An approach toward miRNA detection via different thermo-responsive aggregation/disaggregation of CdTe quantum dots

MicroRNA-155 regulates the expression of 147 target genes that are involved in cancer pathways, and its expression level has been shown to be up-regulated in breast cancer. Thus, it is necessary to investigate the value of microRNA-155 for early diagnosis and prognosis of breast cancer. Here we present a novel and "light shift" spectral method for the detection of miRNA based on different thermo-responsive aggregation/disaggregation of CdTe quantum dots (CdTe QDs) by using single stranded DNA or a DNA/RNA heteroduplex as a template after heat treatment. In this method upon addition of the DNA/RNA heteroduplex, the CdTe QDs aggregate strongly due to their strong interaction with the double stranded nucleic acid, which results in fluorescence quenching. By applying the melting temperature (T _m), the DNA/RNA heteroduplex denatures and two strands are dissociated, which disaggregates the QDs, effectively switching to fluorescence emission of QDs. These processes were investigated with Atomic Force Microscopy (AFM) and fluorescence spectroscopy. The proposed method has been used also for the determination of miR-155 in total RNAs extracted from the human breast carcinoma SK-BR-3 cells and normal human embryonic kidney cell line (HEK 293).