Fabrication Of Disposable Electrochemical Aptasensor Based On Morphology-Controllable Au Nanostructures And Its Applications In Aflatoxin Detection

Mycotoxins are highly toxic and harmful,and it is of great significance to develop simple,fast,sensitive reliable analysis methods.The electrochemical analysis method has the advantages of high sensitivity,fast responding speed,high reliability,low instrument cost,and simple operation.In this paper,indium tin oxide electrodes?ITO?and screen-printed carbon electrodes?SPCE?are used as substrates,development a series of simple operation,cheap and high detection sensitivity disposable electrochemical Aptsensors.Differently shapes Au nanomaterials are modified on the woke electrodes,likes gold nanoflowers?AuNFs?,gold nanowires?AuNWs?and gold nanocages?AuNCs?,which in order to improve the chemical properties of the electrode surface.The electrochemical measurement method was selected as differential pulse voltammetry?DPV?and electrochemical impedance spectroscopy?EIS?.The aptasensors can be used for sensitive detection of a single subtype of aflatoxin or detect two subtypes of aflatoxin simultaneously.The specific research contents were mainly focused on:1.AuNFs modified ITO?ITO-AuNFs?were prepared by the in-situ growth of AuNFs on the surface of ITO.Ferrocene?Fc?labeled aptamer?Apt-Fc?and methylene blue?MB?labeled thiol-cDNA?cDNA-MB?constitute a complementary chain modification on the surface of ITO-AuNFs to construct a radiometric disposable electrochemical Aptsensor.Due to the rigid structure of the double-stranded DNA,the Fc end of Apt-Fc is close to the electrode surface,while the MB end of cDNA-MB is far from the electrode surface.When AFB1 is present,the aptamer specifically binds to the target to form a complex?Apt-Fc/AFB1?and detaches from the electrode surface,meanwhile,MB end of cDNA-MB is close to the electrode,which causes the DPV signal of the MB to increase and the Fc to decrease.In this process,Exo I was introduced to decompose Apt-Fc/AFB1,and the released AFB1 entered the next round of circulation,which formed the recycling of the target and improved the sensitivity of the aptamer sensor.The ratio of I_MB/I_Fc and the logarithm of the concentration of AFB1showed a good linear relationship in the range of 0.1 pg mL^-1–1000 pg mL^-1 with a limit of detection?LOD?of 0.03 pg mL^–1?S/N=3?.2.AuNWs modified ITO?ITO-AuNWs?was prepared by growing AuNWs in situ on the surface of ITO,using thiol-cDNA?including cDNA1 and cDNA2:complementary to AFB1 aptamer?Apt1?,AFB2 aptamer?Apt2?respectively?and Fc-Apt1?Fc-labeled Apt1?,MB-Apt2?MB-labeled Apt2?construct electrochemical Aptsensors for the simultaneous detection of AFB1 and AFB2.In the presence of the target,the aptamer specifically binds to the target form Fc-Apt1/AFB1 and MB-Apt2/AFB2 complexes,that detaches from the electrode surface,resulting in the I_Fc and I_MB are reduced.In this process,Exo I was introduced to decompose Apt1-Fc/AFB1 and Apt2-MB/AFB1 the released the target entered the next round of circulation,which can greatly improve the detection sensitivity.Under optimized conditions,the Aptsensors have good electrochemical responses to both AFB1 and AFB2,with linear response ranges of 0.08pg mL^-1–250 pg mL^-1 and 0.4 pg mL^-1–1250 pg mL^-1,respectively,with the LOD is0.03 pg mL^-1 and 0.13 pg mL^-1?S/N=3?.3.Gold is expensive precious metal,and increasing the gold atom utilization rate of the nano-gold modified on the electrode surface can effectively reduce the preparation cost of the Aptsensor.Porous hollow gold nanocages?AuNCs?were prepared by displacement reaction,Ag nanocubes?AgNCs?as templates,and the AuNCs were electrostatically assembled on the surface of SPCE modified with PDDA,and then the thiol-aptamer?Apt-AFB1?passed through Au-S.The bond is modified on the surface of the inner and outer walls of AuNCs,and an impedance-type electrochemical aptamer sensor is constructed for label-free detection of AFB1.When the target is present,the aptamer and target specifically recognize to form an Apt-AFB1/AFB1 complex,which hinders the transfer of electrons on the SPCE surface,resulting in an increase in electron transfer impedance.Under optimal conditions,this Aptsensor could detect AFB1 in a wide range of 0.1 pg mL^–1–100000 pg mL^–1 with a high linear fit and has an ultra-low detection limit of 0.03 pg mL^–1?S/N=3?.