Raman-SERS Spectroscopy

Surface-Enhanced Raman Scattering (SERS) is characterized by a dramatic enhancement of the Raman cross-section (up to 10¹⁴ times) and it occurs when molecules are adsorbed onto nano-sized metal surfaces (nanoparticles or rough substrates).

SERS, which combines chemical information with single molecule sensitivity, can be applied in fundamental biophysics to follow the dynamics of single biomolecules and in nanomedicine for ultra-sensitive detection.

Applications of SERS in nanomedicine

• We have developed an approach to detect the tumor suppressor p53 at extremely low concentration by exploiting the complex that p53 forms with the copper protein Azurin.

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• p53 molecules have been anchored to gold nanoparticles by means of the bifunctional linker 4-aminothiophenol (4-ATP). The characteristic vibrational bands of the p53-(4-ATP-Np) system have been then used to identify the p53 molecules when they are captured by a recognition substrate, constituted by a monolayer of Azurin molecules possessing a significant affinity for this tumor suppressor.

The Raman signal enhancement resulting by the 4-ATP mediated cross-linking of p53 to 50 nm gold nanoparticles has allowed us to detect this protein at a concentration down to 5·10^-13 M.

SERS of single molecules

We have investigated different molecules at single molecule level.

Myoglobin Cytochrome c Iron-Proto Porphyrin IX

We are particularly interested in the study of temporal fluctuations of single molecule SERS spectra.

Raman shift (cm^-1)

· Random apperance of peaks

· The vibrational modes of the molecule undergo an on-off switching

· Correlation in peak appearance