Comparison of the sensitivity of colored silica nanoparticle-based immunosensor with culture and PCR methods in detection of Brucella abortus

Brucellosis has always been a threat to the health and economy of the community. The limitations of human and animal disease detection methods justify the need for new diagnostic methods. This study was aimed to compare the sensitivity of colorimetric strategy based- immunosensors in the diagnosis of Brucella abortus with those of culturing and PCR methods.

The colored silica nanoparticles and paramagnetic nanoparticles after synthesis were conjugated with polyclonal antibody to form EDC/NHS complexes to form probe sequences, respectively. These probes were collected after being added to serial dilutions of B. abortus and completing the reaction. Then, with releasing organic dye from the silica structure, absorbance intensity was measured at 670 nm. On the other hand, at the time of each dilution, the corresponding chromosomal DNA was extracted by a DNA extraction kit and used for PCR analysis. The results of all three tests were ultimately compared.

Based on the results, the detection range of the immunosensor and culture was the same and equal to 1.5×103 - 1.5×108 CFU mL-1. But, the limit of detection for immunosensor and culture was measured as 450 CFU mL-1 and 400 CFU mL-1, respectively. The results of the PCR test exhibited a wide dynamic range of 1.5×104 to1.5×108 CFU mL-1, with LOD of 5000 CFU mL-1.

Comparing the results of this study showed that the proposed immunosensor is capable of replacing conventional B. abortus detection methods and can be considered as an on-site diagnostic tool, with high sensitivity.