The Study On Aptasensor Of Food-borne Pathogens Based On Graphene Oxide Nanomaterials

Foodborne pathogens is one of the important reasons that result to food security incidents.According to the World Health Organization, over70%of foodborne diseases was caused bypathogenic bacteria every year. The development of novel detection method is very important,simultaneity point out the disadvantages of traditional detection methods, such as lowsensitivity and time-consuming. In recent years, the electrochemical sensor has been a hot areaof research owing to its low-cost and high specificity and sensitivity. To achieve the aim ofrapid detection of pathogens, a series of research has been carried in this work based on theaptamer-recognize technology and new nano materials:Firstly, a novel amperometric aptamer biosensor was designed for determination ofSalmonella in food. The aptasensor was assembled by a nanocomposite prepared from reducedgraphene oxide (rGO) and gold nanoparticles (AuNPs), then the aptamer which was modifiedwith sulfhydryl in5’ end is self-assemblied on the surface of the modified glassy carbonelectrode. The good electron transport capabilities of rGO and the large surface area of AuNPscan improve electron transport properties of the biosensor. When incubated in Salmonella, theaptamer can selectively captured the bacteria in its three-dimensional space and the currentchanges after the capture of Salmonella. Under optimized conditions, the aptasensor exhibiteda wide linear range from2.5×102cfu/mL to2.5×105cfu/mL (R2=0.9904) with a low detectionlimit (LOD) of80cfu/mL (S/N=3). The detection can be completed within1hour. In addition,the biosensor exhibits high selectivity over other pathogens.Secondly, a novel label-free impedimetric biosensor was designed for determination ofStaphylococcus aureus in food. The thiol-ssDNA, which non-covalently adsorbed on grapheneoxide (GO) and covalently connected to AuNPs by Au-S bonds, linked AuNPs to rGO-thusensuring AuNPs deposition. Before AuNPs deposition, GO was electrochemically reduced.Afterwards, the probe DNA was immobilized on the surface of the AuNPs-modified glassycarbon electrode to capture and concentrate S. aureus. When incubated in S. aureus, the probeDNA of aptasensor selectively captured target bacteria in its three-dimensional space. Thecapturing of S. aureus resulted in a dramatic increase in impedance, and this effect was utilizedto quantify the bacteria. Under optimized conditions, the aptasensor possessed a linear range of10cfu/mL to106cfu/mL (R2=0.9933) and a detection limit of10cfu/mL (S/N=3). In addition,the biosensor exhibited high selectivity against other pathogens.Finally, an impedimetric biosensor fabricated by one-step electrodeposition of reducedgraphene oxide (rGO) and carbon nanotubes (CNTs) was designed for detecting Salmonella infood. The nanomaterials was synthesized by graphene oxide and carboxylic multi-walledcarbon nanotubes, and electrodeposited on the electrode afterwards. The Salmonella aptamer, which was modified with amino, covalently binded with CNTs through amide bonds after anelectrochemically reduction of GO. When incubated in Salmonella, the aptamer selectivelycaptured target bacteria and resulted in a dramatic increase in impedance, which can be utilizedto quantify the bacteria. Under optimized conditions, the aptasensor possessed a linear range of7.5×101cfu/mL to7.5×105cfu/mL(R2=0.9640) and a detection limit of25cfu/mL (S/N=3).