Journal
BIOSENSORS & BIOELECTRONICS
Volume 29, Issue 1, Pages 23-28Publisher
ELSEVIER ADVANCED TECHNOLOGY
DOI: 10.1016/j.bios.2011.07.059
Keywords
E. coli O157:H7; Immunosensor; Quartz crystal microbalance; Micro/nanobeads; Coupled-oscillator theory
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Funding
- National Natural Science Foundation of China [30825027]
- Ministry of Education in China
- USDA/FAS
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Micro/nanobeads with different materials (magnetic, silica and polymer) and different sizes (diameters from 30 nm to 970 nm) were investigated for their use as amplifiers in a quartz crystal microbalance (QCM) immunosensor for more sensitive detection of Escherichia coli O157:H7. The micro/nanobeads were conjugated with anti-E. coli antibodies. E. coli O157:H7 cells were first captured by the first antibody immobilized on the electrode surface, and then micro/nanobeads labeled secondary antibodies attached to the cells, and finally the complexes of antibody-E. coli-antibody modified beads were formed. The results showed that antibody-labeled beads lead to signal amplification in both the change in frequency (Delta F) and the change in resistance (Delta R). Since the penetration depth of the oscillation-induced shear-waves for a similar to 8 MHz crystal is limited to 200 nm, the interpretation of how the signal is amplified by the adsorbed particles was represented in terms of the coupled-oscillator theory. The amplification is not sensed in terms of increase in mass on the sensor surface. Amplification is sensed as a change in bacterial resonance frequency when the spheres adsorb to the bacteria. The change in the values of Delta F caused by different micro/nanobeads (amplifiers) attaching on target bacterial cells is indicative of the ratio between the resonance frequency of the absorbed bacterial-particle complex (omega(s)), and the resonance frequency of the crystal (omega). (C) 2011 Elsevier B.V. All rights reserved.
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