Designing a biostable L-DNAzyme for lead(II) ion detection in practical samples

A promising biosensor for effective lead(II) ion detection in practical applications was developed by constructing a Pb2+-specific L-DNAzyme, the enantiomer of the natural nucleic acid-constructed D-DNAzyme. This fluorescence sensor contains the L-enzyme strand with a quencher at the 3' end, and the L-substrate strand with a fluorophore at the 5' and a quencher at the 30 ends that formed a complex. In the presence of Pb2+, the L-substrate is cut into two fragments, leading to the recovery of fluorescence. The sensor shows high sensitivity and selectivity for Pb2+ detection with a linear response in the range of 5-100 nM and a detection limit of 3 nM in aqueous solution. Importantly, based on the fact that L-DNAzyme consists of non-natural nucleic acids, which are insensitive to nuclease digestion, protein adsorption and D-DNA hybridization, our sensor shows a specific response to Pb2+ in practical water and serum samples. Therefore, it is expected that our L-DNAzyme-based strategy may offer a new method for developing simple, rapid and sensitive sensors in complex systems.