Thin Film Point of Care Diagnostic and the Potential Mitigation of Antimicrobial Resistance

  • Author / Creator
    Terry, Ciaran
  • Antimicrobial resistance is an emerging worldwide threat that endangers the effectiveness of many of the gains of modern medicine. Therapies are becoming less effective through their overuse even while antimicrobial stewardship programs have been developed to measure and improve how antibiotics are prescribed by clinicians and used by patients. Bacterial and viral infections have many overlapping symptoms, but the use of antibiotics for viral infections are ineffective and can lead to the development of drug-resistant microbes. There are biomarker distinctions between viral and bacterial infections. Procalcitonin is a biomarker whose circulating levels are only detectable during a bacterial infection. Therefore, a rapid point-of-care procalcitonin diagnostic could diagnose bacterial infections, guide antibiotic therapy, improve patient outcomes and promote antimicrobial stewardship.

    This thesis investigates the development of a qualitative procalcitonin diagnostic that uses a solid-state version of the same thin film colour generating phenomena as seen from an oil slick on wet tarmac. A test strip would have a layer of procalcitonin antibody adsorbed to the aluminum oxide surface—this would produce a colour. Any procalcitonin in a 20—100µl sample of patient blood would bind to the antiprocalcitonin and the formation of this immunocomplex would produce a different colour and signify a bacterial infection. Light’s optical path length can be altered by changing two parameters: the physical distance the light travels through a medium and the refractive index of that medium. A matrix was designed to test 10nm increment changes in an aluminum oxide layer on tantalum pentoxide between 80—130nm and 2V increments in the voltage at which the thin films were anodized between 2-10V. An increase in anodization voltage increases the refractive index. Additionally, four different procalcitonin antibodies were engineered so they would orient perpendicular to the alumina surface exposing the binding sites and minimizing the variability in the physical distance light would travel through the system. Two different combinations were standouts: 2V/120nm/Antibody C and 10V/90nm/Antibody C. The former produced the most substantial colour shift without amplification, while the latter produced a significant colour shift following a second application of antibody C. These optimal combinations were used in following studies.
    In buffer, clinically relevant picomolar procalcitonin sensitivity was shown, in addition to an experiment designed to show procalcitonin’s specificity to antiprocalcitonin. A blinded validation experiment was designed for an independent observer to distinguish between procalcitonin-spiked blood, but there were significant issues with non-specific binding of different blood proteins to the alumina surface.
    A 3D-printed procalcitonin kit prototype was developed that included everything necessary to conduct a point-of-care test that could diagnose bacterial infections and guide antibiotic therapy at a tenth of the cost of a procalcitonin lab test.
    This device shows promise as a visually qualitative point-of-care procalcitonin test, but a solution to the blood’s non-specific binding on the device’s aluminum oxide surface is necessary.

  • Subjects / Keywords
  • Graduation date
    Fall 2021
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.