Stable polydentate europium complex for lateral flow immunoassay

Europium complexes are widely used as immunomarkers for lateral flow immunoassay (LFIA) because of their long luminescent lifetime, large Stokes shift, and high luminous color purity. However, most europium complexes exhibit inadequate stability in complex environments, and their fluorescence is readily quenched in an aqueous phase, thereby compromising the detection sensitivity and accuracy of LFIA. Herein, to overcome this challenge, we synthesized a polydentate europium complex, Eu(TTA)3[Phen(PO-8)2], characterized by robust stability. Finally, Eu(TTA)3[Phen(PO-8)2] was employed to fabricate polystyrene (PS) fluorescent microspheres for LFIA, demonstrating remarkable sensitivity and selectivity detecting serum amyloid A (SAA) at concentration as high as 220 μg/mL, with a detection limit of 0.5 μg/mL. More importantly, the SAA testing strips exhibit excellent long-term storage stability. Such stable polydentate europium complexes are anticipated to supplant existing commercial europium complexes, becoming a staple in LFIA applications.