Measuring Perfusion Pressure and Flow Resistance in a Microfluidic Device Using an External Optical System.

The pathology of human diseases is now investigated using vascularized microphysiological systems (MPSs). Efforts to increase physiological relevance of these platforms have centered on the incorporation of organ-specific cellular and noncellular constituents. However, tissue-specific cellular constituents must experience appropriate physical forces to faithfully replicate physiological function. Quantification of physical forces in MPS has received little attention. The goal of this study was to establish a simple and robust system capable of interfacing with existing pumps to quantitatively characterize the flow delivered to an MPS. The system assessed both the fluid pressure driving flow through a microphysiological platform and the resistance to flow of glass capillary tubes or a model vascular network. The system showed excellent qualitative and quantitative agreement with resistance values measured by a hydrostatic approach and predicted for laminar flow through a smooth capillary tube. Importantly, the system is optically based without sensors contacting the circulating fluid making it ideally suited for long-term biological studies where sterility is paramount. Benchmarking experiments were supplemented with measurements of driving pressure and flow resistance from vascular structures within an MPS in a humidified incubator. Vascular resistance measurements were consistent with published results obtained from similar microvascular networks.