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The increasing need for advanced orthopaedic implants necessitates improved materials that offer better biocompatibility and mechanical properties, addressing issues such as implant failure due to poor integration and corrosion. A 3″ diameter, 5-mm-thick pellet of hydroxyapatite (HAP) was prepared and was used as the cathode for the radio frequency (RF) magnetron sputtering system. One hundred nm nanocoating on alumina substrates (HAP/Al2O3) was done using RF magnetron sputtering. The hexagonal (HCP) HAP structure was chosen to deposit on hexagonal α-alumina for better growth and adhesion of the HAP film. The microstructure was analysed using field emission scanning electron microscopy, atomic force microscopy, and glancing angle X-ray diffraction. Elemental analysis was carried out using energy-dispersive X-ray spectroscopy. Mechanical and film adhesion properties were studied using Vicker's hardness and scratch test, respectively. The hardness of the coated sample increases 2.5 times. The optical contact angle increased from 82.88° for pure alumina to 113.53° for HAP/Al2O3 due to the decreased roughness, indicating enhanced hydrophobicity. Pore size, area, and volume were studied using the Brunauer–Emmett–Teller technique. Corrosion resistance in Ringer's solution and dielectric properties were investigated. The antimicrobial investigation was carried out against two different bacteria, namely gram-negative Escherichia coli (E. coli) and gram-positive Staphylococcus aureus (S. aureus). Improved adhesion, hardness, corrosion resistance, and biocompatibility properties are correlated with the surface and structural properties. [ABSTRACT FROM AUTHOR]

Periosteal expansion osteogenesis (PEO) is a technique for augmenting bone by creating a gradual separation between the bone and periosteum. This study assessed PEO‐induced bone formation around the femurs of rats using a dynamic frame device (DFD), consisting of a shape memory membrane made of polyethylene terephthalate (PET) formed into a tubular shape. The DFDs, consisting of a PET membrane coated with hydroxyapatite (HA)/gelatin on the bone‐contact surface, were inserted between the periosteum and bone of the femurs of rats. In the experimental group, DFDs were suture‐fixed to the femur with 4–0 Vicryl Rapid; in the control group, 4–0 silk thread was used for fixation. Five rats per group were euthanized at intervals of 3, 5, and 8 weeks postoperatively. Bone formation was evaluated via micro‐CT imaging, histomorphometry, and histological analysis. Morphological analysis revealed new bone between the femur and the periosteum, expanded by the DFD, in all groups. The mean values of new bone were 0.30 mm2 proximally, 0.18 mm2 centrally, and 0.82 mm2 distally in the control group, compared to 1.05 mm2 proximally, 0.27 mm2 centrally, and 0.84 mm2 distally in the experimental group. A significant difference in new bone was observed in the proximal region of the experimental group. Histological examination showed that a single layer of newly formed neoplastic bone was noted on the cortical bone surface across all sites. The proximal portion displayed a bone marrow cavity at the center, encircled by a thick bone cortex with a layered structure. New bone formation was notable between existing cortical bone and the periosteum, particularly at both ends of the DFD. The use of PET in PEO was a viable option for achieving ideal bone morphology. [ABSTRACT FROM AUTHOR]

A novel ultra-sound assisted method was used to grow zinc-metal organic framework (Zn-MOF) film on magnesium oxide/hydroxyapatite (MgO/HA) composite layer developed using plasma electrolytic oxidation (PEO) on Mg-5Sn-0.2Mn-0.2Ca alloy. The microstructure surface roughness and microhardness tests were performed on the samples to evaluate the mechanical properties of the coatings. The electrochemical corrosion test was performed to evaluate the corrosion resistance of the coated Mg alloy. Further, an in-vitro bioactivity test was performed to study the biocompatibility and bioactivity of the coated alloy, which is an essential aspect of biomedical applications. Results showed that the MgO/HA composite coating was helpful in the in-situ growth of the Zn-MOF particles by mechanically interlocking them. Further, incorporating hydroxyapatite in the coating could also increase the bioactivity. The study also confirmed that the bi-layer coating of Zn-MOF on the MgO/HA composite layer improved the surface roughness, hardness, biocorrosion resistance, and bioactivity making it more likely to be used for orthopedic internal fixation devices. [ABSTRACT FROM AUTHOR]

AbstractIn this manuscript, the application of hydroxyapatite coatings to total ossicular reconstruction prostheses (TORPs) using finite element modeling simulations was investigated to enhance the biocompatibility and mechanical performance of these prosthetic devices for middle ear implants. We focused on evaluating biocompatible materials, particularly polyetheretherketone (PEEK) and titanium, by analyzing their mechanical behavior under simulated conditions. The results revealed that PEEK demonstrates mechanical performance almost on par with titanium, exhibiting excellent stability and resilience within the middle ear environment. PEEK offers several key advantages over titanium, including easier fabrication, greater availability, and a simplified application process for hydroxyapatite coatings. These benefits suggest that PEEK could be a highly effective alternative to titanium for use in middle ear prostheses. The findings of this study highlight the potential of PEEK to improve the design and functionality of middle ear implants, providing a promising direction for future research and development in this field. By leveraging the advantages of PEEK, we can advance the effectiveness and accessibility of middle ear prosthetic devices, ultimately benefiting patients requiring such interventions. [ABSTRACT FROM AUTHOR]

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]

In this research, Sr-doped hydroxyapatite, HAp and NiO nanoparticles were used to produce a novel nanocomposite, Sr-doped HAp/NiO. Various analytical and instrumentation techniques such as FTIR, PXRD, UV-DRS, SEM, TEM, and XPS were used to characterize the as synthesized composite material. The nanocomposite acts as an efficient photocatalyst and is able to degrade Congo red (CR) dye up to 95.6% within 40 min under solar light irradiation without any kind of external additive. The HR LC–MS spectrum was recorded to determine the degradation products of the chosen organic dye. Furthermore, the as prepared nanocatalyst also effectively reduced 98.7% of carcinogenic Cr(VI) to Cr(III) within just 10 min. In order to propose the photocatalytic mechanism and to detect the active radicals present, a radical trapping experiment was conducted. As an appealing photocatalyst for wastewater treatment and reduction of toxic chemicals, the research concluded with a methodical and cost-effective process for producing the Sr-doped HAp/NiO nanocomposite. [ABSTRACT FROM AUTHOR]

Titanium alloy Ti6Al4V is widely used in the production of bone implants due to its favorable mechanical properties and biocompatibility. However, implant failures still occur due to lack of osseointegration, tissue infection, and fatigue. Laser shock peening (LSP) is a surface treatment method that can improve the physical, mechanical, and biological properties of Ti6Al4V implants. This method enhances the fatigue life of implants by inducing compressive residual stress on their surface region. In this study, Ti6Al4V samples were subjected to LSP treatment using different laser power densities (9.6 and 14.9 GW / cm 2 ) and with (vinyl tape and commercial black color) and without a protective layer. LSP-treated samples with higher power density exhibited maximum compressive residual stresses. Furthermore, hydrophobicity increased in all samples with increasing laser power density. Notably, the surface roughness results demonstrated significant improvement where the roughness increased with increasing the laser power density. The sample without a protective layer exhibited the highest surface roughness, followed by the black color coated and vinyl tape surface protected samples. The residual stress, surface roughness, and hydrophilicity of the samples were evaluated to determine the optimal LSP parameters. Fatigue tests revealed a remarkable enhancement in the fatigue life of the LSPed samples compared to untreated samples (3 and 2.9 times longer life for black-color coated and without coating samples, respectively). Moreover, the microstructure of laser peening samples and the fracture surface of the fatigue samples were characterized using field emission scanning electron microscopy (FE-SEM). To evaluate the biological characteristics of the optimal LSP-treated samples, a hydroxyapatite coating was applied, and their biological characteristics, including cell viability and adhesion, were investigated. Furthermore, the combination of LSP with hydroxyapatite coating offers a potential solution to promote osseointegration and reduce implant failures. [ABSTRACT FROM AUTHOR]

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

Background: Periosteal expansion (PEO) results in the formation of new bone in the space created between existing bone by expanding the periosteum. PEO has already been performed on rabbit parietal bone and effective new bone formation has been demonstrated. In this study, the utility of a polyethylene terephthalate (PET) membrane as an activator was evaluated in the more complex morphology of the mandible. Methods: A PET membrane coated with hydroxyapatite (HA)/gelatine was placed in the rabbit mandibular bone at lower margin of mandibular molar region underneath periosteum, and screw‐fixed. In the experimental group, the membrane was bent and screw‐fixed along the lateral surface of the bone, with removal of the outer screw after 7 days followed by activation of the membrane. The experimental group was divided into two subgroups: with and without a waiting period for activation. Three animals were euthanized at 3 weeks and another three at 5 weeks postoperatively. Bone formation was assessed using micro‐CT as well as histomorphometric and histological methods. Results: No PET membrane‐related complications were observed. The area of newly formed bone and the percentage of new bone in the space created by the stretched periosteum did not significantly differ between the control and experimental groups. However, in the experimental group a greater volume was present after 5 weeks than after 3 weeks. Histologically, bone formation occurred close to the site of cortical bone perforation, with many sinusoidal vessels extending through the perforations in the new bone into the overlying fibrous tissue. Inflammatory cells were not seen in the bone. [ABSTRACT FROM AUTHOR]

The present work aimed to produce HAp nanoparticles doped with Zn and Ni in order to analyze the incorporation of these elements in the catalytic and antimicrobial properties of HAp. The samples were obtained by the microwave-assisted hydrothermal method in 30 min at 150 °C. XRD and FTIR results showed that HAp was formed without the presence of secondary phases, and Rietveld refinement indicated a reduction in crystallite size after doping. Nanorod-like morphologies were observed by SEM-FEG with reduction in particle size and increase in specific surface area. Furthermore, the hidden gap at 3.26 eV, photoluminescence indicated that there was a predominance of deep defects and XPS showed the presence of dopants on the HAp surface. The catalytic results in the degradation of methylene blue dye indicated that the zinc-doped sample removed 97.85 % under sunlight, 66.81 % under UV light and 70.64 % under ultrasound. After four cycles of reuse under sunlight, good photocatalytic performance was maintained, and inhibition tests indicated that holes and hydroxyls are the active radicals. Antimicrobial activity tests showed that zinc-doped and co-doped samples were efficient in inhibiting Gram-negative bacteria (Escherichia coli). This work brings a promising alternative application for hydroxyapatite in environmental and microbial remediation. [ABSTRACT FROM AUTHOR]

NiTi alloys are actively used in medicine as implants because of their mechanical properties. At the same time, however, the NiTi surface is not biologically active, which has a negative effect on osteogenesis. In addition, Ni is capable of causing various toxic reactions in the human body. It is therefore necessary to create a composite coating that is both bioactive and prevents the release of Ni ions. It has been shown that by changing the modes of plasma assisted RF sputtering of a calcium phosphate target, it is possible to obtain coatings with different contents of the amorphous phase. The coatings formed consist of hydroxyapatite and amorphous calcium phosphate. On the surface of a sample not treated with argon plasma, there are no phases containing calcium or phosphorus, although these elements are present on the surface. The different ways in which the CaP coatings were applied also affected their structure. It was found that the CaP coatings of samples M2 and M3 have mediocre corrosion resistance, dissolving quickly. This has a positive effect on the ability to osteogenesis, which was discovered as a result of in vitro tests. These tests have shown that the sample obtained at I discharge = 30 A and U bias = 30 V has the highest bioactivity and produces the lowest percentage of dead cells. [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]

Controlling blood loss is crucial for saving lives during trauma. Based on the current application of solid waste in hemostatic materials, this study reports the synthesis of a hydroxyapatite/tourmaline composite material (referred to as ST) and a hemostatic sponge (referred to as STS). These materials were synthesized through hydrothermal processes and lyophilization techniques using seashells, tourmaline, and chitosan as precursors. The phase analysis and microstructure characterization were performed using XRD, SEM, TEM, and HRTEM. Owing to the spontaneous polarization of tourmaline attracting free ions in the system, the shells were deposited on the surface of tourmaline particles in the form of hydroxyapatite (HA) through dissolution and recrystallization during the hydrothermal process. HA can release free Ca2+, an important component in the coagulation system, while tourmaline can enhance cell metabolism by reducing water molecular clusters, thereby altering the permeability of cell membranes. ST particles were incorporated into the chitosan sponge matrix to prevent particle shedding. Through orthogonal design experiments on the preparation process of ST, the optimal preparation conditions were determined as follows: a hydrothermal temperature of 180 °C, a hydrothermal time of 12 h, a pH value of 8, and a shell-to-tourmaline ratio of 8 : 1. The composite materials were evaluated for their adsorption capacity, clotting time, hemolysis rate, antibacterial rate, and cytotoxicity. The results demonstrated a higher liquid adsorption rate, significantly reduced clotting time, a hemolysis rate of <5.0%, an antibacterial capacity of 88.5%, and lower cytotoxicity. These findings suggest that STS has the potential to be a safe, effective, and cost-efficient hemostatic agent. [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]

Simple Summary: This research investigated the impact of different surface modifications on the osseointegration of dental implants. The study conducted experiments on rabbit tibiae comparing conventional machined surfaces (MSs) with those modified using a laser beam (LSs) or a laser beam incorporating hydroxyapatite (HA) by means of biomimetic methods without thermic treatment (LHSs). Utilizing scanning electron microscopy coupled with energy-dispersive X-ray spectrometry (SEM/EDX) and fluorochrome labeling techniques, the study evaluated bone formation over a four-week period. The results demonstrated significantly improved bone contact and newly formed bone area with LSs and LHSs compared to MSs. These findings suggest that surface modifications, particularly LS modifications and LHS modifications, enhance osseointegration, potentially leading to an enhanced longevity and performance of dental implants in clinical settings. (1) Objective: The aim of this study was to assess the biological behavior of bone tissue on a machined surface (MS) and modifications made by a laser beam (LS) and by a laser beam incorporated with hydroxyapatite (HA) using a biomimetic method without thermic treatment (LHS). (2) Methods: Scanning electron microscopy coupled with energy-dispersive X-ray spectrometry (SEM/EDX) was performed before and after installation in the rabbit tibiae. A total of 20 Albinus rabbits randomly received 30 implants of 3.75 × 10 mm in the right and left tibias, with two implants on each surface in each tibia. In the animals belonging to the 4-week euthanasia period group, intramuscular application of the fluorochromes calcein and alizarin was performed. In implants placed mesially in the tibiofemoral joint, biomechanical analysis was performed by means of a removal torque (N/cm). The tibias with the implants located distally to the joint were submitted for analysis by confocal laser microscopy (mineral apposition rate) and for histometric analysis by bone contact implant (%BIC) and newly formed bone area (%NBA). (3) Results: The SEM showed differences between the surfaces. The biomechanical analysis revealed significant differences in removal torque values between the MSs and LHSs over a 2-week period. Over a 4-week period, both the LSs and LHSs demonstrated removal torque values statistically higher than the MSs. BIC of the LHS implants were statistically superior to MS at the 2-week period and LHS and LS surfaces were statistically superior to MS at the 4-week period. Statistical analysis of the NBA of the implants showed difference between the LHS and MS in the period of 2 weeks. (4) Conclusions: The modifications of the LSs and LHSs provided important physicochemical modifications that favored the deposition of bone tissue on the surface of the implants. [ABSTRACT FROM AUTHOR]

Buttermilk differs from skim milk by the presence of milk fat globule membrane (MFGM) fragments that are released during cream churning. Milk fat globule membrane is rich in health-promoting components, such as phospholipids and membrane proteins, but these compounds have a negative impact on buttermilk techno-functional properties in dairy applications. The isolation of MFGM from buttermilk improved its functionality while also recovering the MFGM bioactive components. Hydroxyapatite (HA) can be used to extract MFGM by adsorption via charged site interactions. However, the affinity of HA to MFGM or the main buttermilk proteins (casein micelles [CM], β-LG, and α-LA) is not known. The influence of important physicochemical parameters such as pH and temperature on these interactions is also unclear. For each buttermilk component, a quartz crystal microbalance diffusion analysis was performed to determine the maximum adsorption time and the attached mass density on HA-coated gold sensors. The influence of pH, ionic strength (IS), and temperature (T) on the affinity of each buttermilk component for HA particles was assessed using a 3-levels and 3-factors Box-Behnken design. The absorption rate was highest for the CM, followed by β-LG and α-LA, and then by the MFGM. Nevertheless, the final maximal attached mass densities to the HA were similar for the MFGM and CM, and 2.5 times higher than for β-LG and α-LA. This difference can be explained by the higher number of binding sites found in CM and their heavier mass. The model obtained by the Box-Behnken design plan showed that the adsorption of the CM changed with T, pH, and IS. These results suggest that the techno-functional properties of buttermilk may be restored by specifically extracting MFGM with HA. Experiments are ongoing to determine conditions for fractionating MFGM directly from buttermilk. [Display omitted] [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]

The aim of the present study is to create porous poly lactic acid (PLA)-based temporal cellular scaffolds with specifically designed topographical orientation by means of femtosecond laser (fs)-induced microstructuring, additionally functionalized by a nanometric layer of hydroxyapatite (HA) by the pulse laser deposition (PLD) method. For this purpose, surface micromodification of PLA samples by means of a CPA Ti:sapphire fs laser system (τ = 150 fs, λ = 800 nm, ѵ = 0.5 kHz), operating at fluence F = 0.8 J/cm2 and scanning velocity V = 3.8 mm/s, was combined with PLD of thin layer of HA on the patterned PLA matrices for cellular scaffold surface additional nanofunctionalization. Each laser structured PLA scaffold was analyzed with respect to its control and laser processed surface, covered with HA. The multilevel structured scaffolds were investigated by SEM, EDX, 3D profilometer, AFM, micro-Raman and WCA analyses. Cytocompatibility studies with MG63 osteoblastic cells were also performed. Moreover, the cellular behavior was compared with the one observed on HA spin-coated fs microstructured PLA temporary scaffolds, in order to compare the two methods of functionalization. A disordered spreading on smooth surfaces to a tendency of cell orientation and elongation along the laser created grooves was monitored, along with increased alkaline phosphatase activity, which could essentially improve their subsequent practical application in engineering of personalized bone tissue. [ABSTRACT FROM AUTHOR]

Keeping safety and sustainability in view with managing radioactive aqueous wastes and other wastewaters containing Sr(II) ions, the current work was designed and performed to immobilize this ion in ceramic matrices. The adsorption properties of Ti–Ca–Mg composite phosphates with different ratios of Ti/(Ca + Mg) towards Sr(II) ions have been studied. Chemical structures and phase transformations of phosphate adsorbents and Sr(II)-loaded products after heat treatment in the range of 20–1000 °C were scrutinized by XRD, DTA-DTG, FTIR and elemental analyses. Hardly soluble calcium, magnesium pyrophosphates, Ca–Mg and Ca–Ti phosphates with a NaZr 2 (PO 4) 3 or CaTi 4 (PO 4) 6 skeleton structure (abbreviated as NZP or CTP) were obtained through heat treatment of composite phosphates at 800–1000 °C. The effect of the Ti/(Ca + Mg) ratio existing in the initial adsorbents on the phase and chemical composition of heat-treated products was studied, and the mechanism of their formation was proposed. Heat treatment of Sr-saturated Ti–Ca–Mg phosphates at 1000 °C led to the formation of Sr-substituted hydroxyapatite and whitlockite, which caused a high immobilization strength for Sr(II) ions. The degree of desorption of Sr(II) ions after heat-treatment of Sr-saturated adsorbents decreased by 10–120 times, declining to the amounts of 0.31–0.54% in seawater and 0.03–0.12% in artesian. The obtained Ti–Ca–Mg composite phosphates are of interest for the adsorption and immobilization of Sr(II) ions from liquid radioactive wastes (LRW) into ceramic matrices and can be used in full-scale plants. [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]

[Display omitted] Stone-built cultural heritage faces threats from natural forces and anthropogenic pollutants, including local climate, acid rain, and outdoor conditions like temperature fluctuations and wind exposure, all of which impact their structural integrity and lead to their degradation. The development of a water-based, environmentally-friendly protective coatings that meet a combination of requirements posed by the diversity of the substrates, different environmental conditions, and structures with complex geometries remains a formidable challenge, given the numerous obstacles faced by current conservation strategies. Here we report the structural, electrical, and mechanical characterization, along with performance testing, of a nanostructured hydrophilic and self-healing hybrid coating based on hydroxyapatite (HAp) nanocrystals and polyelectrolyte multilayers (PEM), formed in-situ on Greek marble through a simple spray layer-by-layer surface functionalization technique. The polyelectrolyte-hydroxyapatite multilayer (PHM) structure resembled the design of naturally forming trabecular bone, attained at a short procedural time. It exhibited chemical affinity, aesthetical compatibility and resistance to weathering while offering reversibility. The proposed method is able to generate micron-sized coatings with controlled properties, such as adhesion and self-healing, leading to less weathered surfaces. Our results show that the PHM is a highly effective protective material that can be applied for stone protection and other similar applications. [ABSTRACT FROM AUTHOR]

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

In this study, a biogenic magnetic nanocomposite, HAP@DEX@MNP, using hydroxyapatite from eggshell waste and dextran was developed to efficiently remove 2,4-D from aqueous solutions. The magnetic nano biocomposite underwent rigorous characterization using a comprehensive suite of analytical techniques, including FTIR, XRD, FESEM, EDX, TEM, and VSM. FTIR analysis was used to validate the existence of pivotal functional groups, such as phosphate, carbonyl, hydroxyl, and iron oxide. XRD analysis verified both the crystalline nature of hydroxyapatite and the successful integration of dextran and hematite within the composite structure. FESEM and EDX examinations provided valuable insights into the surface morphology and elemental composition. TEM observations elucidated the existence of nano-sized particles underscoring the unique structural characteristics of the nanocomposite. Batch adsorption experiments were conducted under optimized conditions, highlighting the critical role of pH 2 for efficient 2,4-D removal. The mechanisms driving the binding of 2,4-D to HAP@DEX@MNP were found to encompass diverse interactions, encompassing electrostatic forces, hydrogen bonding, π-π interactions, and van der Waals forces. Adsorption isotherm studies revealed both monolayer and multilayer adsorption, with the Langmuir and Freundlich models fitting well, indicating a maximal adsorption capacity of 217.39 µg/g at 25 °C. Kinetic investigations supported the pseudo-second-order model for efficient adsorption dynamics, and thermodynamic analysis emphasized the versatility of HAP@DEX@MNP across different temperatures. Importantly, the study highlighted the remarkable regenerative capacity of the nanocomposite using a 0.1 M NaOH solution, positioning it as an environmentally friendly option for water treatment. In conclusion, HAP@DEX@MNP holds significant potential for diverse applications in addressing global water treatment and environmental challenges. [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]

Background/Objectives: A highly porous titanium cup with a three-dimensional metal interface was recently introduced to improve biological fixation and survival. However, radiography has revealed concerns regarding these cups, despite their excellent short- and mid-term clinical outcomes. This study compared the clinical and radiographic results of a highly porous titanium cup with those of a hydroxyapatite-coated porous titanium cup after primary total hip arthroplasty (THA). Methods: Fifty-one primary THAs were investigated. A highly porous titanium cup was used in 17 hips, and a hydroxyapatite-coated porous titanium cup was used in 34 hips. No significant differences in preoperative patient demographic characteristics were observed between the two groups. The 2-year postoperative clinical and radiographic results were compared. Results: Radiolucent lines were observed in 13 (76%) of 17 hips with highly porous titanium cups and in none (0%) of 34 hips with hydroxyapatite-coated porous titanium cups (p < 0.001). In the highly porous titanium cup group, radiolucent lines were observed in five hips (29%) in one zone, two hips (11%) in two zones, and six hips (35%) in three zones. No cup loosening was observed in either group. Conclusions: Radiolucent lines were significantly more frequent in highly porous titanium cups. This study suggests that, compared to the three-dimensional structure of porous titanium, the hydroxyapatite coating of porous titanium had a greater influence on bone ingrowth in the short term. The meaning of these findings in the long-term is unclear yet. [ABSTRACT FROM AUTHOR]

[3H]Hyaluronic acid with a molecular weight of 2.37 MDa and a specific radioactivity of 35 GBq/g was obtained using the tritium thermal activation method. Tritium labeled hyaluronic acid (HA) with a molecular weight of 2.37, 0.20, and 0.10 MDa were used to study their adsorption on hydroxyapatite (HAP) in two textural modifications: aqueous suspension and powder. Differences in adsorption kinetics and adsorption isotherms were observed due to variations in the interaction between polysaccharide molecules and the sorbent forms under consideration. The adsorption isotherms of HA on HAP were proven linear. It is shown that strong HA–HAP complexes are formed, and no desorption of HA into water and 0.9% NaCl solution were detected in 2 days. [ABSTRACT FROM AUTHOR]

Bone tissue engineering (BTE) is the most promising strategy to repair bones injuries and defects. It relies on the utilization of a temporary support to host the cells and promote nutrient exchange (i.e., the scaffold). Supercritical CO2 assisted drying can preserve scaffold nanostructure, crucial for cell attachment and proliferation. In this work, agarose aerogels, loaded with hydroxyapatite were produced in view of BTE applications. Different combinations of agarose concentration and hydroxyapatite loadings were tested. FESEM and EDX analyses showed that scaffold structure suffered from partial closure when increasing filler concentration; hydroxyapatite distribution was homogenous, and Young's modulus improved. Looking at BTE applications, the optimal combination of agarose and hydroxyapatite resulted to be 1% w/w and 10% w/v, respectively. Mechanical properties showed that the produced composites could be eligible as starting scaffold for BTE, with a Young's Modulus larger than 100 kPa for every blend. [ABSTRACT FROM AUTHOR]

In this study, to reactivate the oxide film and to secure biocompatibility, plasma electrolytic oxidation (PEO) treatment and hydroxyapatite (HA) deposition via mechanical coating (MC) processes were investigated. This experimental approach involved subjecting the Ti–6Al–4V alloy specimens to PEO treatment, followed by MC with HA powder for different hours as HA has the potential to increase bioactivity and surface characteristics due to its chemical composition and structural properties similar to natural bone. Therefore, the study aimed to examine the effects of MC with HA powder for 0, 1, 3, 5, 7, and 9 h on PEO-coated Ti–6Al–4V alloy discs for analyzing the surface characterization, phase analysis, surface roughness, wettability, adhesion strength, hardness, corrosion behavior, and cell proliferation properties for dental implant use. The findings demonstrate that prolonged HA milling enhances the substrate's mechanical strength, corrosion resistance, and adhesion properties. The presence of prominent anatase and HA peaks, particularly in the 5 MC-PEO, 7MC-PEO, and 9 MC-PEO samples, validates the synergistic impact of the PEO oxide layer and HA milling, resulting in outstanding corrosion resistance and biocompatibility. Cell culture analysis reveals a positive correlation between increased milling time and enhanced cell proliferation, particularly towards small-sized HA particles. [Display omitted] [ABSTRACT FROM AUTHOR]

To investigate the reinforcing effect of nanoflower‐like hydroxyapatite (NFHA) in resin‐based dental composites, we synthesized a novel NFHA using microwave irradiation (MW), hydrothermal treatment (HT), and sonochemical synthesis (SS). Silanized NFHA was then used as the reinforcing filler in dental resin composites. We characterized the structure and morphology of various HA nanostructures using x‐ray diffraction, scanning electron microscope, and TEM. The mechanical performance of dental resin composites reinforced with silanized NFHA was measured using a universal testing machine. Spherical HA, synthesized through chemical precipitation (CP), served as the control group. One‐way analysis of variance was employed for the statistical analysis of the acquired data. The results demonstrate that the nanoflower morphology significantly was improved mechanical and physical properties. After conducting trials, the NFHA synthesized using MW and HT showed a substantial enhancement in mechanical and physical properties compared to the other structures. Therefore, it can be concluded that NFHA can serve as a novel reinforcing HA filler, providing regenerative properties to resin composites with sufficient mechanical strength. [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]

Biochar with abundant functional groups, porous structure, and high specific surface area has been widely used as an adsorbent for the removal of metal ions, and its low production costs make it economically suitable for large-scale application in various industries. Hydroxyapatite nanoparticles were used to functionalize magnetic rice husk biochar (MBC) to produce hydroxyapatite functionalized magnetic rice husk biochar (HAP@MBC) in this study. The functional groups, magnetism performance, surface morphology, and aperture structure of HAP@MBC were characterized to explore the feasibility of its application in the treatment of wastewater containing Cu(II) ions. It is found that the maximum adsorption removal rate reaches 96.02% at 35°C, pH=5.0 , with an adsorbent dosage of 0.65 g/L and an initial Cu(II) ion concentration of 50 mg/L. Additionally, adsorption kinetics, isotherms, and thermodynamics were analyzed to probe into the adsorption mechanism of Cu(II) ions by HAP@MBC. The results show that the adsorption process is very close to the pseudo-second-order model, indicating that the adsorption process is mainly controlled by chemisorption. The adsorption of Cu(II) ions can also be fitted by the intraparticle diffusion model, revealing that the adsorption rate is limited by intraparticle diffusion as well as other factors. Moreover, the adsorption process is consistent with the Langmuir isotherm, and the saturated adsorption capacity is calculated to be 81.59 mg/g. Thermodynamic analysis shows that the value of adsorption enthalpy change is 48.35 kJ/mol , suggesting the adsorption process is chemisorption. More precisely, it is a spontaneous entropy-increasing reaction, and an increase in the temperature is conducive to the adsorption. To sum up, HAP@MBC exhibits perfect adsorption properties and has the potential to be a novel and promising adsorbent for the removal of Cu(II) ions. [ABSTRACT FROM AUTHOR]

Low P-containing wastewaters (LPWs) exhibit huge P recovery potential, considering their larger volume. P recovery via CaP crystallization using apatite as seed is documented as being potentially well suited for LPWs. However, its responsible mechanisms remain a subject for debate. Taking hydroxyapatite (HAP) as the seed of LPWs, this paper conducted HAP adsorption/dissolution experiments, titration experiments, and P recovery experiments to distinguish the primary responsible mechanism. Results showed that it was HAP dissolution, not P adsorption, that occurred when the initial P concentration was no higher than 5 mg/L, ruling out adsorption mechanism of P recovery from LPWs using HAP as the seed. Significant OH− consumption and rapid P recovery occurred simultaneously within the first 60 s in titration experiments, suggesting CaP crystallization should be responsible for P recovery. Moreover, the continuous increase in P recovery efficiency with seed dosages observed in P recovery experiments seemed to follow well the mechanism of pre-nucleation ion clusters (PNCs) aggregation. During PNCs aggregation, P aggregates with Ca2+ quickly, generating CaP PNCs; then, CaP PNCs aggregate with seed particles, followed by CaP PNCs fusion, and ultimately transform into fines attached to the seed surface. PNCs' aggregation mechanism was further supported by a comparison of seed SEM images before and after P recovery, since denser and smaller rod-shaped fines were observed on the seed surface after P recovery. This study suggests that PNCs' aggregation is the dominant mechanism responsible for the recovery of P from LPWs via CaP crystallization using HAP as the seed. [ABSTRACT FROM AUTHOR]

• Nano AlPO 4 can be obtained by sol–gel method. • Introduced nano AlPO 4 improves the integrity of the hydroxyapatite coating. • Nano AlPO 4 enhances the protective effect of the hydroxyapatite for stone relics. Open-air marble relics in Beijing are experiencing degradation due to sugaring, dissolution and other illnesses. Therefore, it is necessary to apply a protective and reinforcing coating to the weathered surface. Hydroxyapatite (HAP) has significantly lower solubility and dissolution rate compared to calcite. Additionally, HAP has similar lattice parameters with calcite, suggesting that a cohesive layer of HAP can be formed over calcite. In fact, HAP exhibits a lattice mismatch of 5 % with calcite, which might potentially lead to stress if the layer exceeds a few nanometre in thickness. On the other hand, aluminum phosphates (ideally, B-AlPO 4) only exhibit a 1 % mismatch with calcite and have a solubility lower than that of calcite. In this study, in order to improve the property of HAP in marble conservation, sol–gel method was employed to synthesize nano AlPO 4 , which were then incorporated into the phosphate solution to produce protective coating on the stone surface. The coatingʼs morphology and the structure were characterized by Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), high capacity 3D X-ray microscopy (XRM), optical microscope, and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). Moreover, the color, the contact angle, the three-point bending strength measurements, as well as the simulated acid rain test and freeze–thaw treatment were performed to assess the chromatic aberration, hydrophilicity, reliability, and durability of the coating. Results indicated that the nano AlPO 4 , with its matched lattice parameters and nucleation site provision, facilitated the formation a coherent HAP layer of crystal flakes. Subsequently, the anti‑corrosion property, freeze-thaw resistance and consolidation property of the coating were improved, demonstrating the potential application the hybrid of HAP with nano AlPO 4 in the preservation of marble. [ABSTRACT FROM AUTHOR]

In this study, pure and 10% wt. Titania-Stabilised Zirconia (TiSZ) -reinforced Hydroxyapatite (HA) coatings were deposited on magnesium substrate using plasma spray as a single layer and double layer with an HVOF sprayed Ti bond coat. The coated specimens were characterised by X-ray diffraction (XRD) analysis, and scanning electron microscopy equipped with energy dispersive spectroscopy (SEM, EDS). Rockwell-C adhesion and scratch tests were performed. The corrosion behaviours in simulated body fluid (SBF) of coatings were investigated by an electrochemical corrosion test. Analyses confirmed successful coating with a dense titanium buffer layer. The double-layered HA-titanium combination offered superior corrosion resistance compared to single layers. While adding TiSZ enhanced adhesion, it compromised scratch resistance. The titanium bond coat had minimal impact on adhesion and cohesion behaviour of coatings. [ABSTRACT FROM AUTHOR]

In this study, a high-efficiency strontium-doped hydroxyapatite (Sr-HAP) adsorbent was synthesized by a sol-gel method for removing cobaltous ions (Co(II)) from water. The effects of adsorbent dose, initial solution pH, initial Co(II) concentration and temperature on the removal performance of Co(II) were investigated. Experimental results indicated that the optimum Sr-HAP dose was 0.30 g/50 mL solution, the Sr-HAP adsorbent could effectively remove Co(II) in a wide pH range of 3–8. Increasing temperature was conducive to the adsorption, and the maximum Co(II) adsorption capacity by Sr-HAP reached 48.467 mg/g at 45 °C. The adsorption of Co(II) followed the pseudo-second-order kinetic model, indicating that the Co(II) adsorption by Sr-HAP was attributed mainly to chemisorption. The isothermal adsorption results showed that at lower Co(II) equilibrium concentration, the Langmuir model fitted the data better than the Freundlich model but opposite at higher Co(II) equilibrium concentration. Therefore, the adsorption of Co(II) was a process from monolayer adsorption to multilayer adsorption with the increase of the Co(II) equilibrium concentration. The diffusion analysis of Co(II) to Sr-HAP indicated that the internal diffusion and surface adsorption were the rate-controlled steps of Co(II) adsorption. Thermodynamic study demonstrated that the Co(II) adsorption process was spontaneous and endothermic. The mechanism study revealed that in addition to chemisorption, Sr-HAP also removed Co(II) ions from water via ion exchange and surface complexation. [ABSTRACT FROM AUTHOR]

This study explores the electrochemical deposition (ECD) of hydroxyapatite (HA) coatings onto commercially pure titanium (CP–Ti) substrates, with a focus on biomedical implant applications. The ECD process serves as a useful approach for controlling the growth and characteristics of these HA coatings. Additionally, to refine the crystalline structure and bolster biocompatibility, annealing techniques were employed. The results unveiled distinctive morphologies for HA coatings under varying pH levels of the electrolyte: granular at pH 4, flake-like at pH 6, and needle-like at pH 9, emphasizing the significant impact of electrolyte pH on coating structure. Surface roughness exhibited its peak at pH 4, indicative of the most uneven HA layer formation. In particular, all HA-coated samples displayed heightened hydrophilicity compared to their uncoated CP-Ti counterparts, with pH 6 showing the most substantial decrease in contact angle, suggesting pronounced biocompatibility enhancements. X-ray Diffraction affirmed HA as the predominant phase in the annealed coatings. Electrochemical assessments were conducted to gauge the electrochemical behavior of HA-coated samples. The findings revealed that pH 6 offered the most robust electrochemical behavior, rendering it a promising electrolyte pH condition for HA-coated CP-Ti biomedical implants. This comprehensive investigation highlights the profound influence of the pH of the electrolyte on HA morphology and surface properties, which in turn impact electrochemical behavior in HA-coated CP-Ti for biomedical implant applications. As such, the application of ECD techniques across varying pH levels of the electrolyte emerges as an effective strategy for tailoring HA coatings, thus enhancing their suitability for biomedical implants. [ABSTRACT FROM AUTHOR]

Effective prevention of recurrent kidney stone disease requires the understanding of the mechanisms of its formation. Numerous in vivo observations have demonstrated that a large number of pathological calcium oxalate kidney stones develop on an apatitic calcium phosphate deposit, known as Randall's plaque. In an attempt to understand the role of the inorganic hydroxyapatite phase in the formation and habits of calcium oxalates, we confined their growth under dynamic physicochemical and flow conditions in a reversible microfluidic channel coated with hydroxyapatite. Using multi-scale characterization techniques including scanning electron and Raman microscopy, we showed the successful formation of carbonated hydroxyapatite as found in Randall's plaque. This was possible due to a new two-step flow seed-mediated growth strategy which allowed us to coat the channel with carbonated hydroxyapatite. Precipitation of calcium oxalates under laminar flow from supersaturated solutions of oxalate and calcium ions showed that the formation of crystals is a substrate and time dependent complex process where diffusion of oxalate ions to the surface of carbonated hydroxyapatite and the solubility of the latter are among the most important steps for the formation of calcium oxalate crystals. Indeed when an oxalate solution was flushed for 24 h, dissolution of the apatite layer and formation of calcium carbonate calcite crystals occurred which seems to promote calcium oxalate crystal formation. Such a growth route has never been observed in vivo in the context of kidney stones. Under our experimental conditions, our results do not show any direct promoting role of carbonated hydroxyapatite in the formation of calcium oxalate crystals, consolidating therefore the important role that macromolecules can play in the process of nucleation and growth of calcium oxalate crystals on Randall's plaque. [ABSTRACT FROM AUTHOR]

BACKGROUND: Medical titanium and titanium alloy have achieved good therapeutic effects in clinical applications, but there are still some phenomena such as peri-implant inflammation, loosening and shedding. OBJECTIVE: To explore the physicochemical properties of graphene oxide coating materials and their effects on bone marrow mesenchymal stem cells. METHODS: (1) Hydroxyapatite coating and graphene oxide/hydroxyapatite composite coating were prepared on a titanium surface by electrochemical deposition. The surface morphology, phase structure, functional groups, elemental composition and surface hydrophilicity of the coating were analyzed by scanning electron microscopy, X-ray energy dispersion spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Raman spectroscopy, and contact angle measurement instrument. (2) Mouse bone marrow mesenchymal stem cells were isolated and cultured and inoculated on pure titanium, hydroxyapatite coating and graphene oxide/hydroxyapatite composite coating, respectively. CCK-8 assay and scanning electron microscopy were used to evaluate the proliferation, morphology and growth status of the coated cells. RESULTS AND CONCLUSION: (1) Scanning electron microscopy and X-ray energy dispersion spectra showed that the surface of graphene oxide/hydroxyapatite composite coating was more flat, compact and uniform than that of hydroxyapatite coating and pure titanium. X-ray photoelectron spectroscopy, X-ray diffraction and Raman spectroscopy showed that hydroxyapatite coating and graphene oxide/hydroxyapatite composite coating were successfully prepared on the surface of the titanium sheet. The hydrophilicity of graphene oxide/hydroxyapatite composite coating was better than that of hydroxyapatite coating and pure titanium. (2) CCK-8 assay showed that the number of bone marrow mesenchymal stem cells on the surface of the three groups increased with the extension of co-culture time. On days 1, 4, and 7, the proliferative absorbance of the cells on the graphene oxide/hydroxyapatite composite coating was higher than that on hydroxyapatite coating and pure titanium (P < 0.000 1). Scanning electron microscopy after 4 days of co-culture showed that bone marrow mesenchymal stem cells on the surface of the three groups of materials were fusiform. The cells on the surface of graphene oxide/hydroxyapatite composite coating showed good tensile properties and were polygonal. Multiple antennae could be seen attached to the coating surface at the edge of the cells, and the elongation of the filamentous foot on the surface was more than that on pure titanium and hydroxyapatite coatings. (3) The results show that graphene oxide/ hydroxyapatite composite coating material is a kind of coating material with excellent physicochemical and biological properties. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Titanium and its alloys are extensively applied in artificial tooth roots because of their excellent corrosion resistance, high specific strength, and low elastic modulus. However, because of their biological inertness, their surface needs to be modified to improve the osteointegration of titanium implants. The preparation of biologically active calcium–phosphorus coatings on the surface of an implant is one effective method for enhancing the likelihood of bone integration. In this study, osteoinductive peptides were extracted from oyster shells by using acetic acid. Two peptide-containing hydroxyapatite (HA) composite coatings were then prepared: one coating was prepared by hydrothermally synthesizing an HA coating in the presence of peptides (HA/P/M), and the other coating was prepared by hydrothermally synthesizing HA and then immersing the hydrothermally synthesized HA in a peptide solution (HA/P/S). Characterization results indicated that the composite HA coatings containing oyster shell-based peptides were successfully prepared on the alkali-treated pure titanium surfaces. The HA/P/M and HA/P/S composite coatings were found to exhibit excellent hydrophilicity. Protein adsorption tests confirmed that the HA/P/M and HA/P/S coatings had an approximately 2.3 times higher concentration of adsorbed proteins than the pure HA coating. [ABSTRACT FROM AUTHOR]

This study focuses on the usage of chitosan/hydroxyapatite composites for pertechnetate removal from aqueous solutions. Pertechnetate, a prominent radionuclide in nuclear waste, presents environmental hazards due to its long half-life and mobility. The composites, formed by intergrating hydroxyapatite into chitosan matrices, demonstrate in situ nanohydroxyapatite generation. Investigation of the adsorption process involves assessing parameters like pH, contact time, and the influence of competetive ions. This research provides valuable insights for using composites to mitigate pertechnetate contamination. [ABSTRACT FROM AUTHOR]

Electrophoretic deposition (EPD) is a versatile fabrication method allowing the deposition of coatings on substrates with complicated shapes. The main disadvantage of this method, especially in relation to bio applications, lies in hazardous stabilisers frequently used to optimise suspension parameters. This work deals with the plasma treatment of hydroxyapatite (HA) powder for stabilising the suspension without any additives. This approach was already successfully used for alumina powder. EPD of untreated and plasma treated HA powder is performed to compare the final deposits' microstructure. Besides this primary goal, the powder and suspension characteristics are monitored to clarify the effect of plasma treatment on processing and final properties. Moreover, the impact of the rapid sintering approach on deposits' densification is tested. Finally, the suitability of EPD of plasma treated powder for the preparation of homogeneous coating on the orthopaedic screw is manifested. • Electrophoretic deposition of ceramics usually requires physical, environmental, or health hazardous additives. • Atmospheric plasma treatment changes the powder's surface properties. • Homogeneous and uniform hydroxyapatite coatings are obtained without additives. • Rapid pressureless sintering leads to quick and sufficient densification in a fraction of the time. • Orthopaedic screws are uniformly coated. [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]

Bone tissue engineering (BTE) is a biomedical area that develops scaffolds capable of mimicking and repairing damage on bone tissue. For this, a popular and nonexpensive 3D printing technique named fused deposition modeling (FDM) has been used. The potential use of 3D scaffolds of poly(butylene adipate-co-terephthalate (PBAT) has been investigated in BTE since this polymer presents good biocompatibility and degradability, as well as mechanical properties like those offered by the natural bone. A single material does not have the features to promote cell adhesion, proliferation, and differentiation; the incorporation of bioactive substances can overcome this issue. This work aimed to develop 3D printed PBAT scaffolds by FDM technique and coated them with hydroxyapatite (H), bioglass (B), and gelatin (G) by solution immersion technique to obtain a functional biomaterial to be applied on the BTE. Structural characteristics and morphological and mechanical properties of the 3D scaffolds were evaluated. The cell proliferation and mineralization of pre-osteoblastic cells (MC3T3-E1) were accessed by methylthiazolyldiphenyl-tetrazolium bromide, sulphorodhamine B, and Alizarin red assay, respectively. 3D printed PBAT scaffolds were successfully obtained by FDM, and the surface modification of 3D PBAT was proven through the changes observed in structural and morphological characteristics. In addition, the mechanical properties were improved in the modified scaffolds. Also, the coated 3D PBAT scaffolds with any bioactive substance increased and promoted cell proliferation and pre-osteoblastic differentiation. Therefore, the combination of 3D PBAT scaffolds and H, G, and/or B (doped with niobium) is an alternative to produce functional biomaterials for BTE. [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]