Development of novel immobilization matrices via surface modification approach for glucose detection and their biosensor applications

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2014

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Demirci Uzun, Sema

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Biosensors which include biorecognition element and the transducer are widely used devices in many research areas. In an electrochemical biosensor construction, immobilization of redox enzymes on conductive surfaces is a crucial step to obtain stable electrodes. The use of conducting polymers as appropriate immobilization matrices for biomolecules leads to the improvement of biosensors as economical tools for clinical and pharmaceutical analyses. In that manner, electrically conducting polymers can be deposited on an electrode surface as immobilization matrices for biomolecules to enhance stability, sensitivity and efficient electron transfer ability of biosensors. Also, electropolymerization enables easy control over the several properties such as morphology and thickness. Furthermore, their chemical functionalization offers a better microenvironment for biomolecules and electrochemical transduction of biological events. In this thesis, it is aimed to create conducting polymer based new immobilization matrices providing high stability, sensitivity and electron transfer ability for glucose detection. Recently synthesized poly(2-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl) (SNS) acetic acid) and 4-(4,7-di(thiophen-2-yl)-1H-benzo[d]imidazol-2- yl) benzaldehyde (BIBA) were electrochemically deposited on graphite electrodes. SNS acetic acid polymer was functionalized with lysine (Lys) amino acid and poly(amidoamine) vi derivatives (PAMAM G2 and PAMAM G4) to investigate their matrix properties for biosensor applications. Glucose oxidase (GOx) was immobilized onto the modified surface as the model enzyme. X-Ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were used to report the surface properties of the matrices in each step of the biosensor construction. The biosensors were characterized in terms of their operational and storage stabilities and the kinetic parameters (Kmapp and Imax). Three new glucose biosensors revealed good stability, promising low detection limit and prolonged the shelf lives. The proposed biosensors were tested for glucose detection on real human blood serum samples. To develop different immobilization matrices, glucose oxidase (GOx) was immobilized as a model enzyme on PBIBA polymer coated graphite electrode with the help of glutaraldehyde (GA). Besides non-modified PBIBA biosensor, other electrode surfaces were modified with gold nanorods (AuNRs) and single-walled carbon nano tubes (SWCNTs) to enhance sensitivity and electron transfer ability of desired biosensors. The surface characterization and morphology were investigated to confirm bioconjugation by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) at each step of biosensor fabrication. Three new optimized biosensors show good linearity and low limit of detection (LOD) values. Kinetic parameters Kmapp and Imax were also determined for each biosensor. Furthermore, biosensors were tested for real samples.

Subject Keywords

Conducting polymers., Biosensors., Glucose., Oxidases., Surface chemistry., Immobilized enzymes.

URI

http://etd.lib.metu.edu.tr/upload/12617013/index.pdf
https://hdl.handle.net/11511/23386

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

S. Demirci Uzun, “Development of novel immobilization matrices via surface modification approach for glucose detection and their biosensor applications,” Ph.D. - Doctoral Program, Middle East Technical University, 2014.