Rapid detection of Brucella cells using a gold nanoparticle-based aptasensor via a simple colorimetric method

Brucellosis is a major worldwide zoonotic disease that is caused by Brucella spp. and threatens the health of communities. Novel methods for rapid detection of Brucella bacteria are beneficial and necessary in preventing infection and subsequent economic losses. Constructing biosensors with nanoparticles is a promising approach for identification of pathogenic bacteria in a short time. This study aimed to introduce a new detection method of Brucella cells using a biosensor, based on gold nanoparticles and a specific aptamer, via a colorimetric reaction. In this work, gold nanoparticles (GNPs) were synthesized and attached to the aptamer through electrostatic bonding. The binding of aptamer to gold nanoparticles was confirmed by Uv/vis spectrophotometry, FT-IR, transmission electron microscope (TEM) and zeta sizer (DLS).

In the presence of the bacterial cells, aptamers were bound to their targets, and the surfaces of the nanoparticles were depleted from aptamers resulting in intensified peroxidation activity of GNPs, and with the addition of 3, 3', 5, 5'-tetramethylbenzidine (TMB), the color of the solution was changed from red to purple, which indicated the presence of Brucella. The sensitivity of the aptasensor was investigated using different concentrations of Brucella cells and its specificity was confirmed against several species of bacteria. The results showed that the designed aptasensor was more sensitive compared to PCR assay method with the ability to detect 1.5 × 10¹ CFU/mL of the bacterial cells.

These findings indicate that the designed aptasensor can be used as a simple and rapid diagnostic tool to detect Brucella cells without need to experts and expensive laboratory equipment.