Colorimetric and energy transfer based fluorometric turn-on method for determination of microRNA using silver nanoclusters and gold nanoparticles

摘要

The authors describe a dual (colorimetric and fluorometric) detection scheme for microRNA. The method is based on the use of fluorescent DNA-modified silver nanoclusters (DNA-AgNCs) and gold nanoparticles (AuNPs). The DNA-AgNCs were linked to AuNPs via the interaction of ssDNA-AgNC probes with AuNPs. This led to quenching of the fluorescence of the DNAAgNCs (best measured at excitation/emission peaks of 370/450 nm) and also prevents salt-induced aggregation of the AuNPs. Upon addition of microRNA, the DNA on the AgNCs hybridizes with microRNA. This led to the formation of a DNA-AgNC/miRNA hetero-duplex and increase of the distance to the AuNPs. Quenching was suppressed and fluorescence was restored. The presence of microRNA also affected salt-induced particle aggregation as reflected by a color change from red to purple that is visible with bare eyes. The visual detection limit for microRNA is 0.6 nM, and the fluorometric detection limit is 0.4 pM.