A QCM-D-based biosensor for E. coli O157:H7 highlighting the relevance of the dissipation slope as a transduction signal.

A biosensor for detection of viable Escherichia coli (E. coli) O157:H7 is developed using a quartz crystal microbalance with dissipation monitoring (QCM-D). The detection platform is based on the immobilization of affinity purified polyclonal antibodies onto gold-coated QCM-D quartz crystals via a cysteamine self-assembled monolayer. QCM-D measurements conducted over a broad range of bacterial cell concentrations show that the optimal biosensor response is the initial slope of the dissipation shift as a function of elapsed time (D(slope)). A highly log-log linear response in the initial D(slope) is obtained for detection of E. coli O157:H7 over a wide range of cell concentrations from 3 x 10(5) to 1 x 10(9)cells/mL. The prepared biosensor also exhibits a log-log linear working range from 10(7) to 10(9)cells/mL for E. coli K12 D21, a non-pathogenic model organism and further shows satisfactory selectivity using Bacillus subtilis. To our knowledge, this is the first study demonstrating the use of the initial D(slope) as a sensor response when using QCM-D technology.