Makine Mühendisliği Bölümü Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/206

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In vitro contact guidance of glioblastoma cells on metallic biomaterials
(SPRINGERVAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS, 2021) Uzer, Benay; 0000-0001-8778-1660; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Uzer, Benay
Cancer cells' ability to sense their microenvironment and interpret these signals for the regulation of directional adhesion plays crucial role in cancer invasion. Furthermore, given the established influence of mechanical properties of the substrate on cell behavior, the present study aims to elucidate the relationship between the contact guidance of glioblastoma cell (GBM) and evolution of microstructural and mechanical properties of the implants. SEM analyses of the specimens subjected to 5 and 25% of plastic strains revealed directional groove-like structures in micro and submicro-sizes, respectively. Microscale cytoplasmic protrusions of GBMs showed elongation favored along the grooves created via deformation markings on 5% deformed sample. Whereas filopodia, submicro-sized protrusions facilitating cancer invasion, elongated in the direction perpendicular to the deformation markings on the 25% deformed sample, which might lead to easy and rapid retraction. Furthermore, number of cell attachment was 1.7-fold greater on 25% deformed sample, where these cells showed the greatest cellular aspect ratio. The directional attachment and contact guidance of GBMs was reported for the first time on metallic implants and these findings propose the idea that GBM response could be regulated by controlling the spacing of the deformation markings, namely the degree of plastic deformation. These findings can be applied in the design of cell-instructive implants for therapeutic purposes to suppress cancer dissemination.
The influence of plastic deformation mechanisms on the adhesion behavior and collagen formation in osteoblast cells
(SPRINGER, 2018) Uzer-Yilmaz, Benay; Monte F.; Awad, Kamal R.; Aswath, Pranesh B.; Varanasi, Venu G.; Canadinç D.; 0000-0001-8778-1660; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Uzer-Yilmaz, Benay
In many of biomedical applications, the implant might get in direct contact with the bone tissue where the osteogenesis needs to be stimulated. If osteoblasts can not successfully attach on the implant surface, the bone might resorb and implant can fail. In the current study MC3T3 cells were cultured on the 316L stainless steel samples which were deformed up to four different strain levels (5, 15, 25 and 35%) to activate plastic deformation mechanisms (slip and twinning) in different volume fractions. Scanning electron microscopy (SEM) images showed that cells adhered and spread significantly on the 25 and 35% deformed samples owing to the greater surface roughness and energy provided by the increased density of micro-deformation mechanisms which promoted the formation of focal contacts. In addition, significant amount of collagen formation was observed on the sample deformed up to 25% of strain which can be due to the ideal match of the surface roughness and collagen molecules. Overall these results show that material’s microstructure can be manipulated through plastic deformation mechanisms in order to enhance the cell response and collagen deposition. As a result long lasting implants could be obtained which would eliminate additional surgical interventions and provide a successful treatment.
Modulating the Surface Properties of Metallic Implants and the Response of Breast Cancer Cells by Surface Relief Induced via Bulk Plastic Deformation
(FRONTIERS MEDIA SA, AVENUE DU TRIBUNAL FEDERAL 34, LAUSANNE, CH-1015, SWITZERLAND, 2020) Uzer, Benay; 0000-0001-8778-1660; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü
Micro/nanoscale textured surfaces have presented promising tissue-implant integration via increasing surface roughness, energy, and wettability. Recent studies indicate that surface texture imparted on the metallic implants via surface relief induced with simple bulk plastic deformation methods (e.g., tension or compression tests) does result in enhanced cell response. Considering these recent findings, this study presents a thorough investigation of the effects of surface relief on surface properties of implants and cell adhesion. Experiments are conducted on the samples subjected to interrupted tensile tests up to the plastic strains of 5, 15, 25, and 35%. Main findings from these experiments suggest that, as the plastic deformation level increases up to 35% from the undeformed (control) level, (1) average surface roughness (R-a) increases from 17.58 to 595.29 nm; (2) water contact angle decreases from 84.28 to 58.07 degrees; (3) surface free energy (SFE) increases from 36.06 to 48.89 mJ/m(2); and (4) breast cancer cells show 2.4-fold increased number of attachment. Increased surface roughness indicates the distorted topography via surface relief and leads to increased wettability, consistent with Wenzel's theory. The higher levels of SFE observed were related to high-energy regions provided via activation of strengthening mechanisms, which increased in volume fraction concomitant with plastic deformation. Eventually, the displayed improvements in surface properties have increased the number of breast cancer cell attachments. These findings indicate that surface relief induced upon plastic deformation processes could be utilized in the design of implants for therapeutic or diagnostic purposes through capturing breast cancer cells on the material surface.
The relationship of surface roughness and wettability of 316L stainless steel implants with plastic deformation mechanisms
(ELSEVIER SCIENCE BV, PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS, 01.01.2019) Cicek, S.; Karaca, A.; Torun, I.; Onses, M. S.; Uzer, B.; 0000-0001-6898-7700; 0000-0001-8778-1660; 0000-0001-9820-6565; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü
The wettability of the implant plays significant role in successful tissue-implant integration and shows strong dependence on the surface topography of the material. Recent studies showed that the plastic deformation mechanisms can improve cell response, and increase surface roughness and energy. In order to understand the effect of these mechanisms on wettability, 316L stainless steel samples were subjected to tensile test and deformed up to 15% to 35% of strain levels. Atomic force microscopy (AFM) presented approximately 22-fold greater average surface roughness on the 35% deformed sample compared to undeformed one. On the other hand, sessile drop test showed contact angle decrease from 82 degrees to 52 degrees as the deformation increased. This finding is significant since much higher contact angle value at similar surface roughness was presented in the literature. This demonstrates that the plastic deformation mechanisms can play significant role in enhancing the surface wettability without a need for a surface treatment technique. Hence, through the activation of these mechanisms, wettability and surface energy of the implant materials could be further increased which would result with enhanced cell response and lessened post-surgical complications. (C) 2018 Elsevier Ltd. All rights reserved.

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