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.