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Proceedings Paper

Design and study of activatable ("OFF/ON") quantum dots (Qdots): ligand selection for Qdot surface modification for controlling Qdot fluorescence quenching and restoration
Author(s): Andrew Teblum; Srijita Basumallick; Rikhav Shah; Rajendra Narayan Mitra; Subhash Banerjee; Swadeshmukul Santra
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Paper Abstract

We report design and synthesis of a series of activatable "OFF/ON" CdS:Mn/ZnS quantum dot (Qdot) based sensing probes. The Qdot "OFF" state represent the "quenched state" where the Qdot fluorescence is quenched by ligands attached to Qdot surface. Fluorescence quenching is likely due to ligand assisted electron transfer process. Qdot fluorescence is restored when the electron transfer process is stopped. Using this activatable Qdots, we have successfully demonstrated usefulness of these Qdot probes for reliable detection of toxic cadmium ions in solution, selective detection of glutathione and sensitive detection of intracellular cancer drug release event. In this paper, we will discuss a simple but robust method of making water-soluble CdS:Mn/ZnS Qdots at the room-temperature. Two different water-soluble biomolecules, the N-acetyl cysteine (NAC) and the glutathione (GSH) were used as surface coating ligands. This is a singlestep, one-pot synthesis where the Qdot nanocrystals were grown in the presence of the biomolecules. These Qdots were characterized by fluorescence spectroscopy. Stability of the GSH coated Qdots and the NAC coated Qdots were studied by treating with ethylenediaminetetraacetic acid (EDTA, a strong chelating agent for Zn and Cd ions). Our results show that fluorescence properties of Qdots are affected by the type of surface coated ligands. In comparison to the GSH coated Qdots, the NAC coated Qdots show broad but strong emission towards near infra-red region. When treated with EDTA, fluorescence property of the GSH coated Qdot was affected less than the NAC coated Qdots. This preliminary study shows that NAC coated Qdots could potentially be used to develop activatable ("OFF/ON") probes for potential deep-tissue imaging applications. Similarly, the GSH coated Qdots could be applied for probing desired analytes or for bioimaging purposes in environmentally harsh conditions.

Paper Details

Date Published: 2 February 2012
PDF: 11 pages
Proc. SPIE 8232, Colloidal Nanocrystals for Biomedical Applications VII, 82321H (2 February 2012); doi: 10.1117/12.912799
Show Author Affiliations
Andrew Teblum, Univ. of Central Florida (United States)
Srijita Basumallick, Univ. of Central Florida (United States)
Rikhav Shah, Univ. of Central Florida (United States)
Rajendra Narayan Mitra, Univ. of Central Florida (United States)
Subhash Banerjee, Univ. of Central Florida (United States)
Swadeshmukul Santra, Univ. of Central Florida (United States)

Published in SPIE Proceedings Vol. 8232:
Colloidal Nanocrystals for Biomedical Applications VII
Wolfgang J. Parak; Kenji Yamamoto M.D.; Marek Osinski, Editor(s)

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