Studies and Applications of Microfludics and Microsystems for Molecular Detection

Abstract

Microfluidic is a technique for precisely controlling and manipulating microscale fluids, an interdisciplinary field including engineering, physics, chemistry, micromachining and bioengineering, etc. Microfluidic chip is the main platform and device for implementing microfluidic technology, its main feature is that the effective structure (microchannels or microchambers) containing the fluid is on the micrometer scale in at least one dimension. In this thesis, we primarily studied microfluidics and its related microsystems and applied this novel technology in the field of molecular biology including nucleic acid extraction and its subsequent detection and quantification. Foremost, we introduced basic concepts and advantages of microfluidics, and we also elaborated on current materials and methods used to fabricate microfluidic chips and the manipulation of fluids within microchip. Next, we presented background information regarding nucleic acid extraction and purification since it is the fundamental step of all downstream modern molecular biology detections such as polymerase chain reaction (PCR). Microchip-based nucleic acid extraction and PCR were emphasised because they are important application of microfluidics. Based on the abovementioned reports, we developed an automated and miniaturized device for rapid nucleic acid extraction which eliminates external centrifugation and precipitation equipments and can perform the whole extraction process within 10 minutes. 293T cells were extraction through the device and the extracted total RNA was verified by real-time PCR and post gel electrophoresis. Furthermore, we presented a portable microchip realtime PCR to enable rapid detection of the extracted nucleic acid. Actual samples were used to justify the performance of our device and the detection limit is as low as 1 pg=μL with a reaction time of 25 minutes. Microchips were fabricated using silicon and glass, and we carefully designed the microchip to achieve simple yet effective sample introduction and sealing method. Finally, we reported a digital PCR microchip for high dynamic range nucleic acid detection. The silicon and glass based microchips prevents water evaporation during the PCR reaction, and we adopted passive power source which is capillary force to implement sample introduction which does not require external cumbersome power supply and also avoid errors caused by different user operations as well as improve uniformity of the experiment results.