Study On The Molecularly Imprinted Polymers-based Sensor Using Electrochemical Impedance And Piezoelectric Quartz Crystal Microbalance

The design of chemo/biosensors is an important and interesting subject in analytical chemistry and biochemistry and has been extensively studied. The design and synthesis of biomimetic receptor systems capable of binding a target molecule with similar affinity and specificity to antibodies has been a long-term goal in bioorganic chemistry. In recent decades, a novel strategy for the design of sensors, molecular imprinting technology, has been developed. This is a process where functional and cross-linking monomers are copolymerized in the presence of target analyte (the imprinting molecule), which acts as a molecular template. The functional monomers initially form a complex with the template molecules, and following polymerization, their functional groups are held in position by the highly cross-linked polymeric structure. Subsequent removal of the template molecules reveals the rebinding sites that are complementary in size and shape to the analyte. Compared with the biosensing componets, molecularly imprinted polymers have many advantages. Capacitive sensors, which are based on the principle of plate-capacitor capacitance, have been reported in recent years. The capacitance of the sensor is depended on the thickness and dielectric behavior of its dielectric layer. Capacitive sensor has many advantages, such as, low detection limit, rapid response, real-time determination, etc. The research of normal piezoelectric quartz crystal (PQC) was carried out in earlier 1980's, which has been widely applied in the fields of clinic immunology, hemorheology, biochemistry, and molecular biology.The main work of this thesis, which was based on the techniques mentioned above, is summarized as follows:1. L-histidine / D-histidine-imprinted membranes have been synthesized by electropolymerizing acrylamide onto Au electrodes or Au-coated quartz crystal electrodes. AC impedance spectroscopy and piezoelectric quartz crystal (PQC) technique were employed to verify the template effect of the membranes. The selectively rebinding of the enantiomers of histidine by their respective imprinted polymer membranes was confirmed.2. MlPs-based capacitive sensor specific for tegafur was constructed by electropolymerization of m-aminophenol onto the surface of gold electrode and the Au-coated quartz crystal. Unlike the capacitive sensors reported in the previous literatures, the present sensors were not treated with alkanethiol afterelectropolymerization and show even more satisfactory performance. QCM measurements also confirmed the imprinting effect of the polymer layers.3. Histamine sensor was constructed based on molecularly imprinted polymer-modified electrode with m-aminophenol used as the functional monomer. The imprinting effect of the membrane was verified by electrochemical impedance and piezoelectric quartz crystal microbalance mesurements.4. Polyacrylamide membrane was electrogenerated in the presense of 7-hydroxyflavone. AC impedance spectroscopy and piezoelectric quartz crystal (PQC) experiments reveal the selectively binding affinity of the membrane to the template.