| "Food and safety come as the first".Food safety is a hot topic attracting widespread from the society.Aflatoxin contamination incidents occur frequently,and food safety testing and monitoring has become one of the effective methods to prevent its harm.In this paper,we have constructed rapid and sensitive methods for detection of aflatoxin in food based on aptamers,which provide a new idea for the rapid detection of mycotoxin and also have certain reference value for the development and research of practical sensor.The specific research results are as follows:1.A novel electrochemical aptasensor for sensitive and selective detection of aflatoxin B1(AFB1)was successfully constructed.The thiolated complementary strand(cDNA)of the AFB1 aptamer(Apt)was immobilized on the surface of the glassy carbon electrode(GCE)modified with gold nanoparticles(AuNPs)through Au-S bond.Then Apt was attached on the surface of GCE via by specific base pairing.In the presence of AFB1,the Apt was detached from the electrode surface by specific recognition between the AFB1 and Apt,forming Apt-AFB1 conjugates in solution.The conjugates were digested by exonuclease I(Exo I)to trigger AFB1 recycling.Finally,DNA-AuNPs-horseradish peroxidase(DNA-AuNPs-HRP)nanoprobes was bound with cDNA on the surface of electrode by specific base pairing.HRP could catalyze the oxidation of hydroquinone(HQ)to benzoquinone(BQ)by hydrogen peroxide(H2O2)for producing a strong electrochemical signal.Under the optimized conditions,the electrochemical signals increased with increasing concentrations of AFB1 in a range from 10-3 ng/mL to 200ng/mL with a low detection limit of 3.3×10-4ng/mL.Moreover,the aptasensor has been successfully applied for the determination of AFB1 in peanuts samples and the recoveries were 93.6%～107.0%.2.In this work,we constructed a novel electrochemical aptasensor for AFM1 detection on a basis of layer-by-layer assembly of DNA-Au@Ag conjugates.The thiolated complementary strand(SH-cDNA)of the AFM1 aptamer(Apt)was immobilized on the Au electrode surface through strong Au-S bond.Then Apts-Au@Ag and cDNA2-Au@Ag were attached successively on the electrode via specific base pairing to form dual Au@Ag nanoparticle conjugates.When AFM1 was present,partial dual conjugates was detached from the electrode due to the high affinity between the AFM1 and its Apts.Subsequently methylene blue(MB)as an electrochemical indicator was intercalated into the remaining double-stranded DNA on the electrode surface and bound specifically to guanine(G),producing a measurable electrochemical signal,and the electrochemical signal decreased linearly with increasing AFM1 concentration.Upon the optimal conditions,the electrochemical aptasensor showed a low detection limit of 0.033ng/mL within the AFM1 concentration from 0.1ng/mL～200ng/mL.In addition,the method has been also successfully applied to the detection of AFM1 in goat milk samples and the recoveries were 94.66%～103.35%,which can be a promising one in the field of simple,rapid and accurate detection of AFM1.3.In this study,a fast and sensitive electrochemical aptamer sensor based on reduced graphene oxide(RGO)was constructed to detect aflatoxin M1.RGO is prepared by reducing graphene oxide with jujube juice.The synthesized RGO was modified on the surface of GCE,and then gold nanoparticles were electrodeposited on the surface of GCE.The aptamer of aflatoxin M1 was fixed on the surface of the modified GCE by strong Au-S bond.In the presence of the AFM1,AFM1 binds specifically to the aptamer,hindering electron transfer due to the large size of the AFM1 molecule.The results showed that the electrochemical aptasensor has the advantages of high sensitivity,good selectivity and good repeatability.The linear range was 1×10-7ng.mL-1～1×10-3ng.mL-1,and the detection limit was 3×10-2 fg.mL-1.The aptasensor was successfully applied for detection of AFM1 in goat milk samples,and a satisfactory recovery rate was obtained. |
