The Application Research On Piezoelectric Biosensor For Detecting Metabolite Of Microorganism

Piezoelectric sensor has many advantages, such as broad sensing spectrum, high sensitivity, easy to operate, real-time and on-line measurement etc and can be widely used in many areas, such as analytical chemistry, life science, environmental monitoring etc. In this thesis, new microbial sensing methods were presented base on the special response of piezoelectric sensor which related to some characteristics of microbial growth and metabolism. These new methods were simple to operate and broaden their application in environmental monitoring and life science. The detection was rapid and accurate. The main work of this thesis could be summarized as follows:1. A novel piezoelectric quartz crystal microbalance (QCM) device with gas permeable membrane is proposed for detection of microorganisms producing H₂S. The detection theory is based on the adsorption of hydrogen sulfide onto the silver electrode of the piezoelectric crystal sensor and caused a dramatic decrease in the resonant frequency of QCM. Factors affecting detection such as humidity, ammonia, carbon dioxide and L-cysteine HCl concentration in culture medium were investigated. P. mirabilis, S. typhi, E. tarda, C. freundii, E. coli, P. aeruginosa and S. aureus were determined in this paper, which proved the feasibility of the proposed method.2. A new gas permeable membrane device associated with series piezoelectric quartz crystal was developed to detect Mycobacterium tuberculosis respiration. The response mechanism is barium hydroxide (Ba(OH)₂) reacting with carbon dioxide, which causes the changes of conductance in Ba(OH)2 solution,and then the changes of conductance can be monitored by SPQC. The effect of Ba(OH)₂ concentration on sensitivity was discussed. The influence of gas permeable membrane properties on detection was discussed in detail. The method was applied to detect Mycobacterium tuberculosis H37Ra which good result was obtained.3. The carbon dioxide piezoelectric sensor was proposed to study the effect of different carbon source and nitrogen source on bacteria metabolism. Combining with the metabolic pathways of pyruvic acid, lactic acid,α-ketoglutaric acid, glycerol, L-asparagine and glutamic acid in organisms, the function of different nutriment on the rate of bacteria breathing out CO₂ were investigated. It came to the conclusion that pyruvic acid and glutamic acid can accelerate the respiration of mycobacterium tuberculosis most effectively.