Reduced Graphene Oxide on Screen-Printed Carbon Electrodes as Biosensor for Escherichia coli O157:H7 Detection

Mixture of drinking-water supplies with sewage discharges poses disease threats in flood-stricken areas. In such exigent conditions, on-site testing of water samples is the only option, as water samples cannot be transported to laboratories owing to severely impacted transportation services. Hence, we developed a low-cost electrochemical biosensor fabricated from a screen-printed carbon electrode (SPCE) to detect E. coli O157:H7, a virulent pathogen often found in sewage discharges. We focused on understanding antigen-antibody interaction when the antibody used is not specific for E. coli O157:H7. We found that antibody immobilized on a reduced graphene oxide (rGO)–modified SPCEs distinguished between E. coli O157:H7 concentrations of 4 × 108 and 4 CFU/ml, with lowest current reported for 4 × 108 CFU/ml. In contrast, a reduced graphene oxide–modified SPCEs without antibody immobilization does not produce a prominent peak that distinguishes the highest and lowest E. coli concentrations. However, a few E. coli cells were still attached to the rGO/SPCEs in the absence of antibody, as shown in FESEM images. A processing step of differential readings from reference and active electrodes needs to be programmed into an Arduino® microprocessor to realize a prototype of a bacteria sensor for field use.

Detection of drinking water contamination by an optical real-time bacteria sensor

In a drinking water distribution system, little is known about the characteristics of a microbiological pollution, how it enters the system, and how it can be detected. The drinking water industry has relied on various pollution indicators, through grab sampling and laboratory analyses, revealing results long after the water has been used. To be able to react more proactively to pollution events, many drinking water distributors supplement grab sampling with proportional sampling and/or real-time sensors. We have tested the ability of a new bacteria monitor to detect four different pollution events: wastewater intrusion, rainwater runoff, resuspension of drinking water sediments, and bird droppings entering the distribution system. The monitor response, in terms of bacteria and abiotic particle concentrations, was compared with traditional laboratory methods. The results illustrate the benefits of using such real-time bacteria sensors for monitoring the dynamics of drinking water microbiology and for early warning of potential pollution events.