Synthesis And Characterisation Of Raman Nanotags For Molecular Detection

The realization that most diseases are preceded or accompanied by changes in the genetic and cellular level of an organism has increased with the need for imaging modalities, with the sensitivity and specificity, to quantitatively detect biomolecules at those levels. Specifically there has been a need for the development of a modality that has the ability to detect multiple biomolecules from a single sample in order to increase accuracy of molecular diagnosis and allow for early detection of terminal diseases. Surface enhanced Raman spectroscopy provides potential for such a modality. The distinct spectrum of each Raman active molecule serves as a molecular "fingerprint" enabling it to be clearly distinguished from other Raman spectra. Although Raman signals are fundamentally much weaker than signals produced by most other modalities, they can be enhanced by the use of electron rich metallic nanoparticles such as gold nanoparticles by 14 - 15 orders of magnitude. Additionally, gold's reported biocompatibility and its well documented use in dentistry and in the treatment of Rheumatoid Arthritis give it a unique advantage over other labeling materials. In this thesis, the synthesis and characterization of gold nanoparticles for optimum Surface Enhanced Raman Scattering within the optical window is described. Using these nanoparticles, five of nanotags were developed distinguished from each other by the different reporter molecules on them. These nanotags are shown to remain stable under harsh conditions and have a great potential for detection of multi-cellular expression in vivo and in vitro.