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Abstract
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A novel fluorometric sensor based on catalyzed 5-aminosalicylic acid (5-ASA)/H2O2 systems was developed
to detect trace levels of H2O2 in exhaled breath condensate (EBC). It relies on the oxidative conversion of
the fluorophore (5-ASA) into its non-fluorescent product (5-ASAox). The fluorescence intensity of 5-ASA
was lost by the reaction with H2O2 in the presence of horseradish peroxidase (HRP) or CuO nanoparticles
(NPs). As the decrease in the fluorescence intensity is proportional to H2O2 concentration, new
methods were developed for the monitoring of H2O2 in EBC samples using the HRP- and CuO NPcatalyzed
5-ASA/H2O2 assays. The methods were optimized and validated according to the standard
validation techniques in EBC samples. Under the optimized experimental conditions, linear calibration
graphs were obtained in the range of 200–8000 nmol L1 and 50–500 nmol L1 for the HRP-catalyzed
and CuO NP-catalyzed 5-ASA/H2O2 assays, respectively. The limits of detection, evaluated as 3Sb/m
(where Sb and m are the standard deviation of the blank and slope of the calibration curves, respectively),
were found to be 137.0 nmol L1 and 33.6 nmol L1 for HRP-catalyzed and CuO NP-catalyzed 5-ASA/
H2O2 systems, respectively. These developed systems are promising for application in the detection of
trace amounts of H2O2 in oxidative stress studies.
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