A Highly Selective Mn(II)-Specific DNAzyme and Its Application in Intracellular Sensing.

Manganese is an essential trace element in the human body that acts as a cofactor in many enzymes and metabolisms. It is important to develop methods to detect Mn in living cells. While fluorescent sensors have been very effective in detecting other metal ions, Mn-specific fluorescent sensors are rarely reported due to nonspecific fluorescence quenching by the paramagnetism of Mn and poor selectivity against other metal ions such as Ca and Mg. To address these issues, we herein report in vitro selection of an RNA-cleaving DNAzyme with exceptionally high selectivity for Mn. Through converting it into a fluorescent sensor using a catalytic beacon approach, Mn sensing in immune cells and tumor cells has been achieved. The sensor is also used to monitor degradation of manganese-based nanomaterials such as MnOx in tumor cells. Therefore, this work provides an excellent tool to detect Mn in biological systems and monitor the Mn-involved immune response and antitumor therapy.