Date of Award

5-2012

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Bioengineering

Advisor

Dean, Delphine

Committee Member

Goldsmith , Edie

Committee Member

Simionescu , Dan

Abstract

In this Master's thesis we examine the effect of surface modified gold nanorods (AuNRs) coated with polyelectrolyte multilayers (PEMs) on the mechanical properties of porcine mitral valve tissue ex vivo. The presence of healthy mitral valve tissue in the body is important to ensuring unidirectional flow of blood through the systemic circuit. Unfortunately, due to its anatomic complexity and unique mechanical behavior, pathological mitral valve tissue remains difficult to treat with conventional methods. We hope that the knowledge gleaned from these studies could be useful for developing new and novel treatments treating pathological mitral valve mechanical properties.
Specifically, we examine the localized changes in apparent elastic modulus and stress relaxation behavior for the porcine mitral valve leaflets treated with the AuNRs with the atomic force microscope (AFM). We study these effects specifically because there is little literature available that examines the unique changes in mechanical properties of tissues treated with nanorods. Nanorods are used exclusively because they have already been shown to have a general effect on the properties of collagen gels, which are a good model for atrioventricular valve tissues. Our studies indicate that the presence of these AuNRs initiate an increase in the apparent stiffness of the valvular tissue while leaving the observed stress relaxation behavior unchanged.
In addition to examining the overall effect of the AuNRs in the tissue, we also examine the effect of differing surface charges on the apparent elastic modulus and stress relaxation of the tissue by using two types of PEM coated AuNRs. The first type of PEM coated AuNR possesses a negatively charged terminal layer, while the second type of PEM coated AuNR possesses a positively charged terminal layer. These AuNRs are used at differing concentrations to better understand how many nanorods are necessary to observe an effect on the apparent elastic modulus and stress relaxation behavior. Overall, there was little difference in effect between the two types of AuNRs and the two concentrations of AuNRs.

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