Comparison of the Spreeta (R) 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 produc ts in food and water supplies would facilitate environmental monitoring. Ho wever, they must be sufficiently easy to use and reliable enough to be wide ly deployed. In this study, a small surface plasmon resonance sensor (Spree ta((R)) SPR) and a quartz crystal microbalance (QCM) have been evaluated to determine whether the sensitivity, reliability, and ease of operation of o ne or both devices would be suitable for flow-cell format detection of path ogenic agents. Both make use of a gold-coated surface modified by depositio n of a suitable capture agent. In each case, analyte binding to the capture agent results in a quantifiable signal. The model system consisted of Esch erichia coli heat-labile enterotoxin (LT), responsible for travelers' diarr hea, and its receptor analog, ganglioside GM(1). Each device provided a rou ghly proportional response in a range between 3 (35 pmol) and 25 mug (300 p mol) of toxin protein, but began to saturate the adlayer of capture agent a t higher toxin concentrations. The Spreeta((R)) SPR produced a significant response to 6 mug (70 pmol) of E. coli enterotoxin, while the QCM device pr oduced a measurable response to 3 mug (35 pmol) of E. coli enterotoxin. The two devices are comparable with respect to ease of operation and reliabili ty. Both devices could be suitable for remote sensing of analyte from a flo w stream with suitable enclosures and temperature-controlled buffering to p revent artifacts induced by temperature fluctuation. There appear to be no significant differences between the Spreeta((R)) SPR device compared to a Q CM device as a small, low-cost, rapid biodetector. While neither device mat ches the sensitivity of enzyme-linked immunosorbant assay(ELISA) for detect ion of picograms amounts of analyte, measurements can be obtained directly, in minutes, rather than the hours required to visualize results of an ELIS A. (C) 2001 Elsevier Science B.V. All rights reserved.