Ultrasensitive and Label-Free Detection of Copper Ions by GHK-Modified Asymmetric Nanochannels

Artificial solid-state nanochannels have garnered considerable attention as promising nanofluidic tools for ion/molecular detection, DNA sequencing, and biomimicry. Recently, nanofluidic devices have emerged as cost-effective detection tools for heavy metal ions by modifying stimuli-responsive materials. In this work, high-purity glycyl-l-histidyl-l-lysine (GHK) peptide is synthesized by using 7-diphenylphosphonooxycoumarin-4-methanol (DPCM) as a protecting group and auxiliary carrier by homogeneous synthesis of photocleavable groups. Subsequently, we developed a GHK-modified asymmetric nanochannel nanofluidic diode by covalently attaching the GHK peptide to the inner surface of the nanochannels. This modification facilitated specific recognition and ultra-trace level detection of Cu²⁺ ions, achieving a detection limit of 10^-15 M. Due to the robust complexing ability between Cu²⁺ and GHK peptide, the GHK-modified asymmetric nanochannels can form GHK-Cu complexes on the inner surface of nanochannels when Cu²⁺ passes through the nanochannels. This results in changes of current-potential (I-V) properties, which facilitated Cu²⁺ detection. Theoretical calculations confirmed the high affinity of the GHK peptide for Cu²⁺, thereby ensuring excellent Cu²⁺ selectivity. To evaluate the applicability of our system for detecting Cu²⁺ in real-world scenarios, we analyzed the concentration of Cu²⁺ in tap water. The GHK-Cu complexes could be dissociated by adding EDTA to the solution, enabling the regeneration and reuse of this ultrasensitive and label-free Cu²⁺ detection system using GHK-modified asymmetric multi-nanochannels. We anticipate that the GHK-modified asymmetric nanochannels will find future applications in the label-free detection of Cu²⁺ in domestic water.