Presence Of HAP Research Articles

Preparation of carbon-coated hydroxyapatite nanorods from bovine bone and application in the photocatalytic N2/H2O synthesis of ammonia

Carbon-coated hydroxyapatite nanorods (HAp–C) were first synthesized using bovine bones from Urumqi as the carbon source. Ti3+-doped TiO2 (Ti3+–TiO2) was obtained via thermal reduction using NaBH4. Ti3+–TiO2 was hydrothermally deposited onto the surface of HAp–C, resulting in Ti3+–TiO2/HAp–C formation. The photocatalytic N2/H2O ammonia synthesis performance of the prepared materials was investigated while analyzing their structure. HAp–C, a stable carbon material derived from bones, exhibits considerable photoluminescence under ultraviolet light. It serves as a substrate for the Ti3+–TiO2 catalyst, reducing particle agglomeration and enhancing the photogenerated electron transfer rate. The presence of HAp–C further enhances the activation of Ti3+–TiO2/HAp–C for N2 adsorption and considerably increases its visible-light absorption compared to pure Ti3+–TiO2. The 85%–Ti3+–TiO2/HAp–C photocatalyst yielded 850.13 mol/(L·g cat.) of ammonia after 4 h of reaction during the photocatalytic N2/H2O ammonia synthesis, representing a 2.93-fold increase over the ammonia yield of pure Ti3+–TiO2 under identical conditions.

Core-shell structured Ag-HAp@Bi2S3 as effective S-scheme heterojunction photocatalyst: Induced with internal polarization electric field effect and co-catalyst fashions

Considering the utilization of solar energy, the low efficiency of photocatalytic reactions is a crucial factor to take into account. One effective solution to this issue is the heterojunction method, deemed as an efficient approach for enhancing photocatalyst performance via optimal sunlight utilization. In this study, a HAp@Bi2S3 core-shell structure was synthesized using a simple microemulsion method, and subsequently, Ag nanoparticles were systematically anchored onto its surface. The Ag-HAp@Bi2S3 nanocomposite was utilized to concurrently achieve the photocatalytic degradation of Bis-phenol A (BPA) and the reduction of Cr6+ ions. The findings indicate that the heterojunction S-scheme and co-catalyst Ag have a significant role in charge separation and accelerating the photocatalytic reaction. Moreover, the presence of HAp as a polarizing substrate in this composite can create an internal polarized electric field, in addition to the electric field generated by the S-scheme heterojunction. This proposed nanocomposite exhibits potential in addressing the challenge of achieving rapid and simultaneous pollutant degradation.

Synthesis of Hydroxyapatite-Polyethylene Glycol with <i>In-Situ</i> Method Using Calcium Oxide from Blood Shells (<i>Anadara granosa</i>)

Hydroxyapatite (Ca10(PO4)6(OH)2, HAp) is a calcium phosphate-based biomaterial that is widely used in bone implants due to its similarity in composition with the constituent elements of bone. However, HAp still has poor mechanical properties, so research was carried out to improve the mechanical properties such as reduced brittleness, less fracture resistance, and a denser structure of HAp by synthesizing composites with PEG. This study used PEG as a filler and HAp as a matrix. HAp was synthesized from blood clam shells (Anadara granosa) using the sol-gel method. HAp-PEG composite was synthesized using the in-situ method with various HAp concentrations of 40, 50, 60, 70, and 80%. FTIR characterization showed the presence of functional groups PO43− and CO23−, which indicated the presence of HAp. Analysis of the XRD pattern showed a crystal size of 24.194 nm. SEM-EDX showed the needle-shaped HAp-PEG composite HAp crystal morphology and obtained a Ca/P ratio of 1.87. Analysis of DTA results showed a weight loss of 65.72% in the composite at a temperature > 200 °C. A degradation test was also carried out to see the percentage of the HAp-PEG composite to be degraded, and the optimum degraded composite with increasing days had a concentration of 70%.

Silver-Releasing Micro-/Nanoporous Coating on Additively Manufactured Macroporous Ti-Ta-Nb-Zr Scaffolds with High Osseointegration and Antibacterial Properties

The two major problems of titanium alloy surface of bone/dental implants were the lack of native tissue integration and associated infection. To solve these problems, the development of self-defending implants with intrinsic osteogenic properties has been highlighted, in which titanium alloy surfaces of bone/dental implants are endowed with antibacterial property by silver (Ag) incorporated in biomaterials. In this study, we biofunctionalized the surface of selective laser melting (SLM) manufactured volume-porous Ti-Ta-Nb-Zr scaffolds by using plasma electrolytic oxidation (PEO) as a way to eliminate the peri-operative bacterial load and promote osseointegration. In the experiment, the PEO process operated with three different concentration (1, 1, and 2 g/L) of a AgNO3 solution. As a result, a titanium oxide coating embedded with calcium and phosphorous and Ag was formed by one-step PEO treatment, and a presence of HAp was detected by X-ray diffraction (XRD) and XPS. In addition, Ag ions were found to be released from the scaffolds for at least 28 days, resulting in an effective prevention of bacterial adhesion and a decrease of the number of planktonic bacteria, with no sign of cytotoxicity shown simultaneously. Highly porosity micropores were formed on the surface of scaffolds after oxidation, and the mechanical properties did not show any signs of change. Besides, a strong calcium deposition and osteoconductive effect were found on the surface of PEO-treated Ag scaffolds. To sum up, this study reveals the potential of PEO coatings to biofunctionalize SLM Ti-Ta-Nb-Zr scaffolds with antibacterial agents. The biomaterials developed here, therefore, exploit the biofunctionalized behavior of Ag to offer strong antibacterial behavior and osteogenic promotion without cytotoxicity of Ag against mammalian cells.

Effect of HAp on Characterization of MgZn-xHAp Biocomposites

Research on Mg as biodegradable materials in orthopedics has been carry out intensively in the 17 years. Various studies conducted to produce material that is superior in mechanical properties and corrosion resistance. One of the developments carry out is to make Mg-based composite. This study aims to see the effect of HAp on Mg6ZnHAp composites. The biocomposites were synthesized by mixing the HAp powder on the Mg6Zn powder mixture with the composition of 5%, 7% and 9% using ball milling for 30 minutes. The material is sintered at 350 o C and held for one hour. Biocomposites were characterized by SEM/EDS, X-ray diffraction (XRD) and Potentiostat. The SEM/EDS results showed that the larger the HAp composition resulted in the smaller grain size. The crystallite size of the material decreases with increasing HAp composition in the material. The presence of HAp in the material also affects the corrosion rate. The greater HAp composition in the material will result in better corrosion resistance.

The bioactivity of titanium-cuttlefish bone-derived hydroxyapatite composites sintered at low temperature

ABSTRACT The most limiting features of titanium as a bone substituent are lack of bioactivity and high Young’s modulus. We have prepared titanium-hydroxyapatite (Ti-HAp) composites using titanium hydride as sintering agent to provide titanium sintering at lower temperature and preserve the stability of apatite phase. After low temperature sintering, no hydroxyapatite decomposition was detected. Pure titanium samples sintered in the presence of hydride showed smooth surface indicating good densification at 800°C. Higher HAp content resulted in decreased density and higher porosity due to the formation of micro- and macro-pores caused by the integration of HAp particles into titanium matrix and titanium hydride decomposition. However, Vickers microhardness test showed increased hardness for Ti-HAp composite with 10% of HAp regarding pure Ti. The bioactivity of Ti-HAp composites evaluated in simulated body fluid significantly improved with HAp content. The presence of HAp has lowered the cytotoxic effect of Ti-based composites on Hek293 cells.

Characterization of a composite polylactic acid-hydroxyapatite 3D-printing filament for bone-regeneration

Autologous cancellous-bone grafts are the current gold standard for therapeutic interventions in which bone-regeneration is desired. The main limitations of these implants are the need for a secondary surgical site, creating a wound on the patient, the limited availability of harvest-safe bone, and the lack of structural integrity of the grafts. Synthetic, resorbable, bone-regeneration materials could pose a viable treatment alternative, that could be implemented through 3D-printing. We present here the development of a polylactic acid-hydroxyapatite (PLA-HAp) composite that can be processed through a commercial-grade 3D-printer. We have shown that this material could be a viable option for the development of therapeutic implants for bone regeneration. Biocompatibility in vitro was demonstrated through cell viability studies using the osteoblastic MG63 cell-line, and we have also provided evidence that the presence of HAp in the polymer matrix enhances cell attachment and osteogenicity of the material. We have also provided guidelines for the optimal PLA-HAp ratio for this application, as well as further characterisation of the mechanical and thermal properties of the composite. This study encompasses the base for further research on the possibilities and safety of 3D-printable, polymer-based, resorbable composites for bone regeneration.

Synthesis and Corrosion Test of Magnesium Zinc-5% Hydroxyapatite (MgZn-5% wt.Hap) Biocomposites as a Bone Biodegradable Implant Material

In recent years, development of magnesium (Mg) as biodegradable implant very rapidly in orthopedic applications . This is due to its young’s modulus close to young modulus of natural bone . However, Mg implants demonstrate higher biological activity which could cause high degradation rate in human bio-environment. Consequently, needed to develop Mg-based alloys with superior corrosion performance. In the present study, it has been attempted to develop biocomposite of Magnesium Zinc-5% Hydroxyapatite (MgZn-5%HAp) as biodegradable bone implant. The biocomposites were prepared by adding 5 wt. % powders to MgZn powder and then were sintered at temperature 350 o C in vacuum furnace for holding an hour. The characterization of MgZn-5 wt %HA p biocomposite was examined by Scanning Electron Microscopy with Energy Dispersive Spectroscopy ( SEM/EDS ) and X-ray diffraction ( XRD ) while corrosion test ed by potensiostat. The SEM / EDS and XRD results indicate d that some of the Zn atoms have dissolved in Mg to form a MgZn solid solution. The SEM results also showed that the MgZn-5%HAp biocomposite has a microstructure with a matrix Mg and HAp at the grain boundary. The presence of HAp in the sample resulted in a smaller crystallite size and corrosion rate compared to the one with MgZn alloy.

Morphological and thermal characterization of zirconia/hydroxyapatite composites prepared via sol-gel for biomedical applications

The thermal behavior of pure ZrO2 and hydroxyapatite (denoted as Z and HAp, respectively), as well as three composites with different content of Z and HAp (Z90HAp10, Z70HAp30 and Z50HAp50) prepared via sol-gel method has been studied by thermogravimetry (TG) and first-order derivative of TG up to 1200 °C under inert gas atmosphere. Dehydration, loss of alcohol and acetylacetone and a multi-step thermal decomposition processes has been identified by analyzing the gases evolved in each step by Fourier transform infrared spectroscopy (FTIR). Fresh samples of Z-rich composites undergo an abrupt ejection of material from the crucible around 200 °C with noticeable increase of the sample temperature. During the occurrence of this phenomenon FTIR spectra demonstrated the evolution of gases (CO, CO2, acetone and ethylene) due to the simultaneous decomposition of acetylacetone and ethanol, not present in the samples calcined at 120 °C. As far as the structural study is concerned, pure Z crystallizes at 1000 °C in the monoclinic system, but the presence of HAp in the composite materials enables the crystallization of Z in the tetragonal phase. Finally, the amorphization degree increases with increasing the content of Z in all the composites treated at 600 and 1000 °C.

Facile synthesis of magnetic hydroxyapatite-supported nickel oxide nanocomposite and its dye adsorption characteristics

A novel magnetic hydroxyapatite-supported nickel oxide nanocomposite (NiO–HAP@γ-Fe2O3) was successfully prepared using a combination of co-precipitation and wet impregnation methods and was applied to the adsorption of methylene blue from aqueous solution. The presence of HAP, γ-Fe2O3, NiO and all elements in NiO–HAP@γ-Fe2O3 was confirmed by XRD, SEM–EDX and ICP-AES. The structure of the resulting nanocomposite was shown by TEM and SEM–EDX to be rod-shaped, measuring 55.8 ± 16.5 nm in length and 27.1 ± 6.2 nm in width, and on the surface of which was uniformly interspersed with NiO nanoparticles (about 21.4 nm average crystallite size) and γ-Fe2O3 nanoparticles (6.7 ± 2.6 nm in diameter). The novel NiO–HAP@γ-Fe2O3 exhibited a high adsorption rate during the first 20 min and reached an equilibrium within 3 h. The adsorption capacity of NiO–HAP@γ-Fe2O3 was significantly higher than that of its precursors (7.20 mg g−1 vs 0.79–1.31 mg g−1). The superior adsorption performance of the novel nanocomposite, which occurred despite its relatively low surface area, is likely attributable to the synergistic mechanisms facilitated by the presence of mixed metal oxides (NiO and γ-Fe2O3) on the adsorbent as well as by the Lewis acidity and basicity of the components of the adsorbent and the adsorbate. The adsorption kinetics and isotherms were well-fitted by the pseudo-second-order kinetic model and the Langmuir isotherm model, respectively.

Silver-containing calcium phosphate materials of marine origin with antibacterial activity

Hydroxyapatite (Ca10(PO4)6(OH)2 – HAp) is a common material for bone replacement in artificial implants and prostheses, due to its high biocompatibility. In this work we report about the preparation of HAp-based materials of marine origin with antibacterial properties. Bones from cod fish (Gadhus morua) were treated with a dilute AgNO3 solution, to obtain HAp-containing samples with silver as a minor component. The samples were characterised by XRD, FT-IR spectroscopy and SEM, indicating the presence of HAp, β–TCP and some metallic silver. The determination of unit cell parameters, however, indicated that the majority of silver is substituted in the β-TCP lattice in ionic form. The antibacterial activity of these materials was tested towards both Gram-positive and Gram-negative bacterias; results showed that the material is very effective with Gram-negative strains such as Escherichia coli (inactivation rates of 99.82% and 99.999% after 2 and 5h, respectively) and had a smaller but still significant effect on Gram-positive MRSA (91% inactivation rate). These results show the potentials of these samples as infection-resistant bone replacement materials.

Microstructural and Mechanical Evaluation of Laser-Assisted Cold Sprayed Bio-ceramic Coatings: Potential Use for Biomedical Applications

Bio-composite coatings of 20 wt.%, HAP and 80 wt.%, HAP were synthesized on Ti-6Al-4V substrates using LACS technique. The coatings were produced with a laser power of 2.5 kW, powder-laser spot trailing by 5 s. The coatings were analyzed for the microstructures, microhardness, composition, and bio-corrosion using SEM-EDS, XRD, hardness tester, and Metrohm PGSTAT101 machine. SEM images indicated least pores and crack-free coating with dark-spots of Ti-HAP for the 20 wt.%, HAP as opposed to the 80 wt.%, HAP coating which was solid, porous and finely cracked and had semi-melted Ti-HAP particles. The EDS mappings showed high content of HAP for the 80 wt.%, HAP coating. The diffraction patterns were similar, even though the Ti-HAP peak was broader in the 80 wt.%, HAP coating and the HAP intensities were lower for this coating except for the (004) peak. The hardness values taken at the interface inferred that the 80 wt.%, HAP coating was least bonded. It was possible to conclude that when this phase material increased the hardness dropped considerably. The bio-corrosion tests indicated that the presence of HAP in coating leads to a kinetically active coating as opposed to pure titanium coating.

Photopolymerization of phosphoric acid ester-based self-etch dental adhesives

The objective of the study was to gain more understanding on the photopolymerization mechanism and the role of individual monomers in the polymerization behavior of a PAE-based self-etch adhesive system with the presence of HAp and water. The photo-polymerization process of the model adhesive system (2MP/HEMA) was monitored by using real-time attenuated total reflectance Fourier transform infrared (ATR/FT-IR) technique. The effect of monomer ratio, HAp incorporation, and water content were investigated. The degree of conversion (DC) and the polymerization rate (PR) of the adhesives were determined to evaluate the polymerization efficacy. The results showed that the DC and PR increased consistently as the 2MP content increased from 30% to 70%, while they declined drastically as the 2MP content was further elevated to 100%. The incorporation of HAp considerably increased the DC and PR; however, the increase in water content was found to have negative influence on the photopolymerization.

In vitro Biomimetic Construction of Hydroxyapatite–Porcine Acellular Dermal Matrix Composite Scaffold for MC3T3-E1 Preosteoblast Culture

The application of porous hydroxyapatite-collagen (HAp-Collagen) as a bone tissue engineering scaffold is hindered by two main problems: its high cost and low initial strength. As a native 3-dimenssional collagen framework, purified porcine acellular dermal matrix (PADM) has been successfully used as a skin tissue engineering scaffold. Here we report its application as a matrix for the preparation of HAp to produce a bone tissue scaffold through a biomimetic chemical process. The HAp-PADM scaffold has two-level pore structure, with large channels (∼100 μm in diameter) inherited from the purified PADM microstructure and small pores (<100 nm in diameter) formed by self-assembled HAp on the channel surfaces. The obtained HAp-PADM scaffold (S15D) has a compressive elastic modulus as high as 600 kPa. The presence of HAp in sample S15D reduces the degradation rate of PADM in collagenase solution at 37°C. After 7 day culture of MC3T3-E1 pre-osteroblasts, MTT data show no statistically significant difference on pure PADM framework and HAp-PADM scaffold (p > 0.05). Because of its high strength and nontoxicity, its simple preparation method, and designable and tailorable properties, the HAp-PADM scaffold is expected to have great potential applications in medical treatment of bone defects.

Microstructure and mechanical properties of Mg-HAP composites

In the present study, it has been attempted to develop biodegradable Mg-HAP (magnesium-hydroxyapatite) composite materials for bone replacement. At first the HAP powders were prepared by chemical synthesis process and synthesized powders were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Synthesized powders contain HAP as a major phase with tricalcium phosphate (β-TCP) as a minor phase. The Mg-HAP composites were prepared by adding different amounts of HAP powders to Mg melts and finally the billets were extruded. The microstructure of Mg-HAP composite was examined by optical microscope (OM). The presence of HAP in Mg matrix results in decrease of grain size of Mg-HAP composites. The theoretical and experimental hardness of the composites are compared with the addition of HAP. The tensile strength of composites is found to decrease with the addition of HAP, whereas compressive strength increases with HAP.

Preparation of Macroporous Hydroxyapatite/Chitosan-Alginate Composite Scaffolds for Bone Implants

Porous HAp/chitosan-alginate composite scaffolds were successfully synthesized by insitu co-precipitation method. During the preparation of HAp/chitosan-alginate composite scaffolds, the interaction between chitosan-alginate molecules would be reduced with increasing HAp content, with the resulting that the chitosan-alginate molecules were homogeneously dispersed in the composite scaffolds. The chitosan-alginate content was found to be almost consistent as initially added during the preparation. These results imply that chitosan-alginate was almost perfectly incorporated into the composites. It was found that the pore structure of the composite scaffolds with low HAp content was similar to chitosan-alginate scaffolds, and the morphology of uniform microstructure was unaffected by the presence of HAp. However, the pore diameter decreased with increasing the HAp content up to HAp content of 30 wt%, eventually the pore structure was collapsed and the composites scaffolds appeared to be agglomerated at higher HAp content.

Prevalence and distribution of adhesins in invasive non-type b encapsulated Haemophilus influenzae.

Adhesion to the respiratory epithelium plays an important role in Haemophilus influenzae infection. The distribution of H. influenzae adhesins in type b and nontypeable strains has been characterized, but little is known about the prevalence of these factors in non-type b encapsulated strains. We analyzed 53 invasive type a, type e, and type f strains for the presence of hap, hia, hmw, and hif genes; Hap, Hia, and HMW1/2 adhesins; and hemagglutinating pili. The hap gene was ubiquitous, and homologs of hmw and hia were present in 7 of 53 (13.2%) and 45 of 53 (84.9%) strains, respectively. Hap was detected in 28 of 45 (62.2%) hap(+) strains, HMW1/2 was detected in 5 of 7 (71.4%) hmw(+) strains, and Hia was detected in 31 of 45 (68.8%) hia(+) strains. The hif gene cluster was present in 26 of 53 strains (49.1%), and 21 of 26 hif(+) strains (80.8%) agglutinated (HA) red blood cells. Nine isolates exhibited HA but lacked the hif gene cluster. The distribution of adhesin genes correlated with the genetic relatedness of the strains. Strains belonging to one type a clonotype and the major type e clonotype possessed hia but lacked the hif cluster. Strains belonging to the second type a clonotype possessed both hia and hif genes. All type f strains belonging to the major type f clonotype possessed hia and lacked hifB. Although the specific complement of adhesin genes in non-type b encapsulated H. influenzae varies, most invasive strains express Hap and Hia, suggesting these adhesins may be especially important to the virulence of these organisms.

Adsorption of arsenate and arsenite on ferrihydrite in the presence and absence of dissolved organic carbon.

The adsorption of As(V) and As(III) on synthetic two-line ferrihydrite in the presence and absence of a peat humic acid (HAp), Suwannee River fulvic acid (FA), or citric acid (CA) was investigated. Previous work with goethite has demonstrated the ability of dissolved organic carbon (DOC) to decrease As(V) and As(III) adsorption. The results obtained demonstrate that As(V) adsorption on ferrihydrite was decreased only in the presence of CA. Arsenate decreased the adsorption of all organic acids except HAp. Both FA and CA reduced As(III) adsorption on ferrihydrite, while HAp had no effect. Fulvic and citric acid adsorption on ferrihydrite was decreased in the presence of As(III); however, FA and CA adsorption increased at lower pH, which was consistent with decreased As(III) adsorption. Peat humic acid did not decrease As(III) adsorption, and we believe that the adsorption process of HAp and As(III) and As(V) on ferrihydrite are independent of each other. Previously, we observed that As(V) adsorption on goethite decreased in the presence of HAp > FA > CA, while As(III) adsorption on goethite was decreased similarly to that on ferrihydrite in the presence of CA > FA approximately HAp, yet As(III) adsorption on ferrihydrite was greater than on goethite. The observed differences between this study and the earlier study on goethite are believed to be an intricate function of ferrihydrite's surface characteristics, which affect the mechanisms of adsorption and hence the affinity of organic acids such as HAp, FA, and CA for the ferrihydrite surface. As such, the adsorption of DOCs to ferrihydrite are assumed to be less favorable and to occur with a fewer number of ligands, resulting in lower surface coverage of weaker bond strength.

Specific factors influencing histotypic aggregation of chick embryo hepatocytes.

Conditions are described for the reproducible assay of substances affecting the in vitro rate of aggregation of isolated chick embryo hepatocytes. Two low molecular weight (less than 1000) fractions--one that promotes hepatocyte aggregation (HAP) and the other that inhibits this stimulation (HAI)--have been isolated and partially purified from adult chicken liver. One major active component of HAP was identified as taurine (2-aminoethanesulfonate). The presence of HAP during the entire time of assay was required for largest aggregate formation. HAP had no effect on aggregation of chick embryo neural retina, kidney, or heart cells. Our results and the fact that puromycin completely inhibits aggregate formation suggest that HAP and HAI influence the specific synthesis and interaction of membrane macromolecules involved in the aggregation process.