A novel biosensor for Escherichia coli O157:H7 based on fluorescein-releasable biolabels

• Published in: Biosensors & bioelectronics 2016-04, Vol.78, p.31-36
• Main Authors: Hu, Rong-Rong, Yin, Zheng-Zhi, Zeng, Yan-Bo, Zhang, Jian, Liu, Hai-Qing, Shao, Yong, Ren, Shi-Bin, Li, Lei
• Format: Article
• Language: English
• Subjects: Biosensing Techniques - methods; Biosensor; Biosensors; Chlorides; Escherichia coli; Escherichia coli O157 - isolation & purification; Escherichia coli O157 - pathogenicity; Escherichia coli O157:H7; Fluorescein; Fluorescein - chemistry; Fluorescein-releasable biolabel; Fluorescence; Humans; Limit of Detection; Magnetic separation; Nanospheres; Nanospheres - chemistry; Scanning electron microscopy; Silicon dioxide; Silicon Dioxide - chemistry
• ISSN: 0956-5663; 1873-4235
• DOI: 10.1016/j.bios.2015.11.018

New techniques are required for the rapid and sensitive detection of Escherichia coli O157:H7 (E. coli O157:H7), a pathogenic bacterium responsible for serious and sometimes life-threatening diseases in humans. In this study, we developed a highly sensitive and efficient biosensor for the quantitative detection of E. coli O157:H7 by integrating fluorescein-releasable biolabels with a magnetism-separable probe. Hollow silica nanospheres with a diameter of approximately 350nm were synthesized, enriched with fluorescein, and surface-protected with macromolecule layers of poly (acrylic acid) and poly (dimethyldiallylammonium chloride). These fluorescein-enriched hollow silica nanospheres were characterized using scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy. They were further functionalized as immune labels of E. coli O157:H7 for a sandwich-type immune reaction between this bacterium and magnetic nanoparticles (Fe3O4@SiO2). Next, the E. coli O157:H7 cells were captured, magnetically separated, and quantified based on the fluorescence intensity of the fluorescein released from the biolabels of the fluorescein-enriched hollow silica nanospheres. This analytic process can be completed within 75min, and the biosensor showed a linear relationship ranging from 4 to 4.0×108cfu/mL with a detection limit of 3cfu/mL. These results show that the developed fluorescent sensor has excellent specificity, and good reproducibility and stability. This study used real spiked samples for detection, indicating that this technique has a wide range of potential applications and may be readily adapted for detecting other pathogens. •Fluorescein-enriched hollow silica nanospheres were synthetized.•Fluorescein-releasable labels and magnetism-separable probe were firstly integrated for a biosensor.•An innovative method for detecting E. coli O157:H7 was established.•This methodology could be readily adapted for detecting other pathogens.