Direct Label-free Surface-Enhanced Raman Scattering Analysis of Nucleic Acids

Identifier:  TDX:2612

Handle: https://hdl.handle.net/20.500.11797/TDX2612

Authors:  Morlà Folch, Judit

Abstract:
The research has been carried out in the context of Surface-Enhanced Raman Scattering (SERS) spectroscopy for nucleic acids analysis. SERS is a powerful analytical technique that combines the structural specificity and high experimental flexibility of Raman spectroscopy with the extremely high sensitivity provided by the metal nanostructure amplification of the optical signal. Characterization of nucleic acids (NAs) has become a major goal in fields such as genetics or drug discovery. NAs are usually found in low amounts which require extremely sensitive techniques to be detected. Sensitivity represents a key requirement for their implementation into easy-to-use, cost-effective, rapid and high accuracy NA sensors. In this regard, the extraordinary sensitivity, in combination with the rich structural information provided by the Raman spectra, turned SERS into a powerful tool for the analysis of NAs. SERS analysis of NAs has been largely restricted to indirect approaches, dismissing the exquisite structural information provided by the direct acquisition of the biomolecular vibrational fingerprint. In this regard, positively charged silver nanoparticles coated with spermine were specifically designed for direct label-free SERS analysis of nucleic acids. By using these cationic nanoparticles the electrostatic interaction between NAs and the colloids is ensured yielding intense and highly reproducible SERS spectra at the ultrasensitive level. This highly sensitive label-free approach was successfully implemented in various applications of biological interest including identification and quantification of chemically-modified nucleobases in single and double stranded DNA, quantification of nucleobase composition in short and genomic DNA, and vibrational classification of structurally similar small RNA. In summary, this thesis demonstrates the tremendous analytical potential of this novel direct SERS method for nucleic acids analysis, opening new ways for the future development of a fast, low-cost, and high-throughput analytical technique for nucleic acids analysis.