Nanopore detection of copper ions using a polyhistidine probe

We report a stochastic nanopore sensing method for the detection of Cu2+ ions. By employing a polyhistidine molecule as a chelating agent, and based on the different signatures of the events produced by the translocation of the chelating agent through an a-hemolysin pore in the absence and presence of target analytes, trace amounts of copper ions could be detected with a detection limit of 40 nM. Importantly, although Co2+, Ni2+, and Zn2+ also interacts with the polyhistidine molecule, since the event residence times and/or blockage amplitudes for these metal chelates are significantly different from those of copper chelates, these metal ions do not interfere with Cu2+ detection. This chelating reaction approach should find useful application in the development of nanopore sensors for other metal ions. (C) 2013 Elsevier B.V. All rights reserved.