Direct detection of potassium and lead (II) ions based on assembly-disassembly of a chiral cyanine dye /TBA complex.

A highly selective and sensitive direct detection of potassium (K) and lead (Pb) ions was developed by using the assembly and disassembly of a chiral cyanine dye/TBA complex. The dye DMSB (3-ethyl-2-[3-(3-ethyl-3H-benzoselenazol-2-ylidene)-2-methylprop-1-enyl] benzoselenazolium bromide) loses the ability of self-assembly, but it can be activated by thrombin-binding aptamer (TBA) G-quadruplex structure. And only the TBA G-quadruplex formed in the presence of K, can strongly induce J-aggregate signals of DMSB. Because the Pb ions can bind and stabilize the TBA G-quadruplex with much higher efficiency than K, the J-aggregate signals of DMSB falls sharply when the Pb is present. As a result, the assembly and disassembly of DMSB allows the selective detection of 10 μM K and 20 nM Pb respectively, even the competitive sodium ion (Na) was as high as 145 mM. The linear correlation existed between the J-aggregate intensity and the concentration of K and Pb over the range of 0.5-5.0 mM and 200-2000 nM, respectively. Moreover, the concentration of K (∼3 mM) and Pb (below 20 nM) in human blood serum samples were determined by the present method, which agreed well with inductively coupled plasma mass spectrometry (ICP-MS). This work not only opens a door for the further development of G-quadruplex-based aptasensor in complex real system, but also provides a simple and versatile sensing platform for ion detection in clinic.