Efficient detection of a biomarker for infant jaundice by a europium(iii)-organic framework luminescence sensor

Efficient detection of excess bilirubin in human serum and urine is highly important for the early diagnosis of infant jaundice. A highly stable Eu(iii)-based microporous framework with bent {Eu(COO)} chains interconnected by pairs of T-shaped 4,4'-(4,4'-bipyridine-2,6-diyl)dibenzoate (bpydb^2-) linkers, {[Eu(H₂O)(HCOO)(bpydb)]·solvent} (1), was solvothermally synthesized and used as a chemical sensor for bilirubin response under clinically-applicable visible-light excitation. Due to the significant synergetic effect of the inner filter effect and photoinduced electron transfer, 1 can effectively probe trace amounts of bilirubin in aqueous solution through fluorescence decay with a strong quenching constant of 6.40 × 10⁴ M^-1 and low detection limit of 1.75 μM. More importantly, a portable test paper made from 1 was further developed to achieve qualitative, naked-eye visualized differentiation for the biomarker in clinical applications. These interesting findings highlight the importance of the π-conjugated antenna ligand for clinically applicable Ln-MOF sensors.