The Application Research Of Piezoelectric Sensor Based On Aptamer And Carbon Nanotubes

The key section of series piezoelectric quartz crystal (SPQC) is composed of an AT cut,9MHz piezoelectric quartz crystal and a pair of parallel-plate metal electrodes inserted into liquid solution in series. It has sensitive response to the electric parameter changes (such as conductance and capacitance) between the electrodes. The multi-channel series piezoelectric quartz crystal (MSPQC) is a new sensor, which is designed based on the principle of series piezoelectric quartz crystal, and can detect multi-samples at one time. MSPQC has attracted many analysts because of its high sensitivity, accurate, low cost and easy operation, real-time and on-line measurement etc. It has been widely used in various fields, such as analytical chemistry, clinical medicine, life science, environmental monitoring etc. The electrode was improved or optimized through the modification of aptamer and carbon nanotubes, which connected with multi-channel series piezoelectric quartz crystal sensor. This kind of sensor technology broadens the applications of MSPQC in life science. The main works of this thesis could be summarized as follows:1. A new graphene/aptamer piezoelectric sensor for rapid and specific detection of Staphylococcus aureus. In this study, a novel graphene/aptamer piezoelectric sensor for Staphylococcus aureus was constructed by immobilizing Staphylococcus aureus aptamers as recognition elements on the surface of interdigital gold electrodes (IDE), which modified with a functional layer of graphene. The detection principle was:When Staphylococcus aureus existed, the aptamers bound with Staphylococcus aureus and dropped from the surface of graphene due to the specific binding of aptamers with Staphylococcus aureus, which would cause the change of oscillator frequency of SPQC. Since the graphene can increase the effective areas and improve the electron transfer rate of the electrode surface and specific recognization of aptamers, this method has a high sensitivity and good selectivity. The detection time was about60min and the limit of detection was41cfu/ml.2. A new piezoelectric sensor for detection of lysozyme based on single-walled carbon nanotubes and anti-lysozyme aptamer. In this work, a sensitive and selective piezoelectric aptasensor for lysozyme detection was constructed using aptamer-wrapped-SWNTs modified interdigital gold electrodes (IDE) which connected with SPQC. The thiol labeled anti-lysozyme aptamers were immobilized on gold surfaces of IDE by self-assembly. Due to the noncovalent assembly between aptamer and SWNTs, SWNTs were bonded to the surface. When immersed the IDE into lysozyme solutions, the anti-lysozyme aptamer would react with lysozyme and leads to the SWNTs breaking off the electrode due to the interactrion of aptamers and their targets, which have weak affinity to SWNTs and keep SWNTs away from electrode surface. Because of the high specific recognition ability of aptamers and powerful conducting property of SWNTs, this proposed approach has a good selectivity and high sensitivity. The detection limit was low0.5nM with a linear detection range from1nM to80nM.3. New study of piezoelectric sensor for rapid detection of Mycobacterium tuberculosis H37Ra based on amine-functional multiwalled carbon nanotubes and polyaniline. In this work, carbonnanotubes functionalized with3-aminopropyl-triethoxysilane (APTS) and polyaniline was modified on the surface of interdigital gold electrode (IDE) and connected with Multi-channel Piezoelectric Quartz Crystal in series (IDE-MSPQC). The response mechanism is the modified materials react with CO2and NH3produced by the growth of bacteria in culture medium and caused the film electrical properties change. This change can be sensitively monitored by MSPQC. The superiorities of the proposed probe were these:first, it was more sensitive to bacteria growth response; second, the probe was not directly contact with the culture medium, so the influence of the electrical parameter caused by medium can neglect; third, it did not require a specially formulated culture medium. The proposed method can be used to detect the concentration of Mycobacterium tuberculosis H37Ra quantitatively in the range of102-107cfu/ml (R2=0.9861). This work mainly discusses the separately and combined response of sensor to CO2and NH3. This method is more accurate, sensitive, fast and simple.