Detection of heavy metal ions using protein-functionalized microcantilever sensors

Microcantilevers functionalized with metal-binding protein, AgNt84-6, are demonstrated to be sensors for the detection of heavy metal ions like Hg2+ and Zn2+. AgNt84-6, a protein that has the ability to bind multiple atoms of Ni2+, Zn2+, Co2+, Cu2+, Cd2+ and Hg2+ was attached to the gold-coated side of silicon nitride cantilevers via linker groups. Upon exposure to 0.1 mM HgCl2 and 0.1 mM ZnCl2 solutions, the microcantilevers underwent bending corresponding to an expanding gold side. Exposure to a 0.1 mM solution of MnCl2 solution did not result in a similar bending indicating a weak or no interaction of Mn2+ ions with the AgNt84-6 protein. The microcantilever bending data were consistent with data from electrophoresis carried out on SDS-PAGE gels containing metal ions that showed protein interaction with Zn2+ ions but not with Mn2+ ions. Thus, we demonstrate that microcantilever bending can be used to discriminate between metal ions that bind and do not bind to AgNt84-6 protein in real time. (C) 2003 Published by Elsevier B.V.