| Microfluidic design forms a basis for precision measurements of even complex biological systems. Among the lines of inquiry that are thriving with the advent of microfluidic tools are biological mimetic tissues created "on-a-chip". In this area, we have constructed a liver-on-a-chip system for drug hepatotoxicity screening. The liver-on-chip model is designed to include the liver's sinusoid structure, oxygen diffusion, and the flow of nutrient supplies, in order to deliver a functional liver mimic for the study of drug metabolism. After design and fabrication of this organ mimic, we observed the liver-on-a-chip to yield improved hepatocyte life span and drug metabolism function, as compared to in vitro sandwich culture.;Cytometry---or single-cell resolution measurements---are another thriving line of inquiry. In cytometry, this dissertation research contributes three measurement aspects made possible with microfluidic tools: genomic processes (miRNA detection); targeted proteomics using electrophoresis, and function. By modeling and measuring the mass and heat transport processes limiting the precision of state-of-the-art cytometry tools, we optimize and validate a suite of new approaches. Specifically, in miRNA cytometry, we designed, fabricated, and demonstrated an isothermal quantification methodology that is coupled with microfluidic single-cell isolation, lysis, and amplification. The platform achieves high throughput and precise measurement of cell-to-cell miRNA levels. We analyzed miRNA expression in cancer cell lines and doxorubicin-resistant counterparts, which point to the existence of microRNA-dependent sub-population dynamics.;In cytometry of protein targets, we study a set of novel device architectures designed to minimize geometry-induced injection dispersion in electrophoresis of single-cell lysates. Single cells are commonly seated in microwells formed in hydrogels. Cells are chemically lysed in-situ, with the lysate subjected to electrophoresis in the surrounding gel. An analytical model was developed and experimentally validated to show that controlling both the geometry of the microwell and the thermodynamic partitioning characteristics of the microwell impact separation resolution and detection sensitivity.;Taken together, we establish a suite of microfluidic tools that mimic, manipulate, and measure processes important to factors that span from the protein to the genome, and from the cell to the whole organ.;In summary, this dissertation focuses on utilizing analytical chemistry and engineering approaches to advance microfluidic applications in tissue engineering and single-cell studies. |
