Detection of Escherichia coli O157:H7 using a QCM Immunosensor with Nanoparticle Amplification

Abstract

Quartz crystal microbalance (QCM) immunosensors, due to their simplicity, low cost, andsuitability for label-free measurement, have been studied for bacterial detection, typically with adetection limit of 105 ~107 CFU/mL. However, for their applications in food safety, the detection limitdefinitely needs to be improved because the infectious dosage of a foodborne pathogen can bemuch lower. In this study, nanoparticle bioconjugates, which were prepared using streptavidinconjugatednanoparticles (145 nm) and biotinylated anti-E. coli antibodies, were used for signalamplification in a QCM biosensor for the detection of Escherichia coli O157:H7. The biosensor wasfabricated by self-assembling of protein A and affinity-purified anti-E. coli O157:H7 antibodies on thegold electrode. After E. coli O157:H7 cells binding with the antibodies, nanoparticle bioconjugateswere applied as mass amplifiers to enhance the QCMs response. The nanoparticle bioconjugateswere The binding of the nanoparticle conjugates further resulted in a decrease in resonant frequencyand an increase in resonant resistance. The biosensor could detect as low as to 102 CFU/mL E. coliO157:H7 of in less than 1.5 h.