Ratiometric fluorescence biosensor based on DNA/miRNA duplex@CdTe QDs and oxidized luminol as a fluorophore for miRNA detection

Breast cancer is the second most diagnosed cancer in women worldwide. Hence, the detection of prognostic and diagnostic biomarkers can improve the patient's quality of life during the course of illness and treatment. Most recently, microRNAs (miRNAs) have been widely studied for non-invasive prediction of prognosis markers in the diagnosis of breast cancer. Herein, we reported a ratiometric fluorescence nanobiosensor for detection of miR-155. The biosensor comprises of 3-mercapropionic acid-coated cadmium telluride (CdTe) quantum dots and oxidized luminol (Lum(ox)) exhibiting emission peaks at 550 and 440 nm, respectively, under single-wavelength excitation (350 nm). In the presence of miR-155, CdTe QDs were aggregated and their fluorescence was quenched via interacting strongly at their metal centers, Cd, with heteroduplex formed between the DNA probe and miR-155. Then, by addition of blue-emitting Lum(ox) with their constant fluorescence emission, a ratiometric means of miR-155 detection was developed. The relative fluorescence intensity ration is directly proportional to the concentration of miR-155 between 20.0 and 100.0 pM. The detection limit is 12.0 pM. This novel assay is "light-on" and has been successfully applied for the detection of miRNA in MCF-7 and HEK 293 cell lysates as real samples.