Trace Immunoassay Of Biotoxin Based On Quantum Dots And Magnetic Nanoparticles

With the development of life quality and economy,people pay more attention to their food safety and environment pollution.However,many accidents related to biotoxin happened these years.Aflatoxins and fumonisins are common carcinogens can be detected in polluted corns and peanuts,which both have have strong pathogenicity to human beings and domestic animals.The currently widely-used trace detection methods for the two carcinogens include HPLC,TLC,GC,HPLC-MS,ELISA and so on.While every method has its obvious disadvantages such as high cost,time-consuming,complicated pre-purification procedures,need to equip with professional person and easy to obtain false-positive results.To overcome these shortcomings,a rapid,high performance and good accuracy method for trace detection is urgently needed.With their outstanding characteristics,such as surface effect,quantum size effect,superparamagnetism and small size effect,magnetic nanoparticles have been widely uesd in many fields,for example,targeted drug delivery,bio-separation,environmental/food microbiology detection,magnetic hyperthermia.Fluorescent quantum dots also have some superior fluorescence properties,including able to tuning of the emission wavelength,broad excitation spectra,narrow emission spectra,and negligible photobleaching,and can be widely used as fluorescently labeled probes.And the modified quantum dots have a good biocompatibility and a relatively low toxicity to organisms.In this paper,a novel competitive fluorescence immunoassay for quantitation of trace biotoxins based on antigen-antibody immunoreaction.First we prepared two detection probes--Fe3O4/PS-Ab and QD-Ag.The antibody labeled with magnetic nanoparticle(MNP)reacted with the isolated antigen existed in the samples at first.Then the quantum dot(QD)modified antigen compete for the extra binding site of the antibody on the surface of MNP.With the increase of isolated antigen amount,less binding site on the surface of MNP-Ab can be occupied by QD-Ag,and the fluorescence intensity produced by QDs became lower.The change in the fluorescence intensity provide a novel method for quantitation of the target.The strong carcinogen AFB1 and FB1 was selected as model analytes.The novel competitive fluorescence immunoassay had a limit of detection of 0.01ng/mL,which is lower than the conventional method such as HPLC-MS and Rapid-test kits.Moreover,this method demonstrates many advantages such as time-consuming,low cost,not require operator with much professional knowledge and easily to be applied for other toxins detection only by using corresponding antibody and antigen.