False Positives in Brucellosis Serology: Wrong Bait and Wrong Pond?

Gated nanoprobe utilizing metal-organic frameworks for identifying and distinguishing between the wild strains and the vaccine strains of brucella

In the assay for Brucella, the identification and differentiation of wild strains and vaccine strains present a significant challenge. Currently, there aren't any commercially available product to address this issue. In this study, we have developed a novel gated nanoprobe by utilizing Metal-Organic Frameworks (MOFs) as a scaffold and hairpin DNA as a "gating switch". Specifically, Probe 1 with hairpin structure (P1h) targets a gene that is present in both wild strains Y3 (B. melitensis biovar 3) and vaccine strains A19 (Brucella abortus strains A19). We successfully applied this probe to screen positive samples of Brucella without any cross-reactivity with other substances. Additionally, we identified another specific gene exclusively found in wild strains, which serves as Probe 2 with hairpin structure (P2h) to confirm the strain type. Simultaneous detachment of both P1h and P2h from the MOFs leads to the release of Rhodamine 6G (Rho 6G) and Fluorescein (Flu), specifically indicating the presence of wild strains. If only P1h detaches and the Flu signal is detected, it suggests the presence of vaccine strains. Importantly, this method offers high accuracy, with a detection rate of 90% and a recovery rate of 94.71% to 107.65%, while avoiding cross-reactions with MO and TB. This one-step experiment provides reliable identification and differentiation of Y3 and A19, addressing concerns related to long periodicity, interference from individual variations, and the complex design of primers in existing laboratory methods. Furthermore, our approach successfully detects target 1 (T1) and target 2 (T2) at concentrations ranging from 10-6 M to 10-9 M, with a detection limit of 6.7 × 10-10 M and 6.4 × 10-10 M, respectively. Importantly, our strategy is cost-effective (around $1) and offers higher detection efficiency compared to traditional laboratory methods.