Purpose: Microfluidic devices have emerged as an essential tool in the study of blood coagulation. (Colace, 2013) An 8-channel device has been developed that allows the simultaneous delivery of eight individual fluid samples (such as human whole blood treated with various agents) over a patterned feature of protein matrix such as fibrillar collagen (Maloney, 2010) (Flamm, 2012) (Li, 2013) The fibrillar collagen (250-μm wide) is patterned on glass with a microfluidic device and can be labeled with additional constituent such as lipidated tissue factor (Colace, 2012, Colace, 2012). The device can be run at constant flowrate or constant pressure drop to achieve venous (wall shear rate = 100 s-1) or arterial hemodynamics (wall shear rate 1000 s-1) (Colace, Diamond, 2012, Colace, Muthard, Diamond, 2012). The device allows multicolor, realtime imaging of cells, proteins and enzyme activity, such as platelet, fibrin, thrombin (Welsh, 2012). Each flow channel has relatively high aspect ratio (250 μm wide x 60 μm high) in order to minimize side-wall effects.
Method of Fabrication/Use: The 8-channel device is fabricated in poly(dimethylsiloxane) (Sylgard, Ellsworth Adhesives) and held to glass by vacuum. The device has 8 separate inlets (20-40 L reservoir) and perfused by withdrawal into a syringe pump (Havard Apparatus) from one common outlet. Approximately 1 cm from the inlet, the channels were spaced close enough to allow all 8 channels to be imaged simultaneously in a single 2x field of view using an inverted microscope equipped with a CCD.
Results: The Diamond Lab has used the 8-channel device to study: clot morphology (Colace, 2013) , antiplatelet agents such as P2Y1 and P2Y12 inhibitors of ADP signaling (Maloney, Brass, Diamond, 2010), thrombus stability in the presence and absence of fibrin (Colace, Diamond, 2013), patient-specific phenotyping (Flamm, 2012), and aspirin sensitivity in humans (Li, Fries, Li, Grosser, Diamond, 2013). It is particularly useful for dose-response IC50 determinations of antiplatelet agents and anticoagulants as well as evaluation of biomaterial blood compatibility.
Colace TV, Tormoen GW, McCarty OJ, Diamond SL. Microfluidics and coagulation biology. Annu Rev Biomed Eng 2013; 15 283-303.
Maloney SF, Brass LF, Diamond SL. P2Y12 or P2Y1 inhibitors reduce platelet deposition in a microfluidic model of thrombosis while apyrase lacks efficacy under flow conditions. Integr Biol (Camb) Apr 2010; 2 (4): 183-192.
Flamm MH, Colace TV, Chatterjee MS, Jing H, Zhou S, Jaeger D, Brass LF, Sinno T, Diamond SL. Multiscale prediction of patient-specific platelet function under flow. Blood Jul 5 2012; 120 (1): 190-198.
Li R, Fries S, Li X, Grosser T, Diamond SL. Microfluidic assay of platelet deposition on collagen by perfusion of whole blood from healthy individuals taking aspirin. Clin Chem Aug 2013; 59 (8): 1195-1204.
Colace TV, Muthard RW, Diamond SL. Thrombus growth and embolism on tissue factor-bearing collagen surfaces under flow: role of thrombin with and without fibrin. Arterioscler Thromb Vasc Biol Jun 2012; 32 (6): 1466-1476.
Colace TV, Diamond SL. Direct observation of von Willebrand factor elongation and fiber formation on collagen during acute whole blood exposure to pathological flow. Arterioscler Thromb Vasc Biol Jan 2012; 33 (1): 105-113.
Welsh JD, Colace TV, Muthard RW, Stalker TJ, Brass LF, Diamond SL. Platelet-targeting sensor reveals thrombin gradients within blood clots forming in microfluidic assays and in mouse. J Thromb Haemost Sep 15 2012;