Signal-boosted Eu₂O₃-based time-resolved fluorescence immunosensor for the ultrasensitive detection of cardiac...

Time-resolved fluorescence immunoassays (TRFIA) have been extensively applied across various fields owing to their low background noise characteristics, particularly in disease diagnosis and prevention. Survival and prognosis of patients with acute myocardial infarction (AMI) are highly dependent on the rapid and accurate detection of myocardial damage. Troponin T (cTnT) is a primary diagnostic biomarker of AMI and is widely used in clinical practice. However, the current bioassays for cTnT detection are complex and time-consuming. Therefore, there is an urgent need for a sensitivity, and rapid diagnostic approach for acute myocardial infarction.

Herein, we report a novel, sensitive, and specific cTnT detection approach using a unique nanoprobe dissolution-enhanced fluorescence amplification strategy. Eu₂O₃ nanocrystals, easily dissolvable in an acidic enhancer solution and transformed into many highly luminescent Eu³⁺ micelles, were utilized as nanoprobes. The released Eu³⁺ further activates the time-resolved fluorescence system, which prevents autofluorescence interference and blood scattering, allowing for the accurate determination of cTnT levels in clinical serum samples. The demonstrated sensitivity of serum cTnT was high with a sensitivity of 3.86 ng·L^-1. In addition, we developed a Eu₂O₃-based lateral flow immunochromatographic test strip for facile cTnT detection, with the sensitivity of 14.14 ng·L^-1 and 6.31 ng·L^-1 using smartphone-integrated app and commercial analyzer respectively.

This Eu₂O₃-nanocrystal-based dissolution-enhanced luminescent bioassay has tremendous potential for ultrasensitive biomarker detection, enabling ultra-trace detection through lanthanide-specific dissolution. Moreover, the surface-functionalized nanocrystals could selectively recognize a variety of analytes, and have excellent photostability with minimal matrix interference, expanding the direction of lanthanide nanoprobes in multifunctional diagnostic and therapeutic areas.