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.
Capturing copper: The Dap‐β‐Ala‐His sequence, which is generated from the amino‐terminal‐CuII and NiII‐binding motif, is used for a selective binding of CuII in presence of NiII and ZnII and was crafted to an ion track‐etched PET membrane. Cu detection was achieved through fluorescence quenching and I–V measurements, enabling femtomolar CuII concentrations to be sensed.