Distinction of Individual Lanthanide Ions with a DNAzyme Beacon Array

Abstract

Developing chemical probes to distinguish each lanthanide ion is a long-standing challenge. Aside from its analytical applications, solving this problem will also enhance our knowledge in metal ligand design. Using in vitro selection, we previously reported four RNA-cleaving DNAzymes, each with a different activity trend cross the lanthanide series. We herein performed another eight in vitro selection experiments using each and every lanthanide from La3+ to Tb3+ but excluding the radioactive Pm3+. A new DNAzyme named Gd2b was identified and characterized. By labeling this DNAzyme with a fluorophore/quencher pair to create a catalytic beacon, a detection limit of 14 nM Gd3+ was achieved. With the same beacon design, all the five lanthanide-specific DNAzymes were used together to form a sensor array. Each lanthanide ion produces a unique response pattern with these five sensors, allowing a pattern-recognition-based linear discriminant analysis (LDA) algorithm to be applied, where separation was achieved between lanthanides and nonlanthanides, light and heavy lanthanides, and for the most part, each lanthanide. These lanthanide specific DNA molecules are useful for understanding lanthanide coordination chemistry, designing hybrid materials, and developing related analytical probes.