Abstract
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 Mn2+ in living cells. While fluorescent sensors have been very effective in detecting other metal ions, Mn2+-specific fluorescent sensors are rarely reported due to nonspecific fluorescence quenching by the paramagnetism of Mn2+ and poor selectivity against other metal ions such as Ca2+ and Mg2+. To address these issues, we herein report in vitro selection of an RNA-cleaving DNAzyme with exceptionally high selectivity for Mn2+. Through converting it into a fluorescent sensor using a catalytic beacon approach, Mn2+ 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 Mn2+ in biological systems and monitor the Mn2+-involved immune response and antitumor therapy.