Creating a hemocompatible small-diameter vascular graft

Creating a hemocompatible small-diameter vascular graft Ali SerpeSouth Carolina Governor’s School for Science and Mathematics, SCGSSMMentor: Dr. Ning ZhangClemson-MUSC Joint Bioengineering ProgramCharleston, SC

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 Failure • Thrombosis – formation/presence of a blood clot in the blood vessel • Neointimal Thickening – thickening of the walls of the blood vessel which prevents blood from flowing properly • Infection • Current grafts are made of Dacron and Teflon • Relatively successful for large diameter vessels • Poor patency (state of being open) for small-diameter grafts (<6mm) • Usually due to neointimal thickening

Project Aims: • The long-term goal is to create a small-diameter vascular graft with: • Microstructures and mechanical properties of the native vessels • Hemocompatiblity • Prevention of clotting and adhesion of blood • Long-term patency in vivo

Vince Beachley (PhD Candidate) Progress 1 Mimicking 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) • Pictures of the Natural Vessel • Wavy and straight components

Progress 1 Continued Mechanical testing indicates a match of the “J” shape stress-strain behaviors of natural blood vessels

Progress 2 (Current Project) • Immobilization of heparin • Standard technique to impart hemocompatibility to surfaces • EDC as a crosslinker • Acts as a spacer • Chemically binds heparin to the surface Enhancing the hemocompatibility of the vascular graft through heparin immobilization EDC reaction scheme for carboxyl-to-amine crosslinking

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

Water Contact Angle (Spin-coated flims)

Water Contact Angle (Electrospun fiber composites)

Results- Toluidine Blue

Results- Plasma Recalcification Time

Results: Activated Partial Thromboplastin Time

Conclusions • The toluidine blue shows favorable results to heparin binding, but could not be quantified • The water contact angle measurements and the APTT showed favorable results to heparin binding • The PRT showed results unfavorable to heparin binding • Further testing must be conducted

Future work • Move to the animal model • Use arteriotomy model in rats • Implant graft and evaluate • Long-term efficacy • Long-term patency • Long-term stability

Acknowledgments • The Governor’s School for Science and Mathematics • The Medical University of South Carolina • Dr. Ning Zhang • Vince Beachley • Clyde Smith

Creating a hemocompatible small-diameter vascular graft