Available at: https://digitalcommons.calpoly.edu/theses/3030
Date of Award
6-2025
Degree Name
MS in Biomedical Engineering
College
College of Agriculture, Food, and Environmental Sciences
Advisor
Ben Hawkins
Advisor Department
Biomedical Engineering
Advisor College
College of Engineering
Abstract
Catheter-associated urinary tract infections remain an ongoing clinical problem due to biofilm persistence and antibiotic resistance. Standard antibiotic susceptibility testing cannot accurately reproduce flow conditions and the spatial complexity of the in vivoenvironment and is thus questionable in relevance to device-related infections. This study examines a microfluidic device designed to simulate physiologically relevant wall shear stress and antibiotic gradients in Escherichia coli biofilms. The polydimethylsiloxane-based system integrates a 16-well culture chamber with a gradient generator. Biofilm growth was observed using fluorescence microscopy of green fluorescent protein-labeled bacteria. Simulations performed using COMSOL Multiphysics software estimated the appropriate range of wall shear stress values (10⁻⁴-10⁻³ Pa) maintained by the device to match indwelling catheter conditions. The consistency analysis of the device indicated that the fabrication temperature had an impact on the retention of tubing and rate of delamination, and the best performance was achieved at 100 °C bonding. Experimental data suggested flow-dependent modulation in growth, spatial growth biases along the direction of seeding inlet, and non-uniform responses to ciprofloxacin gradients, potentially influenced by diffusion at low shear conditions, with small impact on fluorescence at high antibiotic concentrations. While ciprofloxacin exposure produced inconclusive inhibition patterns, the observed biofilm formation under defined flow conditions indicates that the current device design has potential to function as intended. Future improvements, such as vacuum-assisted bonding, enhanced tubing retention, and the use of alternative ciprofloxacin concentrations, may enable more reliable antibiotic susceptibility testing.