Simple and rapid preparation of orange-yellow fluorescent gold nanoclusters using dl-homocysteine as a reducing/stabilizing reagent and their application in cancer cell imaging

Abstract

A simple, convenient and fast preparation for successful fabrication of water-soluble DL-homocysteine capped Au nanoclusters (hcy-AuNCs) was demonstrated. This preparation allowed the generation of water-soluble Au NCs within a short time of 15 min. The resulting hcy-AuNCs were characterized by photoluminescence, UV-Vis absorption, X-ray photoelectron spectroscopy, and transmission electron microscopy (TEM). The mean diameter of hcy-AuNCs was found to be 1.6 ± 0.2 nm. The Au NCs exhibited an orange-yellow fluorescence emission at 560 nm with a large Stokes shift of 120 nm, a quantum yield of 3.01% and a good stability over the physiologically relevant pH range and ionic strength. Furthermore, cytotoxicity studies showed that the Au NCs exhibited negligible effects in altering cell proliferation or triggering apoptosis. Cancer cell imaging of HeLa cell lines indicated that the obtained Au NCs could serve as a promising fluorescent bioprobe for bioimaging. This strategy, based on the one-step preparation using DL-homocysteine as a reducing/stabilizing reagent, may offer a novel approach to fabricate other water-soluble metal nanoclusters for application in biolabelling and bioimaging.