The Color Switching Behavior of DNA-Templated Silver Nanoclusters

Abstract

Oligonucleotide-templated silver nanoclusters (DNA/Ag NCs) are an emerging set of fluorophores that have seen applications in cellular imaging and chemical/biological detection. We discovered the red fluorescence emission of DNA/Ag NCs could be enhanced more than 500 fold when these silver nanoclusters were brought close to a guanine-rich DNA sequence (called an enhancer). Based on this finding, we developed a new type of molecular probe termed NanoCluster Beacon (NCB) that fluoresces upon target DNA binding (1). Expanding upon this work, recently we found non-emissive DNA/Ag NCs can light up into three distinct colors (green, yellow, and red) through interactions with three different DNA enhancers respectively (2), enabling the use of NCBs in multiplexed assays. In order to investigate the enhancer-mediated, color switching behavior of DNA/Ag NCs, a toehold DNA displacement technique was used to replace old enhancers with new enhancers in the proximity of nanoclusters at room temperature. Our results showed that the light-up color can change from green to red if the green enhancer is replaced with the red enhancer, but not vice versa. Similar behavior was also seen from yellow to red color switching. This information may be useful in future silver nanocluster probe design. Reference: [1] H.-C. Yeh, J. Sharma, J.J. Han, J.S. Martinez and J.H. Werner, “A DNA-silver nanocluster probe that fluoresces upon hybridization,” Nano Letters 10(8): 3106-3110, 2010. [2] H.-C. Yeh, J. Sharma, J.J. Han, J.S. Martinez and J.H. Werner, “A beacon of light: a new molecular probe for homogeneous detection of nucleic acid targets,” IEEE Nanotechnology Magazine 5(2): 28-33, 2011.