Microfabricated devices for the spatial and temporal control of the cellular and tissue microenvironment.

摘要

The cell microenvironment is an integral component of cellular behavior. At a given moment, a cell is bombarded by signals and cues from the environment, which all are processed and integrated into specific behaviors. It is difficult examine how a particular cue affects a cell in its natural environment due to the interference of other signals. Therefore, the ability to control the microenvironment of cells and tissues is necessary to study cell interactions. Towards this end, four different devices were developed to aid in the study of cell and tissue behavior.;Oxygen-sensitive microwells are microfabricated polystyrene circular wells that are embedded with an oxygen responsive dye for the purpose of measuring the oxygen tension of isolated cell clusters. Here, both cell-cell interactions and oxygen levels are controlled or monitored by the device. Oxygen is critical in a number of cell pathways, but is often overlooked in cell culture. The device is a simple and quick method to measure the oxygen levels without disturbing the cells in culture. The microwells parameters such as depth and width are adaptable to specific experimental conditions, and the microwells are compatible with high-magnification modalities such as confocal microscopy.;The second device is a calibration tool for fast-scan cyclic voltammetry (FSCV), a commonly used analytical tool to measure chemical species. The microfluidic flow cell (μFC) is a tool that utilizes microfluidics to improve the electrode calibrations for FSCV. The μFC is simple device that switches between buffer and buffer with a known concentration of the analyte of interest – in this case dopamine - in a Y-channel. The ability to quickly switch solutions yielded electrode calibrations with faster rise times and were more stable at peak current values. The μFC reduced the number of external electrical components previously needed for this calibration and produced linear calibrations over a range of concentrations. For proof of concept, an electrode calibrated with the μFC was used to measure changes in dopamine concentration of a rat undergoing behavioral tasks.;The last two devices stem from a common idea – the ability to precisely control chemical delivery to cells and tissues. The first device automates the delivery of chemicals to gain spatially and temporally control. Having this degree of control is important for a variety of studies from yeast chemotropism to neurotransmitter release. The device consists of six valve-actuated channels that are constructed with vias to allow chemical access to the environment. The program LabVIEW is used to determine the duration, repetition, and delay of chemical release. The device was utilized for the study of yeast chemotropism on agarose and was able to produce a consistent gradient that caused orientation of yeast cells towards the higher concentration end of the gradient.;Lastly, the final device is an expansion of the automated chemical delivery device. Instead of six vias for chemical access, the expanded device has an array of 192. This provides an even higher degree of control and allows for several chemicals to be studied in combination. A multiplexor is utilized to increase the number of vias to 192 while only requiring 24 off chip valves for control. A MATLAB GUI allows each individual via to be independently accessed and chemical delivery be independently controlled.;Although these devices are look different on the surface, they share the common design principles such as laminar flow, spatial definition, and diffusion to exert specific constraints on the cell and tissue environment.