Express test for NT-proBNP competitive detection based on lateral flow immunoassay using silanized fluorescent quantum dots
Olga A. Goryacheva, Alina A. Kokorina, Yuliya A. Podkolodnaya, Pradyumna Kumar Mishra, Irina Yu. Goryacheva
Abstract
This paper describes the step-by-step development and the application of a lateral flow immunoassay (LFIA) for the detection of the N-terminal pro-brain natriuretic peptide (NT-proBNP). NT-proBNP is widely used as a biomarker for diagnosing heart failure and other cardiac dysfunctions, distinguishing patients with heart failure from patients without heart failure, and for risk assessment. CdSe/CdS fluorescent quantum dots (QDs) were synthesized as immunoassay labels, carefully coated with a silicon dioxide shell with a high fluorescence quantum yield of 51% for silanized QDs, and finally functionalized with carboxy- or epoxy groups. The conjugation pathways of the resulting silanized QDs with antibodies specific to amino acid residues 61-76 in NT-proBNP were optimized. The LFIA uses the principle of competitive detection with the test line containing proBNP precursor molecule as the cover antigen and the control line containing rabbit anti-mouse immunoglobulins. All components of the LFIA strip, including membrane type, blocking buffer composition, and QD-antibody conjugate composition, were optimized to reduce nonspecific interaction. The LFIA test was applied to determine NT-proBNP in human plasma. The optimal dilution of plasma for application of the test was found to be 10-fold. Under optimized conditions, the LFIA cut-off level was set as 0.5 ng/mL NT-proBNP in human plasma. The LFIA design ensures that the test line fluorescence disappears at the cut-off concentration.