Serotonin-Derived Fluorophore: A Novel Fluorescent Biomaterial for Copper Detection in Urine

We took advantage of the fluorescent features of a serotonin-derived fluorophore to develop a simple and low-cost assay for copper in urine. The quenching-based fluorescence assay linearly responds within the concentration range of clinical interest in buffer and in artificial urine, showing very good reproducibility (CV(av)% = 4% and 3%) and low detection limits (16 ± 1 μg L(−1) and 23 ± 1 μg L(−1)). The Cu(2+) content was also estimated in human urine samples, showing excellent analytical performances (CV(av)% = 1%), with a limit of detection of 59 ± 3 μg L(−1) and a limit of quantification of 97 ± 11 μg L(−1), which are below the reference value for a pathological Cu(2+) concentration. The assay was successfully validated through mass spectrometry measurements. To the best of our knowledge, this is the first example of copper ion detection exploiting the fluorescence quenching of a biopolymer, offering a potential diagnostic tool for copper-dependent diseases.