Development of an Upconversion Luminescence Nanoparticles–Based Immunochromatographic Assay for the Rapid Detection of Dexamethasone in Animal Tissue

Dexamethasone has been illegally used as a growth-promoting agent to obtain an economic benefit from increased muscle development. An immunochromatographic assay was developed for the quantitative detection of dexamethasone using a probe based on upconversion luminescence nanoparticles. Lanthanide-doped upconversion nanoparticles were synthesized in a system comprising water and ethylene glycol. Various parameters, including the immunoreaction time, the structure of the coating hapten, and the type and concentration of surfactant, were optimized. Based on the optimal conditions, the assay exhibits good dynamic linear detection in the range of 0.05–5 ng/mL with an IC50 of 0.58 ng/mL. The detection limits for dexamethasone in tissue are 0.3 μg/kg. The assay worked well using a 30% methanol extraction solution, giving an average recovery of 84.5%. The assay strip can quantitate on-site using a portable upconversion luminescence reader with a cumulative analysis time of only 10 min, and its fluorescence decay after 6 months is < 25%.