Lanthanide coordination polymer-based biosensor for citrate detection in urine

Abstract

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.