Study On The Microbiosensor Technology Responding To The Attack Of Chemicals And Microbial

In recent years, the kinds and amount of contaminant have been increasing remarkably. The toxicity assessment is needed urgently for the safety of the environment. Bioassay tests that employed a wide range of methods have been used to monitor the toxicity of chemicals to aquatic organisms, including plankton test, alga test and fish test, which are time consuming and complicated.Luminous bacteria has caught much interest for its specific physiological characteristic and good match of photoelectric measurements and applied widely to the environmental monitoring. However, traditional microbiol methods used for the environmental monitoring are not on-line, which has the disadvantage of slow assessment, complicated operation, and using expensive instrument. Therefore, the development of on-line monitoring system that can work constantly and rapidly is very important.In this paper, the luminous bacteria sensor technology and E.coli electrochemical sensor technology were developed for the assessment of the environment contaminant. Compared with traditional methods, these methods were rapid and sensitive. Besides, these sensors were also used for the evaluation of the UV-shielding property of nano-oxide. This paper includes two sectors.Part 1 (Chapter 1) OverviewIn chapter 1, we firstly give an interview of the toxicity assessment methods dealing with the attack of the chemicals and microbials, and then introduce the application of the microbial sensor technology in the toxicity assessment. Lastly, we introduce the immobilization technology of the microbial sensor. Chapter 2 Toxicity Assessment of Cyanide and Tetramethylene Disulfoetramine (Tetramine) Using Luminescent Bacteria Vibrio qinghaiensis and E.coli Electrochemical Sensor TechnologyIn chapter 2, The toxicity of cyanide and tetramethylene disulfo tetramine (tetramine) were evaluated by two methods. One was by utilizing Vibrio qinghaiensis -a kind of luminescent bacteria which can produce bioluminescence and the bioluminescence will decrease with the addition of toxicants. Another method was by using a kind of modified electrode on which Escherichia coli(E.coli) shows current response at a certain potential and the current will decrease with the addition of toxicants. Finally, ion-chromatography and GC-MS were utilized to indentify and determine cyanide and tetramine respectively. Compared with traditional toxicity evaluation methods, this method was rapid, sensitive, and needed little sample. Besides, it can also be applied to determine the toxicity of other poisons.Chapter 3 The Development of the Luminescent Bacteria Biosensor and its Application to the Evaluation of Toxicity of PesticidesIn this chapter, Vibrio qinghaiensis(a kind of luminescent bacteria which lives in fresh water) was utilized as an indicator and fixed by sol-gel, combined with a high sensitive silicon diode to form a luminescent bacteria sensor. The bioluminescence of the bacteria will decrease with the contact of pesticides and the sensor was utilized to evaluate the acute toxicity of several pesticides. The toxicity were expressed as EC50 value-the concentration of chemicals which reduces the light current of bacteria by 50% after contact. This method has the advantage of rapid response, high sensitivity and good repeatability, and can be applied to determine the acute toxicity of contaminants on line.Chapter 4 The Preparation of CdTe@SiO₂ Nano particle and its Application to the Toxicity Evaluation of Pesticides by Luminescent Bacteria BiosensorA CdTe@SiO₂ luminescent particle was synthesized and mingled with SiO₂ sol-gel to immobilize the luminescent bacteria. The luminescent bacteria sensor was developed with the combination of the bacteria membrane and silicon diode. It was found that the light current was higher than that of the luminescent bacteria sensor without CdTe@SiO₂. This may be because that the bioluminescence of the bacteria excited the fluorescence of CdTe@SiO₂. The sensor was utilized to evaluate the acute toxicity of several pesticides and the result shows that this sensor was more sensitive to the poisons compared with the luminescent bacteria sensor without CdTe@SiO₂, and so has the good application potential.Chapter 5 The Application of ATP Bioluminescence Method to the Determination of bacteriaIn Chapter 5, the ATP content of a series of bacteria sample were determined by ATP bioluminescence method and the amount of the bacteria were calculated according to the determined ATP content. The result was compared with traditional plate-counting methods.Part 2(Chapter 6) Study on the Application of Luminescent Bacteria to theEvaluation and Analysis of the UV-shielding Property of Nano oxideIn this chapter, it was found that luminescent bacteria could be killed by UV light and the bioluminescence intensity would be decreased. With the protection of nano oxide, the decrease of the bioluminescence could be supressed, therefore luminescent bacteria could be utilized to analyze and evaluate the UV-shielding property of nano oxide. Vibrio-qinghaiensis Q67, a kind of luminescent bacteria, was used here to study the influence of different kinds and concentrations of nano oxide on the luminescence intensity of bacteria, which were illuminated by UV light. A method was established according to the relative value of the decrease of the luminescence intensity, which can be used to analyze and evaluate the UV-shielding property of nano oxide. The determined UV-shielding property sequence of four kinds of nano oxide was: Fluka-TiO₂>P25-TiO₂>CFA-TiO₂>ZnO.Chapter 7 Study on the Application of E.coli electrochemical sensor Technology to the Evaluation and Analysis of the UV-shielding Property of Nano oxideIn this chapter, a nano-PbO₂/AgO electrode was prepared by electro-deposition method. It is found that when a constant potential of 1.0V was applied, using this electrode as the working electrode, an oxidation current will be observed with the addition of Escherichia coli(E.coli). The current is proportional to the cell numbers from 2×10⁵cfu/ml to 1.6×10⁶cfu/ml, and so this electrode can be applied as a microbial sensor to determine the numbers of E.coli. This electrode was used for the determination of the survival ratio of E.coli exposed under the UV-rays with or without the protection of nano-oxide, which provided a new electrochemical method to evaluate the UV-shielding property of nano-oxide or to choose nano-oxide as the sunscreen.