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Permanent URI for this collectionhttps://hdl.handle.net/11443/932

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Author: search.filters.author.Hasirci, Vasif

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Now showing 1 - 6 of 6
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    Evaluating Oxygen Tensions Related to Bone Marrow and Matrix for MSC Differentiation in 2D and 3D Biomimetic Lamellar Scaffolds
    (MDPI, 2021-01-01) Sayin, Esen; Baran, Erkan Turker; Elsheikh, Ahmed; Mudera, Vivek; Cheema, Umber; Hasirci, Vasif
    The physiological O-2 microenvironment of mesenchymal stem cells (MSCs) and osteoblasts and the dimensionality of a substrate are known to be important in regulating cell phenotype and function. By providing the physiologically normoxic environments of bone marrow (5\%) and matrix (12\%), we assessed their potential to maintain stemness, induce osteogenic differentiation, and enhance the material properties in the micropatterned collagen/silk fibroin scaffolds that were produced in 2D or 3D. Expression of osterix (OSX) and vascular endothelial growth factor A (VEGFA) was significantly enhanced in the 3D scaffold in all oxygen environments. At 21\% O-2, OSX and VEGFA expressions in the 3D scaffold were respectively 13,200 and 270 times higher than those of the 2D scaffold. Markers for assessing stemness were significantly more pronounced on tissue culture polystyrene and 2D scaffold incubated at 5\% O-2. At 21\% O-2, we measured significant increases in ultimate tensile strength (p < 0.0001) and Young's modulus (p = 0.003) of the 3D scaffold compared to the 2D scaffold, whilst 5\% O-2 hindered the positive effect of cell seeding on tensile strength. In conclusion, we demonstrated that the 3D culture of MSCs in collagen/silk fibroin scaffolds provided biomimetic cues for bone progenitor cells toward differentiation and enhanced the tensile mechanical properties.
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    Collagen scaffolds with in situ-grown calcium phosphate for osteogenic differentiation of Wharton's jelly and menstrual blood stem cells
    (WILEY, 2014-01-01) Karadas, Ozge; Yucel, Deniz; Kenar, Halime; Kose, Gamze Torun; Hasirci, Vasif
    The aim of this research was to investigate the osteogenic differentiation potential of non-invasively obtained human stem cells on collagen nanocomposite scaffolds with in situ-grown calcium phosphate crystals. The foams had 70\% porosity and pore sizes varying in the range 50-200 mu m. The elastic modulus and compressive strength of the calcium phosphate containing collagen scaffolds were determined to be 234.5 kPa and 127.1 kPa, respectively, prior to in vitro studies. Mesenchymal stem cells (MSCs) obtained from Wharton's jelly and menstrual blood were seeded on the collagen scaffolds and proliferation and osteogenic differentiation capacities of these cells from two different sources were compared. The cells on the composite scaffold showed the highest alkaline phosphatase activity compared to the controls, cells on tissue culture polystyrene and cells on collagen scaffolds without in situ-formed calcium phosphate. MSCs isolated from both Wharton's jelly and menstrual blood showed a significant level of osteogenic activity, but those from Wharton's jelly performed better. In this study it was shown that collagen nanocomposite scaffolds seeded with cells obtained non-invasively from human tissues could represent a potential construct to be used in bone tissue engineering. Copyright (C) 2012 John Wiley \& Sons, Ltd.
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    Square prism micropillars on poly(methyl methacrylate) surfaces modulate the morphology and differentiation of human dental pulp mesenchymal stem cells
    (ELSEVIER, 2019-01-01) Hasturk, Onur; Ermis, Menekse; Demirci, Utkan; Hasirci, Nesrin; Hasirci, Vasif
    Use of soluble factors is the most common strategy to induce osteogenic differentiation of mesenchymal stem cells (MSCs) in vitro, but it may raise potential side effects in vivo. The topographies of the substrate surfaces affect cell behavior, and this could be a promising approach to guide stem cell differentiation. Micropillars have been reported to modulate cellular and subcellular shape, and it is particularly interesting to investigate whether these changes in cell morphology can modulate gene expression and lineage commitment without chemical induction. In this study, poly(methyl methacrylate) (PMMA) films were decorated with square prism micro pillars with different lateral dimensions (4, 8 and 16 mu m), and the surface wettability of the substrates was altered by oxygen plasma treatment. Both, pattern dimensions and hydrophilicity, were found to affect the attachment, proliferation, and most importantly, gene expression of human dental pulp mesenchymal stem cells (DPSCs). Decreasing the pillar width and interpillar spacing of the square prism pillars enhanced cell attachment, cell elongation, and deformation of nuclei, but reduced early proliferation rate. Surfaces with 4 or 8 mu m wide pillars/gaps upregulated the expression of early bone-marker genes and mineralization over 28 days of culture. Exposure to oxygen plasma increased wettability and promoted cell attachment and proliferation but delayed osteogenesis. Our findings showed that surface topography and chemistry are very useful tools in controlling cell behavior on substrates and they can also help create better implants. The most important finding is that hydrophobic micropillars on polymeric substrate surfaces can be exploited in inducing osteogenic differentiation of MSCs without any differentiation supplements.
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    A Cell Culture Chip with Transparent, Micropillar-Decorated Bottom for Live Cell Imaging and Screening of Breast Cancer Cells
    (MDPI, 2022-01-01) Ermis, Menekse; Antmen, Ezgi; Kuren, Ozgur; Demirci, Utkan; Hasirci, Vasif
    In the recent years, microfabrication technologies have been widely used in cell biology, tissue engineering, and regenerative medicine studies. Today, the implementation of microfabricated devices in cancer research is frequent and advantageous because it enables the study of cancer cells in controlled microenvironments provided by the microchips. Breast cancer is one of the most common cancers in women, and the way breast cancer cells interact with their physical microenvironment is still under investigation. In this study, we developed a transparent cell culture chip (Ch-Pattern) with a micropillar-decorated bottom that makes live imaging and monitoring of the metabolic, proliferative, apoptotic, and morphological behavior of breast cancer cells possible. The reason for the use of micropatterned surfaces is because cancer cells deform and lose their shape and acto-myosin integrity on micropatterned substrates, and this allows the quantification of the changes in morphology and through that identification of the cancerous cells. In the last decade, cancer cells were studied on micropatterned substrates of varying sizes and with a variety of biomaterials. These studies were conducted using conventional cell culture plates carrying patterned films. In the present study, cell culture protocols were conducted in the clear-bottom micropatterned chip. This approach adds significantly to the current knowledge and applications by enabling low-volume and high-throughput processing of the cell behavior, especially the cell-micropattern interactions. In this study, two different breast cancer cell lines, MDA-MB-231 and MCF-7, were used. MDA-MB-231 cells are invasive and metastatic, while MCF-7 cells are not metastatic. The nuclei of these two cell types deformed to distinctly different levels on the micropatterns, had different metabolic and proliferation rates, and their cell cycles were affected. The Ch-Pattern chips developed in this study proved to have significant advantages when used in the biological analysis of live cells and highly beneficial in the study of screening breast cancer cell-substrate interactions in vitro.
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    Micropatterned Surfaces Expose the Coupling between Actin Cytoskeleton-Lamin/Nesprin and Nuclear Deformability of Breast Cancer Cells with Different Malignancies
    (WILEY-V C H VERLAG GMBH, 2021-01-01) Antmen, Ezgi; Demirci, Utkan; Hasirci, Vasif
    Mechanotransduction proteins transfer mechanical stimuli through nucleo-cytoskeletal coupling and affect the nuclear morphology of cancer cells. However, the contribution of actin filament integrity has never been studied directly. It is hypothesized that differences in nuclear deformability of cancer cells are influenced by the integrity of actin filaments. In this study, transparent micropatterned surfaces as simple tools to screen cytoskeletal and nuclear distortions are presented. Surfaces decorated with micropillars are used to culture and image breast cancer cells and quantify their deformation using shape descriptors (circularity, area, perimeter). Using two drugs (cytochalasin D and jasplakinolide), actin filaments are disrupted. Deformation of cells on micropillars is decreased upon drug treatment as shown by increased circularity. However, the effect is much smaller on benign MCF10A than on malignant MCF7 and MDAMB231 cells. On micropatterned surfaces, molecular analysis shows that Lamin A/C and Nesprin-2 expressions decreased but, after drug treatment, increased in malignant cells but not in benign cells. These findings suggest that Lamin A/C, Nesprin-2 and actin filaments are critical in mechanotransduction of cancer cells. Consequently, transparent micropatterned surfaces can be used as image analysis platforms to provide robust, high throughput measurements of nuclear deformability of cancer cells, including the effect of cytoskeletal elements.
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    3D and 4D Printing of Polymers for Tissue Engineering Applications
    (FRONTIERS MEDIA SA, 2019-01-01) Tamay, Dilara Goksu; Usal, Tugba Dursun; Alagoz, Ayse Selcen; Yucel, Deniz; Hasirci, Nesrin; Hasirci, Vasif
    Three-dimensional (3D) and Four-dimensional (4D) printing emerged as the next generation of fabrication techniques, spanning across various research areas, such as engineering, chemistry, biology, computer science, and materials science. Three-dimensional printing enables the fabrication of complex forms with high precision, through a layer-by-layer addition of different materials. Use of intelligent materials which change shape or color, produce an electrical current, become bioactive, or perform an intended function in response to an external stimulus, paves the way for the production of dynamic 3D structures, which is now called 4D printing. 3D and 4D printing techniques have great potential in the production of scaffolds to be applied in tissue engineering, especially in constructing patient specific scaffolds. Furthermore, physical and chemical guidance cues can be printed with these methods to improve the extent and rate of targeted tissue regeneration. This review presents a comprehensive survey of 3D and 4D printing methods, and the advantage of their use in tissue regeneration over other scaffold production approaches.