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

Liping Song,Zheyu Shen,Liming Chen,Tao Chen,Ganggang Zhang,Lei Zhang,Jiawei Zhang,Zhidong Xiao,Youju Huang

doi:10.1038/s41598-017-03495-1

Abstract

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@SiO2 with different shell thickness showed finely linear response to the change of surrounding refractive index. The optimized thickness of mesoporous silica of Au NRs@SiO2 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@SiO2 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.

Highlights

The localized surface plasmon resonance (LSPR) is a spectroscopic phenomenon based on the resonant oscillations of free electrons of various materials including noble metal nanoparticles, Al nanoparticles, conventional semiconductors and 2D materials, when stimulated by incident light[1,2,3]
The detection limit of Au nanorods (Au NRs)@SiO2 for E. coli O157:H7 is lower than 10 Colony-Forming Units (CFU), which is superior over the values of traditional methods[34, 35]
In the process of silica coating, Cetyltrimethyl Ammonium Bromide (CTAB) formed a bilayer around Au NRs, which served as organic template for the formation of mesoporous silica shell[40]

Summary

Introduction

The localized surface plasmon resonance (LSPR) is a spectroscopic phenomenon based on the resonant oscillations of free electrons of various materials including noble metal nanoparticles, Al nanoparticles, conventional semiconductors and 2D materials, when stimulated by incident light[1,2,3]. Due to the low detection sensitivity and capacity[7, 12, 13] and poor stability, the development of LSPR sensors is limited, especially in practical applications. The objective of the present study is to develop a high performance LSPR sensor for practical application in real sample analysis (E. coli O157:H7) that would achieve high sensitivity and stability. Surface functionalization served as a powerful means to effectively improve sensitivity and stability of LSPR sensors and flexibly modify plasmonic nanoparticles with desired functions for further applications[24]. The as-prepared Au NRs@ SiO2 with optimal shell thickness showed high sensitivity and used as efficient LSPR biosensor to detect E. coli O157:H7. To verify the performance of Au NRs@ SiO2 as LSPR sensors, Au NRs@SiO2 with optimal thickness was modified with specific antibody to selectively detect E. coli O157:H7 in high sensitivity. The detection limit of Au NRs@SiO2 for E. coli O157:H7 is lower than 10 Colony-Forming Units (CFU), which is superior over the values of traditional methods[34, 35]

Objectives

Methods

Results

Conclusion