Application Of Electrochemical Aptasensor Based On MXene And Mental Organic Framworks In Food Toxin Detection

Electrochemical sensors have been widely used in the detection of toxins in food and cancer markers due to their advantages of good selectivity,simple structure and high sensitivity.In the construction of electrochemical sensors multi-functional metal organic frameworks（MOFs）.Two-dimensional layered materials can be used as electrode modification materials to improve the performance of the electrochemical sensors due to their high specific surface area,good electrical conductivity and high catalytic activity,which have attracted extensive attention from researchers at home and abroad and are widely used in chemical,biological,and medical research fields.Most noble metal nanomaterials have the advantages of small size,good catalytic effect and good biocompatibility.In this paper,two-dimensional materials（g-C₃N₄,MXene）,metal-organic frameworks materials and Au NPs were used to construct electrochemical aptasensors in order to realize the detection of ochratoxin A and aflatoxin B1 in mycotoxins.（1）An iron porphyrin（PAF-40-Fe）modified electrode was prepared to detect morphine by differential pulsed voltammetry between 0.2 V-0.8 V.The experimental results show that the electrode has a good electrical conductivity in the process of morphine detection.Under the optimum conditions,the oxidation peak current of morphine showed a good linear relationship with the concentration of morphine in the range of 1.5-1500μmol/L,R²=0.9945,and the detection limit was 0.5μmol/L.The recovery of this method was 88.9%-105.6%.This method has the advantages of good selectivity,simple sensor preparation and quick detection,and has a good application prospect.（2）Au NPs@g-C₃N₄ composite material was synthesized by loading gold nanoparticles on carbon nitride material,which was fixed on the surface of glassy carbon electrode by chitosan（Chit）as the substrate of electrochemical aptasensor.An electrochemical aptasensor for ochratoxin was constructed by hybridizing DNA1 with the ochratoxin（OTA）aptamer and immobilized the hybrid chain on the substrate of glassy carbon electrode.Electrochemical alternating current impedance（EIS）was used to detect the impedance value of aptasensor when cultivating OTA with different concentrations.The impedance value is inversely proportional to the concentration of OTA,the quantitative detection of OTA can be realized.The linear range was 0.5-100ng/m L,the linear correlation coefficient was 0.9506,and the detecting limit was 0.167ng/m L.The aptasensor provides a novel and effective method for detecting OTA.（3）An aflatoxin aptasensor was constructed based on Au NPs@MXene.At first,the AFB1 aptamer was hybridized with DNA1 to form a double strand,and then methylene blue（MB）,used as the signal label,and was inserted into the double strand as a hybridization indicator.At the same time,the guanine rich structure of DNA1could also bind to MB.When the target AFB1 was added,the AFB1 aptamer specific binding of AFB1 and would open the double chain,which made DNA1 separate from the electrode,methylene blue also separate from the electrode,which result in MB signal on the electrode weakened.Based on this,an AFB1 aptasensor with signal off was constructed.The current response signal of MB in the range of-0.6 V-0.0 V was detected by differential pulse voltammetry.The sensor has a wide linear range between 0.5 ng/m L-100 ng/m L,and the linear equation is△I=7.8397lgc+1.4432,R2=0.9903.（4）Metal organic framework material loaded with gold nanoparticles（Au NPs@Co MOF）was used as the modified material of the electrode to construct an electrochemical aptasensor for the detection of ochratoxin（OTA）.Firstly,Au NPs@Co MOF was modified on the surface of electrode,then the s DNA and OTA aptamer were hybrid to form a double chain through base complementarity,and the hybrid chain and the tetrahedral hairpin structure DNA chain were added to the glassy carbon modified with Au NPs@Co MOF.When the target OTA toxin was added,the OTA aptamer binds with OTA and dissociates from the electrode,and the swing chain s DNA was released and connected to the hairpin structure on the tetrahedral DNA.After adding endonuclease（Nb.Bb VCI）,the hairpin structure was induced to transform into SA aptamer.Then,Au NPs@Cr MOF labeled with SA was added as a signal label,and SA and SA aptamer bind specifically on the electrode surface.The electrode was put in potassium ferricyanide solution for detection.A ratio type electrochemical OTA aptamer sensor was constructed by using the ratio of the current value of Cr MOF to that of potassium ferricyanide as the response signal.The detection range of the sensor is 0.05 ng/m L-50 ng/m L,the linear equation is y=0.3498lg c+0.4177,R2=0.9723(y is the ratio of DPV response current of Au NPs@Cr MOF to DPV response current of Fe（CN）₆^3-/4-)...