Cancer Cell Identification by Using ZnO Nanowires Modified by Carboxyalkylphosphonic Acids
Date Issued
2015
Date
2015
Author(s)
Huang, Po-Hao
Abstract
Among cancer cell detection methods, fluorescence microscopy cancer detection is one of the most common methods. However, there are many disadvantages for fluorescence cancer detection such as the phototoxicity, the limited number of available fluorescent channels, and the overlap of the excitation and emission spectra of the stains. Furthermore, under a constant light illumination, it possesses the issue of photobleaching, making real time surgery difficult. ZnO nanowires, one of the semiconductor materials in nano-scale, have the ability to replace the organic fluorescent substances for those drawbacks mentioned above. ZnO nanowires have exceptional optical properties, and they are often applied to biomedical research and commercial products. In addition, due to great affinities between ZnO nanowires and many proteins, ZnO bounded to specific antibodies are regarded as biomarkers to identify the cancer cells. In this thesis, we applied another kind of the semiconductor materials, TiO2 nanowires, to achieve the bi-color cancer cell identification. TiO2 nanowires also have great optical properties, and they have great affinities to many proteins, too. The ZnO/antibody biomarkers were applied to mark the cancer cells, while the TiO2/antibody biomarkers were applied to mark the normal cells. From PL spectra and bio-images, our idea for cancer cell detection by semiconductor nanowires was confirmed. A series of quantitative analyses, including biomarker concentration limit, the valid range of cell numbers, and co-culture case to simulation the real situation were conducted to examine the relationship between the optical response from biomarkers and cell numbers. Though the attachment of antibodies to the surface of ZnO can be achieved through simple adsorption, formation of a covalent bond between the antibody and the oxide surface via a chemical crosslinker is the preferred method. The covalent bonds makes the conjugation more robust, and prevents low coverage of antibodies or non-specific binding. In this thesis, carboxyalkylphosphonic acid would form the self-assemble monolayers (SAMs) on the nanowires. After the activation of the SAMs by EDC/NHS, the antibodies would be immobilized on the nanowires by the newly-formed covalent bonds. Regarding the results of binding tests of antibodies, Photoluminescence spectra, and the bio-images, we proved that the conjugation between nanowires and antibodies would be stronger during the modification process, so the modification on the ZnO nanowires successfully enhances the sensitivity of the cancer cell detection.
Subjects
Cancer cell detection
ZnO
TiO2
Nanowires
Self-assemble monolayers
SDGs
Type
thesis
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