Publication Date

Fall 2018

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

Advisor

Sang-Joon Lee

Keywords

Blebbistatin, Blood clots, Cytochalasin, Nonlinear stiffness, Tensile testing, Viscoelasticity

Subject Areas

Mechanical engineering

Abstract

Although blood clots are vital to wound healing, little is known about what factors influence clot stiffness and dynamic response. This work investigates the mechanics of inhibitor-treated clots by direct tensile testing using a custom designed system for forces below 1 N. Inhibitors that affect clot formation include blebbistatin, which affects myosin II movement on actin, and cytochalasin D, which affects actin polymerization. The hypothesis of this investigation is that blebbistatin will have a greater effect on mechanical behavior than cytochalasin D, because the inhibition of myosin II will weaken the overall clot more than actin. This hypothesis was investigated using clots that were treated with blebbistatin and cytochalasin, using untreated whole blood as a reference. Clots were tested from five different donors with at least two replicates from each donor. Each clot was subjected to an initial stretch ratio of 1.5 to measure nonlinear stiffness, followed by a series of 1 mm increments to record stress relaxation. At a stretch ratio of 1.5, blebbistatin-treated clots exhibited 4.3% lower tensile stress than cytochalasin-treated clots. The relaxation time constant for blebbistatin-treated clots was 10% faster than for cytochalasin-treated clots. This evidence supports the hypothesis about the role of myosin II in blood and introduces experimental methodology that can be extended to studies on mechanics of other soft biological tissues.

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