Microfluidic device for constant flowrate or constant transmural pressure gradients (Diamond, SL)

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.

(A) Comsol simulation of a microfluidic device that allows perfusion from an inlet (Q1) over a collagen plug held on a micropost array (B) for constant pressure drop (and fluid permeation) across the collagen) (C).

(A) Comsol simulation of a microfluidic device that allows perfusion from an inlet (Q1) over a collagen plug held on a micropost array (B) for constant pressure drop (and fluid permeation) across the collagen) (C).

(A) Microfluidic that allows perfusion from an inlet (Q1) over a collagen plug held on a micropost array (B) to allow a constant pressure drop (and fluid permeation) across the collagen).  PDMS device shown at time of use with 3 pressure sensors and two infusion ports connected (C).

(A) Microfluidic that allows perfusion from an inlet (Q1) over a collagen plug held on a micropost array (B) to allow a constant pressure drop (and fluid permeation) across the collagen). PDMS device shown at time of use with 3 pressure sensors and two infusion ports connected (C).

Perfusion of anti-coagulated whole blood provides reproducible thrombus development at the collagen-blood interface.  Anti-coagulated whole blood was perfused at an initial wall shear stress (33.9 dyne/cm2) while a constant ΔP (23.4 mm Hg) was maintained across the collagen-blood interface.  Dynamic studies of platelet (red) and thrombin (green) development on collagen (A-C) or collagen/TF scaffolds (D-F) allowed for spatial-temporal clot measurements.  Resulting structures were simulated in COMSOL to study time-dependent wall shear stress at the clot boundary (G).

Perfusion of anti-coagulated whole blood provides reproducible thrombus development at the collagen-blood interface. Anti-coagulated whole blood was perfused at an initial wall shear stress (33.9 dyne/cm2) while a constant ΔP (23.4 mm Hg) was maintained across the collagen-blood interface. Dynamic studies of platelet (red) and thrombin (green) development on collagen (A-C) or collagen/TF scaffolds (D-F) allowed for spatial-temporal clot measurements. Resulting structures were simulated in COMSOL to study time-dependent wall shear stress at the clot boundary (G).

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).

 

References

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.

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