Date

2015

Author

Özkayar, Gürhan

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Dielectrophoresis (DEP) is a technique used for separating particles with different sizes and/or dielectric properties. Fabrication of microelectrodes, thanks to MEMS technology, allows DEP to be applied in biomedical applications such as manipulation, separation, and enrichment of targeted cells from untargeted ones without any labeling. Especially, rare cell detection from blood occupies an important place in diagnostics of fatal diseases such as cancer. Circulating tumor cells (CTCs) that are shed into circulatory system has been considered as an important biomarker for the metastatic progression in cancer. Early detection of CTCs has the uttermost importance for the success of the therapy. However, it cannot be used as a diagnostic tool due to difficulties in detecting only a few CTCs in milieu of billions of blood cells. The objective of this thesis is to develop a MEMS-based dielectrophoretic device for the enrichment of cancer cells from blood with a high throughput, sensitivity, and selectivity. To achieve this goal, a wide (1000 m), parylene-based microchannel with V-shaped planar microelectrodes arranged in parallel throughout the channel has been developed. Throughout the thesis, three generations of DEP devices with different electrode and microchannel geometries have been developed. The first and second generation devices contained two consecutive DEP areas, one for focusing of all cells towards the channel walls via negative DEP (nDEP) force, and the other for selective manipulation of red blood cells (RBCs), where their separation from cancer cells and redirection into the waste outlet take place. However, these devices could manipulate cells at low flow rates (up to 1 ul/min), which results in low throughput. To increase the throughput, electrode and channel geometries has been revised so that the cells are manipulated via positive DEP force (pDEP) and slide through the electrodes to the side channels. Also, parylene filters have been included to filter the RBCs due to their size difference, while keeping the large cancer cells inside the main channel. By this way, the flow rate could be increased up to 30 l/min, and the working potential has been decreased from 20 V pp to 10 V pp . Fabricated 3rd generation DEP devices are capable of working with up to 6 million cells/ml cell concentrations including 5 million RBCs/ml and 1 million cancer cells/ml (K562 human leukemia cancer cell lines and MCF7 human breast adenoma cancer cell lines, separately). Cell enrichment factor for rare cells were calculated as 1.3, which means the desired rare cell percentage was increased to 1.3 fold at the output relative to the input. Further improvements in the design and operational conditions would increase enrichment ratio to the ultimate goal, which is enrichment of rare cells from whole blood of real cancer patients.

Subject Keywords

Dielectrophoresis., Blood, Blood cells., Cytology.

URI

http://etd.lib.metu.edu.tr/upload/12619333/index.pdf
https://hdl.handle.net/11511/25048

Collections

Graduate School of Natural and Applied Sciences, Thesis