Globally, point-of-care testing (POCT) is the most preferable on-site technique for disease detection and includes a rapid diagnostic test (RDT) and fluorescent immunochromatographic strip test (FICT). The testing kits are generally insufficient in terms of signal enhancement, which is a major drawback of this approach. Sensitive and timely on-site POCT methods with high signal enhancement are therefore essential for the accurate diagnosis of infectious diseases. Herein, we prepare cysteamine-gold coated carboxylated europium chelated nanoparticle (Cys Au-EuNPs)-mediated POCT for the detection of the H5N1 avian influenza virus (AIV). Commercial nanoparticles were used for comparison. The spectral characteristics, surface morphologies, functional groups, surface charge and stability of the Cys AuNPs, EuNPs, and Cys Au-EuNPs were confirmed by UV-visible spectrophotometry, fluorescence spectrometry, transmission electron microscope with Selected area electron diffraction (TEM-SAED), Fourier-transform infrared spectroscopy (FTIR) and zeta potential analysis. The particle size distribution revealed an average size of ~130 ± 0.66 nm for the Cys Au-EuNPs. The Cys Au-EuNP-mediated RDT (colorimetric analysis) and FICT kit revealed a limit of detection (LOD) of 10 HAU/mL and 2.5 HAU/mL, respectively, for H5N1 under different titer conditions. The obtained LOD is eight-fold that of commercial nanoparticle conjugates. The photo luminance (PL) stability of ~3% the Cys Au-EuNPs conjugates that was obtained under UV light irradiation differs considerably from that of the commercial nanoparticle conjugates. Overall, the developed Cys Au-EuNPs-mediated dual-mode POCT kit can be used as an effective nanocomposite for the development of on-site monitoring systems for infectious disease surveillance.
Keywords: avian influenza virus; cysteamine gold-europium nanocomposite; dual-mode assay; lateral flow immune assay; monoclonal antibody.