Aptamer Sensing Methods Based On Metal-Organic Frameworks (MOFs) And The Detection Of Multiple Organophosphorus Pesticide Residues In Vegetables

Organophosphorus pesticides(OPs)have the advantages of good insecticidal effect,low cost,high efficiency and broad spectrum,so they are widely used in vegetable cultivation.And they account for about 34% of the pesticides produced and sold in agriculture worldwide.The growing environment of vegetables is complex,and the actual planting often requires the combination of a variety of organophosphorus pesticides.This leads to the phenomenon of excessive organophosphorus pesticide residues detected in a vegetable sample often occurring.The large-scale instrument detection method is so complicated and time-consuming that it is difficult to meet the requirements of pesticide supervision under the background of diversified and complicated organophosphorus pesticide residues in vegetables.To ensure vegetable quality and food safety,it is urgent to establish sensitive rapid detection technology for organophosphorus pesticide multi-residues.Aptasensors have the advantages of simple operation,fast detection speed and high sensitivity.By modifying the aptamer to functional materials,the target substance can be quickly detected.Metal-Organic Frameworks(MOFs)have good biocompatibility,easy to modify,and have the advantages of large specific surface area,high porosity,good stability,and highly adjustable material structure.They are widely used in the construction of biosensors.Based on the above considerations,this study constructed two highly sensitive aptasensors based on MOFs for the rapid detection of a variety of organophosphorus pesticides and verified the practicability of the sensors in different vegetables.The main research contents are as follows:(1)Based on the colorimetric principle and the specific recognition of broad-spectrum aptamer for pesticides with the common structure,a visual biological colorimetric sensor with high selectivity and high sensitivity was constructed for the visual detection of four organophosphorus pesticides.Fe-N-C nano-biomimetic enzyme and Fe-Co magnetic nanoparticles(MNPs)were synthesized by calcination of Fe-ZIF-8 and Fe-ZIF-67 respectively.And then modified by a surface modification to form enzyme-like materials with high enzyme activity and magnetic probe with high target specificity.Under optimal conditions,the detection limits(LOD)of phorate,profenofos,isocarbophos,and omethoate were as low as 0.1667 ng/m L,0.1667 ng/m L,0.0333 ng/m L and 1.6667 ng/m L respectively.The recovery rate of OPs residue in vegetable samples was 89.19%～108.35%,and the sensor showed good stability and specificity.(2)Considering the complexity of the fabrication process,a new and simpler process was used to prepare MOF materials for the construction of the aptasensor.Tris(2,2′-bipyridyl)ruthenium(II)chloride hexahydrate was used as the dopant and Eu-MOF was chosen as the pristine MOFs to design Ru@Eu-MOF with layered porous core-shell structure through a hydrothermal method.The fixation of tris(2,2′-bipyridyl)ruthenium(II)chloride hexahydrate ligand on the MOFs could restrict the free rotation of the groups in the molecules and reduce the internal filtration effect.Ru@Eu-MOF was used as a new organic luminous body and its surface was modified with aptamers as an ideal biometric probe for sensors,a high-performance electrochemical luminescence sensor was constructed for the rapid detection of phorate,profenofos,isocarbophos and omethoate.The results showed that the aptasensor had a wide detection range and low detection limit.Under the optimal conditions,the LOD of the aptasensor constructed for the above four pesticides were 0.0482 ng/m L,0.0093 ng/m L,0.0085 ng/m L and0.0893 ng/m L,respectively.The recovery rates of the sensor were 91.47%～104.94%,which showed good practical application effects in the detection of actual vegetable samples.Based on the practical problem of diverse organophosphorus pesticide residues in vegetables,the above study proposed different construction methods of MOFs material-based aptasensors,which could realize the simultaneous detection of organophosphorus pesticide residues in vegetables.By changing the corresponding aptamer sequence on the captured DNA probe,the sensor can also be expanded to achieve the rapid detection of other kinds of pollutant,which is of great significance for ensuring food safety and human health.