The Detection Of Aflatoxic B1 In Peanut Oil By Sers Aptasensor Based On Aptamer-modified Magnetic Core-shell Nanoflowers

Aflatoxin B1（AFB1）is one of the most toxic mycotoxin,it has strong hepatocarcinogenic and mutagenic effects.Agricultural products are particularly vulnerable to AFB1 contamination if they are not stored properly,which causing food safety problems and threatening human health.Therefore,the detection of AFB1 in food is of great significance to ensure food safety and human health.To date,the traditional methods are widely used in AFB1 detection,which are time-consuming,labor-intensive and need tedious detection process,so they can not meet the needs of rapid detection.Compared with these traditional methods,surface-enhanced Raman spectroscopy（SERS）technology possesses a high sensitivity and can provide the specific fingerprints of analyte and realize the rapid detection of analyte.In order to further achieve the specificity detection,SERS is often used in conjunction with aptamer technique for the detection of mycotoxins in food.In this study,multifunctional SERS substrate magnetic core shell nanoflowers（Fe₃O₄@Au NFs）was prepared as capture molecules,and based on this,two SERS aptasensors were constructed for the trace detection of AFB1 in peanut oil.The research contents and results of this article are as follows:（1）The preparation,optimization and characterization of SERS substrate magnetic core shell nanoflowers Fe₃O₄@Au NFs.Fe₃O₄ nanoparticles was prepared by the hydrothermal method,different shapes of Fe₃O₄@Au NFs were synthesized by the polyethyleneimine assisted-seed growth method and the SERS enhancement effect,reproducibility and stability of these Fe₃O₄@Au NFs were studied.The results shown that the synthesized Fe₃O₄ with the uniform morphology and size was approximately 350 nm.After the modification of PEI thin-layer,8-10 nm Au seeds were successfully absorbed to the surface of positively charged Fe₃O₄@PEI as seeds.The Au shell was gradually synthesized with the addition of HAu Cl₄growth solution.The rough and flower-shaped of Fe₃O₄@Au NFs was presented by the addition of 0.4 m M HAu Cl₄,which has the strong SERS enhancement effect with 4-MBA.Besides,the standard deviation of six parallel optimal substracts Fe₃O₄@Au NFs was 8.1%.After stored 4weeks,the SERS enhancement effect of the optimal Fe₃O₄@Au NFs still maintain 83.27%of the original,the Fe₃O₄@Au NFs exhibits good reproducibility and stability.（2）A SERS aptasensorⅠbased on Fe₃O₄@Au NFs magnetically capture Cy3-labelled aptamer was developed for AFB1 detection.Fe₃O₄@Au NFs modified with complementary DNA was acted as capture probes,Cy3-labelled aptamer（Cy3-Apt）was acted as signal probes.After the DNA hybridization of capture probes and signal probs,the SERS aptasensorⅠwas constructed under magnetically capture of Fe₃O₄@Au NFs.The specific recognition of AFB1and the aptamer could trigger the release of signal probe from the aptsensorⅠ,leading to the decrease of SERS signal of Cy3,thus realizing the trace detection of AFB1.And the detection specificity and recovery in peanut oil samples of the aptasensorⅠwere also studied.The results shown a good linear range of 0.01-100 ng/m L under the optimal conditions,and the detection limit was 3.40 pg/m L.In addition,this aptasensorⅠhas good anti-interference effect and a satisfactory recoveries in the range of 84.0%-97.60%in peanut oil samples.（3）A magnetic separation SERS sensorⅡbased on bridging Fe₃O₄@Au NFs and Au@4-MBA@Ag NSs with aptamer was developed for AFB1 detection.Au-4MBA-Ag nanospheres（Au@4-MBA@Ag NSs）prepared by modifying 4-MBA in the middle of Au-Ag core-shell nanoparticles was acted as signal molecular.The AFB1 aptasensorⅡwas developed by recognizing and bridging of the surface aptamer-modified Fe₃O₄@Au NFs and Au@4-MBA@Ag NSs.Based on the same detection principle of the previous chapter,the sensitivity,specificity and recovery were carried out.The results presented a wide linear range from 0.0001to 100 ng/m L and an AFB1 detection limit of 0.40 pg/m L.Besides,this aptasensorⅡ’s recovery rates in peanut oil were between 96.6%and 115%,which could realize the selectivity of AFB1detection.Finally,this aptasensorⅡmethod was compared with the national standard AFB1detection method and AFB1 fast detection card method,the detection limit of AFB1 spiked in peanut oil samples was lower.However,the on-site application of this aptasensorⅡmethod need to be greatly proved.