The Research On Piezoelectric Bulk Acoustic Wave Microbial Sensing Methods And Its Application

In recent years, piezoelectric biosensor has been applied in the area of clinical analysis, analytical chemistry, life science, environmental monitoring, biological technology and food sanitary detection etc. It has many advantages, including high sensitivity, strong specificity, simple construction, small size and on-line detection. Conventional methods for microorganism determination were cumbersome and time-consuming. Many types of piezoelectric biosensors for microorganism detection were proposed in the 1990's, which had advantages over conventional methods and were more rapid and simpler. In this thesis, two systems were involved: one was based on the response of electrode-separated piezoelectric DNA sensor (ESPS) to the mass change caused by hybridization in liquid phase. P.aeruginosa was detected using this system. The other, was based on the response of bulk acoustic wave impedance biosensor (BAWIB) to the characteristic change of solution which caused by the growth and metabolism of the microbial. M.tuberculosis was detected using this system. These proposed methods find their potential application in environmental monitoring and clinical test. The works are summarized as follows:1. A novel process analysis method, with an ESPS based on the mass effect, for real-time monitoring P.aeruginosa was proposed. The set-up sensor was based on the modification of two membranes (nano-TiO₂ and nano-TiO₂-polyethylene glycol hybrid membrane) synthesized by sol-gel method to the ESPS surface. The detection was accomplished by modifying ss-DNA(extracting from P.aeruginosa) on the sensitive membrane and then hybridizing with their complementary strands in liquid phase. UV spectrum was used to identify trie purity and concentration of extracted DNA; IR spectrum and SEM were used to characterize the properties of the membrane. The detection was highly improved by adoption of nanotechnology and hybrid membrane.2. A new type of CO₂ bulk acoustic wave impedance biosensor (BAWIB) has been developed for the rapid and selective determination of the growth of M.tuberculosis. The method is based on the response of bulk acoustic wave impedance sensor to the conductivity change of the solution which resulted by the reaction between CO₂ and Ba(OH)₂ (0.9mM). A pair of steel stainless electrode which connected to the BAWIB was assembled in detection cell containing Ba(OH)₂ solution. The CO₂ evolved from metabolism of M.tuberculosis was conducted to the detection cell and monitored by the BAWIB on-line. The frequency detection time (FDT) was used to quantitativelydetermine M.tuberculosis. It was proportional to logarithm of the concentration of M.tuberculosis presented in specimens in the range from 3×10²cells/ml to 10⁷cells/ml. Experimental results showed that BAWIB is reliable, sensitive and rapid..It gives out the potential use for the real time detecting M.tuberculosis in clinical test. The effects of different acceptor solution, cell constant of the detection cell, addition of sodium hydrogen carbonate solution in culture medium and data processing were discussed detailedly in this paper.3. Cefradine was successfully used to eliminate the influence of other contaminant microorganism. A good response curve for NIM.TB(M.tuberculosis newly separated from patients sputum) was obtained by the proposed method. Compared with traditional assay, it has the features of simple structure, rapid response time and low cost etc. But many problems such as apparatus design, laboratorial operation are being existed and further research is needed.