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Creating a hemocompatible small-diameter vascular graft
Ali SerpeSouth Carolina Governor’s School for Science and
Mathematics, SCGSSM
Mentor: Dr. Ning ZhangClemson-MUSC Joint Bioengineering Program
Charleston, SC
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Small-diameter Vascular Graft
Vascular grafting is a common surgical procedure in the repair or replacement of occluded, dysfunctional, or diseased blood vessels that underlie strokes and many cardiovascular pathologies/traumas.
Mechanisms of Graft FailureThrombosis – formation/presence of a blood clot in the blood vesselNeointimal Thickening – thickening of the walls of the blood vessel which prevents blood from flowing properlyInfection
Current grafts are made of Dacron and TeflonRelatively successful for large diameter vesselsPoor patency (state of being open) for small-diameter grafts (<6mm)
Usually due to neointimal thickening
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Project Aims:
The long-term goal is to create a small-diameter vascular graft with:
Microstructures and mechanical properties of the native vesselsHemocompatiblity
Prevention of clotting and adhesion of blood
Long-term patency in vivo
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Progress 1Mimicking the mechanical properties of the native small- diameter blood vessels using nanofiber composites
•Electrospinning technique
•Nanofiber array composites to mimic native vessels
• Straight PU (elastin)
• Wavy PCL (collagen)
Vince Beachley (PhD Candidate)
•Pictures of the Natural Vessel
•Wavy and straight components
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Mechanical testing indicates a match of the “J” shape Mechanical testing indicates a match of the “J” shape stress-strain behaviors of natural blood vesselsstress-strain behaviors of natural blood vessels
0.00 0.20 0.40 0.60 0.80Strain
Str
ess
Native AortaPU/Waved PCLControl PU/Straight PCL
Progress 1 Continued
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Progress 2 (Current Project)
Immobilization of heparinStandard technique to impart hemocompatibility to surfaces
EDC as a crosslinkerActs as a spacerChemically binds heparin
to the surface
Enhancing the hemocompatibility of the vascular graft through heparin immobilization
EDC reaction scheme for carboxyl-to-amine
crosslinking
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Experimental Design and Methods
Creating Films of nanofiber composites
Electrospinning
Spin Coating
Water Contact Angle
Heparinization
Toluidine Blue Assay
Plasma Recalcification Time
Activated Partial Thromboplastin Time
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Water Contact Angle (Spin-coated flims)
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Water Contact Angle (Electrospun fiber
composites)
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Results- Toluidine Results- Toluidine BlueBlue
% PEG 0% 1% 1% 10%
30%
NH2No No Yes Yes Ye
s
Molecular Weight
n/a 300 800 800 800
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Results- Plasma Recalcification Time
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Results: Results: Activated Partial Activated Partial Thromboplastin TimeThromboplastin Time
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ConclusionsConclusionsThe toluidine blue shows favorable The toluidine blue shows favorable results to heparin binding, but could results to heparin binding, but could not be quantifiednot be quantified
The water contact angle measurements The water contact angle measurements and the APTT showed favorable results and the APTT showed favorable results to heparin bindingto heparin binding
The PRT showed results unfavorable to The PRT showed results unfavorable to heparin bindingheparin binding
Further testing must be conductedFurther testing must be conducted
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Future work
Move to the animal modelMove to the animal model
Use arteriotomy model in ratsUse arteriotomy model in rats
Implant graft and evaluateImplant graft and evaluateLong-term efficacyLong-term efficacy
Long-term patencyLong-term patency
Long-term stabilityLong-term stability
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AcknowledgmentsAcknowledgmentsThe Governor’s School for Science and The Governor’s School for Science and MathematicsMathematics
The Medical University of South The Medical University of South CarolinaCarolina
Dr. Ning ZhangDr. Ning Zhang
Vince BeachleyVince Beachley
Clyde SmithClyde Smith