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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]

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]

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]

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]

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]

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

Porous structures can reduce the elastic modulus of implants, decrease stress shielding, and avoid bone loss in the alveolar bone and aseptic loosening of implants; however, there is a mismatch between yield strength and elastic modulus as well as biocompatibility problems. This study aimed to investigate the parametric design method of porous root-shaped implants to reduce the stress-shielding effect and improve the biocompatibility and long-term stability and effectiveness of the implants. Firstly, the porous structure part was parametrically designed, and the control of porosity gradient distribution was achieved by using the fitting relationship between porosity and bias and the position function of bias. In addition, the optimal distribution law of the porous structure was explored through mechanical and hydrodynamic analyses of the porous structure. Finally, the biomechanical properties were verified using simulated implant–bone tissue interface micromotion values. The results showed that the effects of marginal and central porosity on yield strength were linear, with the elastic modulus decreasing from 18.9 to 10.1 GPa in the range of 20–35% for marginal porosity, with a maximum decrease of 46.6%; the changes in the central porosity had a more consistent effect on the elastic modulus, ranging from 18.9 to 15.3 GPa in the range of 50–90%, with a maximum downward shift of 19%. The central porosity had a more significant effect on permeability, ranging from 1.9 × 10−7 m2 to 4.9 × 10−7 m2 with a maximum enhancement of 61.2%. The analysis showed that the edge structure had a more substantial impact on the mechanical properties. The central structure could increase the permeability more effectively. Hence, the porous structure with reasonable gradient distribution had a better match between mechanical properties and flow properties. The simulated implantation results showed that the porous implant with proper porosity gradient distribution had better biomechanical properties. [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]

The bacterial enzyme chondroitinase ABCI (chABCI), which has been isolated from Proteus Vulgaris, is crucial in the treatment of spinal cord injuries. However, due to its short lifespan, the maintenance and clinical application of this enzyme are very constrained. In this study, the immobilization of this enzyme on hydroxyapatite has been carried out and assessed with the aim of enhancing the characteristics and efficiency of chABCI. Hydroxyapatite particles (HAPs) are a potential candidate for drug-delivery carriers because of their excellent biocompatibility, shape controllability, and high adsorption. The use of the nanometer scale allows efficient access to the enzyme's substrate. It demonstrates important biological application capabilities in this way. Field emission gun-scanning electron microscopy (FEG-SEM), X-ray diffraction (XRD), infrared spectroscopy (FT-IR), in vitro release study, and cytotoxicity test were used to characterize the drug nanosystem's properties. According to the findings, electrostatic bindings was formed between charged groups of the enzyme and hydroxyapatite nanoparticles. The results also demonstrated that immobilized chABCI on hydroxyapatite has beneficial properties, such as more manageable drug release, minimal toxicity and side effects, and a high potential to enhance the efficacy of drug delivery and decrease the need for repeated injections. Key points: It has been proven that hydroxyapatite increases the shelf life of chondroitinase when it is used as a carrier matrix. Stability of the enzyme loaded onto hydroxyapatite was enhanced significantly after immobilization. The proposed process can make the hydroxyapatite nanoparticles a useful stabilizer drug delivery vehicle. The release of the chondroitinase is more controllable than previous studies; therefore the stability of the nanosystem has been increased. [ABSTRACT FROM AUTHOR]

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

Electrospinning is a facile popular method for the creation of nano-micro fibers tissue engineering scaffolds. Here, polycaprolactone (PCL)/collagen (COL): polyvinyl pyrrolidone (PVP) scaffolds (PCL/COL: PVP) were fabricated for bone regeneration. Various concentrations of Cephalexin (CEF) (0.5, 1, 1.5 wt. %) were added to PCL/COL: PVP scaffold to provide an antibacterial scaffold, and different concentrations of hydroxyapatite (HA) (1, 2, 5 wt. %) was electrospray on the surface of the scaffolds. The PCL/COL: PVP scaffold contained 1.5% CEF and coated with 2% HA was introduced as the best sample and in-vitro tests were performed on this scaffold based on the antibacterial and MTT test results. Morphology observations demonstrated a bead-free uniform combined nano-micro fibrous structure. Fourier transform infrared spectroscopy and X-ray diffraction tests confirmed the successful formation of the scaffolds and the wettability, swelling, and biodegradability evaluations of the scaffolds confirmed the hydrophilicity nature of the scaffold with high swelling properties and suitable biodegradation ratio. The scaffolds supported cell adhesion and represented high alkaline phosphatase activity. CEF loading led to antibacterial properties of the designed scaffolds and showed a suitable sustained release rate within 48 h. It seems that the electrospun PCL/COL: PVP scaffold loaded with 1.5% CEF and coated with 2% HA can be useful for bone regeneration applications that need further evaluation in the near future. [ABSTRACT FROM AUTHOR]

In recent years, additive manufacturing of nickel-titanium (NiTi) alloys as medical implant materials have attracted a lot of interest due to their precise, rapid, and integrated molding. However, the NiTi alloy as a bioinert material exhibits poor osteogenic activity and biomineralization properties. In this work, a graphene oxide (GO) coating containing nano-hydroxyapatite (HA) is fabricated on the NiTi alloys by a one-step DC electrodeposition method. The effects of HA (0.1 g/L) on the corrosion resistance, biomineralization properties and long-term stability of GO composite coating were investigated by electrochemical tests and immersion experiments. The result shows that the corrosion current density of GO coating reduces by one order of magnitude due to the introduction of nano-HA (from 2.24 × 10−8 A/cm2 to 3.18 × 10−9 A/cm2), the surface remains dense after 15 days of immersion, and a dense apatite layer is mineralized on the surface. In addition, in vitro MC3T3-E1 cell viability and cell morphology results showed that the coating can effectively enhance the biocompatibility of additively manufactured NiTi alloy because it provides a better microenvironment and interface for cell growth and adhesion. Taken together, the additively manufactured NiTi alloys with GO/HA coating present great potential for biological application, especially as orthopedic implants. [ABSTRACT FROM AUTHOR]

In modern pharmaceutical technology, modified-release dosage forms, such as in situ formed implants, are gaining rapidly in popularity. These dosage forms are created based on a configurable matrix consisting of phase-sensitive polymers capable of biodegradation, a hydrophilic solvent, and the active substance suspended or dissolved in it. The most used phase-sensitive implants are based on a biocompatible and biodegradable polymer, poly(DL-lactide-co-glycolide) (PLGA). Objective: This systematic review examines the reasons for the phenomenon of active ingredient "burst" release, which is a major drawback of PLGA-based in situ formed implants, and the likely ways to correct this phenomenon to improve the quality of in situ formed implants with a poly(DL-lactide-co-glycolide) matrix. Data sources: Actual and relevant publications in PubMed and Google Scholar databases were studied. Study selection: The concept of the review was based on the theory developed during literature analysis of 12 effectors on burst release from in situ forming implants based on PLGA. Only those studies that sufficiently fully disclosed one or another component of the theory were included. Results: The analysis resulted in development of a systematic approach called the "12 Factor System", which considers various constant and variable, endogenous and exogenous factors that can influence the nature of 'burst release' of active ingredients from PLGA polymer-based in situ formed implants. These factors include matrix porosity, polymer swelling, LA:GA ratio, PLGA end groups, polymer molecular weight, active ingredient structure, polymer concentration, polymer loading with active ingredients, polymer combination, use of co-solvents, addition of excipients, and change of dissolution conditions. This review also considered different types of kinetics of active ingredient release from in situ formed implants and the possibility of using the "burst release" phenomenon to modify the active ingredient release profile at the site of application of this dosage form. [ABSTRACT FROM AUTHOR]

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

Instead of employing duplex stainless steel (DSS) alone, the current effort aims to coat the 2205 DSS with hydroxyapatite (HA) coupled with carbon nanotube (CNTs) for biomedical applications to improve corrosion performance and biocompatibility. The surface of 2205 DSS has been coated with hydroxyapatite/Multiwall carbon nanotube composite particles by using the electrophoretic deposition (EPD) process to enhance corrosion resistance, biocompatibility, and osseointegration. In order to identify the ideal values for EPD factors, the current study examines the impact of the two most significant EPD variables (potential and time) on the characteristics of the deposited layer. The scanning electron microscope (SEM) is used to determine the coating properties. Potentiodynamic and cyclic polarization tests are used in Ringer's solution to evaluate the corrosion test of coated and uncoated specimens. According to the results, the ideal suspension has 65 wt.% HA and 35 wt.% multiwall carbonnanotube (MWCNT), is coated at 50 V for 2 min, and has a homogeneous morphology, a thick structure, and no cracks. Additionally, this sample had the least amount of porosity (0.572%) and the maximum rate of corrosion (0.091 mpy), making it well suited to serve as a barrier against the localized corrosion attack caused by the numerous aggressive ions that occurred in Ringer's solution during the corrosion test. [ABSTRACT FROM AUTHOR]

When impaired bones are grafted with bone scaffolds, the behaviors of osteoblast are dependent on the implant materials and surface morphology. To this end, we modulated the surface morphology of scaffolds that promote cell growth. In this study, ice-template and spraying method methods are employed to coat different proportions of PDA and PPy over the PLA/PVA weaving scaffolds, after which HA is Coated over via the electrochemical deposition, forming weaving scaffolds with electrically conductive PDA/PPy/HA coating. The test results indicate that with a PPy/PDA concentration ratio is 30, the PPy particles are more uniformly distributed on the fiber surface. The scaffolds are wrapped in a HA coating layer with a high purity, and calcium and phosphorus elements are evenly dispersed with a Ca/P ratio being 1.69. Owing to the synergistic effect between PDA and PPy coating, the scaffolds demonstrate excellent electrochemical stability and electrochemical activity. The biological activity of the scaffold increased to 274.66% under electrical stimulation. The new thinking proposed by this study extends the worth of applying textile structure to the medical field, the application of which highly increases the prospect of bone tissue engineering. [ABSTRACT FROM AUTHOR]

The main aims of thin biofilm synthesis are to either achieve a new form to promote the transport of drugs in oral delivery systems or as a coating to improve the biocompatibility of the implant's surface. In this study, the Langmuir monolayer technique was employed to obtain films containing Mg-doped hydroxyapatite with 0.5%, 1.0%, and 1.5% Mg(II). The obtained modified HA particles were analysed via the FT-IR, XRD, DLS, and SEM methods. It was shown that the modified hydroxyapatite particles were able to form thin films at the air/water interface. BAM microscopy was employed to characterized the morphology of these films. In the next step, the mixed films were prepared using phospholipid (DPPC) molecules and modified hydroxyapatite particles (HA-Mg(II)). We expected that the presence of phospholipids (DPPC) in thin films improved the biocompatibility of the preparing films, while adding HA-Mg(II) particles will promote antibacterial properties and enhance osteogenesis processes. The films were prepared in two ways: (1) by mixing DPPC and HA-Mg (II) and spreading this solution onto the subphase, or (2) by forming DPPC films, dropping the HA-Mg (II) dispersion onto the phospholipid monolayer. Based on the obtained π–A isotherms, the surface parameters of the achieved thin films were estimated. It was observed that the HA-Mg(II) films can be stabilized with phospholipid molecules, and a more stable structure was obtained from films synthesied via method (2). [ABSTRACT FROM AUTHOR]

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

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]

Improving the functionality of coatings, especially in biomedical applications, has been the major concern of the research community in recent years. For the same purpose, hydroxyapatite (HaP) coatings were synthesized, in this work, by applying the pulsed electrodeposition process by varying the amount of hydrogen peroxide (H2O2) into electrolyte put on Ti6Al4V substrate. The effect of hydrogen peroxide concentration H2O2 and the heat treatment on the surface morphology and the phase composition were investigated using scanning electron microscopy as well as x-ray microanalysis (SEM-EDXS) and x-ray diffraction (XRD). Mechanical properties at the nanoscale were determined by nanoindentation. The corrosion resistance of HaP/Ti6Al4V systems was examined using the two tests (potentio-dynamic polarization and Electrochemical Impedance Spectroscopy (EIS)) in Ringer solution to simulate the human body environment. The obtained results showed that the HaP coating with 9% of H2O2 and after heat treatment is made of two phases stoichiometric hydroxyapatite (HaP) and β-tricalcium phosphate (β-TCP) with a compact and homogeneous microstructure. In this condition, the hardness and Young's modulus were equal to 72,2 MPa and 30,45 GPa, respectively. Highest corrosion resistance was obtained from HaP coating with het treated 9% H2O2 (Ecorr = − 0.189 V and Icorr 1.12 µA cm−2). [ABSTRACT FROM AUTHOR]

Eight pediatric oral nutritional supplements (ONSs) and 0.5% fat bovine milk were examined in vitro regarding their effect on the adhesion of three caries-related bacteria, Streptococcus mutans (strain CCUG 11877T), Lactobacillus gasseri (strain CCUG 31451), and Scardovia wiggsiae (strain CCUG 58090), to saliva-coated hydroxyapatite, as well as their pH and capacity to withstand pH changes. Bacteria were cultivated and radiolabeled. The adhesion assays used synthetic hydroxyapatite coated with whole or parotid saliva. Measurements of pH and titration of the products with HCl and NaOH were conducted in triplicate. Three ONSs promoted the S. mutans adhesion to saliva-coated hydroxyapatite (increase from 35% to >200%), supporting caries risk enhancement. S. wigssiae and L. gasseri adhered only to one and no ONS, respectively. Most supplements had limited buffering capacity to counteract acidification changes, suggesting their low capacity to neutralize acids, and one ONS showed a significant capacity to counteract basic changes, suggesting a high erosive potential. S. mutans adhesion was influenced by the ONS pH and volume NaOH added to reach pH 10. L. gasseri and S. wiggsiae adhesion was influenced by the ONSs' carbohydrate and fat content. Interdisciplinary efforts are needed to increase awareness and prevent the possible negative impact of ONSs on children's oral health. [ABSTRACT FROM AUTHOR]

In this study, a new nanocomposite of hydroxyapatite (HA)/Mg–Al layered double hydroxide (LDH) was successfully formed via a facile co-precipitation method and applied to adsorb three anionic dyes of alizarin red S (ARS), Congo red (CR), and reactive red 120 (RR120) differing in the number of SO3− groups from aqueous solution. Based on a combination of characterization analysis and adsorption experiments, HA/Mg–Al LDH nanocomposite showed better adsorption performance than HA and Mg–Al LDH. Using XRD and TEM analyses, the crystallinity and the presence of nanoparticles were confirmed. According to the SEM investigation, the Mg–Al LDH layers in the nanocomposite structure were delaminated, while HA nanorods were formed at the surface of Mg–Al LDH nanoparticles. The higher BET surface area of the novel HA/Mg–Al LDH nanocomposite compared to HA and Mg–Al LDH provided its superior adsorption performance. Considering an effective amount of adsorbent dosage, pH 5 was selected as the optimum pH for each of the three dye solutions. According to the results from the study of contact time and initial concentration, the pseudo-second-order kinetic (R2 = 0.9987, 0.9951, and 0.9922) and Langmuir isotherm (R2 = 0.9873, 0.9956, and 0.9727) best fitted the data for ARS, CR, and RR120, respectively. Anionic dyes with different numbers of SO3− groups demonstrated distinct adsorption mechanisms for HA and Mg–Al LDH nanoparticles, indicating that the adsorption capacity is influenced by the number of SO3− groups, with HA/Mg–Al LDH nanocomposite offering superior performance toward dyes with higher numbers of SO3− groups. Furthermore, ΔH° less than 40 kJ/mol, positive ΔS°, and negative ΔG° accompanied by the mechanism clarifying show physical spontaneous adsorption without an external source of energy and increase the randomness of the process during the adsorption, respectively. Finally, the regeneration study demonstrated that the nanocomposite could be utilized for multiple adsorption–desorption cycles, proposing the HA/Mg–Al LDH as an economically and environmentally friendly adsorbent in the adsorption of anionic dyes in water treatment processes. [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.

The most important challenge faced in designing orthopedic devices is to control the leaching of ions from the substrate material, and to prevent biofilm formation. Accordingly, the surgical grade stainless steel (316L SS) was electrophoretically deposited with functional composition of biopolymers and bioceramics. The composite coating consisted of: Bioglass (BG), hydroxyapatite (HA), and lawsone, that were loaded into a polymeric matrix of Xanthan Dialdehyde/Chondroitin Sulfate (XDA/CS). The parameters and final composition for electrophoretic deposition were optimized through trial-and-error approach. The composite coating exhibited significant adhesion strength of "4B" (ASTM D3359) with the substrate, suitable wettability of contact angle 48°, and an optimum average surface roughness of 0.32 µm. Thus, promoting proliferation and attachment of bone-forming cells, transcription factors, and proteins. Fourier transformed infrared spectroscopic analysis revealed a strong polymeric network formation between XDA and CS. scanning electron microscopy and energy dispersive X-ray spectroscopy analysis displayed a homogenous surface with invariable dispersion of HA and BG particles. The adhesion, hydrant behavior, and topography of said coatings was optimal to design orthopedic implant devices. The said coatings exhibited a clear inhibition zone of 21.65 mm and 21.04 mm with no bacterial growth against Staphylococcus aureus (S. Aureus) and Escherichia coli (E. Coli) respectively, confirming the antibacterial potential. Furthermore, the crystals related to calcium (Ca) and HA were seen after 28 days of submersion in simulated body fluid. The corrosion current density, of the above-mentioned coating was minimal as compared to the bare 316L SS substrate. The results infer that XDA/CS/BG/HA/lawsone based composite coating can be a candidate to design coatings for orthopedic implant devices. [ABSTRACT FROM AUTHOR]

One of the main targets in modern dentistry is the prevention of caries. Not only daily nutrition plays an important role, but also the so‐called "pellicle" on the outer surface of teeth, which is mainly formed by saliva proteins. Moreover, numerous bacteria are part of this pellicle, which might cause caries by acidic metabolites. In the here‐presented study, a method for electrophoretic deposition (EPD) of hydroxyapatite (HAP) nanoparticles on gold surfaces, suitable for surface plasmon resonance (SPR) measurements, is developed. An "artificial tooth" is created and loaded by natural saliva in different concentrations (to form a natural pellicle), while the influence of an environment with different pH values has been studied. It could be demonstrated that even slight acid solutions damage the pellicle significantly within seconds, exposing the HAP to acidic degradation, which would lead to caries in the human oral cavities. This model allows to study pellicle formation as well as degradation in real time. As a practical example, the influence of beverages on the pellicle could be demonstrated. [ABSTRACT FROM AUTHOR]

BACKGROUND: A combination of synthetic porous materials and BMP-2 has been used to promote fracture healing. For bone healing to be successful, it is important to use growth factor delivery systems that enable continuous release of BMP-2 at the fracture site. We previously reported that in situ-formed gels (IFGs) consisting of hyaluronan (HyA)-tyramine (TA), horseradish peroxidase and hydrogen peroxide enhance the bone formation ability of hydroxyapatite (Hap)/BMP-2 composites in a posterior lumbar fusion model. OBJECTIVE: We examined the effectiveness of IFGs-HyA/Hap/BMP-2 composites for facilitating osteogenesis in refractory fracture model mice. METHODS: After establishing the refractory fracture model, animals were either treated at the site of fracture with Hap harboring BMP-2 (Hap/BMP-2) or IFGs-HyA with Hap harboring BMP-2 (IFGs-HyA/Hap/BMP-2) (n = 10 each). Animals that underwent the fracture surgery but did not receive any treatment were considered the control group (n = 10). We determined the extent of bone formation at the fracture site according to findings on micro-computed tomography and histological studies four weeks following treatment. RESULTS: Animals treated with IFGs-HyA/Hap/BMP-2 demonstrated significantly greater bone volume, bone mineral content and bone union than those treated with vehicle or IFG-HyA/Hap alone. CONCLUSIONS: IFGs-HyA/Hap/BMP-2 could be an effective treatment option for refractory fractures. [ABSTRACT FROM AUTHOR]

In the present article, mesoporous SiO 2 /hydroxyapatite (HA) composite particles were produced via employing CTAB as a template, and then co-electrodeposited on Nitinol biomedical alloy with HA. Characterization results showed the formation of about 200 nm spheres with numerous plate-like particles and slit-shaped pores. The composite coatings were applied by using different concentrations of particles in the deposition electrolyte (500, 750, 1000, and 1250 mg/L). Morphological observations revealed that with an increase in particle concentration, the film exhibited greater compactness, leading to the formation of particle agglomerates in certain regions. This was further proved by the atomic force microscopy analysis where the porosity of the layers decreased, and the roughness diminished by raising particle concentration. This made composite coatings a little more hydrophobic than pure HA coating. Furthermore, the incorporation of these particles significantly enhanced the corrosion protection of the composite coatings. Specifically, the corrosion current density for the sample coated with a solution containing 1000 mg/L of particles decreased to nearly one-fifth of that observed in the pure HA coating. Last but not least, MG-63 osteoblasts were provided with a convenient environment on composite coatings since they fed on Si nutritious element to reproduce and proliferate more aggressively than on pure HA layer. [ABSTRACT FROM AUTHOR]

The study aims to enhance the corrosion resistance and bioactivity of Mg alloy substrates through the development of a zinc/hydroxyapatite multi-layer (Zn/HA-ML) coating. The Zn/HA-ML coating was prepared by depositing a cold-sprayed (CS) Zn underlayer and a high-velocity suspension flame sprayed (HVSFS) Zn/HA multi-layer and was compared with the CS Zn coating and the Zn/HA dual-layer (Zn/HA-DL) coating. Phase, microstructure, and bonding strength were examined, respectively, by X-ray diffraction, scanning electron microscopy, and tensile bonding testing. Corrosion behavior and bioactivity were investigated using potentiodynamic polarization, electrochemical impedance spectroscopy, and immersion testing. Results show that the HVSFS Zn/HA composite layers were mainly composed of Zn, HA, and ZnO and were well bonded to the substrate. The HVSFS HA upper layer on the CS Zn underlayer in the Zn/HA-DL coating exhibited microcracks due to their mismatched thermal expansion coefficient (CTE). The Zn/HA-ML coating exhibited good bonding within different layers and showed a higher bonding strength of 27.3 ± 2.3 MPa than the Zn/HA-DL coating of 20.4 ± 2.7 MPa. The CS Zn coating, Zn/HA-DL coating, and Zn/HA-ML coating decreased the corrosion current density of the Mg alloy substrate by around two–fourfold from 3.12 ± 0.75 mA/cm2 to 1.41 ± 0.82mA/cm2, 1.06 ± 0.31 mA/cm2, and 0.88 ± 0.27 mA/cm2, respectively. The Zn/HA-ML coating showed a sixfold decrease in the corrosion current density and more improvements in the corrosion resistance by twofold after an immersion time of 14 days, which was mainly attributed to newly formed apatite and corrosion by-products of Zn particles. The Zn/HA-ML coating effectively combined the advantages of the corrosion resistance of CS Zn underlayer and the bioactivity of HVSFS Zn/HA multi-layers, which proposed a low-temperature strategy for improving corrosion resistance and bioactivity for implant metals. [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]

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

This study 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]

Magnesium alloy is emerging as a leading choice for biodegradable orthopedic implants, thanks to its superior biocompatibility and mechanical characteristics that align with those of natural bone. Nonetheless, its swift corrosion rate poses a challenge to its use in clinical settings. In this study, two methods were used to apply Cerium and Hydroxyapatite (HA) coatings on Mg AZ31 implants, specifically a one-step process (HA + Ce) and a two-step process (HA + Ce/CeCC), with the aim of improving their resistance to corrosion. The susceptibility of the samples to corrosion and the efficiency of the coatings in a physiological media were evaluated using Electrochemical Impedance Spectroscopy (EIS) and Direct Current (DC) polarization tests in a Simulated Body Fluid (SBF) solution. In the HA + Ce sample, the effect of immersion time was also examined. The Field Emission Scanning Electron Microscope (FE-SEM) results showed that after 15 min of coating process, a very weak and uneven coating is formed on the surface. However, at 30 and 60 min, the structure of the coating changes, forming a more crystalline and denser coating on the surface, which also has greater corrosion resistance. The results of the electrochemical tests showed that the sample prepared using the two-step method (HA + Ce/CeCC sample) had the highest resistance to both corrosion and biocorrosion. The morphology and composition of the coatings were inspected using FE-SEM and X-ray diffraction (XRD), confirming the formation of HA crystals and an amorphous layer of Cerium. Moreover, the HA + Ce/CeCC sample demonstrated the highest level of corrosion resistance in an Simulated Body Fluid (SBF) media over an extended duration of submersion. [ABSTRACT FROM AUTHOR]

In this study, Hydroxyapatite coatings were electrochemically deposited into 316L stainless steel to be used in biomedical applications, such as bone implants. In this regard, the current investigation was conducted on a physiologically mimicked environment to emphasize its effects on the durability and biocompatibility of the coated stainless steel. The study accentuates on three kinds of stainless-steel surfaces: Blank 316L stainless steel surface (SS316L), Anodized surface (ANSS-316L), and Hydroxyapatite treated surface (HASS-316L). The coating surface has been done by a solution containing 0.042 mol/L of calcium nitrate tetrahydrate (Ca (NO3)24H2O) and 0.025 mol/L of orthophosphoric acid. To examine the electrochemical behavior of the three samples and determine their characteristics, Fouriertransform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and polarization Tafel curves with electrochemical impedance spectroscopy (EIS), have been used. The outcomes demonstrate that hydroxyapatite deposited on stainless steel increases the corrosion resistance of metal implants which may enhance its durability and biocompatibility. [ABSTRACT FROM AUTHOR]

Dental surgery needs a biocompatible implant design that can ensure both osseointegration and soft tissue integration. This study aims to investigate the behavior of a hydroxyapatite-based coating, specifically designed to be deposited onto a zirconia substrate that was intentionally made porous through additive manufacturing for the purpose of reducing the cost of material. Layers were made via sol–gel dip coating by immersing the porous substrates into solutions of hydroxyapatite that were mixed with polyethyleneimine to improve the adhesion of hydroxyapatite to the substrate. The microstructure was determined by using X-ray diffraction, which showed the adhesion of hydroxyapatite; and atomic force microscopy was used to highlight the homogeneity of the coating repartition. Thermogravimetric analysis, differential scanning calorimetry, and Fourier transform infrared spectroscopy showed successful, selective removal of the polymer and a preserved hydroxyapatite coating. Finally, scanning electron microscopy pictures of the printed zirconia ceramics, which were obtained through the digital light processing additive manufacturing method, revealed that the mixed coating leads to a thicker, more uniform layer in comparison with a pure hydroxyapatite coating. Therefore, homogeneous coatings can be added to porous zirconia by combining polyethyleneimine with hydroxyapatite. This result has implications for improving global access to dental care. [ABSTRACT FROM AUTHOR]

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

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