|WANG, BIN - University Of Georgia|
|XU, BINGQIAN - University Of Georgia|
|KWON, YONGKUK - Animal And Plant Quarantine Agency|
Submitted to: Journal of Nanobiotechnology (Biomed Central Open Access)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/8/2017
Publication Date: 5/17/2017
Citation: Wang, B., Park, B., Xu, B., Kwon, Y. 2017. Label-free biosensing of Salmonella enterica serovars at single-cell level. Journal of Nanobiotechnology (Biomed Central Open Access). 15:40.
Interpretive Summary: The food industry is consistently facing the challenge for detection of various toxic species that can contaminate food products. Among different foodborne pathogens, Salmonella enterica is one of the major causes of gastrointestinal infections in human and animals, and cause hundreds of death every year. The detection of Salmonella enterica serovars from food sources is critical for the prevention and control of the outbreak of salmonellosis. With an emerging nanotechnology, new label-free detection methods have been developed for fast detection of biological species with high sensitivity and specificity. The label-free biosensors based on nanotechnologies include bulk solution methods such as surface plasmon resonance (SPR), and single-molecule methods such as atomic force microscopy. The SPR technology has the advantages of easily operation and fast detection. Although SPR instruments have been used in detection of bacteria, the dynamic range and the limit of detection of current SPR methods still need a lot of improvements. The detection of those host-specific Salmonella serotypes has become an important issue for the food industry and disease control. Most methods used for Salmonella serotyping are based on genetic analysis, but the fast detections with antibodies or aptamers have drawn increasing attention recently. In this paper, new optical methods with nanotechnology to detect Salmonella serotype were discussed.
Technical Abstract: Nanotechnology has greatly facilitated the development of label-free biosensors. The atomic force microscopy (AFM) has been used to study the molecular mechanism of the reactions for protein and aptamers. The surface plasmon resonance (SPR) have been used in fast detection of various pathogenic bacteria. This study used both AFM and SPR to investigate the complex reactions between aptamers and outer membrane proteins (OMPs) on the surface of Salmonella Typhimurium. Two DNA aptamers were used for the label-free detection of S. Typhimurium with AFM and SPR. The aptamers have specific binding affinity to the OMPs of S. Typhimurium. At the single-molecule level, the high resolution AFM topography and recognition images distinguished the OMPs on the bacterial surface. E. coli in the control experiments didn’t generate recognition signals, which proved the specificity of these two aptamers to S. Typhimurium. The off-rate values for the interactions of these aptamers to the OMPs were estimated by the AFM dynamic force microscopy (DFS) as 5.2 × 10-3 s-1 and 7.4 × 10-3 s-1, respectively. The force and extension values from DFS measurements were used to distinguish the two aptamers. The surface membrane model was proposed to explain the complex correlations among force and extension values. Also, these two aptamers were used in the bulk solution detections of S. Typhimurium. The gold chips in SPR experiments were modified with carboxymethylated-dextran (CD), followed by aptamers immobilization to reduce the non-specific binding signals, resulted in the limit of detection of 3×104 CFU/mL.