Luminescent Nanomaterials for Biological Labelling

LUMINESCENT NANOMATERIALS FOR BIOLOGICAL LABELLING Krpetić, Željka a; Porta, Francesca a *; Scarì, Giorgio b a) Università di Milano, Dip. Chimica Inorganica Metallorganica Analitica, Centre of Excellence, CIMAINA and INSTM Unit, Via Venzian 21, Milano, Italy; b) Università di Milano, Dip. Biologia 7B, Via Celoria 26, Milano, Italy. zeljka.krpetic@unimi.it The introduction of the labelling agents in biological systems is required for a facile microscopy detection of biological systems. Fluorescent labels nowadays represent widely developed tools in biology and medicine.1 Fluorescence parameters are usually used to obtain information on living cells. In this context, modified gold nanoparticles can be used as nano reporters. The cellular environment can be deduced from the fluorescent signals throughout the use of Fluorescence Microscopy, besides Confocal Microscopy. Herein, we report our studies on the application of gold nanoparticles as a successful probe in the Fluorescence Microscopy. We have prepared differently stabilised gold nanoparticles by reduction of NaAuCl4 using different reduction agents (NaBH4, citric acid, ascorbic acid) in the presence of stabilising ligands (fluorescent ligands: Eosin Y, 2,7-dicholorofluorescein; not-fluorescent ligands: 5-aminovaleric acid, tri-sodium citrate). Tuning the reducing agent amount and the reaction temperature, we were able to prepare differently sized gold nanoparticles in the 7-50 nm range. It was recently reported in literature the importance of the size of Au NPs in the cellular uptake. 2 These novel gold colloids were characterised by UV-vis spectroscopy, TEM and HR MASS 1H NMR Spectroscopy. For the entrance of NP in cells, mouse macrophages were incubated with gold nanoparticles for 1 h (37°C, 5% CO2), and the cellular uptake of gold nanoparticles into macrophages cells was confirmed by using Confocal Microscopy and TEM. Besides, in this study, we merged fluorescent ligands with large sized particles in order to verify their facile detection by Fluorescence Microscopy. The results showed that gold nanoparticles stabilised by commonly used fluorescent dyes (like fluorescein and eosin Y) can be applied as bioluminescent markers. These novel systems, coupling gold with the dye, have an advantage of being visualized by all three microscopy techniques, (TEM, Confocal and Fluorescence microscopy) as they satisfy their detection requirements (gold electronic density, gold fluorescence and ligand fluorescence) as they exibit the long fluorescence lifetime. Now, we are expanding the Au-luminescent dye system to lanthanide nanoparticles stabilised by biologically active molecules in order to exploit the luminescent properties of lanthanides and the bioconjugation concept. 1. Wang, F.; Tan, W.B.; Zhang, Y.; Fan, X.; Wang, M. Nanotechnology, 2006, 17, R1-R13 2. Chitrani, B.D.; Ghazani, A.A.; Chan, W.C.W. Nano Letters, 2006, 6, 662-668