Label Free And High Througput Electrical Impedance Detection Of Tumor Cells

Cancer is one of the major diseases threatening human life and health,early diagnosis of cancer can significantly improve the survival rate of patients and reduce the medical burden of family and society.Among various tumor markers,the cellular tumor maker is essential for cancer diagnosis due to the morphology difference between tumor cells and normal cells.The electrical impedance flow cytometer is capable to analyze the biophysical properties of tumor cells including volume,membrane capacitance and nucleocytoplasmic ratio according to tumor cells’ electrical impedance responses,it is an essential tool for high accuracy and rapid identification of tumor cells.However,most electrical impedance devices use planar electrodes and non-uniform electric field,their detection accuracy depend on pre-focusing units.To solve this challenge,this thesis proposes an axisymmetric electrode structure,which not only improves the uniformity of the excitation electric field,but also improves the identification accuracy without the use of pre-focusing units;The multi-frequency electrical impedance responses of typical tumor cells were also studied to further improve the cell classification accuracy;to solve the low throughput problem of single channel devices,this thesis also studied a novel multi-channel impedance detection method.Detailed information about this thesis is listed as follows:(1)High precision axisymmetric electrode electrical impedance flow cytometer design and characterization.In this thesis,the axisymmetric electrode combined with narrow constrained channel was used to improve the uniformity of the excitation electric field in the detection channel,which leads to a high accurate identification of tumor cell.By using numerical electric field analysis tools,the relationship between axisymmetric three-dimensional electrode and constriction channel’ structure and excitation electric field’ uniformity was studied.At the same time,the relationship between cells’ spatial positions and electrical impedance response fluctuation was obtained.The influence of constriction channel’s structure,electrode material on the detection accuracy was verified through experiments.To further verify the effectiveness of the electrode design,the performance of the axisymmetric electrode device and the typical coplanar electrode device were compared.Finally,the axisymmetric electrode device was used to test the low-frequency electrical impedance response of tumor cells,and identify cell type according to their size.(2)Multi-frequency electrical impedance characteristics of typical tumor cells and labelfree detection.In this thesis,the impedance responses of axisymmetric electrode devices at 3k Hz to 2 MHz was studied.Polystyrene particles(ranging from 7 to 20 (?)m)were used to calibrate multi-frequency responses of the device.Next,impedance responses of human breast cancer cells,lung cancer cells and white blood cells were studied.Cell type identification was achieved through the analysis of cells’ electrical opacity.To improve cell identification’s efficiency,gating strategies including linear gating and confidence ellipse gating methods were studied.The Principal Component Analysis(PCA)method were also studied to reduce high dimensional impedance responses.Based on the combination of PCA and a deep learning method,the cell identification accuracy was further improved.The accuracy of the identification of human breast cancer cells,lung cancer cells and leukocytes is great than 95%.(3)High throughput electrical impedance flow deviction based on time-division-multipleaccess(TDMA)techniques.To solve the low throughput problem of a single channel impedance flow device,parallel impedance sensing integrated with TDMA technique was studied in this thesis to achieve a high throughput cellular biomarker analysis.A 4 × 4-channel impedance sensor array was fabricated and used to evaluate the encoding and decoding performance of the TDMA method.The relationship between multiplexing switching frequency,cells’ flow velocity and overall throughput were also studied.Finally,the performance of the device in cell detection was evaluated.