Tag‐free fluorometric aptasensor for detection of chromium(VI) in foods via SYBR Green I signal amplification and aptamer structure transition

BACKGROUND In response to growing concerns regarding heavy metal contamination in food, particularly chromium (Cr)(VI) contamination, this study presented a simple, sensitive and practical method for Cr(VI) detection. RESULTS A magnetic separation‐based capture–exponential enrichment ligand system evolution (SELEX) method was used to identify and characterize DNA aptamers with a high affinity for Cr(VI). An aptamer, Cr‐15, with a dissociation constant ( K d ) of 4.42 ± 0.44 μmol L −1 was obtained after only eight rounds of selection. Further innovative methods combining molecular docking, dynamic simulation and thermodynamic analysis revealed that CrO 4 2− could bind to the 19th and 20th guanine bases of Cr‐15 via hydrogen bonds. Crucially, a label‐free fluorometric aptasensor based on SYBR Green I was successfully constructed to detect CrO 4 2− , achieving a linear detection range of 60–300 nmol L −1 with a lower limit of detection of 44.31 nmol L −1 . Additionally, this aptasensor was able to quantitatively detect CrO 4 2− in grapes and broccoli within 40 min, with spike recovery rates ranging from 89.22% to 108.05%. The designed fluorometric aptasensor exhibited high selectivity and could detect CrO 4 2− in real samples without sample processing or target pre‐enrichment. CONCLUSION The aptasensor demonstrated its potential as a reliable tool for monitoring Cr(VI) contamination in fruit and vegetable products.