Fluorescence-based detection of Let-7a miRNA through HCR-based approach upon the in situ interaction of AuNPs@CdS QDs and FRET mechanism.

A novel strategy is presented based on integration of nanostructures and molecular amplification was developed for detection of Let-7a miRNA as the carcinogenic cancer marker. Hybridization chain reaction (HCR) was triggered through the presence of Let-7a as the initiator target. This reaction resulted to the formation of AuNPs@CdS QDs assembly due to thiol bonding and following FRET occurred between free AuNPs and CdS QDs. Characterization and morphology of AuNPs@CdS QDs showed in situ accumulation of CdS QDs and afterward optical changes in fluorescence emission. The quenching of fluorescence emission was observed which corresponded  to Let-7a concentration in the linear range 10-45 pM with LOD of 2 pM. The sensitivity and selectivity of the performed study confirmed the efficiency of the proposed strategy. Additionally, it demonstrated a high level of specificity and detection performance in real-sample analysis.