8 research outputs found

    Lithographic Micro- and Nanostructuring of SU-8 for Biotechnological Applications

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    En aquesta tesi doctoral s’ha dut a terme recerca en mètodes de fabricació d’estructures micromètriques i nanomètriques de SU-8. La recerca ha partit de la base d’una anàlisi dels treballs anteriors en estructuració de SU-8 i ha tingut com a principal objectiu el d’obtenir noves estructures per a aplicació en biotecnologia. Un dels resultats més importants de la recerca ha estat la proposta d’una tècnica híbrida que combina fotolitografia i litografia per pressió per obtenir superfícies de SU-8 amb estructura jerarquitzada. Les investigacions també han portat a proposar un mecanisme de sensat basat en la fotoluminescència del SU-8. Els experiments demostren que la fotoluminescència es redueix a cada pas de modificació de la química de superfície. Aquesta característica es produeix de forma repetible també quan s’adhereix un antigen (IgG) a una superfície de SU-8 modificada amb l’anticòs corresponent (aIgG). Gràcies a aquest efecte, s’ha proposat un inmunosensor basat en la reducció de fotoluminescència i se n’ha avaluat la seva sensibilitat. El resultat més rellevant demostra que estructures jeràrquicament organitzades mostren una reducció de fotoluminescència major i per tant una millor sensibilitat.En esta tesis doctoral se ha llevado a cabo investigación sobre métodos de fabricación de estructuras micrométricas y nanométricas de SU-8. La investigación ha partido de la base de un análisis de los trabajos anteriores en estructuración de SU-8 y ha tenido como principal objetivo el de obtener nuevas estructuras para la aplicación en biotecnología. Uno de los resultados más relevantes de la investigación ha sido la propuesta de una técnica híbrida que combina fotolitografía con litografía por presión para obtener superficies de SU-8 con una estructura jerarquizada. Las investigaciones también han llevado a proponer un mecanismo de sentado basado en la fotoluminiscencia del SU-8. Los experimentos demuestran que la fotoluminiscencia se reduce a cada paso de modificación de la química de superficie. Esta característica se produce de forma repetible también cuando se adhiere un antigen (IgG) a una superficie de SU-8 modificada con el anticuerpo correspondiente (aIgG). Gracia a este efecto se ha propuesto un inmunosensor basado en la reducción de fotoluminiscencia i se ha evaluado su sensibilidad. El resultado más relevante demuestra que las estructuras jerárquicamente organizadas muestran una reducción de fotoluminiscencia mayor, y por tanto una mejor sensibilidadn this Ph. D. Dissertation research on lithographic methods for the fabrication of micrometric and nanometric SU-8 structures has been carried out. The research has been based on a survey of existing techniques to structure the SU-8 with the main objective of obtaining novel structures for biotechnology applications. One of the main results of the research has been the proposal of an hybrid technique that combines photolithography and soft lithography to obtain hierarchically structured SU-8 surfaces. The investigations have also led to the proposal of a sensing mechanism based on the photoluminescence of SU-8. The experiments show that photoluminescence is reduced with every step of surface chemistry modification. This is a repeatable feature that is observed also upon attachment of an antigen (IgG) onto a SU-8 surface grafted with antibody (aIgG). Thanks to this effect, an immunosensor based on the reduction of photoluminescence has been proposed and its sensitivity has been evaluated. The results show that the hierarchically patterned structures offer a higher photoluminescence reduction and thus a better sensitivity

    Nanofabrication

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    We face many challenges in the 21st century, such as sustainably meeting the world's growing demand for energy and consumer goods. I believe that new developments in science and technology will help solve many of these problems. Nanofabrication is one of the keys to the development of novel materials, devices and systems. Precise control of nanomaterials, nanostructures, nanodevices and their performances is essential for future innovations in technology. The book "Nanofabrication" provides the latest research developments in nanofabrication of organic and inorganic materials, biomaterials and hybrid materials. I hope that "Nanofabrication" will contribute to creating a brighter future for the next generation

    Isolation of Circulating Tumor Cells and Clusters from Blood with Application in Drug Screening

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    Circulating tumor cell (CTC) plays a significant role to lead tumor become life-threatening. The appearance of CTC in the circulating system of tumor patients is deemed as the start of metastasis. To obtain CTC from blood is critical for vast biomedical applications, such as using CTC for DNA sequencing to reveal the gene difference between CTC and tumor cells at original site, creating in vitro tumor models based on CTC, and develop new and effective therapeutic schemes, etc. Based on this, the focus of the dissertation mainly on the research towards CTC. In brief, the dissertation demonstrates several techniques on how to isolate them from patient blood samples, how to use them as seed to form 3D tumor models, and how to use these 3D tumor models for highly efficient anti-tumor drug screening.Firstly, a wavy-herringbone (wavy-HB) structured microfluidic device is developed to effectively and selectively capture and release circulating tumor cells (CTCs) by using immunoaffinity and magnetic force. The device is designed to create passive turbulence and increase the possibility of tumor cells colliding onto the device wall. Under an external magnetic field, magnetic particles (MPs) coated with anti-EpCAM against tumor cell surface protein (EpCAM) are immobilized over the wavy-HB surface to capture tumor cells. After removing the magnetic field, the captured cells with surplus MPs are released from the device and collected, thus cells can be re-cultured for further analysis. On optimized conditions, the capture efficiency of tumor cells can be as high as 92%±2.8%. Capture experiments are also performed on whole blood samples and the capture efficiency is in a high range of 81%-95%, based on different tumor cell concentrations.Next, to isolate CTC clusters (CTCC), which has been shown to have higher invasiveness than CTC, a spiral channeled microfluidic device is introduced. By the centrifugal force created by spiral channels in microfluidic conditions, the device can isolate three types of cells, i.e. white blood cell (WBC), CTC, and CTCC. Due to the size difference among these cells, when flowing into the microfluidic device, the different centrifugal force they experience is different, and this difference enables them to exit from different outlets of the device. At lower flow rate, WBC could be firstly isolated, while CTC and CTCC could be isolated at higher flow rate. This device is able to isolate rare CTC and CTCC from massive WBC, so this device with this method can be potentially used for isolation of CTC and CTCC from patient blood samples.To use the CTC and CTCC obtained from the first two techniques, a facile method for generation of tumor spheroids in large quantity with controllable size and high uniformity is presented. HCT116 cells are used as the model cell line. Individual tumor cells are sparsely seeded onto petri-dishes. After a few days of growth, separated cellular islets are formed and then detached by dispase while maintaining their sheet shape. These detached cell sheets are transferred to dispase-doped media under orbital shaking conditions. Assisted by the shear flow under shaking and inhibition of cell-to-extracellular matrix junctions by dispase, the cell sheets curl up and eventually tumor spheroids are formed. The average size of the spheroids can be controlled by tuning the cell sheet culturing period and spheroid shaking period. The uniformity can be controlled by a set of sieves which were home-made using stainless steel meshes. Since this method is based on simple petri-dish cell culturing and shaking, it is rather facile for forming tumor spheroids with no theoretical quantity limit. This method has been used to form HeLa, A431 and U87 MG tumor spheroids and application of the formed tumor spheroids in drug screening is also demonstrated. The viability, 3D structure, and necrosis of the spheroids are characterized.Finally, to more closely mimicking the microenvironment of in vivo tumor, a bi-layer microfluidic device is presented to facilitate anti-tumor drug screening. The bi-layer microfluidic device consists of two PDMS pieces with channels and the two pieces are separated by a semi-permeable membrane to allow water, oxygen and nutrition supply but prevent cell migration. The two channels on the two PDMS pieces have a long overlapping to ensure a larger exchange area to mimic the blood vessel-tumor model. High concentration of EC is firstly seeded onto the membrane through the apical channel, and after two-day culture to ensure a confluent EC monolayer forming, tumor spheroids laden Matrigel is seeded into the basal channel. After the Matrigel is cured, the device is ready for drug test. Confocal and ImageJ are used to assess the efficacy of different concentration of drugs and combination of drugs therapies. Optical coherence tomography is employed to determine the tumor shrinkage after drug treatment

    Biomimetic Based Applications

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    The interaction between cells, tissues and biomaterial surfaces are the highlights of the book "Biomimetic Based Applications". In this regard the effect of nanostructures and nanotopographies and their effect on the development of a new generation of biomaterials including advanced multifunctional scaffolds for tissue engineering are discussed. The 2 volumes contain articles that cover a wide spectrum of subject matter such as different aspects of the development of scaffolds and coatings with enhanced performance and bioactivity, including investigations of material surface-cell interactions

    Microscopy Conference 2017 (MC 2017) - Proceedings

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    Das Dokument enthält die Kurzfassungen der Beiträge aller Teilnehmer an der Mikroskopiekonferenz "MC 2017", die vom 21. bis 25.08.2017, in Lausanne stattfand

    Microscopy Conference 2017 (MC 2017) - Proceedings

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    Das Dokument enthält die Kurzfassungen der Beiträge aller Teilnehmer an der Mikroskopiekonferenz "MC 2017", die vom 21. bis 25.08.2017, in Lausanne stattfand

    Progenitor cells in auricular cartilage demonstrate promising cartilage regenerative potential in 3D hydrogel culture

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    The reconstruction of auricular deformities is a very challenging surgical procedure that could benefit from a tissue engineering approach. Nevertheless, a major obstacle is presented by the acquisition of sufficient amounts of autologous cells to create a cartilage construct the size of the human ear. Extensively expanded chondrocytes are unable to retain their phenotype, while bone marrow-derived mesenchymal stromal cells (MSC) show endochondral terminal differentiation by formation of a calcified matrix. The identification of tissue-specific progenitor cells in auricular cartilage, which can be expanded to high numbers without loss of cartilage phenotype, has great prospects for cartilage regeneration of larger constructs. This study investigates the largely unexplored potential of auricular progenitor cells for cartilage tissue engineering in 3D hydrogels
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