Biosensors for pathogen detection

Antibiotic resistance is rising and presents an increasing health risk for humans. The selection of effective antibiotic treatment is essential, and rapid diagnostic tools are of the utmost importance. Biosensors have been developed in the past decades and can compete with other current diagnostics. Electrochemical impedance biosensors provide excellent sensitivity, are label-free and rapid, making them ideal for commercialisation. Bioreceptor selection is essential for biosensor fabrication and relies upon the specificity and affinity for the target analyte. The most commonly used bioreceptors are antibodies whilst other common bioreceptors are artificial affinity proteins, oligonucleotides and molecularly imprinted polymers. Extracellular matrix (ECM) proteins could provide detection of groups of pathogens that express adhesins and have not been widely studied in this context. In this project, collagen, an ECM protein, was used to target adhesin-expressing bacteria as bioreceptors within an electrochemical biosensor. Two collagen-based electrochemical biosensors, prepared using different fabrication routes, were studied for their capability to capture whole bacterial cells through a collagen-binding to recombinant E. coli expressing the adhesin YadA. Cyclic voltammetry and electrochemical impedance spectroscopy were employed for biosensor characterisation and to assess the bacterial binding, corroborated by fluorescent binding assays. A collagen-polymer matrix-based biosensor was first developed and detected bacteria over the concentration range 8x10^5 cfu to 8x10^7 cfu in a 10 μL sample. Then, a second step-by-step, fully optimised biosensor was studied based on direct collagen attachment to a polymer-coated electrode, shown to detect bacteria over 8x10^4 cfu to 8x10^7cfu in a 10 μL sample. To conclude, this work has shown that ECM proteins can be used as a bioreceptor for pathogenic bacteria capture. Further development is needed for a fully optimised device.