Efficient DNA-Catalyzed Porphyrin Metalation for Fluorescent Ratiometric Pb2+ Detection

This is the authors' abstract. We don't add key points for this paper.

Developing biosensors for Pb 2+ is an important analytical topic. DNA-based Pb 2+ sensors have been designed mainly based on RNA-cleaving DNAzymes and Pb 2+ -induced folding of G-quadruplex (G4) DNA. Porphyrin metalation is a key reaction in biology and catalysis. Many enzyme mimics have been developed to catalyze this reaction, and some metalation DNAzymes were reported with a G4 structure. Inspired by the excellent G4 binding properties of certain divalent metal ions, we herein screened a few metals and G-rich DNA sequences. The metalation activity of a DNA named T30695 (sequence: (G 3 T) 4 ) was significantly accelerated by Pb 2+ . The reaction of Cu 2+ insertion into the mesoporphyrin IX had a k cat of 0.89 min –1 and a K m of 9.8 μM, representing a catalytic efficiency similar to that of human ferrochelatase. The reason for the acceleration was attributed to Pb 2+ binding of the G4 DNA and the catalytic activity of the large Pb 2+ ion for this reaction. A ratiometric sensor for Pb 2+ was developed by inserting Zn 2+ with a detection limit of 23.5 nM Pb 2+ . This work has established a new DNA-based reaction that can be used for Pb 2+ detection, and it also provides a highly efficient new DNAzyme for porphyrin metalation, which might be used for signal production for other biosensors.