On-chip flow cytometry for cell analysis
Date of Issue2014
School of Chemical and Biomedical Engineering
On-chip flow cytometry provides a powerful tool to characterize the cell samples for point of care diagnosis since they provide an effective solution for low-cost and rapid evaluation of disease prognosis. The on-chip flow cytometry can implement some basic functions, such as loading, focusing, detection and sorting toward even single-cell on-chip analysis. Therefore the overall objective of my dissertation research is to develop the microfluidic cytometry for manipulation and detection of cells and other biological particles. The dissertation first reviewed the background of the on-chip flow cytometry including cell manipulation technique, cell detection techniques and cell sorting techniques. The acoustic manipulation and electrical, optical and image detection of cells are detailed discussed in the following chapters. In the chapter 3, we have conducted a study of standing surface acoustic wave (SSAW) induced acoustophoresis to manipulate the bioparticles in a microchannel. The SSAW generated by two parallel interdigital transducers (IDTs) induce the acoustic radiation force to propel particles toward the pressure node which is tunable. Therefore, the particles can assemble at the desired pressure node. The theoretical analysis also gives the approximated time consuming for particle assembling and the experimental result validates the theoretical value. Due to the advantages of easy-fabrication, lower energy consuming, and easy integration, this method can significantly benefit the development of future on-chip flow cytometry. In chapter 4, we have presented a DC-based microfluidic sensor for the detection and enumeration of circulating tumor cells (CTCs). The working principle of this cytometer is based upon the detection mechanism of bias-potential modulated pulse originating from the biological particle’s physical blockage of the micropore. 7 μm, 10 μm and 16 μm polystyrene particles were used to test and calibrate the proposed chip, respectively. Furthermore, Hela cells (a type of CTC) blood cells including red blood cells (RBCs) and white blood cells (WBCs) are used to assess the performance of this microcytometer for counting and detecting the tumor cells. The proposed microfluidic sensor is able to provide a promising platform to address the current unmet need for the point-of-care clinical diagnostics. In chapter 5, we have presented an AC-based Microfluidic impedance sensor. Conventional microfluidic impedance sensor usually requires the patterned gold electrodes directly in contact with the carrying buffer to measure the electrical current change due to the blockage of cells. However, patterning metal electrode probes on the silicon or glass substrate is a non-trivial task, which increases the fabrication cost of the impedance sensor. In this chapter, we demonstrate an alternating current (AC) impedance based microfluidic cytometer built on a printed circuit board (PCB) coated with polydimethylsiloxane (PDMS) thin film. In addition, circulating tumor cells (Hela cells) are used to successfully demonstrate the feasibility of the microfluidic AC impedance sensor in tumor cell detection. The electrodes pre-deposited PCB costs less than US$2.00 and is widely available in the market. This device has a good potential for point-of-care diagnosis in resource-poor settings. In chapter 6, we have also developed a planar optofluidic chip for circulating tumor cell apoptosis by exciting dual fluorescence through the integrated fibers. In contrast to conventional cell apoptosis study that requires commercial flow cytometer with a very high price tag and bulky optics, our design was realized via a simple single-layer soft lithography fabrication process. This study demonstrated the capability of the proposed optofluidic chip for cell apoptosis assay. In chapter 7, we demonstrate a portable resistive pulse activated lens-free cell imaging system. The system consists of the microfluidic channel and CMOS imaging sensor. Both the particle modulated pulse profile and images can be concurrently recorded in the system which is very useful for the correlation analysis (peak amplitude & pixel size) of biological cells. The advantages of this on-chip flow cytometry include simple fabrication process, compact components, reliable performance, and low manufacturing cost is capable of making it a promising platform for future mass-producible, inexpensive, and disposable on-chip investigation of biological samples.