Highly selective detection of microRNA based on distance-dependent electrochemiluminescence resonance energy transfer between CdTe nanocrystals and Au nanoclusters.

A distance-dependent electrochemiluminescence resonance energy transfer (ERET) system based on CdTe nanocrystals and Au nanoclusters (Au NCs) was designed with the aid of ligase for highly selective detection of microRNA (miRNA). First, Au NCs functionalized hairpin DNA was synthesized via Au-S chemistry, and characterized with transmission electron microscopy and dynamic light scattering. The resulting hairpin DNA-Au NCs composite can be bound to the carboxylated CdTe nanocrystals via amide reaction on glass carbon electrode. The strong interaction between CdTe nanocrystals and AuNCs led to the electrochemiluminescence (ECL) quenching of CdTe nanocrystals. In the presence of assistant DNA and miRNA, the ligase can selectively ligate both of them on the strand of the hairpin DNA to form long DNA-RNA heteroduplexes. Thus the ECL signal was recovered due to the blocking of the ERET. As a comparison, when directly opening the hairpin DNA by the target, the ECL emission signal is weak owing to the presence of ERET effect at the short distance. Based on the distance-dependent ERET, a 'signal on' ECL system was utilized for the detection of miRNA with the advantages of 6 orders magnitude linear range and excellent sequence specificity. The total detection processing time of the biosensor was approximately 70 min. By substituting the hairpin DNA with different sequences, this strategy as a new signal transduction approach could be conveniently extended for detection of other short miRNA and DNA.