Lanthanide coordination polymer-based biosensor for citrate detection in urine

Recently, lanthanide coordination polymers (LCPs) have emerged as promising materials for biosensing due to their tunability. In this study, utilizing terbium ion (Tb3+) as a luminescence center and guanosine-5′-monophosphate (GMP) as an organic ligand, we designed a Tb–GMP LCP-based biosensor for citrate (Cit) detection. Tb–GMP is weakly luminescent in nature; however, interestingly, after the addition of Cit, a 6.5 times fluorescence enhancement was observed owing to the removal of coordinated water molecules by Cit and the intramolecular energy transfer from GMP to Tb3+. In this assay, the fluorescent intensity of Tb–GMP exhibited a good linear response to Cit concentrations in the range of 4–300 μM with a detection limit of 4 μM. Due to its capability of eliminating autofluorescence, we also applied Tb–GMP for time-gated detection of Cit in urine with promising results. We believe that the current strategy would inspire the development of more LCP-based fluorescent assays or medical imaging platforms for various biological applications.