고감도 생물학적/환경학적 검출을 위한 표면 증강 라만 산란 압타센서 개발

Abstract

Surface-enhanced Raman scattering (SERS) is a surface sensitive technique that results in the enhancement of Raman scattering by molecules adsorbed on rough metal surfaces. The enhancement factor can be as much as 14 –15 orders, which allows the technique to be sensitive enough to detect single molecules. Since SERS was first discovered by Martin Fleischmann, and coworkers in 1974, SERS has been extensively applied to environmental and biomedical detection. Unfortunately, however, the lack of reliable and reproducible SERS signals limited its applicability. In recent years, the new techniques for nanofabrication, the design of substrates that maximize the electromagnetic enhancement, and the discovery of single-molecule SERS are raising an interest of its biological sensing application. In this dissertation, we investigated three different issues related to the SERS-based biosensor. In chapter 2, we investigated the rapid and highly sensitive trace analysis of mercury (II) ions in water using a SERS-based microdroplet sensor. Aptamer-modified Au/Ag core-shell nanoparticles have been fabricated and utilized as highly functional sensing probes. All detection processes for the reaction between mercury(II) ions and aptamer-modified nanoparticles were performed in a specially designed microdroplet channel. Small water droplets that included sample reagents were separated from each other by an oil phase that continuously flowed along the channel. This two-phase liquid/liquid segmented flow system prevented adsorption of aggregated colloid to the channel walls due to localized reagents within encapsulated droplets. The result was reduced residence time distributions. The limit of detection (LOD) of mercury(II) ions in water was determined by SERS-based microdroplet sensor to be below 10 pM, which is three orders below the EPA-defined maximum contaminant level. This combination of SERS-based microfluidic sensor with aptamer-based functional nanoprobes can be used for in-the-field sensing platforms due to its size and simplicity. In chapter 3, we investigated the SERS-based sensor for the quantitative analysis of Bisphenol A (BPA). BPA is a widely used chemical and raw material for epoxy resin, flame retardants and polycarbonate in plastic and paper industries. BPA is currently considered as an environmental endocrine disrupting chemical (EDC) that is potentially estrogenic. Thus, ultrasensitive and rapid detection of BPA in drinking water is great importance for protecting human health. In this study, we report a novel trace analysis method for the Bisphenol A in water using a surface-enhanced Raman scattering (SERS) detection technique. Here, aptamer-conjugated Au/Ag core-shell nanoparticles have been used as efficient SERS probes. The SERS detection using aptamer-conjugated Au/Ag core-shell nanoparticles provides a selective detection of Bisphenol A in drinking water. In the presence of BPA, Cy3-labeled DNA aptamers were released from the nanoprobe surface resulting in a decrease in SERS signal. Quantitative analysis of BPA was performed by plotting Cy3 peak intensity at 1,590 cm−1 of SERS spectra as a function of Cy3 concentration. Herein, the aptamer-conjugated nanoparticles showed its applicability for detecting BPA in simple, selective, and quantitative manner. In chapter 4, the antibody drug efficacy was studied using the SERS-based biosensor. Epidermal growth factor receptor (EGFR) has been recognized as an important prognostic marker expressed in cancer cells because its activation associated with key features of cancer including tumor growth, survival, angiogenesis, and metastasis. Cetuximab is the first monoclonal antibody drug that targets EGFR overexpressed in cancer cells. It easily binds to EGFR, thereby down-regulating the receptor, blocking EGFR-mediated tyrosine kinase activity, and inhibiting cellular proliferation. Thus, EGFR-cetuximab binding can be quantified to monitor receptor status and the prognosis of cancer therapy. In this work, we report using SERS imaging to assess the inhibitory effect of cetuximab on EGFR expressed on cancer cells. From SERS mapping images using silica-encapsulated gold nano tags, the localized spatial distribution of EGFR that was not inhibited by cetuximab could be determined. Furthermore, EGFR expression could be accurately quantified through the statistical analysis of surface-enhanced Raman scattering (SERS) spectral data. Our experimental data demonstrate the feasibility of SERS imaging to improve the prognostic efficacy of cetuximab treatment.