Direct visualization of MicroRNA in vivo via an intelligent MnO2-carried catalytic DNA machine

High sensitive detection and monitoring of miRNAs in living cells have obtained considerable attention for clinical diagnosis of diseases. However, there are still enormous challenges for developing new method of quantification of miRNA in vivo. Herein, an intelligent MnO 2 -carried catalytic DNA machine (MCDM) was constructed for direct visualization of MicroRNAs in vivo with high selectivity and extremely low detection limit. MnO 2 nanosheets were used as a degradable carrier to introduce the DNA machine into cells. Benefiting from the enhanced permeability and retention (EPR) effect, the MnO 2 -carried probes could accumulate in tumor tissue, realizing a direct visualization of low concentration of miR-21 in the tumor of living animals in situ.