Preparation Of Upconversion Nanocrystals Encoded Magnetic Microspheres And Their Application In Detection Of Mycotoxins

Food safety is of fundamental importance to our daily life.Mycotoxins are a major class of pollutants in food,which are characterized by their highly toxicity,trace,wide distribution and variety.Currently,the analytical methods for mycotoxins mainly include bioassay,immunoassay?primarily enzyme-linked immunosorbent assay?,and chromatography/mass spectrometry?mainly high performance liquid chromatography,and chromatography-mass spectrometry?.However,the above methods have some disadvantages,such as a single testing sample,complex sample pre-treatment,trivial operation,large sample dosage and time-consuming,which can not meet the the daily analysis of mycotoxins.However,compared with the traditional detection technologies,the cytometric bead array technology can simultaneously detect the multiple target molecules with only small samples,and also has the advantages of simple operation,fastness,high accuracy and a wide detection range.It can realize the accurate sensitive,fast and high-throughput detection of mycotoxins in food.Furthermore,the fluorescent materials for preparating fluorescence-encoded microspheres are mainly organic fluorescent dyes and quantum dots in the cytometric bead array technology.But organic fluorescent dyes and quantum dots have some defects.For example,organic fluorescent dyes and quantum dots are excited with the short-wavelength light sources for the down-conversion light emission,which often accompanied by different levels of background fluorescence and a low signal-to-noise ratio.However,upconversion nanocrystals as the novel fluorescent materiasl can overcome the above-mentioned defects caused by organic fluorescent dyes and quantum dots,which used the near-infrared light as the excitation source.The upconversion nanocrystals have the advantages of a low background signal and high signal-to-noise ratio.Meanwhile,upconversion nanocrystals for optical code can avoid the the spectral interference and overlap between the encoding signal and the detection signal,thus effectively improving the accuracy and sensitivity of detection and analysis.Aiming at the problems above,a new method for the detection of mycotoxins in cereals based on the upconversion nanocrystals encoded microspheres was developed.The specific contents are as follows:?1?The NaYF₄-based upconversion nanocrystals?UCNs?with six different luminescent colors were successfully synthesized by the solvothermal method.The results show that the prepared six-color UCNs have the characteristics of uniform distribution,good dispersibility and different fluorescence spectral.?2?The upconversion nanocrystals encoded magnetic microspheres?UCNMMs?were successfully prepared by high temperature self-healing encapsulation method.The results show that UCNMMs both have the encoding signals of UCNs and good magnetic performance.Compared with the detection system based on the down-conversion encoding materials,the UCNMMs detection system effectively avoids the fluorescence interference between the encoding signal and detection signal.?3?Applying the principle of indirect competitive immunoassay,the cytometry beads array based on UCNMMs was used for detecting aflatoxin B1 and ochratoxin A in corn.The results show that this method has a high sensitivsity,good accuracy and simple operation with small samples,and the limit of detection values were found to be10^-12 g/mL.In conclusion,this study successfully established a new detection system for mycotoxin based on the upconversion nanocrystals encoded magnetic microspheres.Meanwhile,it provides a new research method and important experimental data for the application of multi-color upconversion nanocrystals encoded magnetic microspheres in the high-throughput screening for food safety.