Abstract :
[en] Foot-and-mouth disease (FMD) is a transboundary animal disease, and a disease of great economic significance in the animal husbandry industry. The prevention and control of such epidemic diseases is particularly important. Effective diagnosis is indispensable to accomplish the mission. The common diagnostic methods are based on live virus or inactivated virus, which may cause leakage of virus easily. Some other methods are also time-consuming, labor-consuming or need sophisticated instruments. Considering the biosafety and practicality, the aim of this thesis is to develop simple quantitative real-time diagnostic assay for FMD with high sensitivity, specificity, and stability.
Here, the fluorescent immunochromatographic assays (FICAs) were selected, owing to their simple, rapid, convenient, and safe performance. Rare earth fluorescent nanoparticles exhibit several unique fluorescent properties which make them suitable candidates for detecting biomolecules. Virus-like-particles (VLPs) are capsid proteins of virions, and they are assembled from structural proteins; they are noninfectious, owing to lack of genetic materials. The activated rare earth nanoparticles are integrated with conventional immunochromatography to quantitatively detect foot-and-mouth disease virus (FMDV) antibodies.
First, noninfectious FMDV VLPs are utilized as capture antigen, and fluorescent europium microparticles (EuMSs) are applied as fluorescent labels. The labeled staphylococcal protein-A (SPA) are referred to as fluorescent sensors. The fluorescence signal intensity at test line and control line is associated with the concentration of the target antibody. The EuMSs-based assay showed 30-fold more sensitive through observation in five minutes and 68-fold more sensitive through portable equipment than colloidal gold assay.
Next, to reduce the cost of the fluorescent nanoparticles and enhance the stability of the assembled strips, we prepared upconversion nanoparticles (UCNPs). Rare earth salts reacted under argon atmosphere according to the solvent thermal method, and then they are modified with citric acid using a ligand exchange method. The carboxyl-modified UCNPs were coupled with protein G to form the UCNPs sensor. The UCNPs-based strips showed higher stability at 4 ℃ for about one year.
These assays have been evaluated with real serum samples without cross-interference. Therefore, such assays have great prospects for rapid, sensitive, and quantitative determination of foot-and-mouth disease virus serotype O (O-FMDV) antibodies.
