Application Of Nanofunctional Materials In The Detection Of Mycotoxin And Its Cytotoxicity

Mycotoxins, secondary metabolites of fungi, are very toxic substances to human and animals. It is of great importance to develop simple, sensitive, specific and low-cost techniques for the detection of mycotoxins and their toxic effects. High performance liquid chromatography and gas chromatography/mass spectrometry are two traditional approaches that are widely used to evaluate mycotoxins. Although both methods could provide excellent sensitivity and low detection limit, the complex operating procedures, as well as the requirements of expensive equipment and well-trained professionals, greatly hinder the use of them in daily life. The toxicity of mycotoxin is also investigated with some conventional biological techniques.Nanomaterial may display some unique properties, which cannot be found at a large scale. In the past decades nanomaterials with a variety of structures and functions have been fabricated and applied in various fields such as energy, life sciences and environmental sciences. It has been well documented that the use of nanomaterials in biosensors can significantly enhance the sensing performance. If nanomaterials with some specific optical or electrical properties can be applied to develop novel systems for the detection of mycotoxins and their toxic effects, it may greatly promote the studies on mycotoxin prevention and control as well as its toxic mechanism. In this project, we utilize functional nanomaterials to build novel platforms for the measurements of mycotoxin and its toxicity and carry out the following investigations:Detection of aflatoxin Bl (AFB1) with an aptasensor based on fluorescence quenching from quantum dots (Q-dots) to graphene oxide (GO). The freshly prepared GO was characterized with transmission electron microscopy (TEM) and atomic force microscopy (AFM) to prove its single layer nanosheet structure. AFB1 aptamer molecules were linked on the surface of Q-dots via ligand exchange. Then, fluorescence quenching between aptamer-Q-dots and GO was verified with fluorescence spectra and atomic force microscopy. AFB1 sensing performance of the system was evaluated in both phosphate buffer solution (PBS) and peanut oil. Results show that the aptasensor possess good selectivity, wide dynamic range from 3.2 nM to 320 μM and the limit of detection of 1.0 nM in PBS. As to the real peanut oil samples the sensor exhibits the dynamic range from 1.6 nM to 160 μM and the limit of detection of 1.4 nM.Q-dots-aptamer-MoS2 fluorescence quenching system for the detection of ochratoxin A (OTA). The MoS2 nanosheets were prepared and characterized with TEM and AFM. OTA aptamer molecules were linked on the surface Q-dots to form conjugates. After optimization, the best ratio of Q-dots-aptamer conjugates to MoS2 nanosheets is obtained and used for the following experiments. The performance of the sensing system was evaluated in both phosphate buffer solution (PBS) and wine. It is found that the aptasensor possess a dynamic range from 1 ng/mL tol μg/mL and the limit of detection of 1ng/mL in both PBS and real wine samples.Reduced graphene oxide (rGO)-platinum nanoparticles (PtNPs) functionalized carbon fiber (CF) for in situ detection of nitric oxide released from mycotoxin-stimulated cells. We developed a rGO-PtNPs based CF microelectrode for real-time detection of NO secreting from mycotoxin-stimulated pig intestinal endothelial cell (PIEC) cells. Scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) were conducted to verify the structure of the microelectrode. The electrochemical behaviors and sensing performance of the sensor were analyzed with cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometric tests. The sensor shows high sensitivity, good selectivity and a broad dynamic range. Its application for the in situ NO detection in mycotoxin-stimulated cells has also been demonstrated.In summary, two novel detection methods based on Q-dots-GO and Q-dots-MoS2 systems were developed for the detection of AFB1 and OTA, respectively. A rGO-PtNPs based CF microelectrode was also fabricated to real-time monitor the release of NO from mycotoxin-treated cells. This project not only provides novel approaches for the detection of mycotoxin and its cytotoxicity, but also demonstrates the great potentials of functional nanomaterials in the study of food sciences.