Comparison of the Spreeta® surface plasmon resonance sensor and a quartz crystal microbalance for detection of Escherichia coli heat-labile enterotoxin

Small, low-cost sensors that rapidly detect pathogens or their toxic products in food and water supplies would facilitate environmental monitoring. However, they must be sufficiently easy to use and reliable enough to be widely deployed. In this study, a small surface plasmon resonance sensor (Spreeta® SPR) and a quartz crystal microbalance (QCM) have been evaluated to determine whether the sensitivity, reliability, and ease of operation of one or both devices would be suitable for flow-cell format detection of pathogenic agents. Both make use of a gold-coated surface modified by deposition of a suitable capture agent. In each case, analyte binding to the capture agent results in a quantifiable signal. The model system consisted of Escherichia coli heat-labile enterotoxin (LT), responsible for travelersʹ diarrhea, and its receptor analog, ganglioside GM1. Each device provided a roughly proportional response in a range between 3 (35pmol) and 25µg (300pmol) of toxin protein, but began to saturate the adlayer of capture agent at higher toxin concentrations. The Spreeta® SPR produced a significant response to 6µg (70pmol) of E. coli enterotoxin, while the QCM device produced a measurable response to 3µg (35pmol) of E. coli enterotoxin. The two devices are comparable with respect to ease of operation and reliability. Both devices could be suitable for remote sensing of analyte from a flow stream with suitable enclosures and temperature-controlled buffering to prevent artifacts induced by temperature fluctuation. There appear to be no significant differences between the Spreeta® SPR device compared to a QCM device as a small, low-cost, rapid biodetector. While neither device matches the sensitivity of enzyme-linked immunosorbant assay(ELISA) for detection of picograms amounts of analyte, measurements can be obtained directly, in minutes, rather than the hours required to visualize results of an ELISA.