Study of protein–gold nanoparticle conjugates by fluorescence and surface-enhanced Raman scattering

We investigate the direct interaction between bovine serum albumin (BSA) protein and the surface of gold nanoparticles (GNPs) of different shapes (nanospheres and nanorods) by using localized surface plasmon resonance (LSPR) spectroscopy, fluorescence spectroscopy and surface-enhanced Raman scattering (SERS). The spectral modifications observed in LSPR bands of GNPs after mixing with BSA are consistent with the formation of protein–GNPs bioconjugates. While the monitoring of fluorescence quenching of tryptophan residues from BSA in the presence of GNPs is exploited for determining the binding constant (Kb) and the numbers of binding sites (n), the SERS data allow us to reveal some specific molecular groups involved in conjugation.