Purpose: Microfluidic devices allow the generation of flow fields and localized control of pressure drops across porous matrix or cellular assemblies (Muthard, 2012). These devices have been used to measure endothelial migration and angiogenesis, blood clot permeability, clot retraction, and inner clot reaction dynamics (Muthard, 2013). The design is especially suited for studies of metastasis, matrix proteolysis, wound healing, and actinomyosin-mediated processes.
Method of Fabrication/Use: The side-view matrix chamber is fabricated in PDMS with 3 flow channels per PDMS device (Muthard, Diamond, 2013). A vacuum holds the device to glass. The device requires 2 syringe pumps and 3 pressure sensors which are used to control the down stream syringe pump to achieve constant transmural pressure drop even as a structure grows into the flow field.
Results: The Diamond Lab has used this device to study how prevailing hemodynamics influence thrombus structure and platelet retraction. Platelet sensing of flow cessation triggered a 4.6 to 6.5-fold (n=3, P<0.05) increase in contraction rate. This triggered contraction was blocked by the myosin IIA inhibitor blebbistatin and by inhibitors of thromboxane (TXA2) and ADP signaling. In addition, flow arrest triggered platelet intracellular calcium mobilization, which was blocked by TXA2/ADP inhibitors. Thus, the device allowed the discovery that blood clots are rapidly assembled flow sensors. Without stopping flow, platelet deposits (no fibrin) had a permeability of κplatelet = 5.45 x 10-14 cm2 and platelet-fibrin thrombi had κthrombus = 2.71 x 10-14 cm2 for ∆P = 20.7 to 23.4 mm-Hg, the first ever measurements for clots formed under arterial flow (1130 s-1 wall shear rate).
Muthard RW, Diamond SL. Side view thrombosis microfluidic device with controllable wall shear rate and transthrombus pressure gradient. Lab Chip May 21 2013; 13 (10): 1883-1891.
Muthard RW, Diamond SL. Blood clots are rapidly assembled hemodynamic sensors: flow arrest triggers intraluminal thrombus contraction. Arterioscler Thromb Vasc Biol Dec 2012; 32 (12): 2938-2945.