1. Introduction
Brucella are facultative intracellular bacteria that cause infections in animals and humans called brucellosis. So far, ten species have been characterized with four typical species (Brucella melitensis , Brucella abortus , Brucella suis , andBrucella canis ) which are known to cause disease in humans (S. Li et al., 2019; Pal et al., 2017). Although brucellosis is a common zoonotic disease, it is believed that humans are encountered accidentally (Taheri, Amini, Kamali, Asadi, & Naderlou, 2020). The disease is associated with acute symptoms including fever, lethargy, chill, weight loss, and arthralgia in humans. However, the infection may affect various organs and become chronic with signs such as osteomyelitis, orchitis, and endocarditis, etc (Pereira et al., 2020). But in animals, the infection may cause abortion storm in sensitive herds and therefore, it is very important in livestock and quick diagnosis is necessary to prevent the spread of the infection and subsequent economic losses (Taheri et al., 2020).
Blood culture is considered as the gold standard method to identifyBrucella spp. Hwoever, a sensitivity around 15% to 70% has been reported for this method respect to the PCR (Polymerase chain reaction) assay. Meanwhile, several serological tests are used to detect infections caused by Brucella spp, including the Bengal Rose test, 2-mercaptoethanol, Wright, Coombs Wright, and serum agglutination test. Nevertheless, they have low sensitivity and specificity, long response time, false positive result, operational complexity, and difficulties in real-time monitoring (Alves et al., 2010).
On the other side, the molecular techniques that work on the basis of DNA detection like PCR, are not only fast (>4 hour), but also make it possible to molecularly type the isolates without exposure to the infectious Brucella cells (Alves et al., 2010). Yet, the common PCR assay has its own limitations in detection of PCR products and interpretation of the results e.g. lack of convineincy and sensitivity, need for costly equipment, complex sample preparation, and skilled personnel requirement (Sattarahmady, Kayani, & Heli, 2015). Consequently, it is extremely important to develop more simple, sensitive, and inexpensive methods for detecting Brucella spp to overcome these limitations (Sattarahmady et al., 2015).
Application of biosensors has been the novel approach for the scientists. {Sattarahmady, 2015 #146;Sattarahmady, 2015 #146}Using biosensors, the sensitivity and specificity of detection methods have recently been improved for various pathogenic bacteria. Biosensors are analytical biodevices that convert the biological responses into electrical signals. These agents generally consist of a bioreceptor (e.g., antibodies, enzymes, nucleic acids (DNA/RNA/aptamers), microorganisms, etc.) with a physical transducer (optical, electrochemical, or mass-based) to generate a measurable signal (Rubab, Shahbaz, Olaimat, & Oh, 2018). Many novel signal transduction systems are being developed by using nanoparticles to further improve strategies for detection of pathogens (Narmani et al., 2018).
In this case, several biosensors have been designed based on the engagement of diverse nanoparticles such as magnetic-, silica-, gold-nanoparticles, and quantum dots, and introduced for the characterization of pathogenic bacteria (Ahangari, Salouti, & Saghatchi, 2016; Narmani et al., 2018). The present review has described the recent developments of various nanobiosensors for the detection of Brucella spp.