A Simple Electrochemical Aptasensor For Rapid And Sensitive Detection Of Salmonella Typhimurium

Food safety as a research hot spot has always been attented by human beings. Bacterial microorganism is one of the most common pathogen in the human food chain. The most common bacterial microorganism include E.coli, salmonella, staphylococcus aureus, mycobacterium tuberculosis, colletotrichum, clostridium botulinum, listeria, pork streptococcus, etc. accounting for more than 95% of food contamination caused by bacteria. Salmonella is a kind of gram-negative bacilli parasitized in human and animal gut. The poultry, fresh pork and meat products have the highest infection rate and is the main way of human infection with salmonella disease. Salmonella typhimurium is a kind of important zoonotic pathogen which belongs to B group of salmonella. Its infection rates is the highest in all salmonella and account for about 40%-80% in anthropogenic salmonella infection. The bacteria and its host distributed widely in nature, therefore, has important significance in public health.It was found that extremely trace concentrations of salmonella typhimurium could cause a variety of clinical disease such as acute gastroenteritis, sepsis, and various internal organs damage secondary to sepsis, etc. most of which could cause death. Therefore,it is important and significant to develop a method for detection of salmonella typhimurium in low concentrations timely. Various methods have been reported for the detection of Salmonella typhimurium, such as traditionnal culture methods, enzyme-linked immunosorbant assay (ELISA), polymerase chain reaction (PCR) and surface plasmon resonance(SPR). However, these methods are time-consuming, high cost, low sensitivity and difficult to realize large-scale and high-throughput detection.In our study, the developed electrochemical aptasensor based on gold nanoparticles signal amplification for detection of Salmonella typhimurium could overcome these shortcomings and complete the detection in 4 hours. We hybridized the aptamer of Salmonella with the capture probe immobilized on electrode interface, in the presence of Salmonella as a target analyte, the aptamer dissociated from the capture probe-aptamer duplex as the stronger interaction between the aptamer and the Salmonella. Therefore, the binding sites were exposed again and the single-strand capture probe could be hybridized with biotinylated detection probe assembled on AuNPs and catalyzed by streptavidin-alkaline phosphatase, producing electroactive product and thus sensitive electrochemical response to Salmonella, consequently, improved the sensitivity of the aptasensor. AuNPs on the electrode interface were used to increase the active area and conductivity of electrode and AuNPs assembled with detection probe could amplify the recognition signal. As a result, the designed electrochemical aptasensor shows a linear relationship in the detected range from 2×10-1 to 2×10-6 CFU mL=1 in buffer and 2×10-2 to 2×10-6 CFU mL-1 in real samples. The proposed strategy has a good development prospects in clinical diagnostics, food safety and environmental monitoring.