Upconversion Nanoparticles Synthesis, Modification And Its Application In Immunology Test Strip

Starting from the late 1990s, the field of upconversion nanomaterials has undergone significant development and has become one of the most attractive research areas within the nanoscience. In the last 20 years, a large number of papers published on upconversion nanomaterials, which witnessed a great deal of effort has been made by researcher groups. This kind of material under near-infrared excitation, can emit ultraviolet, visible and near-infrared light, namely of anti-Stokes emission. The unique luminescent properties, eliminate the background fluorescence and light scattering from biological sample, thus can get high SNR. Currently, upconversion nanoparticles can be used for biological markers, photodynamic therapy and biological imaging, and so on. In this paper, we apply the nanoparticles to immune chromatography technology. The experiments results show that, to some extent, improved the detection sensitivity and accuracy of immune chromatography. This paper details the synthetic process and modification method, and combined the nanoparticals with immune chromatography to test C-reactive protein.Our group has some practical experiments of upconversion nanomaterials synthesis. On the basis of it, we synthesize two kinds of upconversion nanomaterials, namely NaYF₄:Yb, Tm/NaYF₄ and NaYF₄:Yb, Er/NaYF₄. In order to facilitate nanoparticals coupling with biological molecules, we through surface ligand adsorption method, absorption of an additional amphiphilic block copolymer onto the nanopartical surface through the hydrophobic attraction between the original ligand and hydrocarbon chain of the polymer. The polymer-coated nanoparticals is water-soluble with hydrophilic outer block of the polymer and permit further surface derivatization. By transmission electron microscopy, we can find that almost all nanoparticles coated on a 2 nm thick layer of polymer film. The surface modification method is less time consuming, simple operation, and the polymer-coated nanoparticals have good dispersibility in aqueous solution. At present, this surface modification method is quite practical and simple.Immune chromatography assay （ICA）, is a method that based on the antigen antibody specificity recognition, using capillary siphon effect, causing the liquid sample on the strip transverse flow, then the target is captured by the capture protein. Finally by measuring fluorescent signal of test line of immunochromatographic strip to detection the concentration of target. To achieve the rapid detection of C-reactive protein of the body, we use upconversion nanoparticles as the fluorescent probe and couple it with immune chromatography technology. The experiments show that this method not only preserves the advantages of immunochromatographic strip for simple, economical, but also improves the detection sensitivity and accuracy of C-reactive protein by upconversion nanoparticles application as fluorescent probe. Moreover it can be used for semi-quantitative and quantitative detection of more kinds of antigen, and will has good market prospects.