Non-invasive detection of gastric cancer biomarker 4-HBA via a ZIF/CDs-based fluorescent sensor.

Urine analysis has become an increasingly valuable tool in modern medical diagnostics due to its non-invasive nature. In this study, we report the development of a novel fluorescent sensor based on ZIF-8 and CDs embedded in a molecularly imprinted polymer matrix (ZIF/CDs@MIPs) for the selective and sensitive detection of 4-hydroxybenzoic acid (4-HBA), a potential gastric cancer biomarker. The integration of ZIF-8 enhanced the sensor's surface area, structural stability, and fluorescence performance. Optimization experiments revealed that a ZIF-8 concentration of 400 mg/L yielded the highest quenching efficiency. The sensor exhibited excellent fluorescence stability under varying pH, ionic strength, and UV exposure. A detailed analysis of the quenching mechanism indicated that dynamic quenching and electron transfer were involved in 4-HBA detection. The sensor showed strong selectivity for 4-HBA over common interferents, with a low detection limit of 0.68 μmol/L and a good linear response in the 0-100 μmol/L range. Application in real urine samples demonstrated high recovery rates (97.71-106.16%) and low relative standard deviations (0.80-2.95%), confirming its reliability and accuracy. These findings highlight the potential of ZIF/CDs@MIPs as a practical and non-invasive fluorescence sensing platform for biomarker monitoring in clinical diagnostics, especially for early gastric cancer detection.