Development of a europium nanoparticles lateral flow immunoassay for NGAL detection in urine and diagnosis of acute kidney injury.

BACKGROUND: AKI is related to severe adverse outcomes and mortality with Coronavirus Disease 2019 (COVID-19) patients, that early diagnosed and intervened is imperative. Neutrophil gelatinase-associated lipocalin (NGAL) is one of the most promising biomarkers for detection of acute kidney injury (AKI), but current detection methods are inadequacy, so more rapid, convenient and accuracy methods are needed to detect NGAL for early diagnosis of AKI. Herein, we established a rapid, reliable and accuracy lateral flow immunoassay (LFIA) based on europium nanoparticles (EU-NPS) for the detection of NGAL in human urine specimens. METHODS: A double-antibody sandwich immunofluorescent assay using europium doped nanoparticles was employed and the NGAL monoclonal antibodies (MAbs) conjugate as labels were generated by optimizing electric fusion parameters. Eighty-three urine samples were used to evaluate the clinical application efficiency of this method. RESULTS: The quantitative detection range of NGAL in AKI was 1-3000 ng/mL, and the detection sensitization was 0.36 ng/mL. The coefficient of variation (CV) of intra-assay and inter-assay were 2.57-4.98 % and 4.11-7.83 %, respectively. Meanwhile, the correlation coefficient between europium nanoparticles-based lateral fluorescence immunoassays (EU-NPS-LFIA) and ARCHITECT analyzer was significant (R2 = 0.9829, n = 83, p < 0.01). CONCLUSIONS: Thus, a faster and easier operation quantitative assay of NGAL for AKI has been established, which is very important and meaningful to diagnose the early AKI, suggesting that the assay can provide an early warning of final outcome of disease.

Determination of human COVID-19 total antibodies in serum using a time-resolved fluorescence immunoassay.

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is spreading rapidly around the world. Antibody detection plays an important role in the diagnosis of COVID-19. Here, we established a new time-resolved fluorescence immunoassay (TRFIA) to determine COVID-19 total antibodies. A double-antigen sandwich TRFIA was optimized and established: recombinant nucleocapsid phosphoprotein (N protein) and spike protein (S protein) of COVID-19 immobilized on 96-well plates captured human COVID-19 antibodies and then banded together with the N/S proteins labeled with europium(III) (Eu3+ ) chelates, and finally, time-resolved fluorometry was used to measure the fluorescence values. We successfully established a TRFIA method for the detection of human COVID-19 total antibodies, and the cutoff value was 2.02. There was no cross-reactivity with the negative reference of the National Reference Panel for IgM and IgG antibodies to COVID-19. The CV of the precision assay was 3.19%, and the assay could be stored stably for 15 days at 37°C. Compared with that of the colloidal gold method and chemiluminescence method, the sensitivity of the TRFIA method was higher, and the false positive/negative rate was lower. This established TRFIA has high sensitivity, accuracy, and specificity, which indicates that this method provides a new detection method for the high-throughput routine diagnosis of COVID-19.