Hydroxyapatite Structure Research Articles

Effect of hydroxyapatite on physical, mechanical, and morphological properties of starch-based bio-nanocomposite films

In this research, nanocomposite films based on starch were developed with the addition of hydroxyapatite nanoparticles as a mineral filler. Hydroxyapatite was synthesized by a chemical method using calcium nitrate and diammonium hydrogen phosphate. Various concentrations of hydroxyapatite nanoparticles were mixed with starch, and the developed films were evaluated in terms of physical, mechanical, and morphological properties. The highest values of mechanical parameters (tensile strength and elongation at break) were determined for the starch/hydroxyapatite film at 15 wt.% hydroxyapatite nanoparticles concentration (3.03 MPa, 37.41%, respectively). As hydroxyapatite concentration was increased from 0 to 20 wt.%, the solubility in water of the films decreased, whereas the solubility in acid increased. The crystalline structure of hydroxyapatite decreased the transparency of film and increased transparency value. Thus, a biodegradable film could be obtained with the addition of hydroxyapatite as a reinforcement filler up to 15 wt.%. It could be developed as a sustainable alternative for packaging industry.

Understanding zinc-doped hydroxyapatite structures using first-principles calculations and convolutional neural network algorithm.

Element doping is widely used to improve the performance of materials by changing their intrinsic properties. However, the lack of direct crystallographic structures for dopants has restricted the effective high-throughput design or refinement of materials using the doping strategy. Herein, Zn-doped hydroxyapatite (HAP) was selected as the template material. The first-principles optimization and machine learning algorithm were combined to understand the mechanism of HAP doped with Zn2+. Our method could effectively locate the structures in the lowest-energy region. Specifically, our results indicate that the first Zn atom showed a tendency to occupy the Ca(II) site first, and the subsequent Zn atoms entering the Ca(II) sites in a symmetrical manner. The symmetrical entrance of Zn atoms to HAP would minimize the interaction energy between the Zn atoms and the degree of crystal deformation. Finally, we performed uniaxial stretching simulations to evaluate the influence of Zn2+ ions on the mechanical behavior of HAP based on the optimally-doped structure obtained by machine learning (ML). The calculation results were consistent with the experimental conclusion that the doping of Zn2+ ions could improve the fracture toughness of HAP. Our work would provide an effective way to locate possible optimized structures in the doping system and subsequently improve the design of materials.

Dual action of polarised zinc hydroxyapatite - guar gum composite as a next generation bone filler material

Implantable filler materials modified with Zn is a growing trend in the engineering of biomaterials for improvement of bone regeneration. Hydroxyapatite is used as a vital component in biocomposites and surgical implant coating. The purpose of this experiment was to synthesize Zn2+ substituted hydroxyapatite to obtain a final composite of Guar gum- zinc substituted hydroxyapatite (ZnHA-GG) composites and the development of surface negative charge on ZnHA-GG composite was carried out using a Corona Poling unit and the assessment of biocompatibility and antibacterial activity were carried out. In vitro culture of MG-63 osteoblast cells and S. aureus bacterial cells were then carried out on polarized composites in conjunction with non-polarized composites to find the effects of polarization on adhesion of cells, osteogenic differentiation as well as antibacterial efficacy. It was inferred that incorporation of Zn2+ ions into composites of Guar Gum hydroxyapatite structure increased the osteoblasts spreading, boosts antibacterial activity on the composite surface, and amplifies RUNX2, osteocalcin, type I collagen formulation by osteoblasts.

Effects of scattering on ultrasound wave transmission through bioinspired scaffolds

Enhancing tissue growth in scaffolds using ultrasound waves while maintaining the structural integrity of the scaffolds is a challenging problem. Previous studies have primarily focused on the effect of ultrasound waves directly on the tissue, but how the ultrasound wave interacts with the scaffold needs to be further understood, which will have a significant effect on the response of tissue to mechanical stimulation. In this study we investigate how ultrasound wave transmission differs between scaffolds with uniform pore shapes (triangle, square, rectangle, hexagon) and a bioinspired scaffold with higher structural integrity that is inspired from the atomic structure of hydroxyapatite which is a primary component of bone. We use finite element method and ultrasound experiments on 3D-printed scaffolds composed of Acrylonitrile butadiene styrene (ABS) with constant porosity to predict the effect of pore shape and wave signal frequency in the range of 1–20 MHz on acoustic wave scattering and transmission. We find that the pore shape of the scaffold affects the magnitude of ultrasound transmission even when porosity is constant, and that the bioinspired scaffolds can allow as much as 67% more wave transmission compared to scaffolds with rectangular or square pore shapes at 1 MHz frequency. Triangular and hexagonal pores are also found to produce more nonuniform transmitted wavefronts compared to the square and rectangular pores. Peak density is defined as the number of local extrema of the transmitted wave frequency power spectrum and measures the uniformity of the transmitted wave. We find that a higher peak density value for the bioinspired scaffold due to its nonsymmetric structure further produces more nonuniform wave scattering. The results of this study are important for designing bioinspired tissue scaffold geometries to control ultrasound wave penetration and to enhance mechanical stimulation for tissue growth and will also aid in the ultrasonic characterization of porous structures based on changes in pore geometry.

Infrared Spectroscopic Analysis of the Inorganic Components from Teeth Exposed to Psychotherapeutic Drugs

Teeth are unique and complex anatomical organs that can provide relevant data about a person's health, and play an important role in forensic medicine. Teeth are exposed to food, drinks, and the microbiota of the oral cavity; therefore, they have developed a high resistance to localized demineralization. Nevertheless, the continuous demineralization–remineralization cycle present in the oral environment can be influenced by stress, medication, mineralization agents, and other factors such as individual habits, especially diet. In this study, based on attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) spectra from tooth samples of 36 patients, several parameters were estimated: the crystallinity index (CI), the phosphate/amide I ratio, and the carbonate/phosphate ratio. In addition, in eight representative samples (six of the root of the tooth and two of the enamel area of the crown), additional characterization by X-ray powder diffraction (XRPD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) was conducted. From the FTIR data, it was observed that the highest CI values were found in patients who smoked. Further, in both root and crown samples, the intensity of the absorption band corresponding to PO43- increased in patients undergoing treatment with psychotherapeutic drugs. On the other hand, the intensity of the absorption band of the amide I group decreased with medical treatment and with the patient's biological age. Moreover, it was found that the remineralization process was more active in enamel than in the root due to direct contact with saliva. Regarding the results obtained from the X-ray powder diffractograms, exposure to psychotherapeutic drugs affected the definition of the peaks corresponding to hydroxyapatite, both in the crown and root samples. Concerning SEM results, qualitative differences in the stratification process in demineralized surfaces were observed, and EDS analyses showed some differences in the Ca/P ratio between pathological samples and control ones, but without clear patterns. The above techniques, in particular ATR-FTIR, showed promise for the investigation of the effect of changes produced in the hydroxyapatite structure in teeth and, consequently, to determine possible strategies in the diagnostic protocol.

3D-Printed Strong Dental Crown with Multi-Scale Ordered Architecture, High-Precision, and Bioactivity.

Mimicking the multi‐scale highly ordered hydroxyapatite (HAp) nanocrystal structure of the natural tooth enamel remains a great challenge. Herein, a bottom‐up step‐by‐step strategy is developed using extrusion‐based 3D printing technology to achieve a high‐precision dental crown with multi‐scale highly ordered HAp structure. In this study, hybrid resin‐based composites (RBCs) with “supergravity +” HAp nanorods can be printed smoothly via direct ink writing (DIW) 3D printing, induced by shear force through a custom‐built nozzle with a gradually shrinking channel. The theoretical simulation results of finite element method are consistent with the experimental results. The HAp nanorods are first highly oriented along a programmable printing direction in a single printed fiber, then arranged in a layer by adjusting the printing path, and finally 3D printed into a highly ordered and complex crown structure. The printed samples with criss‐crossed layers by interrupting crack propagation exhibit a flexural strength of 134.1 ± 3.9 MPa and a compressive strength of 361.6 ± 8.9 MPa, which are superior to the corresponding values of traditional molding counterparts. The HAp‐monodispersed RBCs are successfully used to print strong and bioactive dental crowns with a printing accuracy of 95%. This new approach can help provide customized components for the clinical restoration of teeth.

Nano Hydroxyapatite (nano-HAp): A Potential Bioceramic for Biomedical Applications

Background: Hydroxyapatite (HAp) is one of the most studied biomimetic method for biomedical applications. Especially, nano-HAp has been utilized for bone tissue engineering and various other orthopedic applications. HAp possesses different suitable properties such as bioactivity, biodegradability, and cell proliferation efficiency for bone tissue engineering applications. Yet, it lacks in self-antibacterial activity, high surface area, and target efficiency. Results: In this direction, researchers have focused on exploring the required surface as well as the inherent properties of HAp at the nanoscale. These properties are largely dependent on the composition, size, and morphology of the nano-HAp. Hence, nano-HAp has been found to be an excellent candidate with an attractive combination of properties for selection and use in biomedical applications, those required to enhanced biological responses. Further, depending on the type of application, these factors can be tuned to optimize the performance. Conclusion: In this review article, we focus on the chemical structure of HAp and the routes chosen and used for the synthesis of the nano-HAp. The role of various parameters in controlling synthesis at the nanoscale is presented and briefly discussed. In addition, we provide an overview of the various applications for the pristine and doped nano-HAp with recent examples in areas spanning the following: (i) bone tissue engineering applications, (ii) drug delivery applications, (iii) surface coatings, and (iv) scaffolds. The effect of chemical composition on the mechanical properties, surface properties, and biological properties are also highlighted. Nano-HAp is found to be highly proficient in its biomedical applications, especially bone tissue engineering applications. The nano-- sized properties enhance the biological responses. The dopant ions that replace the Ca ion into the hydroxyapatite (HAp) lattice play a crucial role in its biomedical applications.

Effect of Doping Element and Electrolyte’s pH on the Properties of Hydroxyapatite Coatings Obtained by Pulsed Galvanostatic Technique

Hydroxyapatite (HAp) is the most widely used calcium phosphate as a coating on metal implants due to its biocompatibility and bioactivity. The aim of this research is to evaluate the effect of the pH’s electrolyte and doping element on the morphology, roughness, chemical, and phasic composition of hydroxyapatite-based coatings obtained by pulsed galvanostatic electrochemical deposition. As doping elements, both Sr and Ag were selected due to their good osseoinductive character and antibacterial effect, respectively. The electrolytes were prepared at pH 4 and 5, in which specific concentrations of Sr, Ag, and Sr + Ag were added. In terms of morphology, all coatings consist in ribbon-like crystals, which at pH 5 appear to be a little larger. Addition of Sr did not affect the morphology of HAp, while Ag addition has led to the formation of flower-like crystals agglomeration. When both doping elements were added, the flowers like agglomerations caused by the Ag have diminished, indicating the competition between Sr and Ag. X-Ray Diffraction analysis has highlighted that Sr and/or Ag have successfully substituted the Ca in the HAp structure. Moreover, at higher pH, the crystallinity of all HAp coatings was enhanced. Thus, it can be said that the electrolyte’s pH enhances to some extent the properties of HAp-based coatings, while the addition of Sr and/or Ag does not negatively impact the obtained features of HAp, indicating that by using pulsed galvanostatic electrochemical deposition, materials with tunable features dictated by the function of the coated medical device can be designed.

A novel microbial induced synthesis of hydroxyapatite with highly efficient adsorption of uranyl(VI)

Due to the pore structure and specific surface area of hydroxyapatite (HA), they facilitate their application as an adsorbent material. Herein, assembled from nano-particles, a high specific surface area and porous HA has been synthesized by bacterial induction. The morphology and structure of the as-synthesized products were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, and Brunauer–Emmett–Teller gas sorptometry analyses. The results indicated that the HA with high specific surface area (196.7 m2/g) were prepared successfully. Notably, the batch adsorption experiment for uranyl ions (UO22+) indicated that the maximum adsorption capacity was 1025 mg/g, and the adsorption process remained consistent with the linear pseudo-second-order kinetic and nonlinear Liu isotherm adsorption models. The desorption effect was good (the desorption rate reached 97.94%). And it has excellent biocompatibility. Ultimately, a possible adsorption mechanism for the HA nanoparticles was proposed.

Gallium-Containing Hydroxyapatite as a Promising Material for Photocatalytic Performance

The development of photocatalystsor their modification to obtain new photocatalytic performances for the removal of contaminants is a challenge. Hydroxyapatite (HAp), (Ca10(PO4)6(OH)2), is an inorganic component with a high superficial area and low toxicity and the presence of metal in its structure can be an interesting strategy for the photocatalytic approach. This work aimed to synthesize gallium-containing HAp (Ga-HAp) as a promising material for photocatalytic performance. The synthesis was performed by the suspension–precipitation method. The material was characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Morphological analysis employed field emission scanning electron microscope (FESEM) and the elemental analysis by energy-dispersive spectroscopy (EDS). To evaluate the photocatalytic activity, methylene blue (MB) dye was used as a pollutant model under UV light for 120 min. The influence of Ga-HAp concentration (0.25, 0.50, and 1.00 g·L−1) and kinetic reaction was also studied. The Ga-HAp was successfully obtained by the suspension–precipitation method. The structural characterization by XRD and FESEM-EDS elucidated the presence of gallium in the structure of hydroxyapatite. The XPS results indicated the substitution of gallium in the crystal lattice of the material. The discoloration rate of MB dye using Ga-Hap was calculated by pseudo first-order kinetics, and the best rate constant was 7.5 × 10−3 min−1 using 1.00 g·L−1 of photocatalyst. The concentration of Ga-HAp influenced the photocatalytic process, because the discoloration rate increased as a function of the concentration of material. Therefore, Ga-HAp is a promising material for environmental remediation.

The Heat, Plasma, and Laser Treatments Characteristics of Hydroxyapatite Coatings

In this work, the study of thermal treatment by laser, plasma glow discharge, and tubular furnace on Ti-6Al-4V alloy coated with hydroxyapatite (HA) by methods of dip coating and electrophoretic deposition. The effect of pulsed Nd:YAG laser , oxygen plasma and tubular furnace treatments on structure, morphology and corrosion resistance of HA coating –Ti6Al4V alloy samples were thermal reported. The samples were tested by optical microscope, XRD, SEM, and the corrosion characteristic with open circuit potential (OCP) and polarization curve (Tafel). The results showed that the samples thermal reported by tubular furnace were the best where the corrosion rate was reduced to 3.567×10-4 mm/y for the dip-coated samples and 7.221×10-4 mm/y for the electrophoretically deposited samples compared with 9.396×10-3mm/y for uncoated sample. It was found that the heat, laser and plasma treatment enhanced the structure and corrosion resistance properties of the HA coating on Ti6Al4V substrate for use in biomedical applications. This research demonstrates a new low-cost approach to produce high corrosion resistance biocompatible materials.

Experimental characterization and theoretical investigation of Ce/Yb co-doped hydroxyapatites

In the present study, the effects of variable amounts of Yb addition on the structural, thermal, and in vitro biocompatibility properties of Ce-doped hydroxyapatite (HAp) samples synthesized via the wet chemical method were investigated. Besides, the prepared formulations were also modeled for making the theoretical investigations. The single-phase compositions were detected for all samples, and no formation of additional phases was observed. Doping with Yb was observed to produce some variations in the lattice parameters, unit cell volume, lattice strain, and lattice stress. While a decreasing trend in the crystallite size and crystallization percent with increasing Yb content was found, a gradual increase in the anisotropic energy density was observed. All samples were found to be thermally stable from room temperature to 1000 °C with negligible mass losses during heating. No significant morphological changes were caused by the addition of Yb. For all samples, the numerical values of (Ca + Ce + Yb)/P molar ratio were found to be close to that for stoichiometric HAp (1.67). It was observed that the increased Yb additive caused a decrease in cell viability values. A continuous decrease in the bandgap energy with the increasing amounts of Yb added to the Ce-based HAp structure was observed from the theoretical investigations. A sharp decrease in the cell viability of the Ce-based HAp was observed with the addition of Yb.

Effects of physico-chemical properties of ions-doped hydroxyapatite on adsorption and release performance of doxorubicin as a model anticancer drug

Hydroxyapatite (HAp) is considered to be one of the most promising materials for anticancer drug carrier due to its excellent biocompatibility and adsorption capacity. Herein, we thoroughly evaluated the key factors affecting the performance of HAp used as a drug carrier of doxorubicin (DOX), including ion-doping, specific surface area, zeta potential, binding energy, etc. The results showed that Zn, Ba, F, Zn/F, and Ba/F ions were successfully doped into the lattice structure of HAp by a simple hydrothermal method. Compared with pure HAp, the doping of these ions can not only improve its specific surface area and zeta potential, but also enhance the binding energy between DOX and HAp, and thus improving the DOX loading capacity and sustained release time. Moreover, among all the samples, the Ba/F codoped HAp exhibits the highest DOX loading efficiency (96.3%), followed by Ba doped HAp (93.4%), and both of them shows pH-dependent sustained release behavior. Our study indicates that the DOX loading capacity of HAp can be further improved and the sustained release time can be prolonged by selecting appropriate ions for HAp doping, which is of great significance to promote the clinical application of HAp as a drug carrier of DOX.

Hydroxyapatite nanomaterials with tailored length regulated by different fatty acids

The morphology and structures of hydroxyapatite (HA) nanomaterials greatly influence their physicochemical properties and bio-applications. In this study, HA nanostructures with tailored length regulated by different fatty acids were prepared via a solvothermal route. By using ricinoleic acid, linoleic acid and oleic acid as the template, the growth of HA crystals was regulated and the morphology of HA nanomaterials was transformed from long nanowires to short nanowires and then nanorods. The underlying mechanism for the formation of HA nanomaterials synthesized by different kinds of fatty acids under solvothermal condition was proposed. This study provides a simple and environmentally friendly way to obtain HA nanomaterials with tailored length for biomedical applications.

Bone manganese is a sensitive biomarker of ongoing elevated manganese exposure, but does not accumulate across the lifespan

Studies have established associations between environmental and occupational manganese (Mn) exposure and executive and motor function deficits in children, adolescents, and adults. These health risks from elevated Mn exposure underscore the need for effective exposure biomarkers to improve exposure classification and help detect/diagnose Mn-related impairments. Here, neonate rats were orally exposed to 0, 25, or 50 mg Mn/kg/day during early life (PND 1–21) or lifelong through ∼ PND 500 to determine the relationship between oral Mn exposure and blood, brain, and bone Mn levels over the lifespan, whether Mn accumulates in bone, and whether elevated bone Mn altered the local atomic and mineral structure of bone, or its biomechanical properties. Additionally, we assessed levels of bone Mn compared to bone lead (Pb) in aged humans (age 41–91) living in regions impacted by historic industrial ferromanganese activity. The animal studies show that blood, brain, and bone Mn levels naturally decrease across the lifespan without elevated Mn exposure. With elevated exposure, bone Mn levels were strongly associated with blood Mn levels, bone Mn was more sensitive to elevated exposures than blood or brain Mn, and Mn did not accumulate with lifelong elevated exposure. Elevated early life Mn exposure caused some changes in bone mineral properties, including altered local atomic structure of hydroxyapatite, along with some biomechanical changes in bone stiffness in weanlings or young adult animals. In aged humans, blood Mn ranged from 5.4 to 23.5 ng/mL; bone Mn was universally low, and decreased with age, but did not vary based on sex or female parity history. Unlike Pb, bone Mn showed no evidence of accumulation over the lifespan, and may not be a biomarker of cumulative long-term exposure. Thus, bone may be a useful biomarker of recent ongoing Mn exposure in humans, and may be a relatively minor target of elevated exposure.

Biosynthesized gold nanoparticles-doped hydroxyapatite as antibacterial and antioxidant nanocomposite

A composite of hydroxyapatite (HA) doped with green synthesized gold nanoparticles (Au NPs) was prepared. Au NPs were produced via the bioreduction of HAuCl4 with Clitoria ternatea flower extract and utilized in HA synthesis, using Ca(OH)2 and ammonium diphosphate as precursors. The aim of this research was to analyze the structure of the composite and conduct an antibacterial activity test involving Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, and Streptococcus pyogenes. In addition, antioxidant activity was evaluated by 2,2-diphenyl-1-picrylhydrazyl radical scavenging. Au NP formation monitoring was conducted by UV–visible spectroscopy and particle size analysis, and the synthesized composite was studied using X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results revealed homogeneously dispersed Au NPs (particle size ranging from 5 to 80 nm) in the HA structure. The nanocomposite demonstrated enhanced antibacterial activity against the tested bacteria compared to HA, with minimum inhibition concentrations of 3 μg ml−1 for E.coli and S.aureus and 10 μg ml−1 for K. pneumoniae and S. pyogenes. The nanocomposite expressed antioxidant activity, as shown by 2,2-diphenyl-1-picrylhydrazyl scavenging activities of 66% and 58% at concentrations of 100 μg ml−1 and 50 μg ml−1, respectively.

Promotional effects of defects on Ni/HAP catalyst for carbon resistance and durability during dry reforming of methane

Excellent carbon resistance and stable operations are essential for the industrialization of catalytic dry reforming of methane (DRM). In this study, a series of Ni/HAP and Ni/HAP-D catalysts are used to investigate their DRM reaction performance, including activity, durability, and resistance to carbon deposition. Combined with H2-TPR and XPS results, Ni in the Ni/HAP prefers to replace the external Ca atoms in hydroxyapatite. The inherently “Ca-deficient” HAP-D support facilitates a more robust anchor positioning for the Ni metal, and a significant fraction of the Ni atoms will be embedded in the inner structure of hydroxyapatite in the form of Ni2+[I] and Ni2+[II]. The catalytic activity of the Ni/HAP-D series of catalysts for CH4 and CO2 is significantly higher than that of the Ni/HAP series of catalysts, demonstrating that the Ni morphology, the combined form between Ni and support plays a crucial role in the DRM reaction. The deactivation rate of the Ni0.5/HAP-D catalyst is only 0.008% h−1 and 0.007% h−1 for CH4 and CO2, respectively, in a 200-h durability test. In the spent Ni0.5/HAP catalyst after 118-h reaction, the presence of NiO crystalline phase is detected, indicating that partial Ni is oxidized by CO2 during the reaction, and amorphous carbon and graphitic carbon are also detected. In contrast, no NiO crystalline phase is detected in the spent Ni/HAP-D catalyst after 200-h reaction, and only trace amounts of graphitic carbon are observed, indicating that the Ni presence pattern of Ni0.5/HAP-D contributes to its stability and resistance to carbon deposition. This work provides insights into the design of supported nickel-based catalysts with both excellent stability and surprisingly resistant to carbon deposits for DRM applications.

Structural, spectroscopic, dielectric, and magnetic properties of Fe/Cu co-doped hydroxyapatites prepared by a wet-chemical method

In this study, the effects of Cu and Fe additives on the structural, dielectric, magnetic, thermal and morphology of hydroxyapatite (HAp) samples were investigated and reported in detail for the first time. The prepared systems were also modeled and examined theoretically.It can be said that both additives affect the thermal behavior of the HAp structure. The addition of Cu affected the morphology of submicron-sized particles with spherical-like shapes with a low degree of agglomeration. Diffuse reflection data revealed that the energy band gap values decreased as Cu was added to the Fe-based HAp structure.The dielectric constant (ε′) had high values at low frequencies in all samples and decreased with increasing frequency.It could be concluded that Fe/Cu incorporation to hydroxyapatites enhanced its thermal, magnetic, and dielectric properties required for mimicking natural HAps to open a successful venue for medical application in the healing regeneration of bone.

Simulation and Computer Study of Structures and Physical Properties of Hydroxyapatite with Various Defects.

Simulation and computer studies of the structural and physical properties of hydroxyapatite (HAP) with different defects are presented in this review. HAP is a well-known material that is actively used in various fields of medicine, nanotechnology, and photocatalytic processes. However, all HAP samples have various defects and are still insufficiently studied. First of all, oxygen and OH group vacancies are important defects in HAP, which significantly affect its properties. The properties of HAP are also influenced by various substitutions of atoms in the HAP crystal lattice. The results of calculations by modern density functional theory methods of HAP structures with these different defects, primarily with oxygen and hydroxyl vacancies are analyzed in this review. The results obtained show that during the structural optimization of HAP with various defects, both the parameters of the crystallographic cells of the HAP change and the entire band structure of the HAP changes (changes in the band gap). This affects the electronic, optical, and elastic properties of HAP. The review considers the results of modeling and calculation of HAP containing various defects, the applied calculation methods, and the features of the effect of these defects on the properties of HAP, which is important for many practical applications.

Fabrication of mechanically enhanced hydroxyapatite scaffold with the assistance of numerical analysis

Hydroxyapatite (HAp) has been found to be incompetent as it relates to its mechanical integrity, which somewhat restricts its use for load-bearing clinical applications. Several studies have been conducted doping HAp with foreign elements in order to enhance its mechanical integrity. However, it has been established that foreign elements usually trade off the phase structure and biological integrity of HAp. To avoid this challenge, this study presents a numerical analysis with the aim to fabricate a pure HAp scaffold with high mechanical strength, considering compaction and sintering protocols. The X-ray diffraction (XRD) and Fourier transformed infrared (FTIR) spectroscopy of raw bovine bones (RB) and HAp sintered at 900, 1000, and 1100 °C showed calcium phosphate contents of the bulk materials. It was also observed that increase in sintering temperature made prominent characteristic peaks of HAp phase to become narrower on the XRD patterns. The scanning electron microscope (SEM) analysis on the powdery samples showed that sintering temperature reduced HAp particle size, which resulted to the enhancement noticed in the mechanical properties of the fabricated HAp. Taguchi design analysis on the individual hardness and compressive strength revealed 1100 °C as the optimal sintering temperature, but a disparity in compaction load displaying 5 KN for high hardness and 15 KN for high compressive strength. Conversely, Taguchi grey relational analysis gave common optimal settings for high hardness and compressive strength to fabricate mechanically enhanced HAp scaffold, and are 1100 °C sintering temperature and 5 KN compaction load. Significantly, this study revealed that compaction load has a very high percentage of contribution of 90.15% compared to sintering temperature having a contribution of 7.79%. Confirmation analysis also proved that the experimental grey relational grade of 0.7824 is within 95% confidence interval.