An electrochemical sensing strategy for ultrasensitive detection of glutathione by using two gold electrodes and two complementary oligonucleotides.

We herein report an ultrasensitive electrochemical sensing strategy for picomole determination of glutathione by using two gold electrodes and two complementary thiolated oligonucleotides. When one gold electrode whose surface has been immobilized with one of the two oligonucleotides is immersed in a glutathione solution for detection, due to the ligand release effect, the oligonucleotides will be replaced by glutathione. Consequently, the released oligonucleotide molecules will exist in the solution, and therefore, if the other gold electrode is immersed in this solution, the released oligonucleotide molecules will be immobilized onto this electrode surface. Meanwhile, since the complementary oligonucleotide molecules have been previously modified on the surface of gold nanoparticles, the nanoparticles can be thus immobilized onto this electrode surface through hybridization, and large numbers of [Ru(NH(3))(6)](3+) molecules as electrochemical species can be localized onto the electrode surface via the electrostatic interaction between the electrochemical species and oligonucleotide molecules. And, since the nanoparticles can amplify the detection signal, ultrasensitive detection of glutathione can be achieved in the range of 1 x 10(-12) to 1 x 10(-10)M, with a detection limit as low as 4 x 10(-13)M. Moreover, this method has shown fairly good utility in the detection of glutathione in fetal calf serum.