The Application Research On Piezoelectric Biosensor For Early Identification Of Candida Species And The Study Of The Complex Formation Of Nickel (â…¡) Ions And Citric Acid

The multi-channel series piezoelectric quartz crystal (MSPQC) biosensor 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, clinical medicine etc. In this thesis, new identification methods were presented base on the special response of piezoelectric sensor which related to some characteristics of clinical Candida species'growth and metabolism. These new methods were simple to operate and broaden their application in clinical medicine and life science. The new identification method for Candida species was ease to operate,rapid and accurate. The main work could be summarized as follows:1. We have in this study investigated these Candida species using a method based on the integration of the MSPQC biosensor with pattern recognition for an early identification of the most frequent Candida species encountered in human pathology. Through the careful study of these response signals produced by different Candida species in MSPQC system, we find that under identical experimental conditions, various Candida species produce a significant different type of frequency curve in 1 days'culture. Utilizing the diversity of frequency curve and the partial least square (PLS) technique, we proposed the MSPQC-PLS method for early identification of commonly encountered Candida species. Using the method proposed, we differentiated 5 species (Candida albicans, Candida glabrata, Candida parapsilosis, Candida tropicalis, Candida krusei) from a collection of 73 clinical strains of Candida, isolated from hospitalized patients, with a classification rate of 97.3%. This new proposed MSPQC-PLS method is simple, rapid and convenient to perform. It not only has the ability to differentiate these clinically most frequent encountered Candida species, but also can identify these Candida species at the same time with the culturing of the raw clinical materials. So the time for identification will be greatly shortened.2. We carfully studied the cause of production of significant different type of frequency curve by various Candida species cultured in MSPQC. Using the 9M impedance instrument, the real-time electric parameters change between the two conductive stainless steel electrodes during the culture time of 5 species of Candida were recorded. Comparing to these frequency-shift curve recorded by MSPQC in parallel experiment, we conclude that the chief cause of the special frequency-shift curve is the change of the conductance between the two electrodes and the change of the capacitance caused by the growth of those Candida species is not significant. Through the adsorbtion experiment, we confirmed that the conductance change caused by the adsorbtion effect of fungi is not in dominant. The metallograph of different Candida species in different growing stage showed that the complexity of metabolism caused by the polymorphism of fungi is the chief cause of the production of special frequency curve by various Candida species.3. Under the given conditions(60=℃,I=4mol/L NaCl),the protonation constants of ligand citric acid had been determined by pH potentiometry in aqueous solution. For the binary system Ni(II)-Citric acid,the complexes species as well as their stability constants were determinated under the same conditions as the condition mentioned above. the experimental data was calculated by employing prograins Hyperquad,Glee,and Hyss.