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    Optimization of Molecularly Imprinted Polymers for Electrochemical Sensing of Non-charged Biological Molecules

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    SHA_Thesis_V2.pdf
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    Description:
    Sarah Al Abdulatif - Final Thesis
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    Type
    Thesis
    Authors
    Al Abdullatif, Sarah cc
    Advisors
    McCulloch, Iain cc
    Committee members
    Anthopoulos, Thomas D. cc
    Laquai, Frédéric cc
    Program
    Chemical Science
    KAUST Department
    Physical Science and Engineering (PSE) Division
    Date
    2019-11
    Permanent link to this record
    http://hdl.handle.net/10754/660134
    
    Metadata
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    Abstract
    Biosensors monitor physiological activities for diagnosis and treatment of disease. Molecularly imprinted polymers (MIPs) are a viable synthetic approach for molecular recognition in biosensing. For biosensing purposes, the most important properties in MIP optimization are sensitivity and selectivity towards a desired analyte. This study aims to optimize MIP sensitivity and selectivity by varying the amount and type of cross-linker used in the synthesis of cortisol and melatonin. The four cross-linkers tested were trimethylpropane trimethacrylate (TRIM), ethyleneglycodimethacrylate (EGDMA), divinylbenzene (DVB), and pentaerythritol triacrylate (PETRA). Based on literature, the following ratios were used for the template molecule to functional monomer to cross-linker in MIP synthesis: for EGDMA cross-linked polymers, 1:6:30; for TRIM and PETRA cross-linked polymers, 1:8:8, 1:6:3, and 1:8:35; for DVB cross-linked polymers, 1:6:30, 1:4:16, and 4:1:60. The polymers were ground and washed, then suspended in a polyvinyl matrix which was spin-coated onto an organic electrochemical transducer (OECT). The device performance was evaluated using electrochemical impedance spectroscopy. For each device, the impedance was measured in electrolyte solutions containing target molecules in concentrations ranging from 1 pM to 100 uM. The impedance was plotted against the analyte concentration to give the sensing slope, which is a measurement for the binding affinity of the polymer. For a device to be considered sensitive, its sensing slope should be greater than its non-imprinted counterpart by a factor above the error margin (+/- 1.79). Of the devices tested, CM1835T (highly cross-linked with TRIM) showed sensitivity towards cortisol, but lacks selectivity towards cortisol over its structural analog, estradiol. Of the melatonin selective polymers, MM163T (low cross-linking with TRIM), MM1630D, and MM4160D (both highly cross-linked with DVB) all showed promising results in sensitivity to melatonin. Overall, the results indicate that high degrees of cross-linking in MIPs improve sensitivity for large, rigid, non-aromatic molecules such as cortisol; however there is no correlation between selectivity and the degree of cross-linking. Meanwhile, divinylbenzene as a cross-linker improves sensitivity and selectivity towards aromatic analytes such as melatonin and estradiol. This study could be improved upon by further characterization of imprinted and non-imprinted polymers, investigation of molecular dynamics, and optimization of devices.
    Citation
    Al Abdullatif, S. (2019). Optimization of Molecularly Imprinted Polymers for Electrochemical Sensing of Non-charged Biological Molecules. KAUST Research Repository. https://doi.org/10.25781/KAUST-9ZPU5
    DOI
    10.25781/KAUST-9ZPU5
    ae974a485f413a2113503eed53cd6c53
    10.25781/KAUST-9ZPU5
    Scopus Count
    Collections
    Theses; Physical Science and Engineering (PSE) Division; Chemical Science Program

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