A reaction-based near-infrared fluorescent sensor for Cu²⁺ detection in aqueous buffer and its application in living cells and tissues imaging

Copper (II) is one of the most of important cofactors for numerous enzymes and has captured broad attention due to its role as a neurotransmitters for physiological and pathological functions. In this article, we present a reaction-based fluorescent sensor for Cu²⁺ detection (NIR-Cu) with near-infrared excitation and emission, including probe design, structure characterization, optical property test and biological imaging application. NIR-Cu is equipped with a functional group, 2-picolinic ester, which hydrolyzes in the presence of Cu²⁺ with high selectivity over completed cations. With the experimental conditions optimized, NIR-Cu (5 μM) exhibits linear response for Cu²⁺ range from 0.1 to 5 μM, with a detection limit of 29 nM. NIR-Cu also shows excellent water solubility and are highly responsive, both desirable properties for Cu²⁺ detection in water samples. In addition, due to its near-infrared excitation and emission properties, NIR-Cu demonstrates outstanding fluorescent imaging in living cells and tissues.