A Colorimetric Pb(II) Sensor Based on a Gold Nanoparticle DNA-zyme System

2003 Summer Research Students: Alison Williams and Chorthip Peeraphatdit (chemistry)

Fall 2003, General Biology Student Research Project:

For more advanced chemistry classes, we have developed an experiment that uses the gold nanoparticles to create a novel and very sensitive colorimetric sensor for the detection of Pb(II). This sensor is based upon the ability of a 17-base DNAzyme oligonucleotide to cleave a substrate DNA/RNA hybrid only in the presence of Pb(II). The DNA/RNA hybrid is anchored to a number of gold nanoparticles through gold-sulfur linkages. The clustering of the gold nanoparticles imparts a deep purple color to the lead sensor. However, in the presence of increasing amounts of lead, the DNAzyme is activated, cleaving the substrate and dispersing the gold nanoparticle clusters, thus imparting a red color to the sensor. Students can learn about the properties of nanoparticles that impart the color change observed as well as the hazards posed by lead. They can also garner an appreciation of the thermodynamic and catalytic properties of the DNA polymer widely considered to only be a storage device for genetic information. Through the use of a visible spectrometer formatted plate reader students can determine the lead content of samples they collect themselves or test hypotheses about the solution parameters (ionic strength, pH etc) that are important for the reaction to proceed.

Reference: Liu, J., Lu, Y, J. Am. Chem. Soc., 2003, 125, 6642.

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Last updated June , 2005

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