title: Ultrasensitive Pb2+ detection by glutathione-capped quantum dots.
abstract: Water-soluble and stable quantum dots (QDs), CdTe and CdZnSe, are applied for ultrasensitive Pb(2+) detection. These QDs are capped with glutathione (GSH) shells. GSH and its polymeric form, phytochelatin, are employed by nature to detoxify heavy metal ions. As a result of specific interaction, the fluorescence intensity of GSH-capped QDs is selectively reduced in the presence of heavy metal ions such as Pb(2+). The detection limit of Pb(2+) is found to be 20 nM due to the superior fluorescence properties of QDs. Detailed studies by spectroscopy, microscopy, and dynamic light scattering show that competitive GSH binding of Pb(2+) with the QD core changed both the surface and photophysical properties of the QDs. Fluorescence of QDs is quenched, and QD aggregation occurs. Coupling the GSH-capped QDs with a high-throughput detection system, we have developed a simple scheme for quick and ultrasensitive Pb(2+) detection without the need for additional electronic devices. In the presence of ionic mixtures, our system is still capable of Pb(2+) detection with a detection limit as low as 40 nM. The system only becomes less sensitive when the ionic mixture is present at a very high concentration (i.e., > or =50 microM).
authors.affiliation: Institute of Bioengineering and Nanotechnology, 31 Biopolis Way, The Nanos, Singapore 138669.
authors.forename: Emril Mohamed
authors.initials: EM
authors.lastname: Ali
authors.forename: Yuangang
authors.initials: Y
authors.lastname: Zheng
authors.forename: Hsiao-Hua
authors.initials: HH
authors.lastname: Yu
authors.forename: Jackie Y
authors.initials: JY
authors.lastname: Ying
mesh_terms: D005453:Fluorescence; D005978:Glutathione; D007477:Ions; D007854:Lead / Q000032:analysis*; D019216:Metals, Heavy / Q000032:analysis; D045663:Quantum Dots
chemical_list: D007477:Ions; D019216:Metals, Heavy; D007854:Lead; D005978:Glutathione