Person: OKTAR, FAİK NÜZHET
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OKTAR
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FAİK NÜZHET
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Publication Metadata only Synthesis and characterization of antibacterial drug loaded beta-tricalcium phosphate powders for bone engineering applications(SPRINGER, 2020) OKTAR, FAİK NÜZHET; Topsakal, Aysenur; Ekren, Nazmi; Kilic, Osman; Oktar, Faik N.; Mahirogullari, Mahir; Ozkan, Ozan; Sasmazel, Hilal Turkoglu; Turk, Mustafa; Bogdan, Iuliana M.; Stan, George E.; Gunduz, OguzhanPowders of beta-tricalcium phosphate [beta-TCP, beta-Ca-3(PO4)(2)] and composite powders of beta-TCP and polyvinyl alcohol (PVA) were synthesized by using wet precipitation methods. First, the conditions for the preparation of single phase beta-TCP have been delineated. In the co-precipitation procedure, calcium nitrate and diammonium hydrogen phosphate were used as calcium and phosphorous precursors, respectively. The pH of the system was varied in the range 7-11 by adding designed amounts of ammonia solution. The filtered cakes were desiccated at 80 degrees C and subsequently calcined at different temperatures in the range between 700-1100 degrees C. Later on, rifampicin form II was used to produce drug-loaded beta-TCP and PVA/beta-TCP powders. All the synthesized materials have been characterized from morphological (by scanning electron microscopy) and structural-chemical (by X-ray diffraction and Fourier transform infrared spectroscopy) point of view. The drug loading capacity of the selected pure beta-TCP powder has been assessed. The biological performance (cytocompatibility in fibroblast cell culture and antibacterial efficacy against Escherichia coli and Staphylococcus aureus) has been tested with promising results. Application perspectives of the designed drug-bioceramic-polymer blends are advanced and discussed. [GRAPHICS] .Publication Metadata only Part 2: biocompatibility evaluation of hydroxyapatite-based clinoptilolite and Al2O3 composites(SPRINGER, 2017) OKTAR, FAİK NÜZHET; Kalkandelen, C.; Suleymanoglu, M.; Kuruca, S. E.; Akan, A.; Oktar, F. N.; Gunduz, O.The biocompatibility of clinoptilolite/alumina/bovine hydroxyapatite (Cp - Al2O3 - BHA) composite, at different ratio obtained by powder pressing process, were investigated studying the behavior of osteosarcoma (SAOS-2) cells. The biocompatibility was examined by means of cytotoxicity and cytocompatibility tests. The structure and morphology of bioceramic composites were studied by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) technique. The results showed that these materials have no toxic effects. The natural composite that fabricated in this study may be a promising approach for bone engineering applications.Publication Metadata only Studies on goat hydroxyapatite/commercial inert glass biocomposites(SPRINGER, 2019) OKTAR, FAİK NÜZHET; Akyurt, N.; Yetmez, M.; Oktar, F. N.In this study, mechanical properties and microstructural analysis of goat-derived hydroxyapatite/commercial inert glass biocomposites are considered in the temperature range between 1000 and 1300 degrees C. The results indicate that the best values of maximum compressive strength and microhardness are achieved in the samples sintered at 1200 degrees C for the glass in the weight of 5 and 10%. Moreover, above 1000 degrees C, decomposition of hydroxyapatite and new phase formations such as whitlockite and silicocarnotite play also a major role in the hardness and strength for goat hydroxyapatite/commercial inert glass biocomposites.Publication Metadata only Hydroxyapatite-TiO2 composites(ELSEVIER SCIENCE BV, 2006) OKTAR, FAİK NÜZHET; Oktar, FNThis article reports the mechanical properties, the microstructure, and the crystallography of composite materials made of hydroxyapatite, obtained from natural bovine bone, and TiO2 (5 and 10 wt.%), which were sintered at different temperatures between 1000 and 1300 degrees C. Higher sintering temperatures resulted in better densification. The samples sintered at 1300 degrees C had the highest microhardness. The best compressive strengths were obtained after sintering at 1300 degrees C for the samples containing 5% TiO2, and at 1200 degrees C for the samples with 10% TiO2. (c) 2005 Elsevier B.V. All rights reserved.Publication Metadata only Preparation and evaluation of cerium oxide-bovine hydroxyapatite composites for biomedical engineering applications(ELSEVIER SCIENCE BV, 2014) OKTAR, FAİK NÜZHET; Gunduz, O.; Gode, C.; Ahmad, Z.; Gokce, H.; Yetmez, M.; Kalkandelen, C.; Sahin, Y. M.; Oktar, F. N.The fabrication and characterization of bovine hydroxyapatite (BHA) and cerium oxide (CeO2) composites are presented. CeO2 (at varying concentrations 1, 5 and 10 wt%) were added to calcinated BHA powder. The resulting mixtures were shaped into green cylindrical samples by powder pressing (350 MPa) followed by sintering in air (1000-1300 degrees C for 4 h). Density, Vickers microhardness (HV), compression strength, scanning electron microscopy (SEM) and X-ray diffraction (XRD) studies were performed on the products. The sintering behavior, microstructural characteristics and mechanical properties were evaluated. Differences in the sintering temperature (for 1 wt% CeO2 composites) between 1200 and 1300 degrees C, show a 3.3% increase in the microhardness (564 and 582.75 HV, respectively). Composites prepared at 1300 degrees C demonstrate the greatest compression strength with comparable results for 5 and 10 wt% CeO2 content (106 and 107 MPa) which are significantly better than those for 1 wt% and those that do not include any CeO2 (90 and below 60 MPa, respectively). The results obtained suggest optimal parameters to be used in preparation of BHA and CeO2 composites, while also highlighting the potential of such materials in several biomedical engineering applications. (C) 2014 Elsevier Ltd. All rights reserved.Publication Metadata only Glioblastoma cell adhesion properties through bacterial cellulose nanocrystals in polycaprolactone/gelatin electrospun nanofibers(ELSEVIER SCI LTD, 2020) YILMAZ, BETÜL; Unal, Semra; Arslan, Sema; Yilmaz, Betul Karademir; Kazan, Dilek; Oktar, Faik Nuzhet; Gunduz, OguzhanGlioblastoma (GBM), the most common and extremely lethal type of brain tumor, is resistant to treatment and shows high recurrence rates. In the last decades, it is indicated that standard two-dimensional (2D) cell culture is inadequate to improve new therapeutic strategies and drug development. Hence, well-mimicked three-dimensional (3D) tumor platforms are needed to bridge the gap between in vitro and in vivo cancer models. In this study, bacterial cellulose nano-crystal (BCNC) containing polycaprolactone (PCL) /gelatin (Gel) nanofibrous composite scaffolds were successfully fabricated by electrospinning for mimicking the extracellular matrix of GBM tumor. The fiber diameters in the nanofibrous matrix were increased with an increased concentration of BCNC. Moreover, fiber morphology changed from the smooth formation to the beaded formation by increasing the concentration of the BCNC suspension. In-vitro biocompatibilities of nanofibrous scaffolds were tested with U251 MG glioblastoma cells and improved cell adhesion and proliferation was compared with PCL/Gel. PCL/Gel/BCNC were found suitable for enhancing axon growth and elongation supporting communication between tumor cells and the microenvironment, triggering the process of tumor recurrence. Based on these results, PCL/Gel/BCNC composite scaffolds are a good candidate for biomimetic GBM tumor platform.Publication Metadata only Reinforcing of Biologically Derived Apatite with Commercial Inert Glass(SAGE PUBLICATIONS LTD, 2009) OKTAR, FAİK NÜZHET; Gunduz, O.; Ahmad, Z.; Ekren, N.; Agathopoulos, S.; Salman, S.; Oktar, F. N.Apatite-based ceramics, derived from fine powder of calcinated bovine-bone (BHA), were successfully reinforced with 5 and 10 wt% commercial inert glass (CIG), which contained biocompatible elements, via sintering at different temperatures between 1000 and 1300 degrees C. The products were subjected to mechanical testing and microstructural and crystallographic analyses. Comparison of the experimental results with those from earlier similar studies shows that CIG is superior for reinforcing of BHA ceramics compared with other bioactive glasses. Provided that the CIG addition does not exceed a certain limit, optimally being approximately 5 wt%, the resultant BHA-CIG materials can exhibit high strength after sintering and remarkable resistance toward over-firing at 1300 degrees C. The influence of the amount of CIG on the developed microstructure and crystalline structure after sintering at different temperatures is discussed.Publication Metadata only Synthesis, characterization, and biological properties of composites of hydroxyapatite and hexagonal boron nitride(WILEY, 2018) OKTAR, FAİK NÜZHET; Unal, Semra; Ekren, Nazmi; Sengil, Ahmet Z.; Oktar, Faik N.; Irmak, Ster; Oral, Ozlem; Sahin, Yesim M.; Kilic, Osman; Agathopoulos, Simeon; Gunduz, OguzhanHydroxyapatite (HA), obtained from bovine bones, was successfully reinforced with hexagonal boron nitrite (h-BN). h-BN/HA composites, with BN content up to 1.5 wt %, were sintered at various temperatures between 1000 and 1300 degrees C, in air. Well-sintered samples were obtained after sintering at 1200 and 1300 degrees C. The presence of h-BN contributed to dense, fine, and well-crystallized microstructure. The results of X-ray diffraction analysis and FT-IR spectroscopy showed that the produced composites comprised biphasic beta-TCP/HCA (HCA: carbonate partially substituted HA). High values of mechanical properties were achieved, namely compression strength 155 MPa for the sample 0.5% h-BN/HA and Vickers microhardness of 716 HV for the samples 1.5% h-BN/HA, both sintered at 1300 degrees C. U2OS human bone osteosarcoma proliferation and cell viability showed no adverse effect in the presence of h-BN/HA, suggesting the potential use of the produced materials as safe biomaterials in bone tissue engineering. (C) 2017 Wiley Periodicals, Inc.Publication Metadata only Water resistance of bone-cements reinforced with bioceramics(ELSEVIER SCIENCE BV, 2007) OKTAR, FAİK NÜZHET; Daglilar, S.; Erkan, M. E.; Gunduz, O.; Ozyegin, L. S.; Salman, S.; Agathopoulos, S.; Oktar, F. N.The water absorption behavior of bone-cements of PMMA reinforced with 1.5 wt.%, 2.5 wt.%, and 3.5 wt.% silane-treated powders of hydroxyapatite (synthetic, or derived from bovine bones, or teeth enamel), beta-tricalcium phosphate (TCP), bioactive glass (45S5), and zirconia, was investigated. The experimental results showed that addition of calcium phosphate in the polymeric matrix favors water absorption except in the case of enamel hydroxyapatite. Water uptake is also suppressed when 45S5-bioglass or zirconia is added. The solubility is not affected by addition of hydroxyapatite or 45S5-bioglass but it increases when beta-TCP or zirconia is added. A superior behavior of bone-cements reinforced with bioglass-45S5 and enamel hydroxyapatite can be suggested. (c) 2006 Elsevier B.V. All rights reserved.Publication Metadata only Bond-coating in plasma-sprayed calcium-phosphate coatings(SPRINGER, 2006) OKTAR, FAİK NÜZHET; Oktar, F. N.; Yetmez, M.; Agathopoulos, S.; Goerne, T. M. Lopez; Goller, G.; Ipeker, I.; Ferreira, J. M. F.The influence of bond-coating on the mechanical properties of plasma-spray coatings of hydroxyatite on Ti was investigated. Plasma-spray powder was produced from human teeth enamel and dentine. Before processing the main apatite coating, a very thin layer of Al2O3/TiO2 was applied on super clean and roughened, by Al2O3 blasting, Ti surface as bond-coating. The experimental results showed that bond-coating caused significant increase of the mechanical properties of the coating layer: In the case of the enamel powder from 6.66 MPa of the simple coating to 9.71 MPa for the bond-coating and in the case of the dentine powder from 6.27 MPa to 7.84 MPa, respectively. Both tooth derived powders feature high thermal stability likely due to their relatively high content of fluorine. Therefore, F-rich apatites, such those investigated in this study, emerge themselves as superior candidate materials for calcium phosphate coatings of producing medical devices. The methods of apatite powder production and shaping optimization of powder particles are both key factors of a successful coating. The methods used in this study can be adopted as handy, inexpensive and reliable ways to produce high quality of powders for plasma spray purposes.