Abstract
Abstract Circulating tumor cells (CTCs) are being significantly explored as a potential tool for cancer diagnosis with high sensitivity and specificity. However, the detection of CTCs is a challenge because of the difficulty in isolation from whole blood as they are shed into the vasculature from primary tumor and circulate irregularly in the bloodstream. Recently, microfluidic platforms have been utilized for the isolation of CTCs. To improve the recovery rate of CTCs, we, herein, report a new integrated microfluidic system capable of performing red blood cells (RBCs) lysis, which is a negative selection process for depleting white blood cells (WBCs) accompanied by a positive selection process for specifically capturing target cancer cells to effectively detect CTCs from the blood by cancer cell-specific aptamers. A single miniature chip has been used to perform the entire process in one hour without human intervention. Our integrated microfluidic system shows higher efficiency for the isolation of CTCs in order to effectively diagnose the cancer cells in short time when compared to the traditional negative or positive selection approach. Furthermore, all possibilities of “false positive” results could be overcome by the specificity of the aptamer. In order to improve the accuracy of the process of detecting CTCs from human whole blood after the process of isolation, a single cell captured by magnetic beads was allowed to pass through the field-effect-transistor (FET) sensing area by means of a flow-focusing device. The detected cells from the FET area were collected using a flow-switching device for subsequent operation. Experimental results showed that the spiked cancer cells could be differentiated effectively from phosphate-buffered saline (PBS, negative control) buffer. Furthermore, the FET was successfully integrated into the microfluidic control thereby making it feasible for cell isolation, cell detecting, and automated collection. In order to facilitate the passage of cells through the FET one by one precisely, a microstructure with flow focusing mode was fabricated to accurately focus a flow stream. The flow stream with a width limitation of 20 µm was designed to deliver cells to the FET area by means of a pump. Thereafter the number of cancer cells captured from whole blood was determined by analyzing the FET sensor signal. The results of this work prove that a new integrated microfluidic system is an effective alternative to detect CTCs incorporated in a single chip and it shows promise for further development as a biosensor for clinical applications in the future.