Microfluidic Systems for Bioprocessing and Biodetection

Microfluidics enables for the development of portable device and systems that can efficiently process and precisely detect biological samples for a wide array of applications. Specifically, microfluidics offers numerous advantages in fluidic processing, sample preparation and the detection of biological cells and molecules. Recent advancements in micro-/nanotechnologies have allowed for the development of integrated lab-on-a-chips (LOCs), which greatly improve the convenience, affordability and accessibility of such systems. These systems are typically faster, consume smaller sample and reagent volumes and are capable of higher resolution compared with conventional technologies. In this work, microfluidic devices were designed, fabricated and tested for various emerging bioprocessing and biodetection applications. A novel cell sorter was developed which utilizes strategically-configured pillars within a microchannel to separate particles solely based on their size. This device was used to sort heterogeneous populations of embryoid bodies (EBs) into size-specific groups with separation efficiencies approaching 81%. We have also developed a microfluidic platform for trapping and lysing single and small populations of Pseudo-nitzschia , which employed hydrodynamic flow focusing and ultrasonication. This device achieved cell trapping efficiencies up to 96% and was capable of fully lysing cells within a few seconds. While bioprocessing is one major application for microfluidic systems, the detection of biological samples is another key application with equal importance. Towards this end, an electrical impedance biosensor was developed for the detection of bacterial pathogens which utilizes an array of microelectrodes coated with custom synthesized, cell-targeting peptides. Two types of disease-causing pathogens ( Streptococcus mutans and Pseudomonas aerugionsa) could be simultaneously targeted and sensed within a polymicrobial sample in a timely manner. This thesis concludes with the presentation of an automated, fully-functional LOC that can rapidly detect minute quantities of toxins. A hydrophilic poly(dimethylsiloxane) (PDMS) coating was developed and utilized for autonomous delivery of liquid samples and an electrochemical sensor enabled for highly-sensitive measurements. Botulinum neurotoxin (BoNT) was used as a model system, which could be detected at concentrations as low as 1 ng/mL in less than 15 min. Ultimately, the devices presented in this dissertation demonstrate the immense potential of microfluidics for developing new tools and technologies for the advancement of science, medicine and technology.