| Mycotoxins were defined as potent human carcinogens (aflatoxin B1-first hazard class according to the IARC classification). Enormous health risk and economic loss caused by its contamination have captured more and more attentions. Food-borne pathogenic bacteria, such as E. coli O157:H7, also bring large economic loss and health risks. Developing of rapid detection methods on pathogenic bacteria and mycotoxins in food products is necessary. This thesis reviewed systematic studies related on food safety, developed novel biosensing methods for toxins detection in food products.Details are as follows:(1) A combination of screen-printed electrodes and interdigitated microelectrodes, namely, screen-printed interdigitated microelectrodes (SPIMs), may integrate their merits to develop highly sensitive, rapid-responding, cost-effective biosensors for detection of pathogenic bacteria. However, related research is rarely reported. As far as we know, the application of lectin as signal amplification for bacteria detection has not been reported. In this research, an electrochemical impedance immunosensor based on self-assembled monolayers was proposed for rapid detection of E. coli O157:H7 with signal amplification using wheat germ agglutinin (WGA). With the optimized parameters, the proposed impedance immunosensor could detect E. coli O157:H7 at concentrations as low as 102 cfu-mL"1 with a linear detection range between 102 and 106 cfu·mL-1 and a total detection time of less than 1 h. The method we proposed presents an opportunity to develop a portable biosensing system for routine monitoring of food-borne pathogens.(2) The commercial electrochemical stations have drawn great attention and been widely used due to their high sensitivity and the combination of multi-techniques. However, these large and expensive instrumentations were unfavorable for in-field applications. As alternatives, portable electrochemical detectors with advantages of miniaturization, low-cost, rapid response and simplified data analysis system, are widely concerned. In this research, we proposed an electrochemical biosensor based on SPIMs and portable detector to achieve low-cost, highly selective and sensitive detection of AFB1 in rice. Under optimized conditions, the immunosensor provided a detection limit lower than the allowable concentration. More importantly, the results obtained from the developed portable detection system and the commercial electrochemical station in the laboratory were comparable. An USB compatible sensor was also designed and then printed by a 3D printer, which could be plugged into the portable detector through USB interface to make a completed portable biosensing system.(3) Separation and purification process play important role for food samples detection. How to rapidly separate aflatoxins from vegetable oils is one of the top priorities for the related subsequent research. Based on the introduction of separation methods, the synthesized Fe3O4 magnetic nanobeads can combine with antibodies to form immunomagnetic beads complexs. The complexs can be used in vegetable oil to complete separation and purification process. The results were verified using HPLC-FID method which indicated that the proposed method was a promising and rapid separation method for trace toxins in complicated food matrixs. The proposed magnetic separation method have the potential to improve the analysis performance for the trace mycotoxins in complicated food matrices.(4) The droplets exhibit different coverage on the microelectrode surface, depending on the hydrophobicity of the microelectrode surface which may trigger irregular signal change. The influence of droplets coverage which is important but less concerned. In this manuscript, we investigate the influence of droplets coverage on the electrochemical response of SPIMs.3D technology was employed to print smart nest-like devices with different diameters based on nesting concept. The results indicated that the influence of coverage on electrochemical response was significant. Moreover, ring devices on the surface of the SPIMs effectively improve the stability of the signal and also verified the such influence. Detection cost can also be greatly reduced by recycling of the printed devices. All the devices improved the stability of the signal and eliminate the irregular signal change successfully. Our proposed design and concept show great potential for application in the field of electrodes fabrication and stable electrochemical biosensors construction. The design of electrode base can avoid the different concentration and quantity of the biomaterial, thus eliminate the irregular signal change. The design is completed using software which is easily to adjust according to actual requirements, which possess the wide practicability. |
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