Development of a dual sensor polymer-based system for antibiotic detection in water samples

Abstract

In April 2019, the UN issued a warning that the overuse of antibiotics could lead to 10 million fatalities annually by 2050. It would also be a significant financial burden as there can be losses of €1.6 billion per single strain of antimicrobial resistant (AMR) bacteria, occurring primarily but not limited to the costs of medical care, hospitalisation, and patient care. Infiltration of antibiotics into groundwater arises from multiple sources; agriculture, highly populated residential areas and pharmaceutical effluents. These leached antibiotics journey to river systems cause selective pressure, thereby giving rise to accelerated AMR development. One route for aiding this issue is to slow the growth rate the emergence of AMR by controlling the levels of antibiotics that gain entry to water systems. To monitor this, a low-cost and reliable sensor platform is needed that can rapidly and on-site identify contaminated areas. Molecularly Imprinted Polymers (MIPs) are synthetic receptors that have potential for specific detection of contaminants in complicated matrices but have found limited commercial applications. The work within this thesis will explore the rational design of MIPs, their optimisation for a plethora of targets and the investigation of various applications to exploit their favourable characteristics when deployed as sensor platforms. Looking at how these imprinted polymers have been developed and utilised in recent times (primarily 2010-2020) and assessing any limitations encountered. These limitations have holstered MIP use, giving rise to the need for the critical review, which has been carried out in this thesis, on what development is needed to boost their applications to convert them into a mainstream commercial tool. Most MIP-based sensor systems focus primarily on a single analysis technique. Chapter 3 sees a novel, dual detection system developed which facilitates direct validation of the results and therefore can realise reliable detection of antibiotics in aqueous samples. Fluorescent monomers have been incorporated into the MIP complex allowing for fluorescent analysis as well as thermal, producing a dual sensor platform thus vastly enhancing the reliability of the biosensor. 3 Two applications of MIPs, that have been deployed as sensors, have been experimentally assessed. A focus on mounting these polymers onto Screen Printed Electrodes (SPEs) and the subsequent thermal analysis will be describe in chapter 4. This work comprised of a comparison of two techniques was carried out to determine the most appropriate method for attaching the polymers to the surface of the SPE, direct polymerisation onto the SPE against dropcasting of MIP particles synthesized by free radical polymerisation on the SPE surface. The direct polymerisation proved to afford MIP-modified SPEs to have higher levels of binding affinity. Chapter 5 explores an investigation into the evolution from small molecule targets to large macromolecules including whole bacteria. This proof-of-concept study saw a yeast mixture used as a target for MIP detection since yeast resembles bacteria in size and shape but does not need to be handled in a certified biosafety lab. A full evaluation of the work carried out concludes the thesis with an aim to gauge how the work undertaken will contribute to the development of a new division of quantitative sensor platforms. Secondly, the work produced will construct foundations for what is still needed to push the use of MIPs into commercial use to combat the rise in AMR