A novel, environmentally friendly dual-signal water toxicity biosensor developed through the continuous release of...

In this work, a novel, environmentally friendly and simple electrochemical/colorimetric water toxicity biosensor was rationally developed by the continuous release of Fe³⁺ in a medium. The bioluminescent bacterium Vibrio Fischeri (V. fischeri) was used for the first time as a model bacterium to assess water toxicity for a mediated electrochemical biosensor. The green substance composited by Prussian blue (PB) and yellow K₃[Fe(CN)₆] was used as the indicator of the colorimetric biosensor. To obtain an ideal electrochemical/colorimetric performance, analytical conditions of the bioassay including NaCl concentration, temperature, concentrations of cells and K₃[Fe(CN)₆], and incubation time were optimized to 0.5%, 22 ^oC, 4 (OD₆₀₀), 10 mM, and 15 min, respectively. The IC₅₀ values of Zn²⁺, Hg²⁺, Cd²⁺ and 3,5-dichlorophenol (3,5-DCP) obtained by electrochemical method were 4.7, 5.0, 17.6 and 10.6 mg/L, respectively. The limits of detection (LODs) of Zn²⁺, Hg²⁺, Cd²⁺ and 3,5-DCP obtained by the naked eye were 6.3, 1.6, 12.5 and 12.5 mg/L, respectively. Two real water samples taken from tap water pipe and the Yitong river were also detected sensitively, and the inhibition ratios obtained were 3.8% and 14.0%, respectively. These results indicate that the V. fischeri-based bioassay is simple, sensitive and inexpensive, which is promising alternative for acute biotoxicity assessment.