Sensitive detection and intracellular imaging of free copper ions based on DNA-templated silver nanoclusters aggregation-inducing fluorescence enhancement effect.

Free copper ions (Cu and Cu) have critical toxicity to cells, although copper is an essential element for human body. Hence, sensitive monitoring is crucial to avoid over intake of Cu/Cu. We herein designed a ssDNA sequence (A) for synthetizing A-templated silver nanoclusters (AgNCs), and demonstrated that Cu/Cu can induce the aggregation of A-templated AgNCs and thus greatly enhanced the fluorescence emission of A-templated AgNCs. Based on Cu/Cu-induced fluorescence enhancement effect of A-templated AgNCs, a label-free and signal-on fluorescent sensing platform was developed for the specific and sensitive detection of Cu/Cu in biological samples and intracellular imaging of Cu/Cu in cells. The signal-on fluorescent sensing platform could be used to rapidly detect Cu and Cu with a detection limit of 0.1 µM within 30 min., and to perform the intracellular imaging of Cu and Cu in cells with good cell permeability and biocompatibility. By using the signal-on fluorescent sensing platform, we have successfully detected Cu and Cu in cells fluids and human serum with a recovery of 90-104% and a RSD (n = 5) < 5%, and performed the imaging of Cu/Cu in Hela cells. The developed fluorescent sensing platform has obvious analytical and imaging advantages such as signal-on, simple operation, short analysis time, both Cu and Cu detection, similar or higher sensitivity, good cell permeability and biocompatibility, which promising a reliable approach for the rapid and on-site detection or imaging of free copper ions in biological samples in clinical diagnosis.