Construction Of Functional Nanomaterial Aptasensors And Their Application In Visual Detection Of Ochratoxin A

Food contamination is an increasingly serious public health problem.Ochratoxin A（OTA）is a typical mycotoxin,which is often found in food and can harm human and animal life and health.To ensure food safety at all stages from production to marketing,it is imperative to develop low-cost,highly sensitive,accurate and rapid OTA testing methods.In this study,different functionalized nanomaterials and aptamers were used to construct biosensors for OTA detection.Finally,these biosensors were used for actual samples analysis.The detailed research contents are as follows:（1）As a recognition unit,OTA aptamer was modified onto the surface of dendritic mesoporous silica nanospheres enriched with quantum dots（MSNQs-apt）.Meanwhile,the complementary DNA（c DNA）of the aptamer and were connected with magnetic nanoparticles（MNPs）as the separation elements（MNPs-c DNA）.Under the optimal conditions,the detection range for OTA of the prepared aptasensor is from 2.56 pg/m L to 8 ng/m L,with the detection limit of 1.402 pg/m L.This strategy shows high stability and specificity for OTA in real wheat flour and red wine samples,thus providing a new way for mycotoxin detection.It has the advantages of simple operation,low cost,fast analysis and strong anti-interference ability.However,visual detection requires the use of instruments and equipment,so colorimetric methods are sought to achieve visual inspection.（2）WSe₂ nanosheets were prepared by ultrasonic exfoliation and their catalytic properties were studied.Then free OTA aptamers were first adsorbed to the surface of WSe₂ nanosheets to form a complex based on the WSe₂ nanosheet’s large surface area and strong catalytic activity.With the help of H ₂O₂,the affinity between the complex and the chromogenetic substrate TMB was enhanced,and their peroxida se activity significantly increased.A colorimetric sensor with WSe ₂ nanoplate aptamer was constructed for visual detection of OTA.Under the best conditions,the detection range of OTA is from 0.50 to 50 ng/m L,and the detection limit is 0.16 ng/m L.Due to the excellent selectivity of the probe,the proposed strategy showed strong OTA specificity in complex wheat flour and red wine samples.Peroxidases require the use of H₂O₂ to catalyze the color reaction of substrate TMB,but high concentrations of H₂O₂ have certain physiological toxicity and are not environmentally friendly.Therefore,it is imperative to find nanoenzymes that directly catalyze substrates.（3）A label-free colorimetric aptasensor for OTA assay was successfully constructed based on the enhanced catalytic activity of MnO₂ nanoflowers after aptamer adsorption.When the aptamer was adsorbed to the MnO ₂ nanoflowers,the catalytic activity of the nanoflowers was enhanced due to the increased affinity of the chromogenetic substrate,and the mech anism was elucidated.This aptasensor has high sensitivity and selectivityfor OTA detection,and its performance is comparable to or better than that of previously reported sensors.Under optimal conditions,the detection range of OTA is from 0.05 to 33.35 ng/m L and the detection limit is 0.069ng/m L.Due to the excellent selectivity of the aptasensor,the proposed strategy demonstrated high stability and specificity for OTA in complex wheat flour and red wine samples.In addition to OTA detection,the desi gn strategy can also be applied to other analytical systems by modulating the catalytic activity of nanozyme,which may be helpful in the construction of nanozyme-based aptamer sensors.In view of these characteristics,this strategy has great prospects fo r the quantitative detection and screening of mycotoxins in food samples.