Simultaneous detection of Cu⁺ and Cu²⁺ using dual-functionalized glass micropipette sensors

Copper ions (Cu⁺ and Cu²⁺) paly essential roles in physiological processes, and their imbalance is associated with disease progression. However, the simultaneous detection of both oxidation states remains challenging due to their similar physicochemical properties. Herein, we present a dual-functionalized glass micropipette sensor that independently detects Cu⁺ and Cu²⁺. UiO-66-NH₂ is grown in situ on the inner wall to selectively capture Cu²⁺ through amino coordination, thereby reducing the ionic current. Glutathione-functionalized carbon nanotubes (GCNTs) are coated on the outer surface to bind Cu⁺,which enhance the SERS signal by increasing surface defects. The sensor covers a broad detection range (10^-1-10⁵ μM), achieves a detection limit of 0.1 μM, and enables simultaneous monitoring of Cu⁺/Cu²⁺ in the physiological range (2-10 μM). Moreover, it differentiates copper ion levels in MCF-10A and MCF-7 cells, uncovering disrupted copper homeostasis in cancer. This work provides a sensitive and selective platform for investigating copper speciation in biological systems.