Quantitative Detection of Zn2+ in Infant Formula and Living Cells Using Quinoline-Based Fluorescent Probes

Zinc is an essential trace element and its deficiency has been related to skin conditions, Alzheimer’s disease, and some types of cancer. Therefore, detecting zinc ions in the human body with high sensitivity is important. Here, two “turn-on” quinoline-based fluorescent probes ( E )-2-((2-(quinolin-2-yl) hydrazono) methyl) phenol ( QSP-H ) and ( E )-4-chloro-2-((2-(quinolin-2-yl) hydrazono) methyl) phenol ( QSP-Cl ) were fabricated for the detection of Zn 2+ . Both the QSP-H and QSP-Cl revealed low LOD (71 nM for QSP-H , 67 nM for QSP-Cl ) and high selectivity, and worked across a broad pH range (3 ‒12 for QSP-H , 3 ‒11 for QSP-Cl ). The HRMS, 1 H NMR titration, DFT calculations and Job’s plot analysis were employed to explore the mechanism of Zn 2+ detection through QSP-H and QSP-Cl . QSP-H and QSP-Cl were effectively applied to the quantitative assessment of Zn 2+ in two infant formula samples and to the bioimaging-based detection of exogenous Zn 2+ in living cells.