Study On Nanocomposite Based Electrochemical Biosensor For F-2 Toxin Detection

F-2 toxin is a mycotoxin widely existing in corn,wheat,barley,rice and other food crops,which has caused serious pollution to human food and animal feed.Meanwhile,the high water insolubility and thermal stability of F-2 toxin induced the expansion of contamination.Therefore,the development of highly sensitive and rapid F-2 toxin contamination monitoring technology is of great significance to food safety and public health.Electrochemical biosensor can be an ideal choice for detection and analysis due to its high sensitivity,strong specificity and fast response.In view of the small molecule characteristics of F-2 toxin,it usually found in low concentration in food crops or food,the study has construct three different electrochemical biosensors with a variety of nanocomposite materials and signal amplification strategies to achieve highly specific trace detection of F-2toxin.The main research contents are shown as follows1.An immunosensor for F-2 toxin detection with PEI-r GO/Pt@Au NRs nanocomposite as the modification material was constucted.PEI-r GO/Pt@Au NRs nanocomposite have good stability,conductivity and a large specific surface area,so they are chosen as the substrate material for the modified electrode,which is beneficial in improving the detection performance of the sensor.When antibody binds to F-2 toxin,the current signal decreases,and the response signal changes after F-2 toxin incubation,recorded by differential pulse voltammetry（DPV）methods.Under the optimised conditions,the electrochemical response of the constructed immunosensor shows a linear relation to a wide concentration range from 1×10^-2 to 1×10⁴ ng·m L^-1 with a detection limit of 2×10^-4 ng·m L^-1.Additionally,the proposed electrochemical immunosensor has high selectivity,good stability and great potential for the trace detection of F-2 toxin in real samples.2.In order to improve the low utilization rate of target molecules,which restricts the further improvement of biosensor sensitivity.Herein,an electrochemical aptasensor combining Nb.Bbv CI-triggered bipedal DNA walking strategy was constructed for ultrasensitive assay of F-2 toxin.The aptasensor used Ce₃Nb O₇/Ce O₂@Au hollow nanospheres as electrode modification material and Pd Ni@Mn O₂/MB as the signal label.Importantly,the Ce₃Nb O₇/Ce O₂ synthesized by hydrothermal method were combined with Au nanoparticles and applied to the electrode surface.The as-prepared Ce₃Nb O₇/Ce O₂@Au possessed a large surface area,excellent electrical conductivity,stability and more binding sites.Pd Ni@Mn O₂ with high specific surface area and porosity combined with molecule methylene blue（MB）was introduced into electrodes as the signal label.The proposed aptasensor utilized the advantages of specific recognition of aptamers and target molecules to release bipedal DNA walker（w-DNA）,and then the w-DNA was triggered by Nb.Bbv CI and entered the cycle to release more signal probes.The feasibility of this strategy was recorded by DPV`method.Under the optimized conditions,the electrochemical aptasensor exhibited a wide linear dynamic range from 1×10^-4 to 1×10³ ng·m L^-1 with a low detection limit of 4.57×10^–6 ng·m L^-1.Moreover,the aptasensor had high selectivity,good stability,excellent repeatability and provided an effective method for the trace detection of F-2 toxin in real samples.3.Due to the complex and time-consuming in vitro preparation process during sensor construction,the application of electrochemical sensor in practical assays will be limited.In order to improve this issue,an electrochemical aptasensor based on the high-specificity CRISPR/Cas12a system and DNAzyme-assisted amplification strategy is constructed.NH₂-Mn O₂/Pd@Au NBs was used as the electrode modification material,and Pt Pd@Fe₃O₄was used as the signal label to load MB.The target recognition of aptamers and F-2 toxins was converted into DNA signal,then the collateral cleavage activity of CRISPR/Cas12a on Mg²⁺-DNAzyme was regulated.Based on the MB signal changes caused by the catalytic cracking of the signal label on the electrode surface by Mg²⁺-DNAzyme,the quantitative detection of F-2 toxin was ultimately achieved.The feasibility of the strategy was recorded by DPV.Under optimal conditions,the linear detection range of the electrochemical aptasensor is 1×10^-5 to 10 ng·m L^-1,and the detection limit is 6.27×10^-6 ng·m L^-1.In addition,the aptasensor has high selectivity,good stability,excellent repeatability,and good recovery in the spiked corn flour samples.