Binding strategies for capturing and growing Escherichia coli on surfaces of biosensing devices
Résumé
Antibiotic resistant bacteria have become a threat to world health. An advanced method
of detection, based on the matrix assisted laser desorption ionisation time-of-flight mass
spectroscopy can identify bacteria relatively rapidly, but it is not suitable to measure
bacterial antibiotic resistance. Biosensors may be able to detect resistance by monitoring
growth after capture on sensor surfaces but this option has not been addressed adequately.
We have evaluated the growth of Escherichia coli after capture in 96 well microplates
and observed that growth/capture efficiency was relatively similar for antibody-based
techniques, but non-specific capture varied considerably. We confirm that neutravidin
binds E. coli non-specifically, which limited its use with biotinylated antibodies or
aptamers. Centrifugation enhanced bacterial growth/capture considerably, indicating that
procedures enhancing the interaction between bacteria and surface-bound antibody have
the potential to improve growth efficiency. Capture and growth required larger numbers
of bacteria than capture and detection on biosensor surfaces. Previously, we reported that
the minimum concentration of live E. coli required for initiating growth on a
GaAs/AlGaAs biosensor was ~ 10 5 CFU/mL [Nazemi et al., Talanta 178 (2018) 69-77],
and we speculated that this could be related to the poisonous effect of Ga- and As-ions
released during dark corrosion of the biosensor, however in the present report we
observed that the same minimum concentration of E. coli was required for growth in an
ELISA plate. Thus, we argue that this limitation was related rather to bacterial inhibition
by the capture antibodies. Indeed, antibodies at titres designed to capture bacteria
inhibited bacterial growth when the bacteria were added to growth medium at titres less
than 10 5 CFU/mL, indicating that antibodies may be responsible for the higher limits of
sensitivity due to their potential to restrict bacterial growth. However, we did not observe
E. coli release after 6 h following the capture indicating that these bacteria did not
degrade antibodies.
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