Raman dye-labeled nanoparticles probes for DNA studies


Thesis Type: Postgraduate

Institution Of The Thesis: Middle East Technical University, Faculty of Arts and Sciences, Department of Chemistry, Turkey

Approval Date: 2012

Thesis Language: English

Student: Ceren Uzun

Supervisor: MÜRVET VOLKAN

Abstract:

The interaction between nanoscience and biomedicine is one of the important developing areas of modern science. The usage of functional nanoparticles with biological molecules provides sensitive and selective detection, labeling and sensing of biomolecules. Until today, several novel types of tagging materials have been used in bioassays, such as plasmon-resonant particles, quantum dots (QDs), and metal nanoshells. However, nowadays, Surface enhanced raman scattering (SERS) tags have been attracting considerable attention as a tagging system. SERS-tags provide high signal enhancement, and they enable multiplex detection of biomolecules due to high specificity. This thesis is focused on the designing proper SERS nanotags for DNA studies. SERS nano-tags are nanostructures consisting of core nanoparticle generally silver, Raman reporter molecule for labeling, and shell to make surface modifications and to prevent deterioration arising from environmental impact. Based on this information, silver core synthesized by thermal decomposition and chemical reduction methods. Thermal decomposition method provides synthesis of silver nanoparticles in hydrophobic medium, resulting in proper silica coating by reverse microemulsion method. On the other hand, silver nanoparticles sythesized by chemical reduction method exhibit hydrophilic property. Due to capping reagents, negatively charged silver nanoparticles could easily attach with positively charged Raman dye which is brilliant cresyl blue (BCB). After addition of Raman active molecule, silica coating process was done by using modified Stöber method. The resulting particles were characterized by Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX) ,UV-vis Spectrometry (UV-vis) and Surface-Enhanced Raman Spectroscopy (SERS). In recent years, DNA detection has gained importance for cancer and disease diagnosis and the detection of harmful microorganisms in food and drink. In this study, gene sequences were detected via SERS. For this, probe sequences were labelled with Raman reporter molecule, BCB,and SERS nano-tags and were called as SERGen probes. Then, after hybridization of DNA targets to complementary probe sequences onto gold substrate, SERS peak was followed.