QCM immunosensor with nanoparticle amplification for detection of Escherichia coli

A quartz crystal microbalance (QCM) immunosensor was developed and evaluated for detection of Escherichia coli O157:H7. The immunosensor was fabricated by self-assembling of protein A and affinity-purified anti- E. coli O157:H7 antibodies on the gold electrode of the immunosensor. To enhance the performance of the QCM immunosensor, nanoparticle-antibody conjugates were employed for signal amplification. After the binding of E. coli O157:H7 cells with the antibodies immobilized on the electrode, nanoparticle-antibody conjugates were introduced as mass amplifiers. Compared to the direct detection of E. coli O157:H7, the binding of the nanoparticle conjugates further resulted in a decrease in resonant frequency and an increase in resonant resistance. The biosensor could detect as low as 102 CFU/mL of E. coli O157:H7 in less than 1.5 h. The nonspecific adsorption of nanoparticle-antibody conjugates on the surface of the QCM immunosensor was also investigated to improve the specificity of this detection method.;Key words. Immunosensor, E. coli O157:H7, quartz crystal microbalance, nanoparticle, bacteria detection...