title: Evaluation of different micro/nanobeads used as amplifiers in QCM immunosensor for more sensitive detection of E. coli O157:H7.
abstract: Micro/nanobeads with different materials (magnetic, silica and polymer) and different sizes (diameters from 30nm to 970nm) 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 (ΔF) and the change in resistance (ΔR). Since the penetration depth of the oscillation-induced shear-waves for a ∼8MHz crystal is limited to 200nm, 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 ΔF 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 (ω(s)), and the resonance frequency of the crystal (ω).
authors.affiliation: College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou, China.
authors.forename: Xuesong
authors.initials: X
authors.lastname: Jiang
authors.forename: Ronghui
authors.initials: R
authors.lastname: Wang
authors.forename: Yun
authors.initials: Y
authors.lastname: Wang
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Su
authors.forename: Yibin
authors.initials: Y
authors.lastname: Ying
authors.forename: Jianping
authors.initials: J
authors.lastname: Wang
authors.forename: Yanbin
authors.initials: Y
authors.lastname: Li
mesh_terms: D000907:Antibodies, Bacterial; D001431:Bacteriological Techniques / Q000379:methods / Q000706:statistics & numerical data; D015374:Biosensing Techniques / Q000379:methods* / Q000706:statistics & numerical data; D019453:Escherichia coli O157 / Q000276:immunology / Q000302:isolation & purification* / Q000648:ultrastructure; D006801:Humans; D008855:Microscopy, Electron, Scanning; D058726:Nanoconjugates / Q000648:ultrastructure; D010316:Particle Size; D058525:Quartz Crystal Microbalance Techniques / Q000379:methods* / Q000706:statistics & numerical data
chemical_list: D000907:Antibodies, Bacterial; D058726:Nanoconjugates