Browsing by Author "Tasdemir, S"

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    In vitro engineered models of neurodegenerative diseases
    Morcimen, ZG; Tasdemir, S; Sendemir, A
    Neurodegeneration is a catastrophic process that develops progressive damage leading to functional and structural loss of the cells of the nervous system and is among the biggest unavoidable problems of our age. Animal models do not reflect the pathophysiology observed in humans due to distinct differences between the neural pathways, gene expression patterns, neuronal plasticity, and other disease-related mechanisms in animals and humans. Classical in vitro cell culture models are also not sufficient for pre-clinical drug testing in reflecting the complex pathophysiology of neurodegenerative diseases. Today, modern, engineered techniques are applied to develop multicellular, intricate in vitro models and to create the closest microenvironment simulating biological, biochemical, and mechanical characteristics of the in vivo degenerating tissue. In THIS review, the capabilities and shortcomings of scaffold-based and scaffold-free techniques, organoids, and microfluidic models that best reflect neurodegeneration in vitro in the biomimetic framework are discussed.
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    Surface Area of Graphene Governs Its Neurotoxicity
    Tasdemir, S; Morçimen, ZG; Dogan, AA; Görgün, C; Sendemir, A
    Due to their uniquephysicochemical properties, graphene and itsderivatives are widely exploited for biomedical applications. It hasbeen shown that graphene may exert different degrees of toxicity inin vivo or in vitro models when administered via different routesand penetrated through physiological barriers, subsequently beingdistributed within tissues or located within cells. In this study,in vitro neurotoxicity of graphene with different surface areas (150and 750 m(2)/g) was examined on dopaminergic neuron modelcells. SH-SY5Y cells were treated with graphene possessing two differentsurface areas (150 and 750 m(2)/g) in different concentrationsbetween 400 and 3.125 mu g/mL, and the cytotoxic and genotoxiceffects were investigated. Both sizes of graphene have shown increasedcell viability in decreasing concentrations. Cell damage increasedwith higher surface area. Lactate dehydrogenase (LDH) results haveconcluded that the viability loss of the cells is not through membranedamage. Neither of the two graphene types showed damage through lipidperoxidation (MDA) oxidative stress pathway. Glutathione (GSH) valuesincreased within the first 24 and 48 h for both types of graphene.This increase suggests that graphene has an antioxidant effect onthe SH-SY5Y model neurons. Comet analysis shows that graphene doesnot show genotoxicity on either surface area. Although there are manystudies on graphene and its derivatives on their use with differentcells in the literature, there are conflicting results in these studies,and most of the literature is focused on graphene oxide. Among thesestudies, no study examining the effect of graphene surface areas onthe cell was found. Our study contributes to the literature in termsof examining the cytotoxic and genotoxic behavior of graphene withdifferent surface areas.
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    Design of chemobrionic and biochemobrionic scaffolds for bone tissue engineering
    Guler, BA; Morçimen, ZG; Tasdemir, S; Demirel, Z; Turunç, E; Sendemir, A; Imamoglu, E
    Chemobrionic systems have attracted great attention in material science for development of novel biomimetic materials. This study aims to design a new bioactive material by integrating biosilica into chemobrionic structure, which will be called biochemobrionic, and to comparatively investigate the use of both chemobrionic and biochemobrionic materials as bone scaffolds. Biosilica, isolated from Amphora sp. diatom, was integrated into chemobrionic structure, and a comprehensive set of analysis was conducted to evaluate their morphological, chemical, mechanical, thermal, and biodegradation properties. Then, the effects of both scaffolds on cell biocompatibility and osteogenic differentiation capacity were assessed. Cells attached to the scaffolds, spread out, and covered the entire surface, indicating the absence of cytotoxicity. Biochemobrionic scaffold exhibited a higher level of mineralization and bone formation than the chemobrionic structure due to the osteogenic activity of biosilica. These results present a comprehensive and pioneering understanding of the potential of (bio)chemobrionics for bone regeneration.
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    Beneficial effects of apricot-feeding on myocardial ischemia-reperfusion injury in rats
    Parlakpinar, H; Olmez, E; Acet, A; Ozturk, F; Tasdemir, S; Ates, B; Gul, M; Otlu, A
    The present study was undertaken to evaluate the cardio-protective potential of apricot-feeding in the ischemia-reperfusion (I/R) model of rats in vivo. Rats were divided into three groups of 12 rats each. Group 1 was fed with a standard rat chow, groups 2 and 3 were fed with a standard rat chow supplemented with 10% or 20% dried apricot during 3 months before the beginning of I/R studies. To produce I/R, the left main coronary artery was occluded for 30 min, followed by 120 min reperfusion, in anesthetized rats. Infarct sizes were found significantly decreased in 10% (55.0 +/- 4.3%) and 20% (57.0 +/- 2.9%) apricot-fed groups compared to control group (68.7 +/- 2.0%). Light and electron microscopic evaluations of hearts also demonstrated similar beneficial effects on I/R injury in apricot-fed both groups. Total phenolic contents, DPPH radical scavenging and ferric-reducing power as in vitro antioxidant capacities of rat chows were significantly increased after supplementation with apricot for each ratio. Cu, Zn Superoxide dismutase (Cu, Zn SOD) and catalase (CAT) activities were increased, and lipid peroxidation was decreased significantly in the hearts of 20% apricot-fed group after I/R. In conclusion, we clearly demonstrated in vivo cardio-protective activity of apricot-feeding related to its antioxidant phenolic contents in rats subjected to myocardial I/R. (C) 2009 Elsevier Ltd. All rights reserved.
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    Comparison of the osteogenic differentiation capacity of adipose tissue derived mesenchymal stem cells from humans and rats
    Erden Tayhan, S; Tasdemir, S; Deliloglu Gürhan, SI; Mir, E
    Mesenchymal stem cells (MSCs) can be found in many types of adult tissues such as the bone marrow, adipose, placenta, liver, and periosteum. Recently, adipose tissue-derived MSCs (ADMSCs) have become one the most preferred MSC types because of their fast proliferation rate, abundance, and high plasticity for variable cell types. It is known that ADMSCs are able to differentiate into various cells, including osteoblasts, so they are quite promising for orthopedic clinical trials. The present study aimed to compare the osteogenic differentiation conditions of MSCs from human adipose tissue (hADMSC) and those of MSCs from rat adipose tissue (rADMSC). Therefore, differentiation experiments with five different media and two (human and rat) ADMSC types were performed and the mineralization responses of hADMSCs and rADMSCs were different.