New Biosensing Techniques For Cancer Cells And Apoptotic Cells

The sensitive and accurate diagnosis and prognosis of leukemia is essential for its prevention, therapy and minimal residual disease detection. Conventional diagnostic methods have many drawbacks, such as the increased complexity and cost, which limit their effectiveness. So the developments of simple, time-saving and more economical methods for leukemia detection are still needed. The diagnosis of cell apoptosis is important for the early detection of therapy efficiency and the evaluation of disease progression. Quartz crystal microbalance (QCM) sensors are sensitive, simple, time-saving and economic. Therefore, QCM has been used for the detection of cancer cells and apoptotic cells. The main points of this thesis are summarized as follows:1. A novel method for collection and detection of leukemia cells has been proposed using aptamer-conjugated magnetic beads (apt-MBs) and a magnet-quartz crystal microbalance (QCM) system. The sgc8c-MBs specifically binding to CCRF-CEM cells were used for cell extraction from complex matrixes, and the magnet-QCM system was applied for cell detection, requiring no further labeling of cells. The accumulation of MBs-conjugated CCRF-CEM cells on a quartz crystal under a magnetic field resulted in decreased resonant frequency (f). A linear relationship betweenâ–³f and cell concentration over the range of 1×10⁴ to 1.5×10⁵ cells mL^-1 was obtained, with a detection limit of 8×10³ cells mL^-1. The applicability of the method for target cell detection from cell mixture was satisfactory.2. A quartz crystal microbalance (QCM) sensor has been developed for the detection of cell apoptosis based on the immobilization of Annexin V on a quartz crystal surface. Poly-o-phenylenediamine film was first formed on the gold electrode, and then streptavidin was immobilized using glutaraldehyde as a crosslinking agent, followed by the immobilization of biotin-Annexin V. Annexin V has high affinity to phosphatidylserine on the membrane of apoptosis cells. So, the frequency response of the Annexin V-modified quartz crystal upon the binding of cells can be used for the discrimination between normal cells and apoptotic cells.