Yazar "Yildiz-Ozturk E." seçeneğine göre listele
Listeleniyor 1 - 4 / 4
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Diffusion phenomena of cells and biomolecules in microfluidic devices(American Institute of Physics Inc., 2015) Yildiz-Ozturk E.; Yesil-Celiktas O.Biomicrofluidics is an emerging field at the cross roads of microfluidics and life sciences which requires intensive research efforts in terms of introducing appropriate designs, production techniques, and analysis. The ultimate goal is to deliver innovative and cost-effective microfluidic devices to biotech, biomedical, and pharmaceutical industries. Therefore, creating an in-depth understanding of the transport phenomena of cells and biomolecules becomes vital and concurrently poses significant challenges. The present article outlines the recent advancements in diffusion phenomena of cells and biomolecules by highlighting transport principles from an engineering perspective, cell responses in microfluidic devices with emphases on diffusion- and flow-based microfluidic gradient platforms, macroscopic and microscopic approaches for investigating the diffusion phenomena of biomolecules, microfluidic platforms for the delivery of these molecules, as well as the state of the art in biological applications of mammalian cell responses and diffusion of biomolecules. © 2015 AIP Publishing LLC.Öğe Formulation of organic and inorganic hydrogel matrices for immobilization of ß-glucosidase in microfluidic platform(Wiley-VCH Verlag, 2017) Kazan A.; Heymuth M.; Karabulut D.; Akay S.; Yildiz-Ozturk E.; Onbas R.; Muderrisoglu C.; Sargin S.; Heils R.; Smirnova I.; Yesil-Celiktas O.The aim of this study was to formulate silica and alginate hydrogels for immobilization of ß-glucosidase. For this purpose, enzyme kinetics in hydrogels were determined, activity of immobilized enzymes was compared with that of free enzyme, and structures of silica and alginate hydrogels were characterized in terms of surface area and pore size. The addition of polyethylene oxide improved the mechanical strength of the silica gels and 68% of the initial activity of the enzyme was preserved after immobilizing into tetraethyl orthosilicate–polyethylene oxide matrix where the relative activity in alginate beads was 87%. The immobilized ß-glucosidase was loaded into glass–silicon–glass microreactors and catalysis of 4-nitrophenyl ß-d-glucopyranoside was carried out at various retention times (5, 10, and 15 min) to compare the performance of silica and alginate hydrogels as immobilization matrices. The results indicated that alginate hydrogels exhibited slightly better properties than silica, which can be utilized for biocatalysis in microfluidic platforms. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimÖğe Lung carcinoma spheroids embedded in a microfluidic platform(Springer Science and Business Media B.V., 2021) Yildiz-Ozturk E.; Saglam-Metiner P.; Yesil-Celiktas O.Three-dimensional (3D) spheroid cell cultures are excellent models used in cancer biology research and drug screening. The objective of this study was to develop a lung carcinoma spheroid based microfluidic platform with perfusion function to mimic lung cancer pathology and investigate the effect of a potential drug molecule, panaxatriol. Spheroids were successfully formed on agar microtissue molds at the end of 10 days, reaching an average diameter of about 317.18 ± 4.05 ?m and subsequently transferred to 3D dynamic microfluidic system with perfusion function. While the size of the 3D spheroids embedded in the Matrigel matrix in the platform had gradually increased both in the static and dynamic control groups, the size of the spheroids were reduced and fragmented in the drug treated groups. Cell viability results showed that panaxatriol exhibited higher cytotoxic effect on cancer cells than healthy cells and the IC50 value was determined as 61.55 µM. Furthermore, panaxatriol has been more effective on single cells around the spheroid structure, whereas less in 3D spheroid tissues with a compact structure in static conditions compared to dynamic systems, where a flow rate of 2 µL/min leading to a shear stress of 0.002 dyne/cm2 was applied. Application of such dynamic systems will contribute to advancing basic research and increasing the predictive accuracy of potential drug molecules, which may accelerate the translation of novel therapeutics to the clinic, possibly decreasing the use of animal models. Graphic abstract: [Figure not available: see fulltext.] © 2021, The Author(s), under exclusive licence to Springer Nature B.V.Öğe Modelling coupled dynamics of diffusive–convective mass transfer in a microfluidic device and determination of hydrodynamic dispersion coefficient(Taiwan Institute of Chemical Engineers, 2017) Yildiz-Ozturk E.; Yucel M.; Muderrisoglu C.; Sargin S.; Yesil-Celiktas O.One of the challenges in mathematical modelling of microchips is the lack of available data for dispersion coefficients of biomolecules. The main focus of this study was to determine the hydrodnamic dispersion coefficients of the model substrates, 4-Nitrophenyl-ß-D-glucopyranoside (pNPG_1) and 4-Nitrophenyl-ß-D-glucuronide (pNPG_2) for ß-glucosidase and ß-glucoronidase. The substrate solutions were pumped through the silica porous gel inside the S-shaped PDMS microreactor at flow rates of 1, 3 and 5 µl/min. The output flow was collected with respect to time and quantified by UPLC. The general mathematical model was derived for the coupled dynamics of convective–diffusive mass transfer and a computational algorithm was developed for the numerical solutions of the derived partial differential equations in MATLAB. The hydrodynamic dispersion coefficients of pNPG_1 were determined as 0.370 × 10-6, 3.638 × 10-6 and 11.680 × 10-6 m2/s, while as 0.368 × 10-6, 1.515 × 10-6and 3.503 × 10-6m2/s for pNPG_2 at respective flow rates. Furthermore, the relations between dispersion coefficients and flow rates were investigated. Obtained hydrodynamic dispersion coefficients can be used for modelling of pNPG reactions which may also be adapted to other enzyme related reactions within life sciences. © 2017 Taiwan Institute of Chemical Engineers
