Behrangzade, Ali
(2023)
Optimizing the Porohyperelastic Response of a layered Vascular Graft to Promote Luminal Reversal Microflow and Improve Hemocompatibility.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Cardiovascular diseases (CVD) claimed close to 1 million lives in 2018 in the U.S. Atherosclerosis is a pathological condition characterized by the formation of fibrous fatty plaque in arteries, specifically coronary and peripheral arteries. One of the treatments for patients with atherosclerotic lesions is vascular bypass surgery to redirect blood flow and improve downstream tissue perfusion. Autologous blood vessels are gold standards in bypass surgeries, but their availability is limited. The use of prosthetic small-diameter vascular grafts results in post-implantation complications including thrombosis and intimal hyperplasia. These complications, in part, stem from the non-optimized properties and inferior biocompatibility of these grafts. This dissertation explores the possibility of using luminal reversal microflow for potential improvement in hemocompatibility. The interstitial fluid velocity in a porous vascular graft depends on the mechanical, transport, and geometrical properties. This fluid velocity can be reversed throughout a cardiac cycle and move back into the luminal space. A high-momentum-carrying reversal microflow can potentially repel the platelets from the vascular graft luminal surface and destabilize the biofilm formation. An axisymmetric porohyperelastic (PHE) finite element model was developed and optimized to maximize the luminal reversal microflow and match the compliance to rat aorta. Our computational findings revealed that a maximum microflow of -59 $\mu m$s is achievable in a compliance-match vascular graft. A thick soft compressible permeable inner layer and a thin soft incompressible outer layer are required to maximize the microflow. We utilized thermal treatment (thermobonding) of electrospun Polycaprolactone (PCL) fibers to create an impermeable outer layer. However, the stiffness of the grafts was also significantly increased which restricts the radial motion of the grafts and reduces the microflow. We fabricated bilayered vascular graft prototypes using electrospinning and thermobonding. The PHE finite element model was validated using dye tests. In-vitro blood tests were performed, and grafts were assessed for platelet adhesion. The platelet adhesion in the microflow-generating grafts was significantly lower than the control grafts with lower microflow, lower compliance, and the same inner layer thickness. The generated microflow in these grafts was small due to the fabrication limitations. This method can potentially be utilized to improve hemocompatibility.
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Details
| Item Type: |
University of Pittsburgh ETD
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| Status: |
Unpublished |
| Creators/Authors: |
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| ETD Committee: |
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| Date: |
19 January 2023 |
| Date Type: |
Publication |
| Defense Date: |
29 August 2022 |
| Approval Date: |
19 January 2023 |
| Submission Date: |
21 November 2022 |
| Access Restriction: |
2 year -- Restrict access to University of Pittsburgh for a period of 2 years. |
| Number of Pages: |
178 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Bioengineering |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
Vascular graft, Porohyperelasticity, Electrospinning, Mechanical properties, permeability, Luminal reversal flow, blood compatibility |
| Date Deposited: |
19 Jan 2024 06:00 |
| Last Modified: |
19 Jan 2024 06:00 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/43877 |
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