Electronic Thesis and Dissertation Repository

Degree

Master of Engineering Science

Program

Biomedical Engineering

Supervisor

Zhang, Jin

Abstract

Various nanostructures have been explored in DNA biosensors to convert the hybridization of DNA sequences to easily measurable processes, including optical, mechanical, magnetic, or electrochemical process. In this thesis, graphene oxide, a two-dimensional nanostructure, is applied in quenching the fluorescence of a core-shell nanoparticles modified with targeted DNA sequences. The core-shell nanoparticles, iron oxide (Fe3O4) core, and fluorescent silica (SiO2) shell, were produced through a wet chemical process which can directly link to a targeted DNA sequence (DNA-t), and the graphene oxide nanosheets were produced by the oxidation of graphite. In the meantime, a complementary- DNA single strand (DNA-c) is designed to interact with graphene oxide. Two different mechanisms have been investigated in the sensing system; (1) Ionic interaction between the DNA sequences and nanostructures through cationic bridging; and (2) covalent binding between the DNA sequences and nanostructures. In the cationic bridge system, the fluorescence intensity changes with the concentration of DNA-t in the range of 0 to 30 µM with the limitation detection at 0.25 µM without graphene oxide; the other system can detect DNA-t in the range of 0 to 4 µM with limitation detection at 0.41 µM. In addition, the effect of concentration of graphene oxide on the fluorescence intensity of core-shell nanoparticles has been investigated.

We hope that the the validation strategy by engineering the two dimensional nanostructured system can be further applied towards more efficient Cancer diagnosis.

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