Author ORCID Identifier

https://orcid.org/0000-0002-9059-947X

Year of Publication

2021

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Engineering

Department/School/Program

Chemical and Materials Engineering

First Advisor

Dr. Bradley J. Berron

Abstract

Cardiovascular disease remains the number one threat to American lives. During an acute myocardial infarction (AMI), blood flow is blocked and results in the formation of scar tissue. As the body’s immune system responds, inflammatory signaling causes an increase in both scar tissue size and the patient’s risk for further chronic heart failure. In order to reduce the risk of continued heart disease inflammatory signaling must be reduced. Stem cell therapies have the ability to alter the immune system’s pro-inflammatory signal. However, stem cell retention is limited due to blood flow shear. Gelatin methacrylate (GelMA) based coatings have been shown to increase the retention of these therapeutic cells inside the infarcted myocardium. This dissertation evaluates the GelMA coating process and aims to optimize this therapy for future trials.

Biotin-streptavidin (SA) affinity is the foundation for our GelMA coating process. GelMA coatings are grown from eosin bound to the cell surface through a biotin-SA complex. In this work, we demonstrate the high binding affinity through a cardiac flow model. We show that biotinylated cardiac cells can be immobilized onto a SA functionalized glass substrate and withstand large shear. While biotin-SA affinity allows for glass immobilization, we have yet to study what drives the adhesion of our biotin-SA grown GelMA coatings in vivo. We examine two different binding sites for GelMA coated cells: the extracellular matrix (ECM) or resident cells that make up the myocardium. GelMA is created from the degradation of collagen, however, our studies show collagen-binding integrins on the surface of cells do not promote adhesion of GelMA. Through decellularization of heart ECM, we were able to show GelMA-ECM is a strong binding mode that is driven by collagen-gelatin binding. As our coatings drive adhesion through collagen-collagen binding, I hypothesize that increasing the amount of GelMA on the cell surface will result in increased retention in vivo. In our previous work, cells were biotinylated through covalent attachment to free cell surface amines. In an effort to increase the density of biotin on a cell surface, we utilize a lipid insertion approach. The use of cholesterol anchors increased streptavidin density on the surface of cells further driving polymerization and allowing for an increased fraction of cells coated with gelatin (83%) when compared to covalent methods (52%). Altogether, through the use of cholesterol anchors and our in vivo understanding of coating specificity, we have created a path towards improving the retention of MSC in vivo for post-MI therapy.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2021.247

Funding Information

Kara Davis Funding:

National Institutes of Health National Center for Advancing Translational Sciences, TL1TR001997, Year: 2019-2021

Berron Lab Funding:

National Heart, Lung and Blood Institute (NHLBI), R01 HL127682, Year: 2015-2019

National Science Foundation, CBET-1351531, Year: 2018-2021

American Heart Association, #18IPA34170059, Year: 2019-2020

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