Fluoridated Hydroxyapatite Research Articles

Seriation of Enzyme-Functionalized Multilayers for the Design of Scalable Biomimetic Mineralized Structures.

Biomimetic hydroxyapatites are widely explored for their potential applications in the repair of mineralized tissues, particularly dental enamel, which is acellular and, thus, not naturally reformed after damage. Enamel is formed with a highly-controlled hierarchical structure, which is difficult to replicate up to the macroscale. A biomimetic approach is thus warranted, based on the same principles that drive biomineralization in vivo. Herein, a strategy for the design of enamel-like architectures is described, utilizing enzymes embedded in polyelectrolyte multilayers to generate inorganic phosphate locally, and provide a favorable chemical environment for the nucleation and growth of minerals. Moreover, a method is proposed to build up seriated mineral layers with scalable thicknesses, continuous mineral growth, and tunable morphology. Results show the outstanding growth of cohesive mineral layers, yielding macroscopic standalone fluoride and/or carbonate-substituted hydroxyapatite materials with comparable crystal structure and composition to native human mineralized tissues. This strategy presents a promising path forward for the biomimetic design of biomineral materials, particularly relevant for restorative applications, with an exquisite level of synthetic control over multiple orders of magnitude.

Remineralization Potential of Nanostrontium/Fluoride Hydroxyapatite on Artificial Enamel Caries

Objectives: This study aimed to evaluate the remineralization efficacy of nano-strontium/ fluoride hydroxyapatite paste on initial enamel caries in comparison with other remineralization products under a simulated pH-cycling model. Methods: Following the artificial caries induction, forty enamel specimens with noncavitated lesion in the same range of lesion depth were selected by mean of micro-CT evaluation. The specimens were block-randomized into four experimental groups regarding remineralizing pastes: 1500 ppm sodium fluoride paste, 10%wt nano-hydroxyapatite paste, 10%wt nano-strontium/fluoride hydroxyapatite paste and 5%wt nano-strontium/ fluoride hydroxyapatite paste. Remineralizing effect was evaluated using micro-CT, while SEM/EDS line scan mode facilitated the investigation of remineralization patterns. Changes in lesion depth (ΔLD) and changes in mineral loss (ΔΔZ) were evaluated at 7 and 14 days of treatment under the pH-cycling model. Statistical analyses were performed using 2-way ANOVA and post hoc Tukey’s test (p<0.05). Results: The use of 5%wt nano-strontium/fluoride hydroxyapatite paste significantly reduced lesion depth in initial caries under experimental conditions. Meanwhile, the 10%wt nano-strontium/fluoride hydroxyapatite paste yielded the highest mineral gain, though statistically insignificant. EDS graphs indicated an increasing calcium and phosphorus deposition trend over time with nano-strontium/fluoride hydroxyapatite paste, revealing a more uniform mineral distribution compared to both sodium fluoride and nano-hydroxyapatite pastes. Nevertheless, neither fluorine nor strontium was detectable in these graphs. Conclusions: The study revealed comparable remineralization efficacy with 5%wt and 10%wt nano-strontium/fluoride hydroxyapatite pastes. The treatment durations of 7 and 14 days showed no significant difference in outcomes.

Optimized regression model for microhardness of experimental dental composite resins with nano-hydroxyapatite filler particles

ABSTRACT Background: Bioactive materials produce a biological reaction such as stimulation of pulpal cells for dentinal repair and induction of the formation of hydroxyapatite. Aim: The study was conducted to evaluate the microhardness of experimental dental composite resins (EDCR) containing nano-hydroxyapatite, zirconia, and glass filler particles. Materials and Methods: The EDCR was prepared with varying concentrations of barium aluminum fluoride glass (5–20 nm), zirconia (4–11 nm), and hydroxyapatite (20–80 nm) filler particles added to the organic matrix. The L9 orthogonal array was used to prepare a sample size of 27 samples. Disc-shaped specimens of 10 mm diameter and 4 mm thickness were prepared using the American Society for Testing and Materials E384 standard for testing the microhardness. The Taguchi’s method of optimization was used to obtain a composite with optimum microhardness. A regression model was developed. Results: EDCR with 23.7% of zirconia, 27.5% of nano-hydroxyapatite, and 20% of glass filler particles gave the optimum microhardness of 222.67 HV. The confirmatory experimental test of EDCR gave a microhardness of 225 HV. The model developed with regression equation for the microhardness was 60–123 Z + 114 H + 17.8 G + 2.48 ZH − 0.02 HG + 0.97 Z2 − 3.40 H2. The difference between the R 2 (99.9) and adjusted R 2 values (99.4) is <0.5, this shows that the model is acceptable. Conclusion: The EDCR developed after using Taguchi’s method of optimization had microhardness superior to that of the commercially available composite resins.

Remineralization Strategies for Teeth with Molar Incisor Hypomineralization (MIH): A Literature Review.

Molar incisor hypomineralization (MIH) is a highly prevalent dental developmental disorder with a significant health burden for patients and high treatment needs, yet no comprehensive review article on all remineralization systems as a non-invasive treatment approach for MIH has been published. Typical characteristics of MIH-affected teeth are a lower mineral density and lower hardness compared to healthy teeth leading to sensitivity and loss of function. Thus, the use of formulations with calcium phosphates to remineralize MIH-affected teeth is reasonable. This review presents an up-to-date overview of remineralization studies focusing on active ingredients investigated for remineralization of MIH, i.e., casein phosphopeptide amorphous calcium phosphate (CPP-ACP), casein phosphopeptide amorphous calcium fluoride phosphate (CPP-ACFP), hydroxyapatite, calcium glycerophosphate, self-assembling peptide, and fluoride. Overall, 19 studies (in vitro, in situ, and in vivo) were found. Furthermore, an additional search for studies focusing on using toothpaste/dentifrices for MIH management resulted in six studies, where three studies were on remineralization and three on reduction of sensitivity. Overall, the studies analyzed in this review showed that MIH-affected teeth could be remineralized using calcium phosphate-based approaches. In conclusion, calcium phosphates like CPP-ACP, calcium glycerophosphate, and hydroxyapatite can be used to remineralize MIH-affected teeth. In addition to MIH-remineralization, CPP-ACP and hydroxyapatite also offer relief from MIH-associated tooth sensitivity.

Green synthesis of Sodium alginate mediated Fluorapatite Nanoparticle via Sol-Gel method

Fluorapatite (FA) can be used as a bioactive substance in the body, especially the teeth implants. The FA nanoparticle was synthesized by adding the fluorine to the structure of HA using sol–gel method and the heat treatment of 700 °C. Being low costs, eco-friendly and safer features are obvious advantages of the green synthesis of FA nanoparticles by using bio stabilizer of sodium alginate. Calcium nitrate tetrahydrate, diammonium phosphate, ammonium fluoride were used as precursors of Ca, P and F respectively with the ratio of 1:67 Ca/P. The presence of crystal structure of HA and FA investigated by the results of XRD which confirmed the substitution of hydroxyl groups with the fluorine in the crystal structure of apatite. FTIR obtained that fluorine was substituted by hydroxyl groups in the structure of fluoridated hydroxyapatite by disappearing the hydroxyl groups at 3600 cm-1 in the FA. TGA investigated the thermal stability of the nanoparticles that showed the discrepancy of weight loss for HA and FA between 600?C to 800?C. By using TEM, average sizes of 35 and 49 nm were determined for HA and FA respectively. FESEM results confirmed the shapes and distribution of particles of HA and FA in that, round like for the former and rode like for the later. The overall performance of utilizing sodium alginate (SA) as a bio-stabilizer is to obtain better precipitate which leads to having better crystallinity and smaller particle size and thermal stability remarkably improved.

Preparation and properties of FHA coatings on micro-arc oxidised AZ91D magnesium alloy with different deposition times

ABSTRACT To improve the corrosion resistance of magnesium (Mg) alloy under the physiological environment, fabrication of fluoridated hydroxyapatite (FHA) coating on micro-arc oxidised AZ91D Mg alloy was carried out by electrochemical deposition. The influence of electrochemical deposition time on surface morphology, phase composition, electrochemical properties, and degradation behaviour of the FHA coating was studied by SEM, XRD, electrochemical testing, and in-vitro immersion test, respectively. The results of the electrochemical test and in-vitro immersion test show that FHA coating can significantly improve corrosion resistance. In particular, the sample with deposition time of 60 min showed the minimum corrosion current density (1.26 × 10−6 A cm−2), which may be attributed to a significant decrease in the imperfections of the coating being achieved after this optimum deposition time.

Electrodeposition of micro-nano hierarchically structured fluoridated hydroxyapatite coating on AZ31B alloy

ABSTRACT In this study, a novel micro-nano hierarchically structured fluoridated hydroxyapatite (FHAp) coating on AZ31B substrate was successfully synthesized via a simple one-step electrochemical deposition method. And the formulation of the electrodeposition solution is simple and environment-friendly without any harmful additives. The FHAp coating consists of a large amount of nanorods and some micro-structured spherical aggregates composed of nanorods. Electrochemical tests demonstrated that the FHAp coating exhibited higher anti-corrosion property and lower degradation rate than that of pure HAp coating. Moreover, the FHAp coating with micro-nano hierarchically structured surface displayed good cell biocompatibility. The addition of fluorine ion into HAp coating can further promote the cell adhesion and proliferation. This work provides a simple, environment-friendly, and efficient way to prepare FHAp coating on AZ31B alloy with improved corrosion resistance and biocompatibility.

Bio-Functional Coating on Ti6Al4V Surface Produced by Using Plasma Electrolytic Oxidation

One way to improve the biofunctionality of titanium alloys is by implementing plasma electrolytic oxidation (PEO) to incorporate bioactive elements such as fluoridated hydroxyapatite, into surface coatings of orthopaedic and dental implants. Hydroxyapatite (HAp) is known as a bioactive coating while fluorapatite (FAp) has an antibacterial effect that would enhance the bio-functionality and reduce the failure rate of orthopaedic and dental implants. The purpose of this study was to develop fluoridated hydroxyapatite as a bio-functional coating on Ti6Al4V with electrolyte containing trisodium orthophosphate, potassium hydroxide, and calcium fluoride. The coating surface and cross-section morphologies were evaluated, and the species in the electrolyte solution were found, and irregular micropores shapes were observed by field emission scanning electron microscopy (FESEM) and energy dispersive spectrometer (EDS). The phase composition of the coating surface containing TiO2 (anatase and rutile), tricalcium orthophosphate, HAp, and FAp was characterized by X-ray diffractometer (XRD). The adhesive strength of the coating was analysed by a micro-scratch test. Simulated body fluid (SBF) immersion test was performed to investigate the bioactivity of the coating. In this study, we demonstrated that the PEO technique has a good potential to develop bio-functional surface modifications that can affect the chemical composition and roughness of the coating surface. The FAp coating may provide insights for subsequent bioactive coatings while improving the antibacterial properties for orthopaedic and dental implants. Future work shall investigate the optimal amount of fluoride in the coating layer that obtains excellent results without causing adverse effects on adjacent tissue.

Low-temperature mineralization sintering process for fabrication of fluoridated hydroxyapatite-containing bioactive glass

Bioactive glasses and glass-ceramics are receiving wide attention for their biomedical applications. We present a novel route to obtain fluoridated hydroxyapatite-containing bioactive glass (FHBG) through a low-temperature mineralization sintering process (LMSP). LMSP is a low-temperature densification procedure that can provide a functionalization of pristine materials through the formation and growth of new phases induced by mineralization. Here, SiO2–CaO–P2O5 bioactive glass nanoparticles (BGNPs) were prepared and mixed with fluorine-containing simulated body fluid (F–SBF) to induce mineralization. Under a uniaxial pressure of 330 MPa and temperature of 120 °C, BGNPs were densified up to 89% of their theoretical density, and the Vickers hardness and fracture toughness of the sintered BGNPs increased to 4.15 ± 0.11 GPa and 1.32 ± 0.12 MPa m1/2, respectively. This densification behavior was strongly influenced by the mineralization that forms nanoscale crystalline phase such as carbonated fluoridated hydroxyapatite (HAp), where part of PO43− and OH− in HAp (Ca10(PO4)6(OH)2) was replaced by CO32− and F−, respectively. The fluorides formed as minor phases in the sintered BGNPs by mineralization were identified as calcium fluorosilicate (CaSiF6) and calcium fluoride (CaF2). After an acid resistance test, because of the presence of fluorides, the sintered BGNPs containing fluorides presented a 38% weight loss, which is lower than that of sintered BGNPs containing no fluorides (54% weight loss). By employing LMSP, we successfully fabricated FHBG from non-fluoride-containing BGNPs and F–SBF at an extremely low temperature at 120 °C. Therefore, this study offers a more efficient method for the manufacturing of glasses and glass-ceramics.

Controllable phase transformation of fluoridated calcium phosphate ultrathin coatings for biomedical applications

Titanium has been widely used in medical implants for hard tissue replacements. Nevertheless, the bioinert innate oxide layer on the titanium implant surface usually makes the implant fail to osseointegrate with the surrounding tissue after surgery. To improve the bioactivity of titanium implants, the deposition of calcium phosphate (CaP) coatings attracts much research interest owing to the excellent bioactivity and biocompatibility of CaP. This work has successfully developed a promising synthetic method to prepare uniform fluoridated CaP coatings with ultrathin thicknesses (∼170 nm) and desired phases on acid-etched titanium (AETi) substrates. A dense ultrathin coating with a dominant phase of fluoridated amorphous CaP (FACP) can be obtained by an electrochemical deposition method in galvanostatic mode. After a heat treatment at 600 °C for 3 h in humid air, the as-prepared coating has been transformed to a coating with a dominant phase of fluoridated hydroxyapatite (FHA). Additionally, the dominant phase of the coating can be transformed from FACP to α-tricalcium phosphate (α-TCP) by a heat treatment at 800 °C for 3h in air. Unlike previously reported fluoridated CaP coatings with thicknesses of around several micrometers, the ultrathin thickness can potentially enhance the adhesive strength and ductility of the coating. Notably, the fluorine incorporation in the coating can bring in additional benefits such as lower solubility, higher antibacterial activity, and higher adhesive strength. The electrochemical deposition associated with different post heat treatments can obtain fluoridated CaP coatings with different desired phases in a controllable manner, which is very important since CaPs with different phases possess different properties and may be suitable for different biomedical applications. This study proposes a promising, simple, and low-cost method which can endow complex-shaped titanium implants with better bioactivity for dental and orthopedic applications.

Cicada-inspired fluoridated hydroxyapatite nanostructured surfaces synthesized by electrochemical additive manufacturing

Recently, the cicada-inspired nanostructured surfaces have attracted much interest because they possess remarkable bactericidal ability. However, Gram-positive bacteria are less damageable by the nanopillar structure of a cicada wing surface compared to Gram-negative species. To overcome this shortcoming, fluoridated hydroxyapatite (FHA) is employed owing to its effective antibacterial ability against both Gram-negative and Gram-positive bacteria. Here, we design a novel potential antibacterial surface by combining the cicada wing-like nanopillar structure and the FHA together to potentially exert the advantages of physical and chemical antibacterial strategies simultaneously for battling the antibiotic-resistant pathogenic bacteria more effectively. Cicada-inspired FHA nanostructured surfaces have been successfully fabricated on acid-etched titanium (AETi) plates using an electrochemical additive manufacturing (ECAM) method for the first time. The as-prepared FHA nanopillar array consists of close-packed individual nanopillars with diameters, heights, and aspect ratios of ~65–95 nm, ~380–510 nm, and ~4.5–7.5, respectively. The chemical composition of the FHA nanopillar array is similar to that of the Ca10(PO4)6(OH)F. Individual FHA nanopillars possess high crystallinity, long-range regularity, and flaw-free lattices with the [0001] orientation. Our new, cost-effective, and time-saving method for fabricating cicada-inspired FHA nanostructured surfaces could potentially endow orthopedic and dental implants with enhanced antibacterial performance for biomedical applications.

Biodegradable Magnesium Bone Implants Coated with a Novel Bioceramic Nanocomposite.

Magnesium (Mg) alloys are being investigated as a biodegradable metallic biomaterial because of their mechanical property profile, which is similar to the human bone. However, implants based on Mg alloys are corroded quickly in the body before the bone fracture is fully healed. Therefore, we aimed to reduce the corrosion rate of Mg using a double protective layer. We used a magnesium-aluminum-zinc alloy (AZ91) and treated its surface with micro-arc oxidation (MAO) technique to first form an intermediate layer. Next, a bioceramic nanocomposite composed of diopside, bredigite, and fluoridated hydroxyapatite (FHA) was coated on the surface of MAO treated AZ91 using the electrophoretic deposition (EPD) technique. Our in vivo results showed a significant enhancement in the bioactivity of the nanocomposite coated AZ91 implant compared to the uncoated control implant. Implantation of the uncoated AZ91 caused a significant release of hydrogen bubbles around the implant, which was reduced when the nanocomposite coated implants were used. Using histology, this reduction in the corrosion rate of the coated implants resulted in an improved new bone formation and reduced inflammation in the interface of the implants and the surrounding tissue. Hence, our strategy using a MAO/EPD of a bioceramic nanocomposite coating (i.e., diopside-bredigite-FHA) can significantly reduce the corrosion rate and improve the bioactivity of the biodegradable AZ91 Mg implant.

Effect of the Fluorine Substitution for –OH Group on the Luminescence Property of Eu3+ Doped Hydroxyapatite

In this study, different fluoridated hydroxyapatite doped with Eu3+ ion nanoparticles were prepared by the hydrothermal method. The relationship between luminescence enhancement of Eu3+ ions and a fluorine substitution ratio for hydroxyl group in hydroxyapatite was discussed. Moreover, the effect of fluorine substitution for a hydroxyl group on phase composition, crystallinity, and crystal size was studied. Phase composition and chemical structures were identified by X-ray diffraction (XRD) and Fourier Transform Infrared (FT-IR) Spectroscopy analyses. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) patterns were performed to analyze the morphology and particle size. X-ray Photoelectron Spectroscopy (XPS) patterns were observed to analyze fluorine substitution for the hydroxyl group and chemical state of Eu3+ ions in fluoridated hydroxyapatite. The results of these experiments indicated that the samples with a different fluorine substitution ratio were prepared successfully by maintaining the apatite structure. With an increasing fluorine substitution ratio, the morphology maintained a rod-like structure but the aspect ratio tended to decrease. XPS patterns displayed that the fluorine replaced the hydroxyl group and brought environmental variation. The fluorine ions could affect the crystal field environment and promote luminescence conversion. There was a linear relationship between the fluorine substitution ratio and luminescence enhancement.

Physicochemical inspection and in vitro bioactivity behavior of bio-nanocomposite alginate hydrogels filled by magnesium fluoro-hydroxyapatite

The effect of magnesium fluoridated hydroxyapatite nanoparticles (Mg-FHA NPs) as ceramic species on the morphology, thermal and in vitro bioactivity properties of sodium alginate (SA) matrix was investigated. Preparation of cross-linked SA/FHA bio-nanocomposites (bio-NC)s was carried out under ultrasonic irradiations as fast and green conditions followed by cross-linking with CaCl2. The sonication influence on the dispersion of Mg-FHA in the alginate was studied thoroughly. Morphology images showed that the size of Mg-FHA NPs in the matrix reduced, considerably and the mean diameter of particles was estimated to be about 4 nm. The thermal stability of the alginate did not show significant changes by loading of 2, 6, and 10 wt% of Mg-FHA NPs. The bio-NCs exhibited the good ability of the formation of apatite in simulated body fluid. Mg-FHA growth on the surface of the samples was proved by a noteworthy increase in the phosphate absorption bands in FT-IR spectra, which shows the potential application of the obtained bio-NCs in tissue engineering.

The electrospun poly(ε‐caprolactone)/fluoridated hydroxyapatite nanocomposite for bone tissue engineering

Biodegradable cell‐incorporated scaffolds can guide the regeneration process of bone defects such as physiological resorption, tooth loss, and trauma which medically, socially, and economically hurt patients. Here, 0, 5, 10, and 15 wt% fluoridated hydroxyapatite (FHA) nanoparticles containing 25 wt% F− and 75 wt% OH− were incorporated into poly(ε‐caprolactone) (PCL) matrix to produce PCL/FHA nanocomposite scaffolds using electrospinning method. Then, scanning electron microscopy (SEM), X‐ray diffraction (XRD) pattern, and Fourier transform infrared spectroscopy (FTIR) were used to evaluate the morphology, phase structure, and functional groups of prepared electrospun scaffolds, respectively. Furthermore, the tensile strength and elastic modulus of electrospun scaffolds were investigated using the tensile test. Moreover, the biodegradation behavior of electrospun PCL/FHA scaffolds was studied by the evaluation of weight loss of mats and the alternation of pH in phosphate buffer saline (PBS) up to 30 days of incubation. Then, the biocompatibility of prepared mats was investigated by culturing MG‐63 osteoblast cell line and performing MTT assay. In addition, the adhesion of osteoblast cells on prepared electrospun scaffolds was studied using their SEM images. Results revealed that the fiber diameter of prepared electrospun PCL/FHA scaffolds alters between 700 and 900 nm. The mechanical assay illustrated the mat with 10 wt% FHA nanoparticles revealed the highest tensile strength and elastic modulus. The weight loss alternation of mats determined around 1% to 8% after 30 days of incubation. The biocompatibility and cell adhesion of mats improved by increasing the amounts of FHA nanoparticles.

Synthesis and characterization of strontium fluor-hydroxyapatite nanoparticles for dental applications

Being biocompatible, bioactive, having low solubility in a wet environment and showing similarities to mineral part of hard tissue in human's body, hydroxyapatite has so many applications in dentistry and related hard tissue concerns. Fluoride ion being found in bone and enamel can be joined to hydroxyapatite and reduce solubility and also hold biocompatibility relatively like hydroxyapatite. Playing main role in bone regeneration, strontium can be used partially or totally to treat biomaterials and increase biocompatibility and bioactivity. In this study hydroxyapatite and strontium hydroxyapatite were synthesized by chemical precipitation of different percentages of strontium by which substitutes calcium. Additionally, Fluoride was incorporated into the apatite structure, using pH-cycling method and producing Strontium- Fluoride hydroxyapatite. Diammonium phosphate, calcium nitrate, strontium nitrate and sodium fluoride were starting materials and solution of sodium hydroxide and nitric acid were used to control pH. Accordingly, synthesized nano-powders characterized by XRD, FTIR, F-selective electrode, inductively coupled plasma spectroscopy and SEM. Subsequently, biological assessment of fluoride's and strontium's influence on the proliferation and differentiation of MG63 cell line was conducted by MTT and ALP tests. Results of XRD and FTIR showed that nano-crystals of HA, SrHA, FHA and F-SrHA were successfully achieved by this method. SEM images revealed that prepared crystalline powders morphology was nano-size and spherical. Biocompatibility also approved by MTT tests. Also, since the process of calcification of hard tissues (bones and teeth) is effected by alkaline phosphatase enzyme (ALP), the influence of both alone and combined fluoride and strontium on cell differentiation was investigated. Consequently, results represent the ability of these elements to enhance remineralization of tooth enamel.

Synthesis and characterization of fluoridated hydroxyapatite nano-powder via microwave irradiation method

Fluoridated hydroxyapatite (FHA) occur in teeth and form the basis for application as a biomaterial. This work aims to synthesize and analyze the characteristic of FHA nano-powder with different degrees of fluoridation via microwave irradiation method. FHA nano-powder with a chemical formula of Ca10(PO4)6(OH2-x)Fx (where degrees of fluoridation, x values were selected equal to 0.7 and 1.3) were synthesized using a mixture of calcium hydroxide, diammonium hydrogen phosphate, and ammonium fluoride solutions by utilizing microwave with the variation of irradiation power. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) spectroscopy analysis techniques were utilized in order to evaluate the characteristic of synthesized FHA nano-powder. The XRD and FTIR results confirmed highly crystalline FHA powder with the carbonate peaks in the IR spectrum. Using a Scherrer formula, the average crystallite size was found to be 30 nm. The SEM and EDX results indicated various element composition and several morphologies with the lattice parameter increased along with irradiation power. FHA nano-powder could be synthesized via microwave irradiation method. The results from different kind of analysis illustrated that synthesized FHA nano-powder could fulfill the requirement of ASTM F1185-88 for used as biomaterial.

Surfactant-free electrochemical synthesis of fluoridated hydroxyapatite nanorods for biomedical applications

Abstract Fluoridated hydroxyapatite (FHA) [Ca10(PO4)6Fx(OH)2−x, x = 0–2] is believed to be a promising calcium phosphate (CaP) to replace pure hydroxyapatite (HA) for next-generation implants, owing to its better biocompatibility, higher antibacterial activity, and lower solubility. Notably, the shape and size of the CaP crystals play key roles in their performance and can influence their applications. One-dimensional (1D) FHA nanorods are important CaP materials which have been widely used in regenerative medicine applications such as restorative dentistry. Unfortunately, the traditional synthesis methods for FHA nanorods either employ surfactants or take a relatively long time. In this study, we aimed to propose a facile synthesis route to fabricate FHA nanorods without any surfactants using an electrochemical deposition method for the first time. This study focused on preparing FHA nanorods without the assistance of any surfactant, unlike the traditional synthesis methods, to avoid chemical impurities. FHA nanorods with lengths of 124–2606 nm, diameters of 28–211 nm, and aspect ratios of 4.4–21.8 were synthesized using the electrochemical method, followed by a heat treatment. For the as-synthesized FHA nanorods, the Ca/P ratio was 1.60 and the atomic concentration of F was 2.06 at.%. An ultrastructure examination revealed that each FHA nanorod possessed long-range order, good crystallinity, and a defect-free lattice with a certain crystallographic plane orientation along the whole rod. In short, we propose a novel, surfactant-free, cost-saving, and more efficient route to synthesize FHA nanorods which can be widely applied in multiple biomedical applications, including drug delivery, bone repair, and restorative dentistry.

In Vitro and in Vivo Degradation Behavior and Biocompatibility Evaluation of Microarc Oxidation-Fluoridated Hydroxyapatite-Coated Mg-Zn-Zr-Sr Alloy for Bone Application.

Magnesium and its alloys are biodegradable materials with great potential for biomedical development; however, their high rate of degradation in biological environments limits the widespread application of these materials. In order to improve the corrosion resistance of magnesium alloy, a functional calcium phosphate coating was prepared on Mg-3Zn-0.5Zr-0.5Sr alloy by microarc oxidation (MAO) combined with chemical deposition of fluoridated hydroxyapatite (FHA). A dense calcium-phosphorus coating 6 μm thick composed of needle-shaped fluoridated hydroxyapatite formed on the surface of the MAO layer. The MAO-FHA coating exhibited good mineralization ability to induce hydroxyapatite deposition on its surface during degradation testing in simulated bodily fluids.

Suspension plasma-sprayed fluoridated hydroxyapatite coatings: Effects of spraying power on microstructure, chemical stability and antibacterial activity

Nanostructured fluoridated hydroxyapatite (FHA) coatings were deposited on Ti substrates using the suspension plasma spraying (SPS) process. The effects of the plasma spraying power on the microstructure and properties of coatings were intensively studied. The X-ray diffraction pattern showed that the as-sprayed coatings mainly consisted of the hydroxyapatite (HA) phase, and the crystal size was estimated to be dozens of nanometers. With the increase of the spraying power, the amount of decomposed phases, crystallinity, and crystal size increased. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy confirmed the presence of fluorine in the as-sprayed coatings. The corrosion in simulated body fluid (SBF) was studied using potentiodynamic polarization tests, and the results indicated that the coating greatly enhanced the corrosion resistance of the Ti substrate. The chemical stability was assessed by measuring the weight loss of the coatings before and after immersion in a citric acid-modified phosphate buffered saline (PBS) solution at various intervals. The results showed that increasing the spraying powers decreased the dissolution rate of coatings. The in vitro bioactivity was characterized by soaking coatings in the SBF solution for different times, and the obtained results suggested that the spraying power levels affected the initial nucleation rate of the bone-like apatite on the coating surface. The antibacterial activity was investigated using optical density (OD) growth curves and colony-forming unit assays. The coating prepared at a low spraying power had relatively high antibacterial activity with respect to Staphylococcus aureus.