A novel and facile immunosensor based on a barometer: Application for rapid analysis of Escherichia coli in waters

A facile immunosensor was constructed based on a barometer indicator using a double-antibody- sandwich method for rapid and sensitive detection of Escherichia coli (E. coli) from water samples. At the present study, Anti- E. coli DH-5 polyclonal antibody was modified through enriching carboxylated magnetic beads and catalase functionalized gold nanoparticles (AuNPs)- loaded nanospheres. The functionalized AuNPs-loaded nanospheres exhibited an excellent catalysis towards decomposition of hydrogen peroxide (H₂O₂), generating a large volume of oxygen (O₂) into waters, increasing the pressure inside the glass vial, which in turn raised the water level in barometer. Under the optimized experimental conditions, the proposed method showed wide linear ranges (10²- 10⁷ cfu mL^-1), good accuracy and precision (recoveries, 86.7- 107%; CV, 3.2- 8.1%) with a limit of detection (LOD, S/N = 3) and the limit of quantification (LOQ, S/N = 10) were 80 cfu mL^-1and 267 cfu mL^-1, respectively. Furthermore, the fabricated portable immunosensor device showed some distinct features in low cost and visibility, suggesting great potential for rapid and on-site analysis of this bacteria from waters in less developed areas of developing countries.