Fig. 3.

Bioluminescence based assay. A) Quantum dot labeled oligonucleotide probe (QD-probe) and Rluc labeled oligonucleotide probe (Rluc-probe) are used in BRET based detection. In the absence of target nucleic acid, QD-probes hybridize with Rluc-probe to generate a signal after addition of coelenterazine. When the target is present, the BRET signal is decreased owing to the competitive inhibition of Rluc hybridization with QD-probe. B) In a modified assay, biotinylated anti-miRNA probes first are immobilized on neutravidin-coated microtiter plate, then Rluc-labeled target miRNAs and unlabeled synthetic target miRNAs are added. Both sample (Rluc labeled) and synthetic (unlabeled) miRNAs compete with each other during hybridization with the immobilized probes. Upon addition of coelenterazine, a decrease in signal intensity is measured as an estimate of target miRNA levels.