Gold nanoparticles biosensor of Brucella spp. genomic DNA: Visual and spectrophotometric detections

•A hybridization assay for detecting Brucella spp. genomic DNA is presented.•Detection was performed in clinical samples.•Detection method is highly simple and visually. The causative agents of brucellosis from genus Brucella can infect a variety of animal species and human. However, conventional methods for the detection of Brucella are time-consuming and the handling of microorganism is hazardous for laboratory personnel. In this study, a nanobiosensor based on gold nanoparticles (AuNPs) and oligonucleotide probe was designed for the visual detection of Brucella spp. A specific oligonucleotide probe from IS711 gene region was functionalized with AuNPs (AuNP-probe). Then, AuNP-probe was exposed to target (complementary) and non-target (non-complementary) DNA for the hybridization. Also, hybridization conditions were analyzed in the presence of Brucella genomic DNA and extracted DNA from clinical samples. Upon acid addition, a red color for the samples containing complementary DNA was observed, whereas in the samples without complementary DNA, AuNP-probe turned blue-purple. The results were investigated visually and also by UV–vis spectroscopic measurements. This method detected up to 1.09pgμL−1 of unamplified Brucella genomic DNA. Since Brucella is a facultative intracellular bacteria, clinical samples were amplified by PCR, and colorimetric detections were performed. The results showed high sensitivity and selectivity for the amplified clinical samples. To the best of our knowledge, this developed assay is highly specific, and this is the first assay that can be used with low cost, and as a method of rapid, direct and visual detection of Brucella spp.