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YÖK Tez ID: 476577 Bu tez çalışmasında hücrelerin sayımı, tanımlanması ve sınıflandırılması için yaygın bir teknik olan empedans akış sitometrisi tekniği kullanılarak mikroakışkan bir sistem geliştirilmiştir. Bu çalışmada kapasitif-impedimetrik biyosensörler araştırılarak, mikroakışkan sistemin duyarlılık sınırlarının geliştirilmesi ve bunun bir sonucu olarak kan hücresi tespiti yapılabilmesi hedeflenmiştir. Hücreler elde edilmesi ve manipüle edilmesi zor parçacıklar olduğundan mikroakışkan sistemi geliştirmek için hücre ile eşdeğer elektriksel özelliğe sahip olan 6 µm çapındaki polistiren mikro küreler kullanılmıştır. Mikroakışkan sistem içerisinden mikro küre taşıyan 2.5 S/m iletkenliğine sahip bir sıvı geçirilerek, sıvı içerisindeki mikro küreler elektriksel empedans ölçümü yoluyla tespit edilmiştir. Mikroakışkan sistemin hassasiyetini artırmak için sonlu elemanlar metodu ile simülasyonlar yapılarak parçacıkların kanal içerisindeki konum ve boyutlarına bağlı olarak verdiği sinyaller hesaplanmıştır. Empedans değişiminin elektro aktif bölgede yer değiştiren parçacığın hacmi ile orantılı olduğunu göstermek için ise farklı boyutlardaki elektrot ve kanalların performansı teorik ve deneysel olarak incelenmiştir. En uygun kanal ve elektrot geometrisini bulabilmek için öncelikle elektrot boyutu sabit tutularak farklı kanal boyutlarına sahip mikroçiplerde, daha sonra kanal boyutu sabit tutularak farklı elektrot boyutlarına sahip mikroçiplerde deneyler yapılmıştır. Kanal ve elektrot genişliği azaldıkça mikro kürenin empedans değişiminin arttığı ve elde edilen sonuçlarında Maxwell mixture teorisi ile uyumlu olduğu gösterilmiştir. Bu ön çalışmalardan yola çıkarak 4, 6 ve 8 µm çaplarındaki polistiren mikro küreleri yüksek hassasiyet ile ayırt edebilen bir elektrot ve kanal yapısı geliştirilmiştir. Hücre sınıflandırma cihazları saniyede binlerce hücre analizi yapabilir fakat genellikle küçük bir örnek hacminin kullanımı için uygun olmayan komplike makinalardır. Bu çalışmada empedansa dayalı mikroakışkan sistem içerisinde alınan bir damla kan örneği kullanılarak kırmızı kan hücreleri sayılmış ve kan örneğindeki farklı mikro parçacıklar tespit edilmiştir. Bu sayede kan sayım cihazı teknolojisine dair bir altyapı geliştirilmiştir. Bu altyapı ile kan hastalıklarının tespitine yönelik, çok az miktarda kan ile dahi cevap verebilen, portatif sistemlerin geliştirilebilmesinin zemini oluşturulmuştur. In this dissertation, a microfluidic system was developed by using the impedance flow cytometry technique that is in common use for cell counting, identification, and classification. Through investigation of capacitive-impedimetric biosensors, this work aimed to improve the sensitivity levels of the microfluidic system and to identify blood cells as a result of it. Since it is difficult to obtain and manipulate cells, 6 µm polystyrene micro beads having equivalent electrical properties with cells were employed to develop the microfluidic system. By passing a fluid, which has 2.5 S/m conductivity and carriers the micro beads within the microfluidic system, the micro beads were identified impedimetrically. To improve the sensitivity of the microfluidic system, simulations were performed with the Finite Element Method (FEM) to calculate the signals that the particles give depending on their locations and sizes within the channels. In order to show that the impedance change is proportional on the volume of the particle changing its location within the electro-active region, the performances of electrodes and channels with different dimensions were investigated both theoretically and experimentally. To find the optimum channel and electrode geometries, firstly, experiments were performed with microchips with fixed electrode dimensions and varying channel dimensions. This was followed by employing microchips with fixed channel dimensions and varying electrode dimensions. It was shown that the impedance change of the bead increases as the channel and electrode widths decrease and the results match well with the Maxwell mixture theory. With these primary works, an electrode-channel structure was developed which can sort 4, 6, 8 µm diameter polystyrene beads with high sensitivity. Cell classification devices can perform thousands of cell analyses within seconds, but they are not suitable for the use of small volume samples. In this work, impedance based microfluidic system was used to count red blood cells and sense different micro particles from a drop of blood sample. Thanks to that, an infrastructure was developed for the blood counter technology. With this infrastructure, a ground was formed to develop portable systems, even sensitive to very small volume blood samples, for the diagnosis of hematologic diseases.

YÖK Tez ID: 344019 Günümüzde nano teknolojik uygulamalarda birçok araştırmacının dikkatlerini üzerine çeken, deneysel ve teorik çalışmalarla hızla trendi yükselen, az miktarda azot eklenen kuantum kuyu lazer sistemleri araştırıldı. Bu çalışmada, uzun dalga boylarında ve özellikle fiber optik kabloların dağılım ve kayıplarının en az olduğu bölgelerden biri olan 1.3 µm dalga boylu ışıma yapan az miktarda azot (N) eklenmiş GaInAs alaşımının materyal parametreleri hesaplandı. Uzun dalga boylu InGaNAs/GaAs kuantum kuyu lazer sistemlerinin dalga boyuna bağlı olarak kendiliğinden ışıma ve kazanç hesaplamaları yapıldı. Dörtlü yarıiletken alaşım (InGaNAs) için Indiyum (In) ve Azot (N) konsantrasyonlarının, sıcaklığın, taşıyıcı konsantrasyonların etkisi gibi parametrelerin kazanç üzerindeki etkileri incelendi. Bu sistemler için yapılan hesaplamalar ve sıcaklığa bağlı tepe (pik) kazanç hesaplamaları kullanılarak yüksek hız uygulamaları için gerekli N ve In oranları belirlendi. Seçilen kuantum kuyu lazer yapılar için Güç-Akım-Voltaj (L-I-V) grafikleri çizildi. The quantum well laser systems that were added dilute nitrogen which attracted many researchers studying on nanotechnological applications and whose popularity is increasing due to both theoretical and experimental researches have been investigated. In this study, material parameters of GalnAs alloy which was added a little amount of nitrogen that radiates 1.3 µm was calculated in the long wave length and particularly at a point where the network and the loss of fiber optic cables is the least. The calculations of spontaneous emission and gain of GalnNAs/GaAs quantum well laser systems with long wave were done depending on wave length. For the semiconduction alloy with four parts (GalnNAs), the Nitrogen (N) concentration and Indiyum (In), the effect of heat, and the effects of the parameters of the carrier concentrations on the gain were examined. N and In rates for these systems that are necessary for high speed applications were determined with the help of the calculations of peak gains. Also, the power, current, and voltage (L-I-V) calculations of the selected laser units were done.

*Bilican, İsmail ( Aksaray, Yazar ) *Akyüz, Lalehan ( Aksaray, Yazar ) *Koç Bilican, Behlül ( Aksaray, Yazar ) *Kaya, Murat ( Aksaray, Yazar ), Chitosan, which is obtained via deacetylation of chitin, has a variety of uses in agriculture, food, medicine, pharmaceuticals, and cosmetics. Industrial chitosan is in a gel form, which is produced by dissolving in acetic acids. These gels can be chitosan-only films or composite films that include other ingredients such as plant extracts or other polymers. Chitosan-based films, however, are not as natural as chitosan dissolved in weak acids, and they lack some of chitosan's innate properties. In this study, natural chitosan films (NCFs) were obtained from the pupa shells of black soldier flies through a process that maintains the original structure. The semisynthetic film (SCF) was then produced by dissolving the same NCF in acetic acid along with glycerol and glutaraldehyde. The semisynthetic film remarkably lost the beneficial properties of the natural film. The deteriorated characteristics include hydrophobicity, crystallinity, thermal properties, as well as a loss of fibril structure and a reduction in bacterial attachment. Moreover, the Ag-deposited NCFs manifested strikingly higher surface-enhanced Raman scattering activity as compared with the semisynthetic ones. These results, including the molecular modeling data, demonstrate that dissolving chitosan in acetic acid changes its polymeric structure. © 2020 American Chemical Society.

Recently, traditional polymer-based surgical meshes have drawn unwanted attention as a result of host tissue complications arising from infection, biocompatibility, and mechanical compatibility. Seeking an alternative solution, we present a hierarchically structured nanofibrous surgical mesh derived from the naturally woven cocoon of the Japanese giant silkworm, termed MothMesh. We report that it displays nontoxicity, biocompatibility, suitable mechanical properties, and porosity while showing no adverse effect in animal trials and even appears to enhance cell proliferation. Hence, we assert that the use of this natural material may provide an effective and improved alternative to existing synthetic meshes.

Although over 80% of the world’s existing animal species are insects, with each of these species having unique eggshell morphologies, limited information is available regarding the use of their eggshells in material science applications. The present research discusses using discarded eggshells of the Chinese oak silkworm (Antheraea pernyi) as a technological material. The 3-dimensional aspects of the insect's eggshell were examined in detail, demonstrating the complexity of their novel surface morphology. The outer surface of the eggshell was comprised of a hexagonal structure, whereas the inner surface consists of a mostly smooth surface. Distinctive layers of the eggshell were observed when cross sections of the surface were analyzed. The elastic modulus of the inner part of the eggshell is substantially greater than that of the outer part. The physicochemical properties of the eggshell were characterized and no toxic properties were found. The hexagonal structures found on the outer surface of the eggshell provide a highly suitable template for silver nanostructure deposition. The resulting silver decorated surfaces can be used to detect molecules via surface-enhanced Raman scattering (SERS) effects. The deposition of silver renders the surface antimicrobial, whereas the original surface was microbial. Collectively, the insights gained in this study will be key in developing advanced engineering applications of the insect eggshells.

*Bilican, İsmail ( Aksaray, Yazar ), In this study, a new method for the fabrication of polydimethylsiloxane (PDMS) microchannels through the replication of plexiglass molds was developed. A plexiglass slab is machined with CO2 laser in the raster mode to produce the mold for the PDMS casting. Then, the PDMS replica of the mold is plasma bonded to a substrate by applying more pressure than standard to overcome the surface roughness inherited from the laser machining process. Depending on the channel complexity, a ready to cast mold in the size of a glass slide can be achieved in 5–20 min, including the design, machining, and cleaning steps. This fully automated and cost-effective mold making method proved to be the fastest among all methods, and it enables up to 2.5 aspect ratio microchannels, down to a width of 60 μm, and a height of 23 μm. The raster mode of the laser provides features lower, in size, then the laser beam waist radius. The produced microchannels were validated using several applications, such as droplet generation, nanofiber production, and viscoelastic microparticle focusing.

*Bilican, Ismail ( Aksaray, Yazar ), Porous, bioactive microspheres have always been a dream material to biomedical scientists for bone regeneration and drug delivery applications due to their interconnectivity, unique pore geometry, encapsulation ability and porosity spanning macroscopic, microscopic and nanoscopic length scales. Extensive efforts have been made to produce such materials synthetically at a great cost of money, time and labor. Herein, naturally-assembled multifunctional, open-channeled and hollow bioactive micro silica spheres (diameter 209.4 +/- 38.5 mu m) were discovered in a marine sponge (Geodia macandrewii), by peeling the outer surface of the sterrasters using hydrogen fluoride. The obtained micro silica spheres exhibited valuable characteristics such as homogeneously distributed pores, a cavity in the center of the sphere, and channels (approx. 3000) opening from each pore into the central cavity. Simulated body fluid analysis demonstrated the bioactivity of the micro silica spheres; whereas, no bioactivity was recorded for the original untreated sterrasters. The non-cytotoxicity and osteogenic ability of the isolated microspheres were confirmed through osteoblast cell culture. Finally, these silica based porous microspheres were tested for controlled drug release capacity. The spheres showed excellent loading and release abilities for an anti-cancer drug, carboplatin, in simulated solutions and in human cancer cell culture, HeLa, through a real time cell analyzer system. The drug loading capacity of the porous beads was determined as 10.59%. Considering the unique biological and physicochemical properties, these novel bioactive silica spheres, which we name as giant macroporous silica (GMS), are promising materials for a range of applications including bone tissue engineering and drug delivery.

Implementation of viscoelasticity-based particle migration techniques has attracted significant interest thanks to its simplicity to achieve particle separation and enrichment at high sensitivity and accuracy for the last decade. Many methods have previously been developed for particle focusing and separation, but they all require long fluidic channels to enable the desired elastic force on particles. Here, a cascade contraction-expansion microfluidic system with a much shorter channel length is presented. Experimental results show that this system achieved continuous, sheathless particle separation in a viscoelastic fluid, and Enterococcus faecalis was successfully separated from red blood cells (RBCs). Thanks to its small size, the system provides extra advantage for its integration into small chips. (c) 2021 Elsevier B.V. All rights reserved.

*Bilican, İsmail ( Aksaray, Yazar ) *Bahadır, Tolga ( Aksaray, Yazar ), Pseudomonas aeruginosa is a pathogenic bacterium in fresh water supplies that creates a risk for public health. Microbiological analysis of drinking water samples is time consuming and requires qualified personnel. Here we offer a screening system for rapid analysis of spring water that has the potential to be turned into a point-of-need system by means of simple mechanism. The test, which takes 1 h to complete, electrically interrogates the particles through a microfluidic chip suspended in the water sample. We tested the platform using water samples with micro beads and water samples spiked with P. aeruginosa at various concentrations. The mono disperse micro beads were used to evaluate the performance of the system. The results were verified by the gold standard membrane filtration method, which yielded a positive test result only for the P. aeruginosa spiked samples. Detection of 0–11 k bacteria in 30 μL samples was successfully completed in 1 h and compared with a conventional microbiological method. The presented method is a good candidate for a rapid, on-site, screening test that can result in a significant reduction in cost and analysis time compared to microbiological analyses routinely used in practice.