Date of Award

5-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Bioengineering

Committee Member

John DesJardins

Committee Member

Tzuen-Rong Jeremy Tzeng

Committee Member

Kyle Jeray

Committee Member

Jeremy Mercuri

Abstract

A major cause of the high risk of infection following implantations is that the biomaterial implanted provides a surface for the bacteria to adhere and form a biofilm [1]. Altering the surfaces of biomaterials being implanted in the body has been a topic of interest in biofilm prevention research. In this proposed study, the implant surfaces are modified with two proprietary surface modification techniques, CoBlast™ and BioDep™ (ENBIO, Dublin, Ireland). The ambient temperature CoBlast™ technique sprays a stream of abrasive particles such as alumina with or without a dopant such as polytetrafluoroethylene (PTFE) to permeate the surface of materials such as metals at a micron level [2]. The BioDep™ process involves a plasma deposition of biomolecules such as chitosan and vancomycin at an ambient temperature, so antibiotic can reach the area of interest locally.

Material characterization assessments examined the surface roughness, wear resistance, and wettability of the CoBlast™ and BioDep™ surface modifications. The surface roughness of stainless steel and titanium alloy samples could be directly affected by the particle size of the abrasive used in the CoBlast™ process and was not significantly affected by the BioDep™ deposition. The CoBlast™ surface modification also successfully improved the wear resistance of the samples, regardless if their base material was stainless steel or titanium alloy. Finally, the inclusion of the dopant PTFE in the CoBlast™ process increased the hydrophobicity of the samples, regardless of their base material. All of these characterizations influenced recommendations for parameters for different future applications of these surface modification techniques.

In vitro analysis of the BioDep™ deposition process yielded recommendations for the animal study to follow. BioDep™ successfully deterred bacteria from the surface of the material regardless if the surface below it was an unmodified stainless steel or titanium sample or a CoBlast™ modified sample, however the degree to which it was effective was dependent on the number of layers of BioDep™ applied. An increase in number of layers increased the zone of inhibition that formed around the samples, however eventually too many layers caused manufacturing concerns. It was decided that a 9-layer option deposited at a high power setting was the optimal BioDep™ treatment for implants in the animal study.

The animal study examined the efficacy of an unmodified titanium dynamic compression plate (DCP), a titanium DCP modified with an alumina-only CoBlast™ process and a 9-layer high power BioDep™ coating of chitosan + vancomycin, and an unmodified titanium DCP with a 9-layer high power BioDep™ coating of chitosan + vancomycin at preventing biofilm formation after 28 days implanted on a rabbit femur. The implants with the BioDep™ coating all successfully prevented bacterial adhesion whereas the unmodified titanium implants did not.

Available for download on Monday, May 10, 2021

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