Electrosynthesis of molecularly imprinted polymer films on quartz crystal microbalances for the detection of some biomolecules

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Electrosynthesis of molecularly imprinted polymer films on quartz crystal microbalances for the detection of some biomolecules

 

Author: Hong, Shuangjin
Title: Electrosynthesis of molecularly imprinted polymer films on quartz crystal microbalances for the detection of some biomolecules
Degree: Ph.D.
Year: 2005
Subject: Hong Kong Polytechnic University -- Dissertations
Electrochemistry
Electrochemical sensors
Biomolecules
Polyelectrolytes
Department: Dept. of Applied Biology and Chemical Technology
Pages: x, 180 leaves : ill. ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1809917
URI: http://theses.lib.polyu.edu.hk/handle/200/2065
Abstract: Molecular imprinting, in which specific binding sites are created by polymerization of functional monomers in the presence of template molecules followed by their subsequent removal, has been recognized as a powerful tool for the preparation of artificial receptors for specific binding with target molecules. Though molecular imprinting can be employed for the preparation of the recognition sites in chemical sensors, the development of sensors based on molecularly imprinted polymer (MIPs) is relatively slow mainly due to the difficulties in integrating the imprinted polymers to the sensor transducer. The objective of this thesis is to develop sensors for biomolecules based on electrosynthesized imprinted polymer films. In the first part of this study, molecularly imprinted polymer films of polypyrrole and poly(o-phenylenedamine) have been prepared by electropolymerization on EQCM electrodes in the presence of adenosine-5'-triphoshate disodium salt (ATP). These ATP sensors exhibit high selectivity against ADP and AMP. A pyrrole:ATP mole ratio of 2:1 was found to be the best for the preparation of the MIP polypyrrole films by electropolymerization. On the other hand, the poly(o-phenylenediamine) film has low conductivity and therefore only very thin polymer film could be obtained. Nevertheless, this allows the poly(o-phenylenediamine) MIP films to have short response time towards the analytes. The poly(o-phenylenediamine) MIP film was found to exhibit better selectivity but lower sensitivity towards ATP. In the second part of this project, a functionalized monomer, glucose-boronate-substituted aniline, was synthesized by cyclic esterification of glucose with aminophenylboronic acid. Glucose imprinted co-polymer films of boronate-substituted monomer and aniline were prepared by electropolymerization in nonaqueous media and gradually transferred into aqueous media. At physiological pH, the EQCM sensor based on this glucose imprinted polymer film showed linear frequency response toward glucose solution in the concentration range of 2.0 x 10-5 to 7.5 x 10-4 mol dm-3. Substantial uptake of fructose by the glucose imprinted polymer film was also observed. This was due to the high association constant (Ka) between fructose and bronic acid. The effect of various parameters such as electrode potential, solution pH and functionalized monomer to aniline ratio on the analytical performance of glucose imprinted polymer film were examined. In the third part of this study, molecularly imprinted polymer films of acrylamidophenylboronic acid were prepared by electropolymerization on EQCM Au electrodes and Au wire electrodes in the presence of dopamine. After removal of the template molecules, a MIP film with both high affinity towards dopamine and permselectivity against ascorbic acid (AA) was prepared. The electrochemical sensor based on the MIP film was used to detect dopamine at different concentrations at physiological pH by means of preconcentration-stripping. Using this dopamine sensor, a linear relationship was observed between the electrochemical redox peak current intensity and dopamine concentration from 5 x 10-6 to 1 x 10-4 mol dm-3. This sensor shows negligible interference from ascorbic acid, even when ascorbic acid's concentration is as high as 1 x 10-3 mol dm-3. The mechanism of the sensor's selectivity was discussed. The effect of various parameters such as electrode potential and solution pH on the performance of the sensor were also investigated.

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