided a comparative study on the ability of Three-dimensional (3D) printed polycaprolactone (PCL) scaffolds and PCL-modified with the hydroxyapatite (HA) and bioglasses (BG) bioceramics scaffolds in newly bone formed in calvaria defect area. The studied 3D-printed PCL scaffolds were fabricated by fused deposition layer-by-layer modeling. After the evaluation of cell adhesion on the surface of the scaffolds, they were implanted into a rat calvarial defect model. The rats were divided into four groups with scaffold graft including PCL, PCL/HA, PCL/BG, and PCL/HA/BG and a non-explant control group. The capacity of the 3D-printed scaffolds in calvarial bone regeneration was investigated using micro computed tomography scan, histological and immunohistochemistry analyses. Lastly, the expression levels of several bone related genes as well as the expression of miR-20a and miR-17-5p as positive regulators and miR-125a as a negative regulator in osteogenesis pathways were also investigated. The results of this comparative study have showed that PCL scaffolds with HA and BG bioceramics have a great range of potential applications in the field of calvaria defect treatment. [ABSTRACT FROM AUTHOR]

Orthopedic-device-related infections are notorious for causing physical and psychological trauma to patients suffering from them. Traditional methods of treating these infections have relied heavily on antibiotics and are becoming ineffectual due to the rise of antibiotic-resistant bacteria. Mimics of antimicrobial peptides have emerged as exciting alternatives due to their favorable antibacterial properties and lack of propensity for generating resistant bacteria. In this study, the efficacy of an antibacterial polymer as a coating material for hydroxyapatite and glass surfaces, two materials with wide ranging application in orthopedics and the biomedical sciences, is demonstrated. Both physical and covalent modes of attachment of the polymer to these materials were explored. Polymer attachment to the material surfaces was confirmed via X-ray photoelectron spectroscopy and contact angle measurements. The modified surfaces exhibited significant antibacterial activity against the Gram-negative bacterium E. coli, and the activity was retained for a prolonged period on the surfaces of the covalently modified materials. [ABSTRACT FROM AUTHOR]

The purpose of this review paper is to describe a noble approach, called Growing Integration Layers (GIL) method, for the application of biocompatible oxide ceramics layers coating on bulk metallic alloys. Since these oxides are utilizing component(s) of the alloy then formed by mostly electrochemical reactions at low temperatures, they are well adhered on the alloy substrate. The GIL strategy differs significantly from so-called layer-by-layer integration, layers are deposited from top-to-top. In the GIL, the oxide layers are produced and grown on the substrate alloy from the bottom. Therefore those layers on metallic substrate is chemically and structurally continuous thus shows excellent adhesion. Using GIL method, a variety of functional and structural ceramic layers can be processed mostly in aqueous solutions, thus they are typical soft and green processes, consuming low energy. These methods can be applied in the preparation of dense/porous and graded intermediate layers of ceramics for a wide variety of applications, including thermal, mechanical, chemical and biomedical. This review concentrate on successful ceramics coating on Titanium based metallic alloys via GIL strategy. The GIL technology improves the adhesion of ceramic layers and introduces bioactivity to bulk metallic alloys. Since bulk metallic glasses and alloys generally contain active components like titanium, it can be used in the formation of titanium oxide and/or hydroxides which are bioactive. During this oxidation/hydroxidation, widely diffused interfaces and continuously graded layers are formed from bulk substrate, even at ambient temperature and pressure. One of the most notable examples of GIL method is the coating of bio-active hydroxyapatite (HA) ceramics on Ti alloys. We have exhibited here with (1) Bioactive ceramic layers on bulk metallic glasses, (2) Hydroxyapatite-like coating on Ti–Cu–Sn alloy and (3) Sr doped apatite-like coating on the same alloy. [ABSTRACT FROM AUTHOR]

Cu-doped hydroxyapatite (HA)/TiO2 (CuHA/TiO2) bioactive ceramic composite coatings were prepared on Ti surfaces using an electrochemical method to enhance their adhesion and antibacterial properties. The obtained coatings were characterized by scanning electron microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy, while their adhesion was measured using a scratch test. The maximum adhesion between the TiO2 layer and the substrate was 39.8 ± 2.6 N at an anodizing voltage of 180 V. Subsequently, the CuHA coatings were successfully deposited on the TiO2 layers and grown outward along TiO2 pores (during this process, Cu atoms are doped into the HA structure in the form of Cu2+ ions). The CuHA adhesion to the TiO2 layer was 26.3 ± 1.9 N, indicating that the TiO2 interlayer significantly enhanced the bonding of CuHA to the substrate. Furthermore, the fabricated CuHA/TiO2 coatings produced a strong antibacterial effect on Escherichia coli and Staphylococcus aureus species, exhibited high biocompatibility, and promoted the proliferation of MC3T3-E1 cells. [ABSTRACT FROM AUTHOR]

A novel method for precipitating hydroxyapatite (HAp) onto cement paste is investigated for protecting concrete infrastructure from radiological contamination. Legacy nuclear sites contain large volumes of contaminated concrete and are expensive and dangerous to decommission. One solution is to 'design for decommissioning' by confining contaminants to a thin layer. Current layering methods, including paints or films, offer poor durability over plant lifespans. Here, we present a mineral-HAp-coated cement, which innovatively serves as a barrier layer to radioactive contaminants (e.g. Sr, U). HAp is shown to directly mineralise onto a cement paste block in a layer several microns thick via a two-step process: first, applying a silica-based scaffold onto a cement paste block; and second, soaking the resulting block in a PO4-enriched Ringer's solution. Strontium ingression was tested on coated and uncoated cement paste (~ 40 × 40 × 40mm cement, 450 mL, 1000 mg L− 1 Sr) for a period of 1-week. While both coated and uncoated samples reduced the solution concentration of Sr by half, Sr was held within the HAp layer of coated cement paste and was not observed within the cement matrix. In the uncoated samples, Sr had penetrated further into the block. Further studies aim to characterise HAp before and after exposure to a range of radioactive contaminants and to develop a method for mechanical layer separation. [ABSTRACT FROM AUTHOR]

Although coating the biomaterials with hydroxyapatite powder (HAp) mixed electro discharge machining (EDM) is required to improve their biological responses, the modified 316L stainless steel shows a low coating adhesion and cracked surface, which is prone to poor corrosion resistance and surface integrity. In addition, inferior biological responses are noticed, since a little amount of HAp is detected in the coating. The primary objective of this study is to assess the CNT reinforced HAp-based coating on a 316L stainless steel to improve the surface features, corrosion and biocompatibility. This study also establishes a link between the process variables and the material's properties and shows the feasibility of multiple additive mixed EDM method. Following ASTM standard, several surface characterization tools were used to characterize the surface of the modified 316L stainless steel. CNT (0.4 g/l) added to the HAp mixed-EDM method results in a uniform and thin coating of 12.4 µm with shallow craters, nanopores and no cracks. A small corrosion rate of 0.00033 mm per annum is recorded. The presence of carbon incorporated Ca–P-based alloys in the coating ensures a high coating adhesion of 32.6 MPa and a high biocompatibility of more than 95% alive cells. [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO) is widely used as an excellent UV absorbent to improve UV‐shielding ability. However, its photocatalytic activity is high, and the UV absorption region and dispersibility within the polymer are poor, which limits the application. This work is based on the design of ZnO nanoparticles via the coating of hydroxyapatite (HA) and (3‐aminopropyl) triethoxysilane (KH550), then it is compounded with polyvinyl chloride (PVC). X‐ray diffraction (XRD), Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), high‐resolution transmission electron microscopy (HRTE), and UV spectrophotometer are used to analyze the microstructure and properties. The results show that the composite films have good UV‐shielding abilities and help reduce the damage of PVC upon exposure or heat. Therefore, this work provides new means to make PVC composites with superior UV‐shielding properties, and the tensile strength at the break of PVC film blended with ZnO@HA/KH550 is effectively improved, which is due to good compatibility between ZnO@HA/KH550 and PVC matrix. [ABSTRACT FROM AUTHOR]

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

Magnetically‐actuated soft robots for medical applications are required to be functional, biocompatible, as well as capable of robust motion inside human organs. In this paper, a ring‐shaped magnetic soft robot, with a flexible biopolymeric film coating, capable of motion on mucus‐coated surfaces is designed and investigated. The biopolymeric film made from chitosan–glycerol (C–G) solution endows the robot with robust locomotion capabilities on surfaces of diverse geometrical shapes and orientations. By utilizing mucoadhesive locomotion, the robot has the potential to carry out clinical procedures on enclosed mucus‐coated tissue surfaces. Material characterization shows that the mucoadhesion increases with the increase of contact times and/or preload forces. The softness of the C–G film can be adjusted by controlling the concentration of glycerol. The ring‐shaped design and magnetization profile decouple the locomotion and functions of the robot. Additionally, the C–G film‐coated robot is tested to be biocompatible for a human colorectal adenocarcinoma cell line with epithelial morphology (HT29). The C–G film reduces the negative effects (superoxide generation) of ferromagnetic particles. Three robot functions including pick‐and‐place, cargo transportation, and liquid capsule release are demonstrated on different surfaces to show the maneuverability, functionality, and potential of implementing clinical procedures through mucoadhesion. [ABSTRACT FROM AUTHOR]

The doping of the second metal Mo is expected to further enhance the carbon deposition resistance of Ni-based catalysts for syngas production via dry reforming of methane (DRM). In this study, the hydroxyapatite (HAP) was used as the support and a small Mo dosage was doped in the Ni-based catalysts to investigate the effect of intrinsic hydroxyl and Mo doping on the catalytic activity and carbon deposition resistance in DRM reaction. The catalyst characterization results show that both Ni and Mo are doped into the HAP structure with relatively uniform dispersion. The basic site strength of Ni4Mo0.2-HAP catalyst containing Mo is significantly higher than that of without Mo. The Mo dopant significantly improves the initial catalytic activity, but has minimal effect on the stability enhancement. Whether the catalyst is pre-reduced or not is crucial to the initial activity of the DRM reaction, the non-pre-reduced catalysts will go through a "self-activation" stage at the beginning of the reaction, where the "hydroxyl group" are proved to play as an "oxygen supply" for the partial oxidation of CH 4 or the oxidation of the carbon deposition in the initial stage. Only trace amount of carbon deposition is found after 100 h of DRM reaction on Ni3Mo0.2-HAP catalyst. The NiMo-HAP catalysts exhibit excellent initial activity and resistance to carbon deposition due to the synergistic effect of Ni–Mo alloy and hydroxyl groups in the hydroxyapatite support. [Display omitted] • The doping of Mo improved the initial activity of the NiMo-HAP catalyst. • NiMo-HAP catalysts exhibited enhanced carbon deposition resistance (during 100 h DRM reaction). • Hydroxyl groups and NiMo alloys synergistically contributed to the DRM catalytic activity and stability. • NiMo-HAP maintained structural stability after 100 h DRM reaction. [ABSTRACT FROM AUTHOR]

BACKGROUND: High density polyethylene has been widely used as a repair material for cranial and maxillofacial bone defects, but its preparation method and surface activity still need further improvement. OBJECTIVE: To optimize the preparation method of high density polyethylene and improve the surface activity of high density polyethylene. METHODS: The high density polyethylene scaffolds were prepared by extrusion 3D printing technology, and the scaffolds were immersed in dopamine solution and simulated body fluid successively to be coated with polydopamine and hydroxyapatite. The microstructure, hydrophilicity and compression modulus of the scaffolds before and after coating were characterized. Mouse embryonic osteogenic precursor cells (MC3T3-E1) and human umbilical vein endothelial cells were inoculated on the surface of the scaffold to evaluate the cytocompatibility and early osteogenic and angiogenic differentiation of the scaffold before and after coating. RESULTS AND CONCLUSION: (1) The 3D printed high density polyethylene scaffold’s fibers were arranged regularly and pores were uniform. Characterization results showed that polydopamine and hydroxyapatite coatings were successful on the surface of the scaffolds. Compared with the unmodified scaffold, the surface water contact angle of the scaffold modified with polydopamine coating and polydopamine + hydroxyapatite coating decreased significantly (P < 0.05), and the compressive modulus did not change significantly. (2) Compared with the unmodified scaffold, the modified scaffold with polydopamine coating and polydopamine + hydroxyapatite coating could promote the adhesion of MC3T3-E1 cells and human umbilical vein endothelial cells (P < 0.05). The cell adhesion promoting effect of double coating modified group was better than that of single coating modified group (P < 0.05). Compared with the unmodified scaffold, the modified scaffold with polydopamine coating and polydopamine + hydroxyapatite coating could promote the proliferation of MC3T3-E1 cells and human umbilical vein endothelial cells (P < 0.05). The proliferation promoting effect of double coating modified group was better than that of single coating modified group (P < 0.05). Compared with unmodified scaffolds, the scaffolds modified with polydopamine coating and polydopamine + hydroxyapatite coating could promote the osteogenic differentiation of MC3T3-E1 cells (P < 0.05), and increase the expression of angiogenic factor CD31 in human umbilical vein endothelial cells. The double-coating modified group was more obvious. (3) The results showed that the high density polyethylene scaffolds coated with polydopamine and hydroxyapatite based on 3D printing technology have good cytocompatibility and early osteogenic and angiogenic differentiation ability. [ABSTRACT FROM AUTHOR]

Hydroxyapatite (Ca10(PO4)6(OH)2) coatings are often made in a two-step process, where hydroxyapatite is firstly synthesized, and then applied as a coating for different applications. One way to make the process more efficient, is to combine the synthesis and coating processes into a single step. Plasma spray is a common method used to apply hydroxyapatite as a coating, as it is a fast and controlled method of coating materials. The aim of the present study was to investigate the inflight reaction of calcium carbonate (CaCO3) and brushite (CaHPO4·2H2O) to synthesize hydroxyapatite using plasma spray. Various plasma spray parameters were used to observe their effect on the quantity of hydroxyapatite produced in the coating. Phase analysis was carried out using XRD, and the morphology of the coatings was observed using SEM. Plasma spray coatings containing hydroxyapatite, tetracalcium phosphate (Ca4(PO4)2O) and calcium oxide (CaO) were successfully made from the reaction between the precursor powders. The plasma spray parameters which influenced the particle velocity were found to have the largest effect on the quantity of hydroxyapatite produced in the coating. The plasma temperature was also found to affect the amount of hydroxyapatite produced. [ABSTRACT FROM AUTHOR]

To develop medical-grade stainless-steel 316L implants that are biocompatible, non-toxic and antibacterial, such implants need to be coated with biomaterials to meet the current demanding properties of biomedical materials. Hydroxyapatite (HA) is commonly used as a bone implant coating due to its excellent biocompatible properties. Zinc oxide (ZnO) nanoparticles are added to HA to increase its antibacterial and cohesion properties. The specimens were made of a stainless-steel grade 316 substrate coated with HA-ZnO using the electrophoretic deposition technique (EPD), and were subsequently characterized using scanning electron microscopy (SEM), energy dispersive X-ray (EDX), stylus profilometry, electrochemical corrosion testing and Fourier transform infrared (FTIR) spectroscopy. Additionally, cross-hatch tests, cell viability assays, antibacterial assessment and in vitro activity tests in simulated body fluid (SBF) were performed. The results showed that the HA-ZnO coating was uniform and resistant to corrosion in an acceptable range. FTIR confirmed the presence of HA-ZnO compositions, and the in vitro response and adhesion were in accordance with standard requirements for biomedical materials. Cell viability confirmed the viability of cells in an acceptable range (>70%). In addition, the antibacterial activity of ZnO was confirmed on Staphylococcus aureus. Thus, the HA-ZnO samples are recommended for biomedical applications. [ABSTRACT FROM AUTHOR]

Calcium phosphate-based coatings are widely studied in orthopedics and dentistry for their similarity to the mineral component of bone and their capability to promote osseointegration. Different calcium phosphates have tunable properties that result in different behaviors in vitro, but the majority of studies focus only on hydroxyapatite. Here, different calcium phosphate-based nanostructured coatings are obtained by ionized jet deposition, starting with hydroxyapatite, brushite and beta-tricalcium phosphate targets. The properties of the coatings obtained from different precursors are systematically compared by assessing their composition, morphology, physical and mechanical properties, dissolution, and in vitro behavior. In addition, for the first time, depositions at high temperature are investigated for the further tuning of the coatings mechanical properties and stability. Results show that different phosphates can be deposited with good composition fidelity even if not in a crystalline phase. All coatings are nanostructured and non-cytotoxic and display variable surface roughness and wettability. Upon heating, higher adhesion and hydrophilicity are obtained as well as higher stability, resulting in better cell viability. Interestingly, different phosphates show very different in vitro behavior, with brushite being the most suitable for promoting cell viability and beta-tricalcium phosphate having a higher impact on cell morphology at the early timepoints. [ABSTRACT FROM AUTHOR]

In this review paper, different methods of hydroxyapatite‐based coatings on external fixation pins with improvement in the adhesion strength are explained. Different coating methods such as dip coating, surface‐induced mineralization, plasma spraying, physical vapor deposition magnetron sputtering, micro‐arc oxidation, electrophoretic deposition, chemical vapor deposition, ion beam assisted deposition, sol‐gel dip coating, pulsed laser deposition, and electrohydrodynamic coating are investigated. The micro‐arc oxidation method showed high degradation delaying of the substrate with a high‐voltage electrolyte solution. Moreover, controlling the coating porosity by applying the gas is a good feature of the physical vapor deposition magnetron sputtering method. The comparison of the hydroxyapatite (HA) coatings method showed that the plasma spraying method leads to better coating features between the coating methods on the implant pins. [ABSTRACT FROM AUTHOR]

The use of toothpastes is the best way to combat enamel loss and degradation. When they also contain hydroxyapatite nanoparticles, HAP NPs, the tooth enamel can be restored by remineralization. In this study, we developed two types of toothpastes, one with nano sized HAP, noted P1, and the other with nano multi-substituted hydroxyapatite (ms-HAP, HAP-Mg-Zn-Si), noted P2, which were used to treat the artificially demineralized teeth enamel surface. The remineralization efficacy of the two toothpastes was determined on artificially created enamel lesions by suspending healthy enamel slices in demineralizing solution, made of orthophosphoric acid of 37.5% for 90 s. For this purpose, six extracted third molars were collected and twenty-four enamel slices were cut and arbitrarily allocated to the four groups, namely n = 6 enamel slices for each group. One group served as untreated (natural) enamel control, and another group comprised demineralized enamel and two test groups, firstly demineralized, and then, they were treated with toothpastes P1 and P2, respectively, each of them for ten days, and finally were noted P1 and P2 enamel surfaces. The surface morphology and roughness of all enamel specimens were studied by atomic force microscopy (AFM) before and after applying the treatment with the toothpastes. The toothpastes effect was evidenced by the average diameter of ceramic nanoparticles deposited within the superficial smooth layer on enamel surface having, at the completion of 10 days treatment, a low surface roughness close to that of natural enamel. This in vitro comparative study demonstrated that both toothpastes P1 and P2 can promote surface enamel repair by remineralization and the formation of a protective hydroxyapatite coating layer on the enamel surface treated with these toothpastes. [ABSTRACT FROM AUTHOR]

This study was aimed to coat a hybrid bioceramic composite onto Ti6Al4V by using hydrothermal method. The Hybrid bioceramic composite for coating was prepared by reinforcing different rations of expanded perlite (EP) and 5 wt.% chitosan into synthesized Hydroxyapatite (HA). Coating was performed at 1800°C for 12 hours. The coated specimens were gradually subjected to a sintering at 6000°C for 1 hour. For in vitro analysis, the specimens were kept in Ringer's solution for 1, 10, and 25 days. All specimens were examined by SEM, EDX, FTIR, and surface roughness analyses for characterizing. It was concluded that as the reinforcement ratio increased, there was an increase in coating thickness and surface roughness. The optimum reinforcement ratio for expanded perlite can be 10 wt.% (A3-B3). With increasing ratio of calcium (Ca) and phosphate (P) (Ca/P), the surface becomes more active in body fluid and then observed the formation of the hydroxycarbonate apatite (HCA) layer. As the waiting time increased, there was an increase in the formation of an apatite structure. [ABSTRACT FROM AUTHOR]

The formation of hydroxyapatite coating on BT6 titanium alloy under the combined treatment: nitriding and plasma-electrolytic oxidation in an alkaline electrolyte (hydroxyapatite + 1M potassium hydroxide) was investigated. Such treatment promotes the growth of the Ca10 (PO4)6(OH)2 hydroxyapatite phase, that can be attributed to an increase of the centers of hydroxyapatite crystallization on the pre-nitrided surface. The hydroxyapatite coating on pre-nitrided surface provided higher hydrophilicity and better corrosion resistance in Ringer's solution at a temperature of 37°C. [ABSTRACT FROM AUTHOR]

In the present work, activated-carbon-containing pellets were preparedby direct chemical activation of sawdust, using clays as a binder. The obtained pellets (ACC) were coated with hydroxyapatite (HAp) nanoparticles (ACC-HAp) to improve adsorption towards Pb(II), Cu(II), Zn(II), and Ni(II). The pellets were characterized by scanning electron microscopy (SEM), by Fourier transform infrared spectroscopy (FTIR), and with a gas sorptometer. The effect of pH, contact time, and initial concentration on adsorption performance was investigated. Additionally, desorption studies were performed, and the regeneration influence on compressive strength and repeated Pb(II) adsorption was investigated. The results showed that, after coating ACC pellets with HAp nanoparticles, the adsorption capacity increased for all applied heavy metal ions. Pb(II) was adsorbed the most, and the best results were achieved at pH 6. The adsorption process followed the pseudo-second-order kinetic model. The adsorption isotherm of Pb(II) is better fitted to the Langmuir model, showing the maximum adsorption capacity of 56 and 47 mg/g by ACC-HAp and ACC pellets, respectively. The desorption efficiency of Pb(II)-loaded ACC-HAp pellets increased by lowering the pH of the acid, resulting in the dissolution of the HAp coating. The best desorption results were achieved with HCl at pH 1 and 1.5. Therefore, the regeneration procedure consisted of desorption, rinsing with distilled water, and re-coating with HAp nanoparticles. After the regeneration process, the Pb(II) adsorption was not affected. However, the desorption stage within the regeneration process decreased the compressive strength of the pellets. [ABSTRACT FROM AUTHOR]

In order to improve the interfacial bonding at coating-substrate, a graphene oxide-hydroxyapatite (GH) coating was designed and constructed. The microstructure, bonding strength and in vitro bioactivity of the coating were analyzed. The results showed that GH coating presented uniform and crack-free structure with a flake morphology. The bonding strength of GH coating was 7.81 MPa, which is about 1.2 times that of pure hydroxyapatite coating. In vitro bioactivity test using simulated body fluid exhibited that GH coating processes the ability to induce apatite formation. The GH coating should have potential application in surface modification for biomedical materials. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to fabricate the scaffolds with different pore architectures using additive manufacturing and analyze its mechanical and biological properties for bone tissue engineering applications. Design/methodology/approach: The polylactic acid (PLA)/composite filament were fabricated through single screw extrusion and scaffolds were printed with four different pore architectures, i.e. circle, square, triangle and parallelogram with fused deposition modelling. Afterwards, scaffolds were coated with hydroxyapatite (HA) using dip coating technique. Various physical and thermo-mechanical tests have been conducted to confirm the feasibility. Furthermore, the biological tests were conducted with MG63 fibroblast cell lines to investigate the biocompatibility of the developed scaffolds. Findings: The scaffolds were successfully printed with different pore architectures. The pore size of the scaffolds was found to be nearly 1,500 µm, and porosity varied between 53% and 63%. The fabricated circular pore architecture resulted in highest average compression strength of 13.7 MPa and modulus of 525 MPa. The characterizations showed the fidelity of the work. After seven days of cell culture, it was observed that the developed composites were non-toxic and supported cellular activities. The coating of HA made the scaffolds bioactive, showing higher wettability, degradation and high cellular responses. Originality/value: The research attempts highlight the development of novel biodegradable and biocompatible polymer (PLA)/bioactive ceramic (Al2O3) composite for additive manufacturing with application in the tissue engineering field. [ABSTRACT FROM AUTHOR]