Preparation and quantitative study of gold nanoparticles forSERS biolabelling

SERS probes based on gold nanoparticles – organic dyes nanocomposites are intensively investigated for in vitro and in vivo labelling or for bio-analytical applications. Their main advantages are: biocompatibility, enormous Raman scattering cross section, analysis at wavelengths in the transparency window of biological tissues, multiplex analysis based on the distinctive fingerprint of each label. Here we report about the preparation of AuNP obtained by laser ablation synthesis in solution (LASiS)1-5 and their functionalization with a series of Raman labels with different properties. The Raman scattering cross section and the minimum number of AuNP observable by Raman spectroscopy in different conditions were measured and used for quantitative comparison of the different labels. Optical microscopy and transmission electron microscopy were coupled to Raman analysis for this purpose. Calibration studies were applied to the quantification of cell uptake studies of nanoparticles. The results suggests that, in the best cases, about ten AuNP in the analysis volume are enough for practical application with common Raman spectrometers. 1 V. Amendola, M. Meneghetti, “Laser ablation synthesis in solution and size manipulation of noble metal nanoparticles”, invited Perspective Article, Phys. Chem. Chem. Phys. 2009, Accepted. 2 V. Amendola, M. Meneghetti, J. Phys. Chem. C 2009, 113, 4277–4285. 3 S. Salmaso, P. Caliceti, V. Amendola, M. Meneghetti, J. P. Magnusson, G. Pasparakis, C. Alexander; J. Mater. Chem. 2009, 19, 1608 – 1615. 4 V. Amendola, M. Meneghetti; J. Mater. Chem. 2007, 17, 4705–4710. 5 V. Amendola, S. Polizzi, M. Meneghetti; J. Phys. Chem. B 2006, 110, 7232 – 7237.