荧光探针置换型核酸适配体传感器检测生物小分子OA北大核心CSTPCD

By using thioflavin T(ThT)as displacement-based fluorescent probes,three kinds of aptasensors were constructed for rapid detection of three kinds of small molecules such as ochratoxin A(OTA),aflatoxin B1(AFB1)and adenosine.In the absence of target molecule,ThT bound with the aptamer to form an aptamer-ThT complex and exhibited a significant fluorescence response.Upon the addition of target molecule,because of the higher affinity between target and aptamer than that between ThT and the aptamer,ThT was displaced by the target molecule from the aptamer-ThT complex,resulting in weakened fluorescence signal.Based on this principle,the target molecule could be detected quantitatively.Further study through circular dichroism spectra showed that there was no significant change in the conformation of the aptamer after addition of ThT or target molecules.The stoichiometric ratios of ThT to OTAapt,AFB1apt and Adeapt measured through the method of equimolar continuous variation was 1∶1,1∶1 and 2∶1,respectively,and their dissociation constants were all larger than those between the target molecule and its aptamer.Therefore,the principle of this detection method was the displacement of fluorescent probe(ThT)in aptamer-ThT complex by target molecule,resulting in decrease of fluorescence intensity.Under optimal experimental conditions,the limits of detection(LODs)were 0.8 nmol/L for OTA,1.3 nmol/L for AFB1,and 0.10 μmol/L for adenosine,respectively.This method was label-free,simple to operate,with low cost,good selectivity and high sensitivity.The developed assay kit based on this method could be used for actual sample detection.