Colorimetric Screening

Probes were prepared by functionalizing two separate batches of 13-nm gold particles with two different thiolmodified oligonucleotide strands, DNA-1 (5’-CTCCCTAATAACAATTTATAACTATTCCTA- A10-SH-3’) and DNA-2(5’-TAGGAATAGTTATAAATTGTTATTAGGGAG-A10- SH-3’). These functionalized particles are denoted DNAAuNP-1 and DNA-AuNP-2. DNA-1 and DNA-2 are complementary to each other. Therefore, DNA-AuNP-1 and DNA-AuNP-2 can hybridize to form a cross-linked network
of nanoparticles, which is purple in color owing to the redshifted plasmon band of the gold nanoparticles (13 nm). This red-shifting is a well-understood process and is a highly diagnostic feature of aggregate formation.[11] These aggregates can then be used as colorimetric indicators of endonuclease activity (Scheme 1). As the endonuclease degrades the DNA-duplex interconnects, particles are released, regenerating a red color due to the dispersed nanoparticles. The color can be observed with the naked eye, or the absorbance (520 nm) can be measured by UV/Vis spectroscopy.
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