Date Available

12-6-2021

Year of Publication

2021

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Engineering

Department/School/Program

Mechanical Engineering

First Advisor

Dr. Martha E. Grady

Abstract

Implant associated infections are one of the leading causes of hospital acquired infections in the United States. Medical orthopedic implant devices are designed to improve adhesion of relevant cells within our body. In the case of orthopedic implants, osteoblast cells will adhere and allow for proper integration with the body’s bones. However, virulent bacteria will also adhere onto medical implants and proliferate into biofilms. Bacterial biofilms become extremely difficult to eradicate clinically as antibiotics are not as effective, resulting in severe infections or loss of implant. The aim of this research is to quantify the adhesion strength differential between relevant bacterial biofilms and osteoblast-like cell monolayers onto orthopedic implant-simulant surfaces. The laser spallation technique, a non-contact and rapid onset thin film adhesion technique is employed to quantify adhesion strength. High-amplitude short-duration stress waves generated by laser pulse absorption are used to spall bacteria and cells from titanium substrates. By carefully controlling laser fluence and calibration of laser fluence with applied stress, the adhesion difference between bacterial biofilms and osteoblast like cell monolayers are obtained. Environmental factors, such as supplement concentration, and surface factors, such as surface roughness and surface preconditioning treatments, are investigated. Several studies are performed to validate and adapt the laser spallation technique for biological purposes, including special calibrations for roughened surfaces and exploring location dependence of biofilm adherence. Finally, the ratio of cell adhesion strength to biofilm adhesion strength, termed the Adhesion Index, is determined as a nondimensionalized parameter for biocompatibility assessment. The Adhesion Index is implemented to determine surface factors that promote favorable adhesion of cells greater than biofilms. Here, an Adhesion Index greater than one suggests favorable biocompatibility. The laser spallation technique provides a platform to examine the tradeoffs of adhesion modulators on both biofilm and cell adhesion.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2021.430

Funding Information

National Institute of Health

P20GM130456 and R03DE029547

2016-2021

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