A dual-responsive fluorescent sensor for selective detection of cyanide ions and histamine via distinct mechanisms in food samples

Ensuring food safety requires rapid, sensitive detection of toxic contaminants like cyanide ions and spoilage markers like biogenic amines (BAs). Here, we present FZ-3 (combining 2,3,3-trimethyl-1-propyl-3H-indole-1-ium iodide with a pyridine moiety), a novel dual-sensitive fluorescent sensor that selectively detects cyanide ions (CN⁻) and histamine (His) through distinct reaction mechanisms. FZ-3 combines an indolium moiety for cyanide ions recognition via nucleophilic addition and, with a chloropyridine unit for His sensing via substitution. With minimal interference from other ions/biogenic amines, the sensor exhibits a turn-on response for CN⁻ ions at 414 nm, while for His it enhances emission with a turn-on response at 463 nm. It demonstrates excellent sensitivity with detection limits of 1.08 μM for CN⁻ and 2.80 μM for His, surpassing many existing single-analyte detection systems. FZ-3's efficacy was validated in food matrices by cyanide ions quantification in bitter almonds (recovery: 85.9–100.8 %) and sprouting potatoes (recovery: 85.4–103.9 %) and His detection in fresh/spoiled anchovies (recovery: 81.4–102.5 %), demonstrating correlation with spoilage levels. Notably, FZ-3 operates at physiological pH (3.9–8.0), requires <20 min for analysis, and surpasses conventional methods in cost, speed, and simplicity. This work advances dual-analyte sensing platforms for real-time food quality monitoring, offering a practical tool for both industrial and regulatory applications.