The Construction And Applications Of Sensing System Based On Functional Nanomaterials And Aptamer Specific For Mycotoxins

In this paper,aptamer?Apt?was used as biorecognition element,and gold nanoparticles?AuNPs?,CdTe quantum dots?QDs?,Fe₃O₄@Au magnetic beads?MBs?and some other functional nanomaterials were used as aptamer carrier or signal probes,to construct a series of aptsensing systems for the sensitive detection of fumonisin B1?FB1?,ochratoxin A?OTA?or aflatoxin B1?AFB1?in corn samples.The details are as follows:1.Firstly,a polydimethylsiloxane?PDMS?film was covered on the non-electrode surface of the screen-printed carbon electrode?SPCE?to form a micro-cell.Then,well-dispersed AuNPs were electrodeposited onto the surface of the working electrode.Finally,the thiolated Apt specific for FB1 was modified on the surface of AuNPs by the cross-linking effect of Au-S bond.A displaceable and impedimetric aptasensor was constructed.The construction process was characterized by cyclic voltammetry,electrochemical impedance spectroscopy,scanning electron microscope,and X-ray photoelectron spectroscopy.The presence of FB1 would trigger the formation of FB1-aptamer complex and inhibite the electron transfer between the redox probe[Fe?CN?₆]^3-/4-and the electrode interface.On this basis,the developed aptasensor showed a good linearity in the range from 10 pg mL^-1to 50 ng mL^-1with a low detection limit of 3.4 pg mL^-1?S/N=3?.The developed aptasensing device has the advantages of less reagent consumption,label-free and low-cost.2.The thiolated AFB1 Apt was modified on the surface of Fe₃O₄@Au?MBs?to obtain the MBs-Apt capture probe,and the complementary DNA strand?cDNA?was modified on the surface of AuNPs prepared by citrate reduction method to obtain the cDNA-AuNPs signal probe based on the Au-S covalent binding,respectively.Furthermore,the two probes were coupled using the hybridization reaction between Apt and cDNA to fabricate MBs-Apt/cDNA-AuNPs,which can be used to detect AFB1 by linear sweep voltammetry?LSV?or colorimetry.Due to the high affinity between Apt and AFB1,cDNA-AuNPs was detached from MBs-Apt,the released signal probes were separated and collected using an external magnetic field and used for colorimetric assay and electrochemicial assay.Bsed on the fact that AuNPs can catalyze H₂O₂ to oxidize 3,3?,5,5?-tetramethylbenzidine which produce colored products to achieve colorimetric detection of AFB1,the linear range was 0.05²00 ng mL^-1.In addition,AuNPs can promote the chemical deposition of Ag in the presence of hydroquinone.With the correlation between the Ag⁺reduction current value and the AFB1 concentration,and the amino-complementary strand of cDNA?ccDNA?modified SPCE electrode to detect AFB1 by LSV method.Within the concentration range of 0.05⁵0 ng mL^-1,the measured LSV signal value is positively correlated with the concentration of AFB1 with the detection limit reaching 16.7 pg mL^-1?S/N=3?.The dual-channel methods can verify each other and improve the accuracy of the test results.3.The green-emitting CdTe QDs?gQDs?and red-emitting CdTe QDs?rQDs?were modified on the surface of Si O₂ nanosphere by electrostatic adsorption to obatain SiO₂@gQDs and SiO₂@rQDs,respectively.And they were further used to label the complementary DNA?cDNA¹ and cDNA²?of the aptamer to obatain cDNA¹-SiO₂@gQDsandcDNA²-SiO₂@rQDsfluorescencesignalprobes,respectively.The Fe₃O₄@Au MBs were used as the carriers of the thiolated Apt specific for OTA?Apt¹?and AFB1?Apt²?to obtain MBs-Apt¹ and MBs-Apt² capture probes,respectively.The magnetically controlled aptasensor was therefore fabricated by the attachment of the fluorescence signal probes onto the magnetic carrier due to thehybridizationreactionbetweenthecDNAandApttoproduce MBs-Apt¹/cDNA¹-SiO₂@gQDs and MBs-Apt²/cDNA²-SiO₂@rQDs.Due to the high affinity between the Apt and target,signal probes were detached from the magnetic carrier,allowing us to simultaneously determine OTA and AFB1 in a single analytical run.Under optimum conditions,the fluorescence intensities of the released labels in supernatant were found to exhibit positive correlation with the dual targets concentrations,in a wide range of 2 pg m L^-15 ng m L^-11 for OTA and 5 pg mL^-110ng mL^-11 for AFB1.The proposed aptasensor had a low LOD of 0.67 pg mL^-11 for OTA and 1.70 pg mL^-11 for AFB1,respectively.The magnetically controlled fluorescence aptasensor shortens the detection time and improves the detection efficiency.