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Title: Molecularly Imprinted Affinity Materials for Selective Recognition of Target Analytes
Authors: Arshad, Usman
Keywords: Physical Sciences
Issue Date: 2021
Publisher: University of the Punjab, Lahore
Abstract: The first chapter of the thesis provides a general overview about chemical sensors, their working principle, sensing elements, types and their applications. In the second chapter, gravimetric sensors are developed to determine artemether i.e., an antimalarial drug. In this work, 10 MHz AT-cut quartz crystal microbalance (QCM) device having dual electrode geometry i.e., developed by customized screen-printing method is coated with artemether imprinted and non-imprinted polymeric layer, respectively. The thickness of molecular imprinted polymer (MIP) coatings is optimized by monitoring the layer heights through network analyzer. The surface morphology and structural characterization of sensor coating are analyzed by atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR), respectively. The developed MIP-QCM sensor exhibited linear response in the concentration range of 30-100 ppm where imprinted channel showed sensitivity of 0.51 Hz/ppm. In comparison, non-imprinted resulted 0.08 Hz/ppm, indicating about 6 folds higher sensitivity by the MIP layer. In selectivity studies, MIP-QCM sensor showed 2.2- and 4.1-folds higher sensor response for artemether compared to artemisinin and lumefantrine, respectively. Moreover, MIP-QCM device showed rapid analyte adsorption, signal saturation, and regeneration of sensor layer. The sensor coatings are robust which offer reproducible sensor shifts as the variations in the response was less than 5% during triplicate measurements on testing different artemether concentrations. The third chapter of the thesis deals with chemical sensing of an antibiotic drug i.e., amoxicillin, which is commonly recommended throughout the world. In this work, the two gold electrodes of QCM are coated with amoxicillin imprinted and non-imprinted polymeric layers, respectively. The initial sensor measurements were carried out in the concentration range of 125-1000 ppm of amoxicillin which exhibited that MIP has sensitivity of 0.52 Hz/ppm whereas the non-imprinted layer showed 0.04 Hz/ppm. Selectivity data showed that the MIP sensor layer is highly selective as it exhibits at least 1.2 folds higher sensor shifts for amoxicillin compared to penicillin G and penicillin V which are structurally similar antibiotics molecules. The stability and reproducibility of sensor shifts are investigated by conducting triplicate sensor measurements at different concentrations (125-1000 ppm) which revealed that MIP sensor response is highly reproducible and stable for repeated cycles of analyte adsorption, saturation and desorption. The fourth chapter of this thesis is focused on surface imprinting of Staphylococcus epidermidis for developing synthetic receptors that could be used for chemical sensing applications. In this study, surface imprinting of the bacteria on styrene/divinylbenzene (DVB) polymer is carried out using two strategies. In the first scheme, bacteria are drop coated on glass slides and then dried to attach them with glass stamps. These stamps are used to carry out surface imprinting on styrene/DVB polymer coated on gold electrode of QCM. As the bacteria have strong affinity for the non-polar polymer matrix so the bacteria leave the stamps and get attached irreversibly to the polymer thus, could not be washed from polymer surface. In the second scheme, the bacteria are first covalently immobilized to the glass stamps and then these stamps are used for surface imprinting at styrene/DVB interface. Here, the bacteria remain on the stamps even after the stamps are peeled off from the surface of the polymer. The bacterial stamps and the polymer surfaces are investigated using different techniques including optical microscopy, scanning electron microscopy (SEM) and Raman spectroscopy. The surface characterization indicated that once the stamps containing covalently attached bacteria are taken off from polymer, there is the presence of complementary cavities for bacteria at polymer surface. This indicates that the second method is suitable for generating surface imprints thus, can be used for developing synthetic receptor coatings having tailored recognition sites.
Gov't Doc #: 26975
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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