Interfacing to Biological Systems Using Microfluidics

Biological systems operate on scales ranging from nanoscale chemical reactions to the global flow of nutrients and energy. Building knowledge of each level requires techniques and technologies that can address the biological system at the chosen level of interest. On the cellular and community levels, microfluidics are able to replicate the spatial scales of the natural system from the cellular, to community through the local microenvironment while providing engineering solutions to control flow through the system and interfaces with the system through microscopy and chemical sampling. Herein, biological interfaces were created using microfluidics to control cellular interactions and chemical reactions. At the subcellular scale, molecular exchange bioreactors enhanced the protein production of a cell-free protein synthesis system by using a microscale serpentine channel to reduce lateral diffusion distances. Size dependent transport of reactants into, and byproducts out of, the reaction channel through the nanoporous barrier extended the reaction time and enhanced protein yield. Nanoporous membranes were also developed for studying cellular interactions. Membranes confined cells within culture chambers while allowing transport of nutrients and signal molecules between the chambers and support channels. Quorum sensing within the microfluidic chambers was modeled using a quasi-steady-state PDE based approach to estimate relative concentrations. The platform facilitated the use of brightfield imaging and analysis to characterize morphological changes of a growing biofilm as the oral microbe Streptococcus gordonii formed aggregates only when co-cultured adjacent to Fusobacterium nucleatum. The investment of capital and time to start incorporating microfluidic into research can be prohibitive. To combat this, tools were created to provide researchers the ability to create microfluidics using 3D printing to simplify the process and remove the need for cumbersome and expensive cleanroom facilities. The technique was used in two common microfluidic applications of chemical gradient and droplet formation in addition to building 3D fluidics that cannot be replicated directly with microfabrication techniques. These microfluidics controlled the spatiotemporal environment on the scales of biological systems to enhance the effectiveness of protein synthesis, give insight to morphological effects of cell signaling, and introduced technology to enable others to do the same