Functional Nucleic Acid-Directed Assembly of Nanomaterials and Their Applications as Colorimetric and Fluorescent Sensors for Trace Contaminants in Water

Largely due to the high extinction coefficients and distance-dependent optical properties, metallic nanoparticles and quantum dots have been shown to be very attractive in DNA-related colorimetric and fluorescent assays, respectively. We have used DNAzymes (DNA molecules with catalytic activities) for directed assembly of gold nanoparticles and its application as colorimetric sensors for metal ions such as lead. This methodology has been expanded to an even broader range of molecules by using aptamers (nucleic acid-based binding molecules obtained through systematic evolution of ligands by exponential enrichment (SELEX)). We have developed a general sensor design method that is simple to design, easy to operate and gives fast color change with minimal materials consumption. To demonstrate the generality, sensors for adenosine and cocaine have been designed, both of which can produce color changes in seconds and at room temperature. Since no special feature on the aptamers is required, the design should be able to be used for any molecule of choice. Finally, to make the operation even easier to use and less venerable to errors, we have demonstrated dipsticks tests for a broad range of contaminants in water. These and other recent advances in this area will be summarized.