Highly sensitive simultaneous detection of lead(II) and barium(II) with G-quadruplex DNA in α-hemolysin nanopore.

Both Pb(2+) and Ba(2+) can bind with high affinity to some specific DNA sequences, inducing the formation of unimolecular G-quadruplex structures. Translocation of a DNA probe containing such sequences through an α-hemolysin nanopore in the presence of Pb(2+) or Ba(2+) would result in much prolonged DNA translocation events. Quantification of these events can reveal the concentrations of Pb(2+) or Ba(2+) at as low as 0.8 nM. Besides, Pb(2+) and Ba(2+) in the solution can be simultaneously detected and individually identified. Furthermore, the probe is highly selective for Pb(2+) and Ba(2+) detection without interference from other metal ions. This sensing strategy can be extended to many other analytes which can bind to DNA molecules with high affinity.