Development and validation of a novel microfluidic platform for studying local microvascular blood flow regulation in vivo

Russell McEvoy, Gaylene M. (2020) Development and validation of a novel microfluidic platform for studying local microvascular blood flow regulation in vivo. Masters thesis, Memorial University of Newfoundland.

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Abstract

Currently, there is no effective way to restrict administration of vasoactive drugs to capillary networks of skeletal muscle and observe the effects on blood flow. The purpose of this project was to develop and validate the efficacy of a novel liquid microfluidic device (LMFD) to manipulate a microscale region of tissue while simultaneously allowing for visualization and quantification of microvascular blood flow. The LMFD was developed and fabricated using soft lithographic techniques. Devices were molded in polydimethylsiloxane and bound to a glass coverslip with a 600 x 300 μm laser cut micro-outlet. Sprague-Dawley rats were anaesthetized with sodium pentobarbital and instrumented to monitor systemic parameters. The extensor digitorum longus muscle was dissected, externalized, and reflected across the LMFD on the stage of an inverted microscope. Doses (10-8 to 10-3 M) of adenosine triphosphate (ATP), acetylcholine, and phenylephrine (PE) were sequentially administered to the muscle via perfusion through the LMFD. Videos of microvascular blood flow at multiple focal planes were recorded directly overlying the micro-outlet. Recordings were analyzed offline for red blood cell (RBC) velocity, supply rate, and hematocrit. ATP significantly increased RBC velocity and supply rate. Increasing concentrations of PE caused a decrease in RBC velocity and supply rate. Changes in perfusion were restricted to areas directly overlying the micro-outlet and within 500 μm. This novel LMFD allows for a controlled delivery of dissolved substances to constrained regions of microvasculature while simultaneously allowing for visualization and measurement of blood flow within discrete vessels and networks.

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