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

A nanopore-based CuII -sensing system is reported that allows for an ultrasensitive and selective detection of CuII 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 CuII ions in the presence of NiII and ZnII and was crafted into ion track-etched nanopores. Upon CuII binding the fluorescence of the peptide sensor is quenched, permitting the detection of CuII in solution. The ion transport characteristics of peptide-modified nanopore are shown to be extremely sensitive and selective towards CuII allowing to sense femtomolar CuII concentrations in human urine mimics. Washing with EDTA fully restores the CuII -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 CuII -sensing device, which will be of great importance for bedside diagnosis and monitor of CuII levels in patients with copper-dysfunctional homeostasis.