Cucurbit[8]uril-mediated fluorescent indicator displacement: a novel “turn-on” fluorescent probe for gentamicin detection in water and food samples

Gentamicin (GEN), an aminoglycoside antibiotic, is widely used in treating infections within the livestock industry but readily causes food residues and environmental pollution. This study developed a novel water-soluble supramolecular fluorescent probe DBTPy 2+ @Q[8], through host–guest interactions between the methylpyridine-modified benzothiophene cationic fluorophore (DBTPy 2+ ) and cucurbit[8]uril (Q[8]). This enabled specific GEN recognition and detection via the fluorescence indicator displacement (FID) mechanism. The DBTPy 2+ -Q[8] assembly induced significant fluorescence quenching, while GEN addition rapidly restored fluorescence. The restored intensity exhibited a good linear relationship with GEN concentration in the range of 0.1–10 μM (R 2  = 0.996), with a limit of detection (LOD) of 0.206 μM. The probe exhibited good selectivity and anti-interference capability, achieving 92.0%–104.1% spiked recoveries in water and food samples, and enabled specific GEN fluorescence imaging in living cells. This work establishes a novel supramolecular host–guest strategy for fluorescent probes enabling rapid, quantitative, specific GEN detection.