Author: LIN LU

Publisher:

Published: 2018

Total Pages: 114

ISBN-13:

Electrochemical sensing methods are highly attractive for the monitoring of biotoxins, infectious diseases, cancer, and other chemicals and biomarkers, due to their high sensitivity, low cost, simple operation, easy miniaturization by microfabrication, and biocompatibility. Give the chemical nature of mycotoxins and the low action levels in food and feed, the development of mycotoxin monitoring methods has been facing many challenges such as unsatisfactory sensitivity, insufficient specificity, time-consuming, food matrix interference, etc. Deficiencies in any of the above-mentioned aspects is generally considered unacceptable. In addition, random interfering signals arising from non-specific adsorption/ foreign chemicals can cause problems in detection reliability. Therefore, much effort has been put into the modification of working electrode surfaces to improve the electron transfer efficiency and the specific target recognition. In this dissertation, to provide a user-friendly tool for quantitatively and effectively monitoring mycotoxins level in grains, special attention has been paid to the design and fabrication of electrochemical biosensors for the detection of mycotoxins aflatoxin B1 (AFB1), fumonisin B1 (FB1) and deoxylnivalenol (DON). We started by designing and fabricating a novel electrochemical immunosensor on screen printed electrode (SPE) platform, with polydiallyldimethylammonium chloride (PDDA), carbon nanotubes (CNTs) and gold nanoparticles (AuNPs) enhanced working electrode surface, which showed excellent sensitivity toward the detection of AfB1. However, a performance stability issue was found with the developed biosensor, which may due to Unoptimized surface modification. This drove us to further optimize the surface modification strategy based on the same underlying principle. To overcome the issues, we modified the working electrode surface of the SPE with new combinations of conducting polymer polypyrrole (ppy), carbon nanomaterial graphene oxide (GO) and AuNPs. The newly fabricated electrode was immobilized with anti-FB1 and anti-DON antibodies respectively, and tested with respective target toxins. The results for both toxins showed great sensitivity, specificity and reliability, as well as wide linear ranges. The sensitivity for the detection of DON was 8.6 ppb and for FB1 was 4.2 ppb. The linear range for the detection of DON was 0.05 to 1 ppm and for FB1 0.2 to 4.5 ppm, which are comparable to most published research results. The developed biosensor was further examined in real food matrix--spiked corn powder sample. Calibration curves with real corn samples were very similar to those obtained with buffer, for both toxins. The as-prepared electrode was able to maintain performance after being stored in buffer at 4 ̊C for two weeks. Since in reality, multiple mycotoxins usually co-occur in grain, we proceeded to the next stage:developing a biosensor for simultaneous detection of multiple mycotoxins. ITO coated glass was used to replace SPE as the sensing platform for more convenient fabrication of multiple working electrodes on one single chip. The ITO sensor was incorporated with capillary based microfluidic method to achieve better sensing performance. The ITO immunosensor incorporated with microfluidic devices was capable of detecting two different mycotoxins FB1 and DON in one sample at very low detection limits (97 pg/mL for FB1 and 35 pg/mL for DON). In summary, the electrochemical immunosensors developed in this PhD work demonstrated high sensitivity and great specificity for the detection of mycotoxins both individually and simultaneously. In particular, the developed double-channel ITO immunosensor incorporated with microfluidic devices demonstrates a promising potential to be applied on site for rapid and simultaneous mycotoxins monitoring.