A sandwich immunoassay for brucellosis diagnosis based on immune magnetic beads and quantum dots.

Brucellosis is a serious zoonosis with a rapid increase in incidence across epidemic regions. Currently, there are numerous methods for diagnosing brucellosis. However, these studies often have a few defects, such as low sensitivity, poor specificity, time consuming, laborious, and even potential biological risk. To overcome these shortcomings, we have developed a rapid, sensitive and accurate diagnosis procedure for brucellosis based on the immune magnetic beads (IMB) probe and quantum dots (QDs) - staphylococcal protein A (SPA) probe. With the presence of Brucella antibody in the tested serum, the QDs-SPA probe links to the IMB probe and an immune-sandwich complex is formed. As a result, the fluorescence intensity from QDs increased significantly and was correlated with the amount of Brucella antibody. Under the optimized conditions, 248 blood samples were detected and the diagnosis effect was evaluated. The area under the receiver-operating characteristic (ROC) curve was 0.970 (95% confidence interval (CI), 0.9479-0.9920). The diagnostic sensitivity was 96.15% (95% CI, 91.82-98.58%), the diagnostic specificity was 94.12% (95% CI, 87.64-97.81%) with a fluorescence intensity cutoff value of 150.4 and the detection time was only 100min. This diagnostic procedure can be satisfactorily applied to the diagnosis of brucellosis.