TiO2@Ag nanozyme enhanced electrochemiluminescent biosensor coupled with DNA nanoframework-carried emitters and enzyme-assisted target recycling amplification for ultrasensitive detection of microRNA

MicroRNAs (miRNAs) have been discovered as promising biomarkers for cancer early diagnosis. Constructing sensitive biosensing strategy for detecting extremely low-abundance miRNAs in biological samples is urgently required. Herein, an efficient electrochemiluminescent (ECL) biosensor was developed for ultrasensitive detec-tion of miRNA coupled with DNA nanoframework-carried emitters (DNF-Dox-ABEI) and T7 exonuclease-assisted target recycling amplification (T7 exo-TRA). The fabricated DNF-Dox-ABEI emitters could load numerous luminophore molecules, and silver nanoparticles-coated TiO2 (TiO2@Ag NPs) nanozymes held excellent peroxidase-like activity in catalyzing H2O2 to produce enormous reactive oxygen species (ROS), which further reacted with ABEI to enhance ECL emission. Meanwhile, the T7 exo-TRA could effectively convert target hy-bridization event into amplifying signals for further improving sensitivity. Consequently, the constructed ECL biosensor enabled ultrasensitive detection of miRNA-155 with a broad linear range from 1.0 fM to 500.0 pM and a low detection limit of 0.45 fM (S/N = 3). Furthermore, it was noted that the biosensing strategy successfully achieved miRNA-155 analysis from breast cancer cells. Therefore, the constructed biosensor in the present study provided a potential tool in cancer early diagnosis and a novel approach for designing efficient ECL nanomaterials.