A pH-based biosensor for detection of arsenic in drinking water

AbstractArsenic contaminated groundwater is estimated to affect over 100 million people worldwide, with Bangladesh and West Bengal being among the worst affected regions. A simple, cheap, accurate and disposable device is required for arsenic field testing. We have previously described a novel biosensor for arsenic in which the output is a change in pH, which can be detected visually as a colour change by the use of a pH indicator. Here, we present an improved formulation allowing sensitive and accurate detection of less than 10 ppb arsenate with static overnight incubation. Furthermore, we describe a cheap and simple high-throughput system for simultaneous monitoring of pH in multiple assays over time. Up to 50 samples can be monitored continuously over the desired time period. Cells can be stored and distributed in either air-dried or freeze-dried form. This system was successfully tested on arsenic-contaminated groundwater samples from the South East region of Hungary. We hope to continue to develop this sensor to produce a device suitable for field trials. FigureArsenic assays using bromothymol blue as a pH indicator. Each arsenic concentration was tested in triplicate on two separated days. Samples (50 μl inoculum) were statically incubated at 37 °C for a period of 65 h. Blue represents a safe level of arsenic while yellow indicates contamination. This figure shows the biosensor tubes in increasing arsenic concentrations at t = 0, 24, 36, 42, 48 and 60 h where the error represents the standard error of six replicates

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