A fluorescent biosensor for the determination of xanthine in tea and coffee via enzymatically generated uric acid

•A biosensor for xanthine is developed via its oxidation product uric acid.•Visual detection is possible due to aggregation of nanoparticles by uric acid.•The developed sensor exhibits high sensitivity and selectivity.•Application studies were carried out in real samples.

Herein, the use of rodamine B capped-thioglycolic acid functionalized gold nanoparticles (RB-capped TGA/GNPs) as a novel fluorescence probe for the sensitive determination of xanthine (XA) has been demonstrated. The sensing mechanism is based on the enzymatically generated uric acid (UA) induced degradation of gold nanoparticles which resulted in the quenching of its fluorescence. By virtue of the specific response, the present assay allowed for the selective determination of XA in the range of 93 nmol/L-0.84 μmol/L with a detection limit of 10.1 nmol/L and that of UA in the range 9.90 nmol/L-65.4 nmol/L with the detection limit being 9.71 nmol/L. In addition, the application of the present approach in real samples like tea and coffee and also in synthetic blood serum has been demonstrated.

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