SERS-based substrate for biological sensing applications
Goh, Douglas Wenda
Date of Issue2014
School of Physical and Mathematical Sciences
Surface enhanced Raman spectroscopy has emerged in recent years as one of the leading ideal optical techniques in analysing vibrational information from molecular bonds of molecules. Plasmonic nanopatterned surfaces provide a platform for enhancing Raman scattering from virtually any molecule that is adsorbed onto those surfaces. Consequently, the phenomenon of surface enhanced Raman scattering (SERS) has seen applications in sensitive detection of otherwise weak photon-scattering molecules, particularly those of biological nature. In this thesis, a facile SERS-based substrate known as bimetallic-film-over-nanosphere (BMFON) substrate was used for biological sensing as such an application is not fully realised based on literature survey. Firstly, a concise introduction to SERS was made, followed by the factors that determine its efficiency. Subsequently, a literature survey of novel substrate designs and their applications was performed. Finally, the use of SERS was demonstrated in 1) the label-free detection of folic acid adsorbed onto the substrate and 2) the characterisation of potential cancer markers on the cellular membrane of a living cell was shown. In light of the first experiment, research has found a potential link between folate levels and malignancy in cancer. Thus, with the use of the substrate, folate concentration can be analysed based on optimized substrate configuration. In the second experiment, the substrate was further shown to sensitively quantify the distribution of sialic acid glycans on the membrane of HeLa cells. Sialic acid is found to closely correlate with the stage in cancer and condition of erythrocytes. Thus, the distribution of glycans on the surface of cell membrane becomes a noteworthy avenue of research for cancer metastases and other haemotopoetic studies. With the use of BMFON substrate, this study can be facilitated using HeLa cells as an example and a Raman probe that is specific to sialic acid on the cell membrane.