Amplifying the signal of localized surface plasmon resonance sensing for the sensitive detection of Escherichia coli O157:H7.

Gold nanorods (Au NRs) based localized surface plasmon resonance (LSPR) sensors have been widely employed in various fields including biology, environment and food safety detection, but their size- and shape-dependent sensitivity limits their practical applications in sensing and biological detection. In our present work, we proposed an approach to maximally amplify the signal of Au NRs based LSPR sensing by coating an optimized thickness of mesoporous silica onto Au NRs. The plasmonic peaks of Au NRs@SiO with different shell thickness showed finely linear response to the change of surrounding refractive index. The optimized thickness of mesoporous silica of Au NRs@SiO not only provided high stability for LSPR sensor,but also displayed much higher sensitivity (390 nm/RIU) than values of Au NRs from previous reports. The obtained Au NRs@SiO based LSPR sensor was further used in practical application for selectively detection of the E. coli O157:H7, and the detection limit achieved 10 CFU, which is much lower than conventional methods such as electrochemical methods and lateral-flow immunochromatography.