Breaking the picomolar barrier in lateral flow assays using Bright-Dtech___ 614 -- Europium nanoparticles for enhanced sensitivity

Abstract: Lateral flow immunoassays (LFIA) are among the most widely used rapid diagnostic tests for point-of-care screening of disease biomarkers. However, their limited sensitivity hinders their use in complex clinical applications that require accurate biomarker quantification for precise medicine. To address this limitation, we evaluated Bright-Dtech_-614 Europium nanoparticles to enhance LFIA assay sensitivity. These nanoparticles exhibited a luminescence quantum yield of 70 % and a 90 % conjugation efficacy with antibodies by direct adsorption. Considering these properties, we developed an LFIA to quantify human lactate dehydrogenase (h-LDH), a biomarker and therapeutic target in cancer disease. The Bright-Dtech-614 Eu nanoparticle-based assay achieved a detection limit of 38 pg mL -1 , representing a 686-fold, 15-fold, and 2.9-fold improvement in sensitivity over conventional LFIA platforms using gold (AuNPs), carbon nanoparticles, and standard ELISA, respectively. The assay exhibited strong accuracy, with a mean recovery rate of 108 $\pm$ 11 %, and demonstrated excellent reproducibility, as evidenced by inter-and intra-batch RSD values of 4.9 % and 9.7 %, respectively, when testing LDH-spiked serum samples. By substituting traditional gold nanoparticles with the Bright-Dtech__-614 Eu nanoparticles, we achieved detection limits in the femtomolar range, significantly broadening the applicability of LFIA for precision medicine.