Feray Bakan

Evaluation of cytotoxic, oxidative stress and genotoxic responses of hydroxyapatite nanoparticles on human blood cells

The present study was designed to investigate genotoxic and cytotoxic effects and oxidative damage of increasing concentrations of nano‐hydroxyapatite (5, 10, 20, 50, 75, 100, 150, 300, 500 and 1000 ppm) in primary human blood cell cultures. Cell viability was detected by [3‐(4,5‐dimethyl‐thiazol‐2‐yl) 2,5‐diphenyltetrazolium bromide] assay and lactate dehydrogenase release, while total antioxidant capacity and total oxidative stress levels were determined to evaluate the oxidative injury. The DNA damage was also analyzed by sister chromatid exchange, micronuclei, chromosome aberration assays and 8‐oxo‐2‐deoxyguanosine level as indicators of genotoxicity. The results of [3‐(4,5‐dimethyl‐thiazol‐2‐yl) 2,5‐diphenyltetrazolium bromide] and lactate dehydrogenase assays showed that the higher concentrations (150, 300, 500 and 1000 ppm) of hydroxyapatite nanoparticles (HAP NPs) decreased cell viability. HAP NPs led to increases of total oxidative stress (300, 500 and 1000 ppm) levels and decreased total antioxidant capacity (150, 300, 500 and 1000 ppm) levels in cultured human blood cells. On the basis of increasing concentrations, HAP NPs caused significant increases of sister chromatid exchange, micronuclei, chromosome aberration rates and 8‐oxo‐2‐deoxyguanosine levels as compared to untreated culture. In conclusion, the obtained in vitro results showed that HAP NPs had dose‐dependent effects on inducing oxidative damage, genotoxicity and cytotoxicity in human blood cells. Copyright

Toxicity assessment of hydroxyapatite nanoparticles in rat liver cell model in vitro

Hydroxyapatite nanoparticles (HAP NPs) are widely used for preparations of biomedical and biotechnological fields such as drug delivery, gene therapy, and molecular imaging. However, the current toxicological knowledge about HAP NPs is relatively limited. The present study was designed to investigate the toxicity potentials of various concentrations (0–1000 µg cm−2) of HAP NPs in cultured primary rat hepatocytes. Cell viability was detected by 3-(4,5-dimethyl-thiazol-2-yl) 2,5-diphenyltetrazolium bromide (MTT) assay and lactate dehydrogenase (LDH) release, while total antioxidant capacity (TAC) and total oxidative stress (TOS) levels were determined to evaluate the oxidative injury. The DNA damage was also analyzed via scoring liver micronuclei rates and determining 8-oxo-2-deoxyguanosine (8-OH-dG) levels. The results of MTT and LDH assays showed that the higher concentrations of dispersed HAP NPs (300, 500, and 1000 µg cm−2) decreased cell viability. Also, HAP NPs increased TOS (500 and 1000 µg cm−2) levels and decreased TAC (300, 500, and 1000 µg cm−2) levels in cultured hepatocytes. On the basis of increasing doses, the NPs as depending on dose caused significant increases of the number of micronucleated hepatocytes and 8-OH-dG levels as compared to control culture. Furthermore, the highest concentration of HAP NPs (1000 µg cm−2) exhibited cytotoxic activity. Based on these results, HAP NPs have a dose-dependent toxic effect in rat hepatocytes. Further extensive research in this field is promising and reasonable.

Electrophoretic deposition of hydroxyapatite-hexagonal boron nitride composite coatings on Ti substrate

In this study, commercial pure titanium samples were coated with nano hydroxyapatite-nano hexagonal boron nitride (nano HA-nano hBN) composite by electrophoretic deposition (EPD). The effect of process parameters (applied voltage, deposition time and solid concentration) on the coating morphology, thickness and the adhesion behavior were studied systematically and crack free nano hBN-nano HA composite coating production was achieved for developing bioactive coatings on titanium substrates for orthopedic applications. For the examination of structural and morphological characteristics of the coating surfaces, various complementary analysis methods were performed. For the structural characterization, XRD and Raman Spectroscopy were used while, Scanning Electron Microscopy (SEM) equipped with an energy dispersive spectrometer (EDS) and Transmission Electron Microscopy (TEM) techniques were carried out for revealing the morphological characterization. The results showed that nano HA-nano hBN were successfully deposited on Ti surface with uniform, crack-free coating by EPD. The amounts of hBN in suspension are considered to have no effect on coating thickness. By adding hBN into HA, the morphology of HA did not change and hBN has no significant effect on porous structure. These nanostructured surfaces are expected to be suitable for proliferation of cells and have high potential for bioactive materials.

Study of the boron levels in serum after implantation of different ratios nano-hexagonal boron nitride-hydroxy apatite in rat femurs.

Boron and its derivatives are effective in bone recovery and osteointegration. However, increasing the boron levels in body liquids may cause toxicity. The aim of our study is to investigate serum boron levels using ICP-MS after implantation of different ratios of nano-hBN-HA composites in rat femurs. All rats were (n=126) divided into five experimental groups (n=24) and one healthy group (6 rats); healthy (Group1), femoral defect + %100 HA (Group2), femoral defect + %2.5 hBN + %97.5 HA (Group3), femoral defect + %5 hBN + %95 HA (Group4), femoral defect + %10 hBN + %90 HA (Group5), femoral defect + %100 hBN (Group6). The femoral defect was created in the distal femur (3mm drill-bit). Each implant group was divided into four different groups (n=24) also 6 rats sacrificed for each groups in one week intervals during four weeks. In our results; at 1, 2, 3, and 4 weeks after implantation near bone tissue, serum levels of boron were evaluated using ICP-MS. We demonstrated that neither short-term nor long-term implantation of hBN-HA composite resulted in statistically increased serum boron levels in experimental groups compared to healthy group. In conclusion, this study investigated the implant material produced form hBN-HA for the first time. Our data suggest that hBN is a new promising target for biomaterial and implant bioengineers.

Diagonal Method to Measure Synergy Among Any Number of Drugs

A synergistic drug combination has a higher efficacy compared to the effects of individual drugs. Checkerboard assays, where drugs are combined in many doses, allow sensitive measurement of drug interactions. However, these assays are costly and do not scale well for measuring interaction among many drugs. Several recent studies have reported drug interaction measurements using a diagonal sampling of the traditional checkerboard assay. This alternative methodology greatly decreases the cost of drug interaction experiments and allows interaction measurement for combinations with many drugs. Here, we describe a protocol to measure the three pairwise interactions and one three-way interaction among three antibiotics in duplicate, in five days, using only three 96-well microplates and standard laboratory equipment. We present representative results showing that the three-antibiotic combination of Levofloxacin + Nalidixic Acid + Penicillin G is synergistic. Our protocol scales up to measure interactions among many drugs and in other biological contexts, allowing for efficient screens for multi-drug synergies against pathogens and tumors.

Analysis of Deterioration Phenomena in a Koran by Nineteenth Century Ottoman Calligrapher Mehmed Şevki

Abstract A Koran written by Mehmed Şevki is the subject of this comparative analysis. This manuscript displayed an extensive degree of deterioration in 28 of the folios, while the rest of the manuscript is in considerably better condition. The aforementioned deteriorated sections of the book proved to be brittle and much darker in colour compared to the rest of this manuscript. The possible cause for this condition was ascertained using complementary techniques including the utilisation of micro-chemical (spot) tests, SEM-EDS, FTIR and Raman spectroscopy. The Micro-chemical Herzberg test indicated rag fibres in the paper used for the Koran, while the Raspail test #1 revealed rosin only in the sizing material of the deteriorated folios. SEM-EDS identified the presence of iron in all layers of the deteriorated folios but not in the stable folios. These results led subsequently to the conclusion that the deterioration of the folios was in fact related to the acid-catalysed hydrolysis due mainly to the presence of rosin and oxidation processes promoted by iron ions. This finding was also supported by FTIR analysis. The analyses indicated that different sizing materials had been used in the papermaking process of the two types of folios. In addition, Raman, EDS and HPLC techniques were also applied for the characterization of the inks and dyes. The results showed that inks and dyes were consistent throughout the entire text, thus suggesting calligrapher Mehmed Şevki and illuminator Hüseyin processed the book continually. It is plausible that calligrapher Mehmed Şevki changed his paper supply during the writing process which is why today we see a variety of differences in the condition of the papers.

Structural and chemical analysis of hydroxyapatite (HA)-Boron nitride (BN) nanocomposites sintered under different atmospheric conditions

Calcium phosphate derivatives have been widely employed in medical and dental applications for hard tissue repair, as they are the main inorganic constitution of hard tissue; such as bones and teeth. Owing to their excellent osteoconductive and bioactive properties, hydroxyapatite- (HA) based ceramics are the best candidates of this group for medical, bioscience, and dental applications. However, when replacing a bone or tooth, HA is not able to sustain similar mechanical properties. In this study, to improve the mechanical properties, nanoscale hexagonal boron nitride with different compositional percentages was added to the nano HA to form composites. The effect of compositional changes and sintering parameters on microstructural and morphological properties of the ceramic composites was comparatively investigated. Detailed chemical characterization of the composite materials was carried out using X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, and energy-dispersive X-ray spectroscopy, whereas scanning electron microscopy and atomic force microscopy investigations were employed to monitor morphological and surface features. Additional transmission electron microscopy investigations were carried out to reveal the nanostructure and crystal structure of the composites.

Development of Functional Surfaces on High-Density Polyethylene (HDPE) via Gas-Assisted Etching (GAE) Using Focused Ion Beams.

Irradiation damage, caused by the use of beams in electron and ion microscopes, leads to undesired physical/chemical material property changes or uncontrollable modification of structures. Particularly, soft matter such as polymers or biological materials is highly susceptible and very much prone to react on electron/ion beam irradiation. Nevertheless, it is possible to turn degradation-dependent physical/chemical changes from negative to positive use when materials are intentionally exposed to beams. Especially, controllable surface modification allows tuning of surface properties for targeted purposes and thus provides the use of ultimate materials and their systems at the micro/nanoscale for creating functional surfaces. In this work, XeF2 and I2 gases were used in the focused ion beam scanning electron microscope instrument in combination with gallium ion etching of high-density polyethylene surfaces with different beam currents and accordingly different gas exposure times resulting at the same ion dose to optimize and develop new polymer surface properties and to create functional polymer surfaces. Alterations in the surface morphologies and surface chemistry due to gas-assisted etching-based nanostructuring with various processing parameters were tracked using high-resolution SEM imaging, complementary energy-dispersive spectroscopic analyses, and atomic force microscopic investigations.

Size and Dispersion Control of Pt Nanoparticles Grown Upon Graphite-Derived Nanosheets

Graphite oxide (GO) nanosheets, graphene nanosheets (GNS), and nanocomposites comprising of GO or GNS coated with polypyrrole (PPy) were prepared and assessed for their ability to influence the surface deposition and growth of Pt nanoparticles. GO was obtained from graphite via oxidation and exfoliation, and GNS was obtained from GO in a subsequent reduction. Both GO and GNS were coated with PPy via in situ polymerization of pyrrole (Py), forming surface-enhanced materials. Scanning electron microscope, energy-dispersive x-ray, transmission electron microscopy, electron energy loss spectroscopy, Raman, and atomic force microscope findings showed that the Pt nanoparticle loading, agglomeration size, aggregate morphology, and surface dispersion varied according to the nanosheet surface, nanocomposite type, and Py/nanosheet feed ratio. Surface oxygen functionalization along GO, GNS, and their nanocomposites influenced the loading, dispersivity, and morphology of nanoparticle agglomerates. PPy/GO nanocomposites yielded an improved nanoagglomerate surface dispersion and loading compared to samples. The PPy-coated substrates offered a greater intrinsic propensity for redox processes, resulting in higher Pt loadings. Additionally, these nanocomposites provided more surface reduction sites compared to bare nanosheets, and the additional sites contributed toward forming smaller, more homogeneously dispersed Pt nanoparticle agglomerates. Bringing together the electrical properties of PPy and physicomechanical traits of carbon nanosheets, it follows to reason that the nanocomposites produced, particularly GO-based nanocomposites, offer promise as a nanoparticle support material for use in catalysis, electrocatalysis, and hydrogen storage.