Date of Award

Summer 8-3-2022

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science in Biomedical Engineering

Department

Biological Engineering

Advisor

Caitlin Howell

Second Committee Member

Bashir Khoda

Third Committee Member

Jean MacRae

Abstract

Reducing or eliminating bacteria on surfaces is vital for medical devices, drinking water quality, and industrial processes. Evaluating surface bacterial growth at buried interfaces can be problematic due to the time-consuming disassembly process required for obtaining standard surface samples. In this work, a continuous, non-destructive, and reusable method was developed to detect surface bacterial growth at buried interfaces. Inspired by vascular systems in nature that permit chemical communication between the surface and underlying tissues of an organism, bacterial-specific signals diffusing from cells on the surface were detected in channels filled with an inert carrier fluid embedded in a polymer matrix. The carrier fluid was analyzed using conductivity, ultraviolet-visible (UV-vis) spectroscopy, and high-performance liquid chromatography (HPLC); methods that ranged in sensitivity and accessibility. A second iteration prototype was developed that addressed delamination and contamination issues. Carrier fluid from the second prototype vascularized polymers with surface Escherichia coli growth recorded greater values in conductivity (9.32 ± 0.22 mS/cm) against controls with no bacteria (7.86 ± 0.29 mS/cm) after 24 hours. Additionally, sample carrier fluid absorbance (0.535 ± 0.041 a.u.) was greater than control carrier fluid absorbance (0.430 ± 0.016 a.u.) after 24 hours. HPLC analysis detected two matrix-specific peaks in carrier fluid from controls and the appearance of a bacterial-specific peak in carrier fluid from samples. Extracting and refilling the vascular channels with new carrier fluid allowed for the system to continuously monitor surface bacterial growth over time and measure early detection. Differences in conductivity, absorbance, and HPLC were observed at 8 hours of surface bacterial growth. Clinically relevant bacterial strains, Staphylococcus aureus and Pseudomonas aeruginosa, were tested and yielded significant increases in carrier fluid in conductivity, absorbance, and HPLC peak areas. This work lays the foundation for the use of vascularized polymers as an adaptive system for the continuous, non-destructive detection of surface bacteria along with multiple methods for analysis.

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