Highly Sensitive Multiplexed Heavy Metal Detection Using Quantum-Dot-Labeled DNAzymes

• Published in: ACS nano Vol. 4; no. 10; pp. 5897 - 5904
• Main Authors: Wu, Chung-Shieh, Khaing Oo, Maung Kyaw, Fan, Xudong
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 26.10.2010
• Subjects: Base Sequence; Biosensing Techniques - methods; Copper - chemistry; DNA, Catalytic - chemistry; Fluorescence Resonance Energy Transfer; Humans; Ions; Lead - chemistry; Metals - chemistry; Metals, Heavy - chemistry; Molecular Sequence Data; Nanotechnology - methods; Oligonucleotides - chemistry; Quantum Dots; Reproducibility of Results; Spectrometry, Fluorescence - methods; quantum dot; heavy metal; FRET; sensor
• ISSN: 1936-0851; 1936-086X
• DOI: 10.1021/nn1021988

We developed highly sensitive and specific nanosensors based on quantum dots (QDs) and DNAzyme for multiplexed detection of heavy metal ions in liquid. The QDs were coated with a thin silica layer for increased stability and higher quantum yield while maintaining a relatively small size for highly efficient energy transfer. The QD−DNAzyme nanosensors were constructed by conjugating quencher-labeled DNAzymes onto the surface of carboxyl-silanized QDs. In the presence of metal ions, the emission is restored due to the cleavage of DNAzymes. The detection could be completed within 25 min with a single laser excitation source. The detection limit of 0.2 and 0.5 nM was experimentally achieved for Pb2+ and Cu2+, respectively, which is a 50- and 70-fold improvement over the recent results obtained with dye molecules. Multiplexed detection was also demonstrated using two different colors of QDs, showing negligible cross-talk between the Pb2+ detection and Cu2+ detection.