Distinction of Individual Lanthanide Ions with a DNAzyme Beacon Array

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.