Detection of copper ions using microcantilever immunosensors and enzyme-linked immunosorbent assay

A sensitive and specific monoclonal antibody (designated as mAb6A9) recognizing a Cu(II)–ethylenediamine–N,N,N′,N′–tetraacetic acid (EDTA) complex but not metal-free EDTA was obtained by using an 1-(4-aminobenzyl)–EDTA–Cu(II) complex covalently coupled to a carrier protein as an immunogen to immunize the Balb/c mice. A mAb6A9-modified microcantilever sensor (MCS) was developed. A bending response was found to occur at or below 1 ng mL−1 of Cu(II)–EDTA complex. An indirect competitive enzyme-linked immunosorbent assay (icELISA) was developed with mAb6A9. The icELISA had a half maximum inhibition concentration and working range of approximately 1.8 and 0.2–17 ng mL−1, respectively. The icELISA showed cross-reactivity of 18.8%, 1.1% and less than 1% with bivalent cobalt, mercury and other metals, respectively. The icELISA and functionalized MCSs were utilized to analyze the content of copper in spiked tap water samples. The assay conditions were optimized. The results of icELISA and MCS correlated well with those obtained by graphite furnace atomic absorption spectrometry.