HAp Phase Research Articles

The importance of ammonium and potassium ions under hydrothermal preparation conditions on the structure and corrosion properties of CaP coatings

CaP coatings were hydrothermally deposited on the AZ31 magnesium alloy in rection mixture containing ammonium or potassium ions. CaP coatings were deposited on AZ31 alloy in reaction mixture at pH 5 and 7 with and without EDTA chelating agent. It was found that the ammonium ions present have a negative effect on the quality of the CaP coating deposited from mixture at pH 7 and their presence at neutral environment results in the formation of structural defects in the coatings. At the same time, the presence of ammonium ions suppresses hydrolysis and crystallization of OCP and HAp. However, pH and the presence of EDTA have a more pronounced effect on the structure and phase composition. The coatings deposited in the reaction mixture, containing potassium-based precursors and EDTA, at pH 7 showed the best thermal stability due to the majority of HAp phase. The uniform CaP coating deposited in the reaction mixture containing EDTA and K+ ions at pH 7 also achieved the best corrosion properties due to the absence of structural defects and dense structure.

Tuning of Graphene oxide - Hydroxyapatite (GO-HAp) composite for enhanced fluorescence and anti-oxidant properties-green approach

Many researchers are working on doping and co-doping of HAp with metal ions and rare earth elements to improve the applicability of HAp, but all these studies question the biocompatibility of HAp. Further, there are no reports on the fluorescence and anti-oxidant aspects. Graphene oxide being a non-toxic material, with excellent physiochemical properties can enhance and induce new properties in HAp. The present study explored the transformation of sea wastes into valuable products such as HAp reduces the negative impact on the environment. GO (from cellulose) and HAp (from Anadara granosa, Crassostrea virginica, synthetic CaCO3). The prepared composite material from two different methods (Post-modification and In situ) of three different precursors are compared and contrasted. From the PXRD results, P-GO-HAp has retained both GO and HAp phases with high crystallinity. The hydrophilicity and higher calcium ratio in P-GO-HApS, the presence of β – TCP phase after composite formation in P-GO-HApC & P-GO-HApO has improved its utility in bone implants. Also, the intense bluish-green emission of P-GO-HApC & P-GO-HApO paves the way for biocompatible imaging. The interplay of calcium, improved hydrophilicity, and stable radical sites of the conjugated π system of GO paved the way for antioxidant property in P-GO-HApS with a radical scavenging potential of 32.88%. With the increase in antioxidant properties, the composite has enhanced inhibition on the most common dental infection caused by Streptococcus mutans.

An approach to investigate the crystallographic unit cell of human tooth enamel.

Human tooth enamel (HTE) is the hardest tissue in the human body and its structural organization shows a hierarchical composite material. At the nanometric level, HTE is composed of approximately 97% hydroxyapatite [HAP, Ca10(PO4)6(OH)2] as inorganic phase, and of 3% as organic phase and water. However, it is still controversial whether the hexagonal HAP phase crystallizes in P63/m or another space group. The observance in HTE of Ca2+, Mg2+ and Na+ ions using X-ray characteristic energy-dispersive spectroscopy in the scanning electron microscope has been explained by substitutions in the HAP unit cell. Thus, Ca2+ can be replaced by Na+ and Mg2+ ions; the PO43- group can be replaced by CO32- ions; and the OH- ions can also be replaced by CO32-. A unit-cell model of the hexagonal structure of HTE is not fully defined yet. In this work, density functional theory calculations are performed to study the hexagonal HAP unit cell when substitution by OH-, CO32-, Mg2+ and Na+ ions are carried out. An approach is presented to study the crystallographic unit cell of HTE by examining the changes resulting from the inclusion of these different ions in the unit cell of HAP. Enthalpies of formation and crystallographic characteristics of the electron diffraction patterns are analysed in each case. The results show an enhancement in structural stability of HAP with OH defects, atomic substitution of Mg2+, carbonate and interstitial Na+. Simulated electron diffraction patterns of the generated structures show similar characteristics to those of human tooth enamel. Hence, the results explain the indiscernible structural changes shown in experimental X-ray diffractograms and electron diffraction patterns.

Synthesis and Characterization of Mg-Hydroxyapatite and Its β-Cyclodextrin Composite as Enhanced Bio-Carrier of 5-Fluorouracil Drug; Equilibrium and Release Kinetics.

An advanced form of magnesium-doped hydroxyapatite (Mg·HAP) was integrated in composite with β-cyclodextrin producing a safe biocomposite (β-CD/HAP) as an enhanced delivery structure of traditional 5-fluorouracil (5-FU) chemotherapy during the treatment stages of colorectal cancer cells. The qualifications of β-CD/HAP as a carrier for 5-FU were followed based on the loading, release, and cytotoxicity as compared to Mg·HAP. β-CD/HAP composite exhibits notably higher 5-FU encapsulation capacity (272.3 mg/g) than Mg·HAP phase (164.9 mg/g). The 5-FU encapsulation processes into β-CD/HAP display the isotherm behavior of the Freundlich model (R2 = 0.99) and kinetic assumptions of pseudo-first order kinetic (R2 > 0.95). The steric studies reflect a strong increment in the quantities of the free sites after the β-CD integration steps (Nm = 61.2 mg/g) as compared to pure Mg·HAP (Nm = 42.4 mg/g). Also, the capacity of each site was enhanced to be loaded by 5 of 5-FU molecules (n = 4.45) in a vertical orientation. The 5-FU encapsulation energy into β-CD/HAP (<40 kJ/mol) reflects physical encapsulation reactions involving van der Waals forces and hydrogen bonding. The 5-FU release profiles of β-CD/HAP exhibit slow and controlled properties for about 80 h either in gastric fluid (pH 1.2) or in intestinal fluid (pH 7.4). The release kinetics and diffusion exponent (>0.45) signify non-Fickian transport and complex erosion/diffusion release mechanism. The free β-CD/HAP particles display a considerable cytotoxic effect on the HCT-116 cancer cells (33.62% cell viability) and its 5-FU-loaded product shows a strong cytotoxic effect (2.91% cell viability).

Preparation of hydroxyapatite nanofibers by using ionic liquids as template and application in enhancing hydrogel performance.

Introduction: Hydroxyapatite (HAP or HA) nanofibers are very attractive in the field of biomedical engineering. However, templates used for preparing HAP nanofibers are usually hydrophobic molecules, like fatty acids and/or surfactants, which are difficult to remove and potentially toxic. Therefore, it is important to develop a green approach to prepare HAP nanofibers. Methods: Imidazolium-based ionic liquids (ILs) were used as templates to control the crystallization of HAP. The obtained HAP nanofibers were composited into polyvinyl alcohol-sodium alginate (PVA-Alg) hydrogel (HAP@H). The rheological performance, stretching, and compression properties were tested. Scanning electron microscope (SEM), high resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), and differential scanning calorimetry (DSC) were adopted to characterize the morphology, size, crystallographic orientations, and phase of HAP@H. Results: HAP nanofibers with a length of ∼50μm were harvested. The DSC results proved that water loss temperature increased from 98°C (for pure hydrogel) to 107°C (for HAP@H). Also, HAP@H hydrogel presented much better porous structure, tensile performance, and compressive performance than that of pure hydrogel. Discussion: The morphology, size, and growth direction of HAP could be modulated easily by altering the alkyl chain length of ILs' cations. This is possibly due to face-specific adsorption of imidazolium moieties on HAP nanocrystals. The enhancing performance of HAP@H is probably due to the composited highly oriented HAP nanofibers.

Effect of thermal treatment on the structural, morphological, and chemical properties of apatite bioceramicsmaterials

Monitoring the synthesis conditions of apatite phosphate by double decomposition seems very useful in view of the simplicity and rapidity of this method. This work is mainly based on production of apatite in the laboratory by the double decomposition method, HAP and TCP were synthesized and studied to demonstrate the influence of thermal treatment and synthesis temperature on the structure of apatite powders. The prepared samples were calcined at 900°C and sintered at 1050, 1100 and 1150°C. The effect of synthesis and sintering temperature on the structure of this material was investigated using XRD, FTIR, and SEM-EDX. This study confirmed that calcination has no effect on the HAP phase stability elaborated. Therefore,for TCP synthesized: β-TCP is the most phase that persists up to, 91% and a minimal partial transformation into Dicalcium Diphosphate is recorded. FTIR spectrum affirms the persistence of OH– and PO43- group bands suggestingthe basic apatite structure for HAP and TCP of the sample, calcination, leads to the crystallization of TCP Ca3(PO4)2. However, the calcined precipitate contains β calcium pyrophosphate Ca2P2O7, and HA:Ca10(PO4)6(OH) 2 constitutes secondary phase. While the calcination of HAP did not affect it. SEM micrograph of synthetic HAP powder treated at 1050°C revealed particle morphology with the dense and cloudy surface while TCP micrograph powder treated at the same temperature shows particle morphology of porous and smoother surfaces and irregular spherical shape. In conclusion thethermal treatments improve the performance of the bioceramic residueand have the potential to create a new type of sustainable and bio-friendly material. Hydroxyapatite and tricalcium phosphate likeotherrelated calcium phosphate minerals, have been used extensively as orthopedic implant material due to their excellent biocompatibility and bone bonding to its structural and composition alsimilarity to that of mineral phase of hard tissue in human bones.

Effect of Sintering Temperature on the Structural and Morphological Properties of Hydroxyapatite Prepared by Precipitation Method

Hydroxyapatite nanoparticles (HAp-NPs) were prepared using a precipitation route from an aqueous solution at a 1.66 Ca/P ion ratio and sintered at different temperatures. X-ray diffraction (XRD) was used to investigate the structural properties of the prepared films. Using a Field Emission Scanning Electron Microscope, the morphology of the surfaces was analyzed. Using Fourier Transform Infrared (FTIR) Spectroscopy, the surface's chemical composition and chemical bonding information were identified. The structural analysis shows that heating treatment reduced the broadening of diffraction peaks, enhancing the Hydroxyapatite phase crystallinity. No phase transition was observed as the sintering temperature increased, revealing the HAp phase's high stability. SEM micrograph images revealed a nanostructured foam-like structure that changed into a flake-shaped structure with diameters between 300 nm and 600 nm after heat treatment. FTIR spectroscopy results revealed that the heat treatment improved the crystallization of the developed HAp-NPs samples. Barrett-Joyner-Halenda (BJH) was used to determine the pore size of HAp NPs, whereas Brunauer-Emmett-Teller (BET) analysis was employed to characterize the surface area of the samples.

Synthesis and characterization of Mg-hydroxyapatite and its cellulose hybridized structure as enhanced bio-carrier of oxaliplatin drug; equilibrium and release kinetics.

An advanced form of magnesium-doped hydroxyapatite (Mg HAP) was synthesized and hybridized with cellulose fibers, producing a safe biocomposite (CF/Mg HAP) as an enhanced delivery structure of traditional oxaliplatin (OXPN) chemotherapy drug during the treatment stages of colorectal cancer. The qualifications of CF/Mg HAP as a carrier for OXPN were followed based on loading, release, and cytotoxicity as compared to Mg HAP. The CF/Mg HAP composite exhibits a notably higher OXPN encapsulation capacity (256.2 mg g-1) than the Mg HAP phase (148.9 mg g-1). The OXPN encapsulation process into CF/Mg HAP displays the isotherm behavior of the Langmuir model (R2 = 0.99) and the kinetic assumptions of pseudo-first-order kinetics (R2 > 0.95). The steric studies reflect a strong increment in the quantities of the free sites after the cellulose hybridization steps (Nm = 178.58 mg g-1) as compared to pure Mg HAP (Nm = 69.39 mg g-1). Also, the capacity of each site was enhanced to be loaded by 2 OXPN molecules (n = 1.43) in a vertical orientation. The OXPN encapsulation energy into CF/Mg HAP (<40 kJ mol-1) reflects physical encapsulation reactions involving van der Waals forces and hydrogen bonding. The OXPN release profiles of CF/Mg HAP exhibit slow and controlled properties for about 100 h, either at pH 5.5 or pH 7.4. The release kinetics and diffusion exponent (>0.45) signify non-Fickian transport and a complex erosion/diffusion release mechanism. The free CF/Mg HAP particles display a considerable cytotoxic effect on the HCT-116 cancer cells (21.82% cell viability), and their OXPN-loaded product shows a strong cytotoxic effect (1.85% cell viability).

Mesoporous graphitic carbon nitride/hydroxyapatite (g-C3N4/HAp) nanocomposites for highly efficient photocatalytic degradation of rhodamine B dye

Recently, there is a rise in demand for low-cost natural source-derived photocatalysts for the degradation of harmful dyes. Here, we report new mesoporous g-C 3 N 4 /HAp nanocomposites prepared by a simple hydrothermal method for efficient photocatalytic degradation of rhodamine B (RhB) dye. Ultrafine g-C 3 N 4 nanosheets were synthesized from the polymerization of melamine and exfoliation of bulk g-C 3 N 4 . HAp nanoparticles were obtained by mixing mussel shell powder with Na 2 HPO 4 and microwave irradiation of the mixture. The g-C 3 N 4 (1-3 wt. %)/HAp was produced from hydrothermally reacting g-C 3 N 4 and HAp. XRD analysis of g-C 3 N 4 /HAp confirms the presence of g-C 3 N 4 and HAp phases. From FT-IR, Raman, NMR, and XPS spectra, the chemical bonds of g-C 3 N 4 /HAp were confirmed. The microscopic (SEM, TEM, and AFM) images illustrate the fine fusion of g-C 3 N 4 and HAp. BET and TG/DTA studies reveal that the g-C 3 N 4 /HAp is mesoporous in nature and is thermally stable. Optoelectronic properties indicate that g-C 3 N 4 /HAp’s luminescence changes with the g-C 3 N 4 concentration. In addition, g-C 3 N 4 /HAp showed high photocatalytic efficiency for RhB degradation (99%) in comparision to g-C 3 N 4 and HAp. The g-C 3 N 4 /HAp is recyclable and possesses good photochemical stability. Superoxide and hydroxyl radicals play a key role in the photodegradation of RhB. A reaction mechanism involving charge (electrons, holes) transfer at Z-scheme heterojunction of g-C 3 N 4 /HAp is proposed. This ‘green’ method, of g-C 3 N 4 /HAp synthesis from g-C 3 N 4 and biowaste-derived HAp, can potentially be applied for catalytic removal of pollutants from industrial effluents.

Effects of Chitosan on Loading and Releasing for Doxorubicin Loaded Porous Hydroxyapatite-Gelatin Composite Microspheres.

Porous hydroxyapatite–gelatin (Hap–Gel) composite microspheres derived by wet chemical methods were used as carriers of doxorubicin (DOX) coupled with chitosan (Chi) for treating cancers. Through X-ray diffraction, specific surface area porosimetry, chemisorption analysis and inductively coupled plasma mass spectrometry, the crystalline phase, composition, morphology, and pore distribution of HAp–Gel microspheres were all characterized. HAp nanosized crystals and Gel polymers form porous microspheres after blending and exhibit a specific surface area of 158.64 m2/g, pore sizes from 3 to 150 nm, and pore volumes of 0.4915 cm3/g. These characteristics are suitable for carriers of DOX. Furthermore, by the addition of chitosan during drug loading, its drug-entrapment efficiency increases from 70% to 99% and the release duration increases from a 100% burst within a day to only 45% over half a year since the pores in the composite microspheres provide a shielding effect throughout the degradation period of the chitosan. According to the MTT tests, cell viability of DOX–Chi/HAp–Gel is 57.64% on day 5, similar to the result treated with DOX only. It is concluded that under the protection of pores in the microspheres, the chitosan abundant of hydroxyls combining HAp–Gel and DOX by forming hydrogen bonds indeed enhances the entrapment efficiency, prolongs the releasing period and maintains DOX’s ability to perform medicine functions unaffected after loading.

Evolution of dynamics of physico-chemical and mechanical properties of hydroxyapatite with fluorine addition and degradation stability of new matrices

This multidisciplinary study examined sensitively the change in the dynamics of main mechanical performance, stability of crystal structure, crystallinity quality, strength, corrosion resistance, biocompatibility, resistance to structural degradation/separations and mechanical durability features of hydroxyapatite (HAp) biomedical materials based on the fluorine addition and degradation process to guide future medical and dental treatment studies. In the study, the fluorine ions were used to be the dental coating, filling and supporting material for biologically or synthetically produced bone minerals. The general characteristic properties were investigated by means of standard spectroscopic, structural and mechanical analysis methods including RAMAN, SEM-EDS, TEM, Vickers micro-indentation hardness and density measurements. A time dependent release test was performed to evaluate possible fluorine ion release after the degradation process. It was found that the fundamental characteristic properties of HAp biomedical materials are noted to improve with the increase in the fluoride level up to 2% due much more stabilization of HAp crystal system. The combination of RAMAN spectra and powder XRD analyzes indicates that 2% addition level affects positively the formation velocity of characteristic HAP phase. Besides, fluorine doped HAp materials all exhibited the main characteristic peaks after degradation process. This is attributed to the fact that the fluorine ions enabled the hydroxyapatite to enhance the structural quality and stability towards the corrosion environment. However, in case of excess dopant level of 3% the degradation rates were obtained to increase due to higher contribution rate and especially electrostatic interactions. As for the surface morphology examinations, 2% fluorine added HAp with the highest density of 3.0879 g/cm3 was determined to present the superior crystallinity quality (smallest grain size, best smooth surface, honeycomb pattern, regular shaped particles and densest particle distributions through the specimen surface). Conversely, the excess fluorine triggered to increase seriously degree of micro/macro porosity in the surface morphology and microscopic structural problems in the crystal system. Thus, the HAp doped with 3% was the most affected material from the degradation process. Additionally, the fluorine ion values read after the release process were quite far from the value that could cause toxic effects. Lastly, the optimum fluorine addition provides the positive effects on the highest durability, stiffness and mechanical fracture strength properties as a consequence of differentiation in the surface residual compressive stress regions (lattice strain fields), amplification sites and active operable slip systems in the matrix. Hence, the crack propagations prefer to proceed in the transcrystalline regions rather than the intergranular parts. Similarly, it was found that Vickers micro-indentation hardness tests showed that the microhardness parameters increased after the degradation process. All in all, the fluorine addition level of 2% was noted to be good choice to improve the fundamental characteristic properties of hydroxyapatite biomedical materials for heavy-duty musculoskeletal, orthopedic implant, biological and therapeutic applications in medicine and dentistry application fields.

Different Methods for Preparation of Hydroxyapatite Nanostructures

Hydroxyapatite could be utilized as a bioceramic owing to its osteoconductivity and bioactivity characteristics. It is obvious that the shape of HAp nanoparticles clearly influences their properties such as bioactivity and surface area. Nano-sized HAp particles with different morphologies were synthesized using a variety of preparation processes such as solvothermal, microwave-solvothermal, precipitation and hydrothermal-precipitation process. The effect of preparation methods on particle morphology was studied. The X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Zeta potential (ZP), were used to validate the composition and structure of the as-formulated HAp nanostructures. A single phase of HAp was obtained using various methods of preparation. According to the TEM analysis of the powders, both the solvothermal and the hydrothermal treatment samples were very diffuse and consisted of fairly homogeneous HAp nanorods.

Gum tragacanth modified nano-hydroxyapatite: An angiogenic- osteogenic biomaterial for bone tissue engineering

Bone tissue engineering (BTE) is an evolving domain and provides encouraging solution to address the current demands in the orthopaedic healthcare system. However, even a well-exploited biomaterial such as synthetic hydroxyapatite (nHAp) fails to induce ideal bone regeneration in the complex in vivo conditions owing to its poor angiogenic potential. Hence, in addition to the osteogenic property, designing smart biomaterials with intrinsic angiogenic property is key for the success of bone tissue engineering implants. Recently, gum tragacanth (TG) has been testified to imbibe both angiogenic and osteogenic characteristics. In this context, TG functionalized nano-hydroxyapatite (TG-HAp) would be an ideal angiogenic-osteogenic material for BTE application. Here, we have reported the biofunctionalization of nHAp with TG through a silanized nHAp intermediate, and its osteogenic and angiogenic properties. X-ray diffraction (XRD) revealed the crystalline apatite phase of HAp. Biofunctionalization of nHAP with TG was confirmed both qualitatively and quantitatively by FTIR and TGA analysis respectively. TEM analysis confirmed the formation of needle shaped nanoparticles having size range (100–300 nm). Biofunctionalization lead to a change in zetapotential of nHAp from – 8.1 mV to 0.1 mV. The existence of multi-layered gum tragacanth on nHAp was confirmed by BET analysis. TG-HAp was found osteogenic when tested invitro using MG-63, (human osteoblast cells) and hMSCs, (human mesenchymal stem cells). Further, TG-HAp was found to increase the cellular VEGF expression in MG-63. Angiogenic property of TG-HAp was confirmed by in vitro tube formation of human umbilical vein endothelial cells (HUVECs). The study altogether indicates about the angiogenic and osteogenic potential of synthesized TG-HAp, which may be used as a new biomaterial in bone tissue engineering.

Microbiology and Outcomes of Institutionalized Patients With Stroke-Associated Pneumonia: An Observational Cohort Study.

Background: The attributable mortality and microbial etiology of stroke-associated pneumonia (SAP) vary among different studies and were inconsistent.Purpose: To determine the microbiology and outcomes of SAP in the lower respiratory tract (LRT) for patients with invasive mechanical ventilation (MV).Methods: In this observational study, included patients were divided into SAP and non-SAP based on a comprehensive analysis of symptom, imaging, and laboratory results. Baseline characteristics, clinical characteristics, microbiology, and outcomes were recorded and evaluated.Results: Of 200 patients, 42.5% developed SAP after the onset of stroke, and they had a lower proportion of non-smokers (p = 0.002), lower GCS score (p < 0.001), higher serum CRP (p < 0.001) at ICU admission, and a higher proportion of males (p < 0.001) and hypertension (p = 0.039) than patients with non-SAP. Gram-negative aerobic bacilli were the predominant organisms isolated (78.8%), followed by Gram-positive aerobic cocci (29.4%). The main pathogens included K. pneumoniae, S. aureus, H. influenzae, A. baumannii, P. aeruginosa, E. aerogenes, Serratia marcescens, and Burkholderia cepacia. SAP prolonged length of MV (p < 0.001), duration of ICU stay (p < 0.001) and hospital stay (p = 0.027), shortened MV-free days by 28 (p < 0.001), and caused elevated vasopressor application (p = 0.001) and 60-day mortality (p = 0.001). Logistic regression analysis suggested that patients with coma (p < 0.001) have a higher risk of developing SAP.Conclusion: The microbiology of SAP is similar to early phase of HAP and VAP. SAP prolongs the duration of MV and length of ICU and hospital stays, but also markedly increases 60-day mortality.

Sintering behavior and mechanical properties of hydroxyapatite ceramics prepared from Nile Tilapia (Oreochromis niloticus) bone and commercial powder for biomedical applications

In this work, Nile tilapia (Oreochromis niloticus) bone was calcined at 800 °C for 5 h in an air atmosphere to obtain hydroxyapatite powder (FB powder). The elemental composition, phase structure, and morphology of the FB powder were investigated and compared with commercial hydroxyapatite powder (SM powder). The FB-powder exhibited 1.01 at. % of Mg while the SM-powder showed Mg in ppm-level. Carbonate groups were detected in the two powders. Both HAp and β-tricalcium phosphate (β-TCP) structures were found in the FB powder, but the SM powder exhibit only the HAp phase. Irregular-shaped particles were observed in the FB powder. After the two HAp powders were sintered at 1200 °C and 1250 °C for 2 h (FB-1200, FB-1250, SM-1200, and SM-1250), the β-TCP intensity peaks of the FB-ceramic samples significantly increased with increasing sintering temperature. The highest relative density, well-packed grains, and β-TCP stabilization by Mg at the Ca5 site of the FB-1250 structure were the dominant factors governing the highest mechanical properties. Although high density was observed in the SM-1200 sample, Vickers hardness of the SM-1200 sample is lower than the FB-1250 sample. This may be attributed to the partial decomposition of HAp into β-TCP, α-tricalcium phosphate (α-TCP), and Ca10(PO4)6O phases. In addition, the increase of grain size was the main factor that governs the increasing compressive strength and Young's modulus instead of density and phase decomposition of the SM-ceramic samples.

In situ loading and x-ray diffraction quantification of strains in hydroxyapatite particles within a 3D printed scaffold

A 3D printed scaffold consisting of a composite with very high volume fraction of particulate hydroxyapatite (hAp, 74 vol.%) and small volume fraction of poly-lactic-co-glycolic acid (26 vol.%) was loaded in compression, and the internal strains in the hAp phase were measured by high-energy x-ray diffraction. Diffraction patterns were recorded at multiple positions in the scaffold at cross-head displacements of 0, -0.52 and -0.62 mm (2.0 mm total scaffold height). The 00.2 and 21.0 hAp strains never exceeded 2 × 10−4, and most positions showed strains ≤ 1 × 10−4, which was the magnitude of the experimental uncertainty.

Mesoporous Mn-doped hydroxyapatite nanorods obtained via pyridinium chloride enabled microwave-assisted synthesis by utilizing Donax variabilis seashells for implant applications

Manganese-doped mesoporous hydroxyapatite (MnHAp) nanorods, a bio-apatite were synthesized via pyridinium chloride mediated microwave approach using bio-waste Donax variabilis seashells to treat orthopedic infections. This is the first report on using pyridinium chloride mediated mesoporous MnHAp nanorods synthesis. Pure and Mn doped HAp samples were examined using Raman spectroscopy, X-ray powder diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) studies to confirm the prepared HAp nanorods. Furthermore, the fabrication of manganese-doped HAp was successful with the formation of a hexagonal crystal lattice without disturbing the HAp phase. It is because, at the time of synthesis, PO43− ions form an electrostatic interaction with the Mn ions. Furthermore, Mn-doped HAp samples showed a reduction in their sizes of 15, 10–15, 5–10 nm width, and 80–100, 10–15, 20–30 nm length with varied pore diameters and surface area. The pure HAp, MnHAp-1, MnHAp-2, and MnHAp-3 nanorods disclose the surface area of 39.4, 18.0, 49.2, and 80.4 m2 g−1, with a pore volume of 0.0102, 0.0047, 0.0143, and 0.0447 cm3 g−1, the corresponding pore diameter was estimated to be 6, 7, 6, and 4 nm, respectively. Moreover, antibacterial activity reveals effective bactericidal action against infections causing pathogens whereas cytotoxicity examination (MTT assay), and zebrafish results reveal their non-toxic behavior. Therefore, it is evident from the study, that rapid fabrication of mesoporous and diverse structured MnHAp nanorods could be convenient with pyridinium chloride enabled microwave-assisted method as a bactericidal biomaterial for implant applications.

Synthesis and structural characterizations of HAp–NaOH–Al2O3 composites for liquid petroleum gas sensing applications

Abstract The main objective of present work was to synthesize sodium doped polycrystalline hydroxyapatite NaHAp (NaOH-HAp) powder by employing wet chemical precipitation method and its composites with alumina (Al2O3; 0, 10, 40, 70 wt%) using a scalable solid-state reaction method. Detailed investigations of NaHAp and its composites using X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, UV–visible spectroscopy, scanning electron microscopy followed by energy-dispersive X-ray spectroscopy and sensing behaviour is carefully described. XRD results exhibited major and minor phase of HAp, Ca2P2O7 and NaOH for NaHAp sample while for all fabricated composites of HAp–NaOH–Al2O3 and revealed the major phase of hibonite CaO(Al2O3)6 along with secondary phases of Ca2P2O7, Na4[Al(PO4)2(OH)], Na3Al(OH)(HPO4)(PO4), NaAl3(PO4)2(OH)4 and NaOH. The crystallite size of NaHAp-based composites was also determined and lies in the range of 200–2800 nm, which is larger than that of Al2O3. FTIR and Raman spectroscopic studies reveal the bonding formation of P–O, O–P–O and Al–O due to intramolecular interaction of Na4(Al(PO4)2(OH)), Na3Al(OH)(HPO4)(PO4) and NaAl3(PO4)2(OH)4 in the HAp–NaOH–Al2O3 composite, while bonding formation of Al–O–H recognized to intermolecular interaction in between Al with H atoms of Na4(Al(PO4)2(OH)), Na3Al(OH)(HPO4)(PO4) and NaAl3(PO4)2(OH)4. The SEM and energy dispersive spectroscopy analysis revealed the presence of all constituent elements of used chemicals which also validate the purity of used materials. It is concluded that the fabricated sensor (60 NaHAp–40 Al2O3) shows lowest response and recovery time, 4 and 3 s for the 0.5 vol.% concentration of the LPG. Therefore, among all composites, this fabricated composite can be used for LPG gas sensing applications.

P.732 Use of optical coherence tomography for the diagnosis of deterioration of functionality in bipolar disorder

Copper-doped hydroxyapatite (CuHAP) mesoporous nanopowders (NPs) with distinct particle morphologies of nanorods-like (CuHAP-NR) and hierarchically assembled micro-spherical (CuHAP-MS) particles were comprehensively characterized for drug delivery applications. Both products were monolithic consisted of HAP phase only. Rietveld refinement suggested deformation led straining of HAP nanocrystals due to substitution of Cu ions in lattice structure of HAP. CuHAP-NR was more crystalline than CuHAP-MS NP. CuHAP-NR and CuHAP-MS NPs were having nanorods-like and microspherical ended hierarchically assembled nanostructured particles, respectively. Atomic structures proposed by XRD and HRTEM corroborated each other. Elemental examination confirmed formation of CuHAP composition in both NPs. Isotherms affirmed mesoporous structure of both products. Surface area of CuHAP-NR was significantly bigger and porous than CuHAP-MS NP. Consequently, former adsorbed 2.5 times more drug than latter. Furthermore, CuHAP-NR NP released drug in sustained and controlled manner, whereas, CuHAP-MS NP exhibited burst-release of drug. Critical analysis concluded that particle architecture of drug carriers significantly influenced their drug loading and releasing abilities.

Piezoelectricity in Sr doped thick films of hydroxyapatite

The current study reports the synthesis, characterization and tape casting of strontium substituted into the calcium sublattice of hydroxyapatite in range of (0–100 mol%). The XRD powder data reveals that a primary HAp phase as well as secondary Ca 3 (PO 4 ) 2 (β-TCP) phase coexist. Our analysis shows that Sr+2 preferentially occupies the HAp lattice sites rather than β-TCP. Developed free-standing tapes of HAp offer unique possibility of custom designed solutions for biomedical applications by controlling shape size and tuned electrical properties. We report piezoelectricity in Sr doped hydroxyapatites thick films, the piezoelectric coefficient is an order of magnitude higher than what has been previously obtained in PLD deposited hydroxyapatite films [15]. The piezoelectricity shows slight improvement with the Sr doping. Despite low piezoelectric coefficient, the generated voltage is of the order of mV which is high enough to have physiological relevance since the resting potential of the cells lie between 60–90 mV. Further improvements in the material design and poling could pave way to understand the role of electricity in bone growth and to use piezoelectric energy harvesting to tune spinal and neuro stimulators.