Omer Kaygili

Synthesis and characterization of Ce-substituted hydroxyapatite by sol-gel method.

Both undoped hydroxyapatite (HAp) and three Ce-substituted HAp samples with variable amounts (from 0.5 to 2 at.%) of Ce were synthesized by sol-gel method. The samples were studied by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy to determine the crystallite size, crystallinity degree, phases, functional groups, morphology and elemental composition. In all samples, the amount of HAp exceeded 92%, while the amount of admixture β-TCP was always below 8% and no changes were observed by addition of Ce. The crystallinity degree of the samples was always within 84-89%, while the calculated dimensions of crystallites appeared to be within 26-35nm. The microstructure and elemental composition of all the samples were found to be affected by the addition of Ce.

Strontium substituted hydroxyapatites: Synthesis and determination of their structural properties, in vitro and in vivo performance.

The objective of this study is to present a detailed report related to the synthesis and characterization of strontium substituted hydroxyapatites. Based on this purpose, hydroxyapatite (HAp) bioceramics with different amounts of strontium (e.g., 0, 0.45, 0.90, 1.35, 1.80 and 2.25 at.%) were prepared using a sol-gel method. The effects of Sr substitution on the structural properties and biocompatibility of the samples were studied by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) techniques, in vitro and in vivo tests. All the samples composed of the nanoparticles ranging from 21 to 27 nm. The presence of Sr at low levels influenced the crystal size, crystallinity degree, lattice parameters and volume of the unit cell of the HAp. Both in vitro conditions and soaking period in simulated body fluid (SBF) significantly affected these properties. Especially, the (Ca+Sr)/P molar ratio gradually decreases with increasing soaking period in SBF. Animal experiments revealed the bone formation and osseointegration for all samples, and as compared with other groups, more reasonable, were observed for the sample with the lowest Sr content.

In vitro characterization of polyvinyl alcohol assisted hydroxyapatite derived by sol-gel method.

The synthesis and characterization of sol-gel derived hydroxyapatite (HAp) were investigated with the effects of the addition of polyvinyl alcohol (PVA) to the structural and material in vitro behavior. All samples were soaked in simulated body fluid (SBF) for 14 and 28 days. The characterization of bioceramics before and after immersing in SBF was carried out by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, differential thermal analysis (DTA), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) techniques. After the simulated body fluid period, the crystal structure and phase of HAp samples did not change significantly. The characteristic bands of hydroxyl, phosphate and carbonate groups were detected. HAp exhibited a thermal stability of room temperature to 1000 °C. The surface morphologies of the samples show an evident change with the soaking period in SBF.

Controlling of dielectrical properties of hydroxyapatite by ethylenediamine tetraacetic acid (EDTA) for bone healing applications

The hydroxyapatite (HAp) samples in the presence of various amounts of ethylenediamine tetraacetic acid (EDTA) were prepared by sol-gel method. The effects of EDTA on the crystallinity, phase structure, chemical, micro-structural and dielectric properties of HAp samples were investigated. With the addition of EDTA, the average crystallite size of the HAp samples is gradually decreased from 30 to 22 nm and the crystallinity is in the range of 65-71%. The values of the lattice parameters (a and c) and volume of the unit cell are decreased by stages with the addition of EDTA. The dielectric parameters such as relative permittivity, dielectric loss and relaxation time are affected by the adding of EDTA. The alternating current conductivity of the as-synthesized hydroxyapatites increases with the increasing frequency and obeys the universal power law behavior. The HAp samples exhibit a non-Debye relaxation mechanism. The obtained results that the dielectrical parameters of the HAp sample can be controlled by EDTA.

Structural and dielectric properties of yttrium-substituted hydroxyapatites.

Hydroxyapatite (HAp) samples doped with 0, 2 and 4 at.% of yttrium (Y) were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy attached with energy dispersive X-ray (EDX) spectroscopy, antimicrobial activity tests and dielectric studies. The hydroxyl groups observed in FTIR spectra confirmed the formation of HAp phase in the studied samples. The crystallite size, crystallinity degree and lattice parameters of the samples were changed with Y content. The volume of the unit cell was gradually decreased with the addition of Y. Undoped and Y-containing HAp samples were screened to determine their in vitro antimicrobial activities against the standard strains. It was found that no samples have any antimicrobial effect. The relative dielectric permittivity and dielectric loss are affected by Y content. While the alternating current conductivity increases with increasing frequency, it decreases with increasing Y content.

The effect of gamma-ray irradiation on the electrical conductivity of CuO–PbO glasses

The effect of gamma-ray irradiation on the dc electrical conductivity of CuO–PbO glasses has been studied as a function of temperature. A 33% CuO–67% PbO glass composition has been prepared, using the melt-quenching technique. The samples have been irradiated to a dose of 0.5 MGy using a 60Co γ-source. The electrical conductivity of this glass composition was investigated before and after gamma-ray irradiation. The values of the dc electrical conductivity have been measured from 303 to 373 K, and the activation energy of samples before and after gamma irradiation has been calculated. The observed data show that the electrical conductivity increases with temperature and following gamma irradiation. The electrical conductivity of CuO–PbO can be interpreted in terms of mixed ionic–electronic conduction.

Phytochemical Compounds and Biological Activities of Celtis tournefortii Fruits

Abstract It is known that Celtis species have been used in healing wound, epilepsy crisis, and stomach pain among the people. The antiradical (DPPH, OH, ABTS) activities, phytochemical compounds (total proanthocyanidin, total flavonoid, total phenolic, flavonoids, phenolic acids, sterols, lipid soluble vitamins, fatty acids), antimicrobial, antiproliferative (MCF-7, HCT-116, A2780, PC-3) activities of water, ethanol, methanol extracts of C. tournefortii fruits were evaluated in this study. All the C. tournefortii fruit water extracts were higher scavenged OH radical than standard antioxidant BHT. It was detected that C. tournefortii includes high amount of α-tocopherol (2.65 mg/kg), vitamin D (10.05 mg/kg), ergosterol (78.70 mg/kg), stigmasterol (185.90 mg/kg), unsaturated fatty acids (74.47%). C. tournefortii extracts showed antiproliferative activity on MCF-7, HCT-116, A2780, PC-3 cancer cell lines and antimicrobial activity on some microorganisms when compared to standard antibiotics. Also, this study is the first report about phytochemical contents, antiproliferative, antimicrobial, antiradical properties of C. tournefortii fruits.