Degradation of methylene blue using co-dopants Mg and Se in an hydroxyapatite composite.

In this work, a comparative study was made of different magnesium ion content incorporated into hydroxyapatite (HAP) and modified with selenite ions, with the aim to develop the degradation performance of methylene blue. Although the dopant metal (Mg2+ ) was present at a relatively low ratio, it induced a change in the microstructure, morphology, surface area, external surface charge, particle size, and degradation performance. The effect of magnesium and selenium binary doping on microstructure and degradation of methylene blue was evaluated. The external surface charge measured by zeta potential clarified that the highest negativity was -11.8 mV and this was accomplished in 1.0 Mg/Se-HAP. Furthermore, the roughness average increased from 36.8 nm, reaching 59.2 nm upon the addition of Mg(II). Moreover, transmission electron microscope micrographs showed that compositions were formed as rod shapes. The process of degradation was optimized, showing effectiveness in methylene blue degradation of 62.4% after 150 min of exposure to visible light. Electrostatic attraction and H-bonding, and coordination played vital roles in the adsorption process. The recyclability of the as-prepared compositions demonstrated that the effectiveness had been reduced to ~54.2% after five times of re-use.

Microstructure, morphology and physicochemical properties of nanocomposites containing hydroxyapatite/vivianite/graphene oxide for biomedical applications.

Designing a nanocomposite that accumulates biocompatibility and antimicrobial behaviour is an essential requirement for biomedical applications. Hydroxyapatite (HAP), graphene oxide, and vivianite in one ternary nanocomposite with three phases and shapes led to an increase in cell viability to 97.6% ± 4 for the osteoblast cells in vitro. The obtained nanocomposites were investigated for their structural features using X-ray diffraction, while the microstructure features were analyzed using a scanning electron microscope (SEM) and a transmission electron microscope. The analysis showed a decrease in the crystal size to 13 nm, while the HAP grains reached 30 nm. The elongated shape of vivianite reached 200 nm on SEM micrographs. The monoclinic and hexagonal crystal systems of HAP and vivianite were presented in the ternary nanocomposite. The maximum roughness peak height reached 236.1 nm for the ternary nanocomposite from 203.3 nm, while the maximum height of the roughness parameter reached 440.7 nm for the di-nanocomposite of HAP/graphene oxide from 419.7 nm. The corrosion current density reached 0.004 µA/cm2 . The ferrous (Fe2+ ) and calcium (Ca2+ ) ions released were measured and confirmed. Therefore, the morphology of the nanocomposites affected bacterial activity. This was estimated as an inhibition zone and reached 14.5 ± 0.9 and 13.4 ± 1.1 mm for Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) after 24 h. The increase in viability and the antibacterial activity refer to the compatibility of the nanocomposite in different medical applications.

Biological response, antibacterial properties of ZrO2/hydroxyapatite/graphene oxide encapsulated into nanofibrous scaffolds of polylactic acid for wound healing applications.

Designing proper nanofibrous scaffolds for wound healing applications is a necessity for improving the health care system. Hydroxyapatite (HAP), zirconia (ZrO2), and graphene oxide (GO) nanosheets have been encapsulated in mono, di, or tri phases into nanofibrous scaffolds of polylactic acid (PLA). The structure of nanofibrous scaffolds is confirmed using XRD, XPS, while FESEM inspected the surface morphology. The surface morphology detection exhibited that the scaffolds have been formed in networked nanofibers with diameters from 1.19 to 2.38 to 0.59-1.42 µm, while the maximum height of the roughness increased from 610.4 to 809 nm for HAP@PLA and HAP/ZrO2/GO@PLA, respectively. The contact angle was measured and showed a decreasing trend from 101.2 ± 4.1° and 89.1 ± 5.4° for HAP@PLA and HAP/ZrO2/GO@PLA nanofibrous scaffolds. Moreover, the mechanical properties were examined and revealed that ZrO2 dopant induced a significant enhancement into the tensile strength, which increased from 3.49 ± 0.3 to 8.45 ± 1.1 MPa for the nanofibrous scaffolds of HAP@PLA and HAP/ZrO2/GO@PLA, respectively. The incorporation of ternary phases into PLA nanofibers promoted the cell viability to be around 98.2 ± 5%. The antibacterial potency has been investigated and showed that the activity increased to 69.2 ± 3.6 and 78.1 ± 4.5% against E. coli and S. aureus, respectively. Additionally, human fibroblasts proliferated on the surface and pores of nanofibrous scaffolds and significantly grown upon the compositional variation.

Nanofibrous scaffolds ofϵ-polycaprolactone containing Sr/Se-hydroxyapatite/graphene oxide for tissue engineering applications.

For wound healing applications, a scaffold of biocompatible/porous networks is crucial to support cell proliferation and spreading. Therefore,ϵ-polycaprolactone (PCL) nanofibrous scaffolds containing co-dopants of strontium/selenium in hydroxyapatite (HAP) were modified with different contributions of graphene oxide (GO) via the laser ablation technique. The obtained compositions were investigated using XRD, TEM and FESEM. It was evident that fiber diameters were in the range of 0.15-0.30µm and 0.35-0.83µm at the lowest and highest concentration of GO respectively, while the maximum height of the roughness progressed to 393 nm. The toughness behavior was promoted from 5.77 ± 0.21 to 9.16 ± 0.29 MJ m-3upon GO from the lowest to the highest contribution, while the maximum strain at break reached 148.1% ± 0.49% at the highest concentration of GO. The cell viability indicated that the fibrous scaffold was biocompatible. The investigation of the HFB4 cell attachments towards the fibrous compositions showed that with the increase of GO, cells tended to grow intensively through the scaffolds. Furthermore, the proliferation of cells was observed to be rooted in the porous structure and spreading on the surface of the scaffold. This progression of cells with an increase in GO content may provide a simple strategy not only to enhance the mechanical properties, but also to manipulate a nanofibrous scaffold with proper behaviors for biomedical applications.

Gold as a dopant in selenium-containing carbonated hydroxyapatite fillers of nanofibrous ε-polycaprolactone scaffolds for tissue engineering.

The necessity for finding a compromise between mechanical and biological properties of biomaterials spurs the investigation of the new methods to control and optimize scaffold processing for tissue engineering applications. A scaffold composed of ε-polycaprolactone fibers reinforced with carbonated hydroxyapatite (CHAP) dually doped with selenite oxyanions (Se) and cationic gold (Au) was synthesized using the electrospinning technique and studied at different contents of Au. Despite the fact that the amount of the Au dopant was relatively low, variations to it induced significant microstructural changes, affecting the cell response and mechanical properties in return. Au nanoparticles segregated as a separate, ternary phase at the highest Au content, corresponding to x = 0.8 in the AuxCa10-1.5x(PO4)5.8(SeO2)0.2-x(CO3)x(OH)2 stoichiometric formula of Au/Se-CHAP. Their appearance coincided with a rapid degeneration in the density and adhesion of osteoblastic cells grown on the scaffolds. In spite of this adverse effect, the cell spreading and proliferation improved with increasing the amount of the Au dopant in the Au/Se-CHAP particles of the scaffold in the x = 0.0-0.6 range, suggesting that the biological effects of Au in the ionic and in the nanoparticulate form on the implant integration process may be diametrically opposite. The addition of Au had a dramatic effect on some mechanical properties, such as toughness and strain at break, which were both reduced twice upon the introduction of Au into Se-CHAP at the lowest amount (x = 0.2) compared to the Au-free composite. The significant variation of physical and biological properties of these composite scaffolds with trace changes in the content of the Au dopant inside the ceramic filler particles is promising, as it provides a new, relatively subtle avenue for tailoring the properties of tissue engineering scaffolds for their intended biomedical applications.

Physico-mechanical and morphological features of zirconia substituted hydroxyapatite nano crystals.

Zirconia doped Hydroxyapatite (HAP) nanocrystals [Ca10(PO4)6-x(ZrO2)x(OH)2]; (0 ≤ x ≤ 1 step 0.2) were synthesized using simple low cost facile method. The crystalline phases were examined by X-ray diffraction (XRD). The crystallinity percentage decreased with increasing zirconia content for the as-synthesized samples. The existence of zirconia as secondary phase on the grain boundaries; as observed from scanning electron micrographs (FESEM); resulted in negative values of microstrain. The crystallite size was computed and the results showed that it increased with increasing annealing temperature. Thermo-gravimetric analysis (TGA) assured the thermal stability of the nano crystals over the temperature from room up to 1200 °C depending on the zirconia content. The corrosion rate was found to decrease around 25 times with increasing zirconia content from x = 0.0 to 1.0. Microhardness displayed both compositional and temperature dependence. For the sample (x = 0.6), annealed at 1200 °C, the former increased up to 1.2 times its original value (x = 0.0).