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 2+ in living cells. While fluorescent sensors have been very effective in detecting other metal ions, Mn 2+ -specific fluorescent sensors are rarely reported due to nonspecific fluorescence quenching by the paramagnetism of Mn 2+ and poor selectivity against other metal ions such as Ca 2+ and Mg 2+ . To address these issues, we herein report in vitro selection of an RNA-cleaving DNAzyme with exceptionally high selectivity for Mn 2+ . Through converting it into a fluorescent sensor using a catalytic beacon approach, Mn 2+ 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 2+ in biological systems and monitor the Mn 2+ -involved immune response and antitumor therapy.