Hydroxyapatite Whiskers Research Articles

Nano-ZnO modified hydroxyapatite whiskers with enhanced osteoinductivity for bone defect repair

Abstract Hydroxyapatite (HA) whisker (HAw) represents a distinct form of HA characterized by its high aspect ratio, offering significant potential for enhancing the mechanical properties of bone tissue engineering scaffolds. However, the limited osteoinductivity of HAw hampers its widespread application. In this investigation, we observed HAw punctured osteoblast membranes and infiltrated the cell body, resulting in mechanical damage to cells that adversely impacted osteoblast proliferation and differentiation. To address this challenge, we developed nano-zinc oxide particle-modified HAw (nano-ZnO/HAw). Acting as a reinforcing and toughening agent, nano-ZnO/HAw augmented the compressive strength and ductility of the matrix materials. At the same time, the surface modification with nano-ZnO particles improved osteoblast differentiation by reducing the mechanical damage from HAw to cells and releasing zinc ion, the two aspects collectively promoted the osteoinductivity of HAw. Encouragingly, the osteoinductive potential of 5%nano-ZnO/HAw and 10%nano-ZnO/HAw was validated in relevant rat models, demonstrating the efficacy of this approach in promoting new bone formation in vivo. Our findings underscore the role of nano-ZnO particle surface modification in enhancing the osteoinductivity of HAw from a physical standpoint, offering valuable insights into the development of bone substitutes with favorable osteoinductive properties while simultaneously bolstering matrix material strength and toughness.

Preparation of magnetic hydroxyapatite whisker and its adsorption capacity to cadmium ion

Hydroxyapatite (HA) is a safe and stable adsorbent that can be used for the removal of Cadmium ions (Cd2+), and non-generation of secondary pollution. In the study, plate-like HA whiskers with well-defined crystallinity, controllable dimensions, and high aspect ratios are synthesized by the hydrothermal method. Magnetic hydroxyapatite (HA@Fe3O4) is then formed by uniformly encapsulating the HA whiskers by nano Fe3O4. With a comparison of HA whiskers prepared with 10 mmol/L Ca2+ concentration, the hydrothermally synthesized HA whiskers with 33 mmol/L Ca2+ concentration exhibit uniform shape and high crystallinity with an aspect ratio of 40–50 and length of 60–100 µm. Not only modification capacity but also aggregation of Fe3O4 on HA whiskers increases with the increase of Fe3O4 content. The addition of 4% Fe3O4 has a higher modification efficiency to HA, low aggregation of Fe3O4 and excellent magnetic responsiveness. HA@Fe3O4 with 4% Fe3O4 demonstrates a strong capacity for cadmium ion immobilization. At an initial Cd2+ concentration of 30 ppm, the Cd2+ removal efficiency of HA@Fe3O4 with 4% Fe3O4 reaches 59% within 20 min, and the Cd2+ concentration remains relatively stable in 48 h. A substantial removal efficiency is 22% after 10 min in the solution of 3000 ppm Cd2+. Importantly, XPS and XRD results indicate that Ca2+ in HA crystals is displaced by Cd2+ and can effectively transform Cd2+ to a more stable state during the removal process. This study provides a simple and convenient method with stable adsorption and magnetic separating, which would be suitable for tackling Cd2+ contamination with different concentrations and have little impact on the environment.

Favorable features of a calcium phosphate cement based on a metastable α ̅-tricalcium phosphate and reinforced by hydroxyapatite whiskers

The composition, impurities, ion substitutions, structure, peculiarities in crystallization and compressive strength were studied in the initial stage of setting (for 15 min) of a new cement based on a metastable -tricalcium phosphate and reinforced by various amounts (up to 15 wt%) of hydroxyapatite whiskers. The set cements were apatitic, highly nonstoichiometric with a Ca/P ratio below 1.5. The compressive strength increased more than twice (up to 8 MPa) at a whisker content of 4 wt% and then decreased again with increasing whisker content. The decline was associated with the growth of nanocrystals on the surface planes of whiskers and formation of micropores in the whisker vicinity caused by the consumption of the surrounding mother phase for the growth. It is expected that the micropores are favorable for the surrounding tissue to grow into enhancing the effectiveness of the set cement. The cement can primarily be used as accessible remedies for treatment of slightly-loaded bone defects.

The effect of extrusion and injection molding on physical, chemical, and biological properties of PLLA/HAp whiskers composites

This paper deals with physical, chemical and biological properties of polymer-ceramic composites based on poly(l-lactide) (PLLA) with the addition of 10, 20 or 30 % (by weight) of hydroxyapatite (HAp) whiskers, produced by a combination of twin-screw extrusion and injection molding techniques. The materials obtained were tested for morphology (scanning electron microscopy), chemical composition (energy dispersive x-ray spectroscopy, infrared spectroscopy), processing properties (melt flow rates and density), thermal properties (differential scanning calorimetry, thermogravimetry), strength (static tensile test, impact strength) and surface properties (optical profilometry, contact angle measurements). The biological evaluation was performed by in vitro assessment of the manufactured materials’ cytotoxicity, level of colonization by osteo- and fibroblasts and level of adhesion displayed by a microbial pathogen, referred to as the Staphylococcus aureus. The results indicate an influence of the applied processing path on the properties of the filler particles − the apatite whiskers were significantly shortened. On the other hand, we have demonstrated the possibility of obtaining PLLA/HAp composites with good strength parameters, precise geometric shape and slightly improved surface properties. The results of biological evaluation revealed that all of the materials obtained displayed low cytotoxicity and a high level of colonization, irrespective of the content of hydroxyapatite. The only exception was the composite containing 10 % HAp, for which we observed weaker fibroblast adhesion compared to other materials. In turn, the level of colonization by S.aureus grew with the increase in HAp content in polymers. Results of biological evaluation indicate that although obtained polymers display favorable properties in terms of eukaryotic cell adhesion/colonization, they may also provide advantageous surface conditions for bacterial development. Therefore, inclusion of antimicrobial to the materials obtained may be necessary and should be further investigated. Nevertheless, the results obtained certainly provide useful information from the point of view of designing and manufacturing of biocomposites for bone tissue engineering applications.

Preparation and properties of silica/hydroxyapatite whiskers porous ceramics scaffold

To investigate the preparation and properties of the novel silica (SiO 2)/hydroxyapatite (HAP) whiskers porous ceramics scaffold. The HAP whiskers were modified by the SiO 2 microspheres using the Stöber method. Three types of SiO 2/HAP whiskers were fabricated under different factors (for the No.1 samples, the content of tetraethoxysilane, stirring time, calcination temperature, and soaking time were 10 mL, 12 hours, 560℃, and 0.5 hours, respectively; and in the No.2 samples, those were 15 mL, 24 hours, 650℃, and 2 hours, respectively; while those in the No.3 samples were 20 mL, 48 hours, 750℃, and 4 hours, respectively). The phase and morphology of the self-made HAP whisker and 3 types of SiO 2/HAP whiskers were detected by the X-ray diffraction analysis and scanning electron microscopy. Taken the self-made HAP whisker and 3 types of SiO 2/HAP whiskers as raw materials, various porous ceramic materials were prepared using the mechanical foaming method combined with extrusion molding method, and the low-temperature heat treatment. The pore structure of porous ceramics was observed by scanning electron microscopy. Its porosity and pore size distribution were measured. And further the axial compressive strength was measured, and the biodegradability was detected by simulated body fluid. Cell counting kit 8 method was used to conduct cytotoxicity experiments on the extract of porous ceramics. The SiO 2 microspheres modified HAP whiskers and its porous ceramic materials were prepared successfully, respectively. In the SiO 2/HAP whiskers, the amorphous SiO 2 microspheres with a diameter of 200 nm, uniform distribution and good adhesion were attached to the surface of the whiskers, and the number of microspheres was controllable. The apparent porosity of the porous ceramic scaffold was about 78%, and its pore structure was composed of neatly arranged longitudinal through-holes and a large number of micro/nano through-holes. Compared with HAP whisker porous ceramic, the axial compressive strength of the SiO 2/HAP whisker porous ceramics could reach 1.0 MPa, which increased the strength by nearly 4 times. Among them, the axial compressive strength of the No.2 SiO 2/HAP whisker porous ceramic was the highest. The SiO 2 microspheres attached to the surface of the whiskers could provide sites for the deposition of apatite. With the content of SiO 2 microspheres increased, the deposition rate of apatite accelerated. The cytotoxicity level of the prepared porous ceramics ranged from 0 to 1, without cytotoxicity. SiO 2/HAP whisker porous ceramics have good biological activity, high porosity, three-dimensional complex pore structure, good axial compressive strength, and no cytotoxicity, which make it a promising scaffold material for bone tissue engineering.

In-situ synthesized hydroxyapatite whiskers on 3D printed titanium cages enhanced osteointegration in a goat spinal fusion model

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

BONE REGENERATION AFTER IMPLANTATION OF CALCIUM PHOSPHATE CEMENTS BASED ON METASTABLE TRICALCIUM PHOSPHATE (IN VIVO EXPERIMENTAL STUDY)

Calcium phosphatCalcium phosphate cement (CPC) is a material used to fill bone defects. Its advantages include being able to fill irregularly shaped spaces, its similarity to bone tissue, and ease of biodegradation. However, insufficient durability and unpredictable rate of resorption limit CPC use. Objective. Study the dynamics of morphological changes in rat femurs after implanting two types of CPC based on metastable αʹ‒tricalcium phosphate(αʹ‒TCP) into defects in the distal metaphysis. Methods. 42 male white rats were used in the study. In each rat, defects were created in the distal metaphysis of the left femur and filled with one of the two types of CPC. The animals were split into two groups: І (n = 21) — CPC based on αʹ‒TCP powder; ІІ (n = 21) — CPС based on αʹ‒TCP powder reinforced with hydroxyapatite (HA) whiskers (4 % mass). Both varieties of CPC were developed and prepared at the Department of Solid-State Physics at the V. N. Karazin Kharkiv National University (Ukraine). 14, 30, and 60 days after the surgery, the animals were sacrificed, and histological analyses were performed. Results. For both types of CPC, inflammation was not observed in the region around the implant at 14, 30, or at 60 days. Bone tissue formed on the surface of the materials. The stages of bone repair were similar to the known stages of bone repair. As a result of the resorption of the CPC, 60 days after surgery the CPC comprised 26.83 % of the area of the defect in group I and 29.93 % in group II. The rest of the area was composed of lamellar bone. The two groups did not differ significantly in rate of CPC resorption or bone tissue formation. Conclusions. The two types of CPC studied, based on αʹ‒TCP (group I) and αʹ‒TCP reinforced with HA whiskers (group II), are biocompatible, osteoconductive, and osteoinductive. In addition, these materials are biodegradable and, with time, are replaced by bone tissue.

Preparation and characterization of porous hydroxyapatite reinforced with hydroxyapatite whiskers

In this study, porous hydroxyapatite scaffolds reinforced with whiskers were fabricated. HAp whiskers were produced by the molten salt synthesis method using 5 different salt-HAp mixtures. The mixtures placed in alumina crucibles were heated to 900 oC with a heating rate of 5 oC/min in a muffle furnace and kept at this temperature for 2 hours and then cooled in the furnace. To clean the HAP crystals formed in the alumina crucibles from the reaction residues, they were washed many times with distilled water heated to 100 oC and filtered. HAp whiskers were mixed with HAp powder in certain proportions, and porous HAp reinforced with HAp whiskers were fabricated by using the sponge replica method. The synthesized whiskers and the scaffold structures were characterized by Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy, X-ray diffractometry, Compression test, and porosity measurement method.XRD analysis of synthesized whiskers confirmed the presence of HAp. SEM images showed interconnected pores in the samples, with pore sizes larger than 100µm. The compressive strengths of the samples were calculated from the stress-strain plateau average. The highest and the lowest compressive stress were calculated as 0,125 and 0,050 MPa respectively. The maximum and minimum porosities of the samples reinforced with whiskers were found to be 67,56% and 61,92%, respectively.

A promising hydroxyapatite whisker with long-term and high-efficiency antibacterial performance and its potential application in implant

• The synergistic effect of nano-zinc oxide and silver ions can realize broad-spectrum antibacterial. • The silver ions in the hydroxyapatite whiskers will gradually dissolve as the whiskers degrade, realizing long-term antibacterial effects. Osteomyelitis remains one of the most challenging diseases for orthopedic doctors despite the advancement of therapeutic techniques. Biomaterials with antibacterial activities are beneficial to prevent infection post implantation. The aim of this study was to evaluate the antibacterial effects of three biomaterials including pure- hydroxyapatite (HA), Ag-HA and Ag-HA/ZnO. The prepared materials were analyzed by X-ray diffractometer (XRD), scanning electron microscope (SEM), cell adhesion and long-service antibacterial ability. The results showed that with the increase of silver content, the growth of whiskers was inhibited and the aspect ratio became smaller. Nano-zinc oxide is evenly attached on the surface of the whiskers. Escherichia coli ( E. coli) and Staphylococcus aureus ( S. aureus) were used for antibacterial tests. The results showed that Ag-HA and Ag-HA/ZnO had good antibacterial ability against E. coli and S. aureus . Thus, the low amount of Ag-HA has a potential of minimizing the risk of bacterial contamination, without compromising the bioactivity, and is expected to display greater biological efficacy in terms of osseointegration. Ag + and ZnO particles have a synergistic effect and can effectively kill most bacteria. At the same time, with the degradation of hydroxyapatite, Ag + is slowly released, which can play a long-term antibacterial effect.

Effects of Sterilization and Hydrolytic Degradation on the Structure, Morphology and Compressive Strength of Polylactide-Hydroxyapatite Composites.

Composites based on polylactide (PLA) and hydroxyapatite (HA) were prepared using a thermally induced phase separation method. In the experimental design, the PLA with low weight-average molar mass (Mw) and high Mw were tested with the inclusion of HA synthesized as whiskers or hexagonal rods. In addition, the structure of HA whiskers was doped with Zn, whereas hexagonal rods were mixed with Sr salt. The composites were sterilized and then incubated in phosphate-buffered saline for 12 weeks at 37 °C, followed by characterization of pore size distribution, molecular properties, density and mechanical strength. Results showed a substantial reduction of PLA Mw for both polymers due to the preparation of composites, their sterilization and incubation. The distribution of pore size effectively increased after the degradation process, whereas the sterilization, furthermore, had an impact on pore size distribution depending on HA added. The inclusion of HA reduced to some extent the degradation of PLA quantitatively in the weight loss in vitro compared to the control without HA. All produced materials showed no cytotoxicity when validated against L929 mouse skin fibroblasts and hFOB 1.19 human osteoblasts. The lack of cytotoxicity was accompanied by the immunocompatibility with human monocytic cells that were able to detect pyrogenic contaminants.

Effect of reaction time, heating and stirring rate on the morphology of HAp obtained by hydrothermal synthesis

Hydroxyapatite (HAp) whiskers were prepared in reaction of calcium lactate pentahydrate and orthophosphoric acid. Synthesis were carried out in different conditions with using hydrothermal reactor. The benefit of the hydrothermal technique is the simple and precise control of the HAp crystals morphology, which is achieved by employing varying initial concentrations of starting reagents as well as different conditions of synthesis. The effect of time of synthesis, stirring and heating rate of the reaction on HAp morphology and composition was investigated. During the synthesis the following experimental parameters were varied independently: time of synthesis (3, 5, 7 h), stirring rate (0, 62.5, 125, 250, 500, 750 rpm), the reaction heating rate (0.2, 0.5, 0.7, 1.0, 1.5, 2.5 °C min−1). All syntheses were carried out with the constant molar Ca/P ratio of 1.67 in starting solutions, which is equivalent to that of stoichiometric HAp. The Ca2+ ion concentrations in starting solutions for synthesis were 0.05 and 0.1 mol dm−3. Syntheses were carried out under 20 bar. The obtained products were characterized using different method like XRD, SEM, and FTIR. It was shown that the significant majority of samples prepared were identified as pure HAp.

Synthesis of hydroxyapatite whisker membranes for use as biocompatible and recyclable filters for bacterial removal

Polymer nanofibers have been applied extensively for developing biocompatible filters to remove bacteria from aqueous solutions. However, recycling and reusing these polymer nanofibers is very difficult. In this study, hydroxyapatite whisker membranes were employed as biocompatible and recyclable filters for bacterial removal. Scanning electron microscopy observations showed that the membranes comprised numerous whiskers with diameters of 286 ± 97 nm, and a fibrous and porous structure. Bacterial filtration experiments showed that the membranes completely removed Staphylococcus aureus (model bacterium) from a bacterial suspension with a filtration efficiency of 100%. After bacterial filtration, the membranes could be recycled by removing the bacteria using the conventional sterilization method. Furthermore, the recycled membranes could be reused as filters for bacterial removal with a filtration efficiency of 100%.

The Synthesis of Hydroxyapatite by Hydrothermal Process with Calcium Lactate Pentahydrate: The Effect of Reagent Concentrations, pH, Temperature, and Pressure.

Hydroxyapatite and other calcium phosphates in the form of whiskers are lately widely considered as fillers for biocomposites due to their special biological and reinforcing properties. Depending on the method of synthesis, apatite whiskers of various sizes and phase composition can be obtained. In our work, hydroxyapatite (HAp) whiskers were successfully prepared in reaction between calcium lactate pentahydrate and orthophosphoric acid. The advantage of the proposed technique is the simple but precise control of the HAp crystal morphology and high product purity which is necessary for biomedical applications. The effect of reagent concentrations, pH, reaction temperature, and pressure on HAp whiskers' morphology and composition was investigated. In the result, we obtained hydroxyapatite of different morphology such as whiskers, hexagonal rods, and nanorods. The products were characterized by SEM, XRD, and FTIR. In this work, the synthesis of HAp whiskers by direct decomposition of calcium lactate pentahydrate chelates under hydrothermal conditions was showed for the first time.

Three Component Composite Scaffolds Based on PCL, Hydroxyapatite, and L-Lysine Obtained in TIPS-SL: Bioactive Material for Bone Tissue Engineering

In this research, we describe the properties of three-component composite foam scaffolds based on poly(ε-caprolactone) (PCL) as a matrix and hydroxyapatite whiskers (HAP) and L-Lysine as fillers (PCL/HAP/Lys with wt% ratio 50/48/2). The scaffolds were prepared using a thermally induced phase separation technique supported by salt leaching (TIPS-SL). All materials were precisely characterized: porosity, density, water uptake, wettability, DSC, and TGA measurements and compression tests were carried out. The microstructure of the obtained scaffolds was analyzed via SEM. It was found that the PCL/HAP/Lys scaffold has a 45% higher Young’s modulus and better wettability compared to the PCL/HAP system. At the same time, the porosity of the system was ~90%. The osteoblast hFOB 1.19 cell response was also investigated in osteogenic conditions (39 °C) and the cytokine release profile of interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α was determined. Modification of PCL scaffolds with HAP and L-Lysine significantly improved the proliferation of pre-osteoblasts cultured on such materials.

Novel Hydroxyapatite Whiskers Modified by Silver Ion and Nano Zinc Oxide Used for Bone Defect Repairment

The hydroxyapatite (HA) is widely used as bone tissue repair material. The improvement of the antibacterial performance is an aroused general interest. In the present study, the silver ion and nano-zinc oxide modified hydroxyapatite whiskers (HAw) were successfully prepared. The microstructure and the composition of the modified HAw were analyzed by Field Emission Scanning Electron Microscopy (FESEM) and X-ray diffractometer (XRD). SEM analysis showed that the length of the whiskers was 70–190 μm, and the aspect ratio was 10–60. With the increase of Ag+ content, the length and aspect ratio of the whiskers gradually decreased and incomplete spherical hydroxyapatite appeared. FEEM analysis showed that nano-zinc oxide particles on ZnO/3Ag-HAw surface are evenly distributed; the average particle size is less than 30 nm. XRD analysis showed that after sol-gel and calcination treatment, the nano-zinc oxide phase appeared in the diffraction pattern of ZnO/Ag-HAw. TEM analysis showed that the interplanar spacing of 5Ag-HAw increased slightly. The CCK-8 and cells co-culture assays were used to assess the proliferation and differentiation of MC3T3-E1 cells, respectively. The antibacterial abilities of the modified HAw against E. coli (ATCC25922) and S. aureus (ATCC6538) were investigated. The cell cytotoxicity test showed that the cytotoxicity level was 0, and there was no cytotoxicity. Cell adhesion experiments showed that ZnO/3Ag-HAw has good cell compatibility and biological activity. The modified hawthorn has a bacteriostatic rate of more than 90% and has good bacteriostatic activity.

Enhanced dispersion of hydroxyapatite whisker in orthopedics 3D printing resin with improved mechanical performance

AbstractOne‐dimensional fillers such as rods and fibers have shown effective mechanical reinforcement in polymer nanocomposites, but their application in vat polymerization‐based 3D printing techniques was hindered due to the rapidly increased viscosity of the resin. In order to improve the fluidity of the composites without sacrificing the mechanical performance, herein we demonstrated that one‐dimensional hydroxyapatite (HAP) whiskers could be surface modified with 3‐(trimethoxysilyl) propyl methacrylate, to decrease the viscosity of the resulting resins and to enhance the interfacial adhesion between the filler and matrix. Rheology results showed that the resin was still fluidic with loading of HAP whiskers up to 20 wt%, with Young's modulus increased by a factor of 98% and the ultimate tensile strength increased by 26%. Successful printing of the resin on a DLP printer was achieved with high resolution and fine surface, and the biocompatibility test showed an increase in cell viability with the addition of HAP whiskers. These results provide a promising approach to develop high‐performance printable resin for orthopedic and related bio‐printing.

Development of bioglass coating reinforced with hydroxyapatite whiskers on TiO2 nanotubes via electrophoretic deposition

Considering the importance of coatings bonding to the substrate, electrophoretic deposition of bioglass coatings reinforced with hydroxyapatite whiskers was performed on anodized titanium substrate. Bioglass powders with both fine particle size (FBG) and coarse particle size (CBG) were used. It was found that Vickers microhardness and bioactivity of the coatings are not affected by titanium anodizing. The enhancement of 58% was obtained for the adhesion strength of FBG based coating due to the interlocking of titania nanotubes with fine bioglass particles entered the voids of nanotubes, which was only 32% for coarse bioglass particles. The microstructure of the coatings demonstrated no changes by anodizing the substrate, while the thickness of the coatings reduced significantly owing to the decreased deposition kinetics. The enhancement of the bactericidal effect and cellular behavior of the coatings indicated the positive impact of the underlaid nanotubes compared with bare titanium. The declined corrosion current density of the coated samples on nanotubes compared to titanium revealed the inhibitory effect of anodizing in terms of corrosion.

Effect of Surface Modification with TiO2 Coating on Improving Filtration Efficiency of Whisker-Hydroxyapatite (HAp) Membrane

Whisker-like hydroxyapatite (HAp) particles were prepared by controlling particle growth via hydrothermal synthesis. The surface modification for the hydrothermally synthesized HAp whiskers was accomplished by TiO2 coating. After the TiO2 modification, the zeta potential of the HAp whiskers was significantly improved from +8.6 to +21 mV at pH = 8.5. A free-standing membrane (diameter of ~4.5 cm and thickness of ~0.2 mm) was fabricated by using the TiO2-coated HAp whiskers and was used to separate the Au nanoparticles (size = 5 nm and zeta potential = −38.6 mV at pH = 8.5) at a significantly high filtration efficiency of ~100%. The achieved high filtration efficiency was considered to be the result of effectively utilizing the electrostatic interaction between the positively-charged TiO2-coated HAp whiskers and negatively-charged Au nanoparticles. The excellently biocompatible and highly effective TiO2-coated HAp membrane would be potentially applied as biological and artificial separators in biotechnology processes for the biomedicine field.

Synthesis of Eu‐doped hydroxyapatite whiskers and fabrication of phosphor layer via electrophoretic deposition process

ABSTRACTHighly biocompatible and efficiently luminescent whiskers of the hydroxyapatite (Ca10(PO4)6(OH)2, HAp) doped with various concentrations (0‐5 at.%) of europium were prepared by hydrothermal synthesis and the Eu‐doped Hap‐coating layers onto the surface of titanium substrate were fabricated by the electrophoretic deposition (EPD) process for fluorescent probe application. The maximum doping concentration of Eu accommodating into the host lattice of HAp was detected as ~1.5 at.% and all the hydrothermally synthesized Eu‐doped HAp whiskers were found to have high crystallinity and orientation growth along the c‐axis by X‐ray diffraction (XRD) identification. The valence of the doped Eu was identified as trivalent and divalent coexistence at a concentration percentage of Eu3+: Eu2+ = 78%: 22% by X‐ray photoelectron spectroscopy (XPS) spectra. The replacement site of the doped Eu ions in the crystal structure of HAp host was clarified by Rietveld refinement. The whisker morphology of the hydrothermally synthesized particle was demonstrated by field‐emission scanning electron microscopy (FE‐SEM) observation and their component elements were analyzed by energy dispersive X‐ray (EDX) mapping. The photoluminescence (PL) emissions of the Eu‐doped HAp whiskers and fabricated their coating layers were both revealed mainly at ~615 nm (5D0 → 7F2) and ~697 nm (5D0 → 7F4), which is a wavelength that easily transmitting through living system for biological imaging. The PL emission are falling in the region of reddish orange and belonging to color temperature below 1500 K. Decay time and internal and external quantum efficiencies (QEs) were also measured to reveal them depending on the doping concentration of Eu. The hydrothermally prepared Eu‐doped HAp whiskers would be aimed at biomedical application, due to their promising fluorescent function of probe for in vivo imaging in medical diagnose by utilizing the superior biocompatibility of the HAp host and highly efficient luminescent property of the Eu activator.

Preparation of HAp whiskers with or without Mg ions and their effects on the mechanical properties and osteogenic activity of poly(d,l-lactide)

Hydroxyapatite whiskers (HAp-Ws) and magnesium-substituted hydroxyapatite whiskers (Mg-HAp-Ws) with 1, 3, and 5 mol% magnesium (Mg) ion substitution contents were successfully prepared by the hydrothermal method. The incorporation of Mg ion into the HAp-Ws led to a morphology including a combination of whiskers and particles and a decrease in the crystal interplanar spacing. Then, the HAp-Ws and Mg-HAp-Ws were further introduced into a poly(d,l-lactide) (PDLLA) matrix to prepare HAp-Ws/PDLLA and Mg-HAp-Ws/PDLLA composite films. The existence of HAp-Ws or Mg-HAp-Ws can endow composite films with superior hydrophilicity and tensile properties. Moreover, since the HAp-Ws have a good morphology and a large aspect ratio, the tensile strength and modulus of the HAp-Ws/PDLLA composite film were reasonably higher than those of the Mg-HAp-Ws/PDLLA composite film. The Mg-HAp-Ws/PDLLA composite films were more beneficial for MC3T3-E1 cell adhesion, proliferation and differentiation due to the presence of Mg ions. More importantly, the osteogenic effect of Mg ions on MC3T3-E1 cells is dose-dependent, and the Mg-HAp-Ws/PDLLA composite films with 1–3 mol% Mg ion contents in the Mg-HAp-Ws showed relatively good cytocompatibility and osteogenic activity. In short, the mechanical properties and osteogenic activity of Mg-HAp-Ws/PDLLA composite films can be regulated by adjusting the Mg/Ca content to better meet the needs of bone repair.