SURFACE PLASMON RESONANCE AND QUARTZ CRYSTAL MICROBALANCE IMMUNOSENSORS FOR DETECTION OF ESCHERICHIA COLI O157:H7.

Surface plasmon resonance (SPR) and quartz crystal microbalance (QCM) techniques have been studied in label-free immunosensors for direct detection of bacteria. However, there is a lack of comparative investigations on SPR and QCM immunosensors. In this study, SPR and QCM immunosensors were compared for their applications in bacterial detection using Escherichia coli O157:H7 as a model pathogen. In both immunosensors, affinity-purified polyclonal antibodies were used as capture antibodies and Protein A method was used for antibody immobilization. The stepwise assembly of the immunosensors was characterized by SPR, QCM, and cyclic voltammetry. Both SPR and QCM could detect E. coli O157:H7 in 1 h with detection ranges of 105 to 108 and 106 to 108 CFU/mL, respectively. QCM was more sensitive than SPR in terms of both detection limit and signal-to-noise ratio. For both immunosensors, no significant interference was found from brain heart infusion (BHI) broth or Salmonella Typhimurium. The binding efficiency of the QCM immunosensor at 105 to 108 CFU/mL was found to be 95.9% to 2.9%, decreasing with increasing cell concentration. [ABSTRACT FROM AUTHOR]