Ultrasensitive and Selective Copper(II) Detection: Introducing a Bioinspired and Robust Sensor

A nanopore-based Cu-II-sensing system is reported that allows for an ultrasensitive and selective detection of Cu(II)with the possibility for a broad range of applications, for example in medical diagnostics. A fluorescent ATCUN-like peptide 5/6-FAM-Dap-beta-Ala-His is employed to selectively bind Cu(II)ions in the presence of Ni(II)and Zn(II)and was crafted into ion track-etched nanopores. Upon Cu(II)binding the fluorescence of the peptide sensor is quenched, permitting the detection of Cu(II)in solution. The ion transport characteristics of peptide-modified nanopore are shown to be extremely sensitive and selective towards Cu(II)allowing to sense femtomolar Cu(II)concentrations in human urine mimics. Washing with EDTA fully restores the Cu-II-binding properties of the sensor, enabling multiple repetitive measurements. The robustness of the system clearly has the potential to be further developed into an easy-to-use, lab-on-chip Cu-II-sensing device, which will be of great importance for bedside diagnosis and monitor of Cu(II)levels in patients with copper-dysfunctional homeostasis.