Multi-modal Separations for the Biosciences

The separation, detection, and quantification of cells and DNA in biological samples is crucial to the fields of biomedical science, forensic science, and clinical diagnostics. Applications of such analyses are numerous and include, but are not limited to, health prognosis, human identification, and cancer diagnostics. The use of microfluidic devices for such separations offers many advantages such as low sample and reagent volume, fast analysis time, potential for integration, low-cost materials, and point-of-collection capabilities.
The chapters that follow describe the development and use of three different modes of separation on the microfluidic scale for DNA quantification, cell counting, human identification, and tumor cell isolation. Chapter 1 provides the necessary background on the three modes of separation, electrophoresis, magnetophoresis, and acoustophoresis, as well as provides many examples of the use of each separation mode in clinical and forensic applications. The work in Chapter 2 describes the development of a dual-force system for multiplexing a bead-based DNA assay that can quantify DNA at the sub-single cell level. This method is also shown to be useful for the counting of white blood cells in patient whole blood samples based on the amount of DNA present in the assay. A further adaptation of the multiplexed bead-based assay is presented in Chapter 3. Here, the system is optimized for separating DNA from cellular components in dried blood and cheek swab samples. In addition to purifying DNA, this method eliminates the need for quantification of DNA prior to amplification, a time-consuming and expensive step in the process of human identification. In Chapter 4, inexpensive, rotationally-driven microfluidic devices are developed for the electrophoretic separation of DNA fragments used in human identification. Furthermore, a multicolor detection system for those fragments was built and optimized. Finally, in Chapter 5, a microfluidic device was designed and optimized for the separation and isolation of circulating tumor cells from whole blood samples.