Research And Applications On A Novel Test Strip For Water Biotoxicity Assessment Using Luminescent Bacteria In Hydrogel

Huge quantities of chemical pollutants were discharged into environment water with increasing of industrial activities since the beginning of the21st century. Serious water pollutant events occurred frequently, and public safety and health were serious threaten. Therefore, rapid toxicity assessment of environmental pollutant is important topic for public safety. To monitor and control the pollution influence, fast and efficient toxicity assessment method is critical. Among all the existed techniques, Vibrio fischeri has the advantages of rapidness and good sensitivity, and can be utilized combined with photo electric techniques, which m has been widely used in ecotoxicology tests for decades.Herein we developed a novel test strip that is capable of water toxicity assessment. Generally, Vibrio fischeri was first encapsulated with PEGDA and HMPP, and then dropwise added onto the strip, followed by fixation with an UV lamp. All the assessment procedures were carried out according to ISO11348.To our knowledge, this is the first report of developing a test strip harboring Vibrio fischeri. Optimizations of the parameters were also carried out for assessment efficient improvement. For economic considerations, we chose firm and cheap bibulous paper as the strip material that showed good water permeability. The bacteria were mixed with hydrogel at a ratio of1:1, which provides both good hydrogel coagulability and bacteria activity. To minimize damages to the Vibrio fischeri while coagulating with hydrogel, UV exposure time was determined as10s for photo crosslinking process. Moreover, the effect of osmotic pressure changes was shown to be insignificant on the encapsulated Vibrio fischeri during toxicity assessment assays.Zinc sulfate heptahydrate (ZnSO4-7H20),3,5-Dichlorophenol (C6H4OC12) and Potassium dichromate (K2Cr2O7) was utilized as standard toxicants. Bio-toxicity assessment was carried out toward the toxicants using both the test strip method and conventional assessment method at the same time. The most significant Light-inhibiting rate for the two methods toward three toxicants was3.8%,5.1%and4.1%, respectively. The30min-EC values for the strip and conventional method also showed similar variance (10.98%for ZnSO4·7H2O,15.96%for C6H4OCl2, and23.67%for K2Cr2O7test). The identification results using the strip showed high reliability and reproducibility when compared with conventional methods, indicating the test strip with hydrogel encapsulated Vibrio fischeri can be used as the alternate for the conventional water toxicity measurements.To verify the reliability of our test strip, real water samples (raw water from water treatment plant, landscape surface water and domestic sewage) were also collected and used for bio-toxicity assessments. The conventional method was also carried out for comparison. The real water samples all showed low toxicity level (below20%) when no heavy metal or toxic organic pollutant existed. There was only1%difference within the bio-toxicity assessment of the same water sample between using the test strip and conventional method, which proved the reliability of the test strip in real water toxicity measurements.