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-β-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.