| Piezoelectric biosensor has many advantages, such as high sensitivity, easy to realize numeralization, broad sensing spectrum, rapid detection, simple operation and low cost etc. So it has been applied in the area of analytical chemistry, life science, environmental monitoring etc. In this thesis, the new microbial sensing methods were presented base on the response of SPQC sensor to the change of electric parameters of medium, which related to some characteristics of microbial growth and metabolism. The new methods are easier and broaden their application in environmental monitoring and life science. The detection is rapid,simple, accurate. The main work of this thesis could be summarized as follows: 1. A new sensor method based on series piezoelectric quartz crystal (SPQC) sensing technique was proposed for studying the effect of surfactants on the growth of Pseudomonas aeruginosa in media. The influence of the concentration and ion type of surfactants (cationic, anion and nonionic surfactants), the type of hydrophilic group and the number of ethoxyl of nonionic surfactants on the growth of bacteria was investigated in detail. The frequency shift curves under different growth conditions were obtained and compared with each other. By fitting frequency shift (?F) curves, three kinetic parameters (μm, λ and A) were gained to describe the growth of microorganisms. This paper has great meaning to application and study of surfactants. 2. A method was proposed for rapid detecting the effect of cationic surfactants cetyltrimethylammonium bromide (CTAB) on the growth of Pseudomonas aeruginosa in media by using multi-channel series piezoelectric quartz crystal (MSPQC) system. The quantitatively calculated nadir time (NT) was proposed to instead of conventional frequency detection time (FDT). The effect of CTAB at different concentration on P.aeruginosa was investigated and the linear relationship between NT and concentration of CTAB was found at 1×10-4 g/l-5×10-2 g/l. The change of CTAB was detected in order to study the interaction between CTAB and P.aeruginosa. In addition, the effect of different concentration of CTAB on P.aeruginosa was discussed. The result showed there was linear relationship between NT and logC (P.aeruginosa) in the range of 1×102-1×107cells/ml when the concentration of CTAB was 5×10-3 g/l. The effect of P.aeruginosa on the biodegradation of CTAB was also discussed 3. A new multi-channel series piezoelectric quartz crystal (MSPQC) system for detection of pathogens was described. Some factors, which affect the detection of pathogens by using MSPQC, were all investigated. A total of 650 clinical samples were detected by MSPQC and licensed BACTEC 9120 system (Becton Dickinson Diagnostic Instrument Systems, Sparks, Md.) simultaneously in the Third Xiangya Hospital of Central South University, China. When the incubation period was 5 days, two systems had similar detected results: the MSPQC system detected 123 growth of 650 (18.92%) bottles while the BACTEC 9120 detected 126 growth of 650 (19.38%) bottles. The MSPQC had 2 false-positive signals and 2 false-negative signals. However, BACTEC 9120 had 3 false-positive signals and 0 false-negative signals. Further identifications of bacteria were run by VITEK-2 (bioMérieux China Ltd.), 5% sheep blood trypticase soy agar (SBA) and chocolate agar (CA) were also used for subculture of bacteria. Comparing with BACTEC 9120, MSPQC system possesses following advantages: shorter average detection time, less false-positive results and low cost. It can also provide information in real time. So MSPQC has a wonderful perspective in clinical application.
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