Whole-cell luminescence-based flow-through biodetector for toxicity testing

A new type of biodetector was designed based on a bioluminescence test with the bacterium Vibrio fischeri performed in a liquid continuous flow-through system. Here we describe the modification of a commercial tube luminescence detector to work in the flow mode by building a new flow cell holder and a new case including “top cover” to connect the flow cell with the waste and the incubation capillary in a light-proof manner. As different samples were injected successively it was necessary to keep the individual peaks separated. This was done using an air-segmented flow in the reaction coil. To afford fast screening, the incubation time of the sample and the Vibrio fischeri, which equaled the dead time of the detection system, was set at 5.6 min. Rapid monitoring of toxic substances is achieved by using 20 μL of sample and flow-rates of 110–150 μL min−1. As a proof-of-principle, we show results for the detection of five selected di-, tri- and tetrachlorophenols at different concentrations varying from 1 to 200 mg L−1. Calculation of inhibition rates and EC50 values were performed and compared with corresponding values from the DIN EN ISO 11348-2 microplate format. Compared with the latter, the inhibition rates obtained with our flow-through biodetector for the compounds tested were generally about twofold lower, but importantly, a much faster detection is possible.