Quantitative microfluidic delivery systems for studying tissue microenvironment and microvascular blood flow regulation in vivo

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BACKGROUND: The nutritive requirements of all body tissues are provided for by the dynamic distribution of blood flow to microvascular networks throughout the body. Studying blood flow regulation in vivo requires specialized, minimally invasive, surgical preparations in order to isolate a tissue of interest while preserving the normal function and control of the regulatory system itself. We have previously developed gas exchange chambers to manipulate gas partial pressures in skeletal muscle of live rats. This work demonstrated the feasibility and efficacy of these devices and that the microcirculation can respond to changes in the surrounding microenvironment. ***We propose the development of novel microfluidic devices that allow for the introduction of dyes and pharmacological agents to skeletal muscle for the purposes of studying blood flow regulation and mass transport. ***OBJECTIVES: 1) Develop a microfluidic device and fluid flow system capable of maintaining a fixed solute concentration, temperature, and physiologic gas conditions, at the surface of an intact tissue in vivo while simultaneously allowing visualization and quantification of blood flow within the tissue. 2) Validate the efficacy of the device to deliver compounds into the overlying tissue using dyes, fluorescent probes, and vasoactive drugs. 3) Create mathematical mass transport models of the microfluidic device and overlying tissue to calculate the tissue concentration and gradients of solutes within the tissue given known conditions within the microfluidic flow chamber, physical properties of the tissue, and blood flow in the microcirculation. 4) Apply the microfluidic system and mathematical model to interrogate microvascular regulatory mechanisms in intact skeletal muscle using various vasoactive agonist, antagonists, and drugs.***SCIENTIFIC APPROACH: Microfluidic devices will be constructed using precision laser cut glass and molded plastics made with soft lithography techniques. Flow within the device will be controlled using standard micro-flow valves connected to a computer system. Visualization and measurement of microvascular blood flow will be achieved using high-powered microscopy of rat skeletal muscle. Computer models will be used to inform the experimental results and calculate the depth to which substances delivered via the microfluidic channel will penetrate into the tissue.***IMPACT: The projects related to this program will provide excellent training opportunities for young scientists and students interested in the fundamental function of our cardiovascular systems. This research will produce a novel technology for studying microvascular function in vivo as well as a platform for interrogating the microenvironment of living tissue. These innovations will influence many areas in biomedical research, particularly those related to understanding integrated microcirculation.