Biosensors Based On AIE Fluorescent Probes And Graphene Oxide

Fluorescent biosensors have shown broad application prospects in molecular diagnosis,biochemical detection,food safety and environmental monitoring due to their advantages of simple operation,high sensitivity,high selectivity and fast response.As an important signal tool in biosensors,fluorescent probes carry the important role of the response and output of the optical signal in the detection process and are directly related to the sensitivity of the sensing platform.However,conventional organic fluorescent probes often undergo fluorescence quenching when bound to the target molecule or in the aggregate state?aggregation-caused quenching,ACQ?.This kind of high background"turn-off"detection mode severely limits its practical application.The appearance of aggregation-induced emission?AIE?fluorescent probes effectively solves the problem of ACQ phenomenon of traditional probes,and provides new approaches and methods for the development of"turn-on"fluorescent biosensors.However,since AIE probes and target molecules are usually bound by electrostatic or hydrophobic interactions,AIE probes will also have the same fluorescence response to other interferent in addition to the target molecules,which seriously affects the selectivity of the sensing platform.Graphene oxide?GO?,a novel two-dimensional one-atom-thick nanomaterial with unique optical,electronic,thermal,mechanical and magnetic properties,has shown a favorable prospect in the construction of fluorescent biosensors due to its excellent water solubility,biocompatibility and fluorescent quenching ability.And the sensitivity,selectivity and stability of the biosensors can be effectively improved by introducing it to the sensing platform.Herein,two label-free and turn-on aptasensors were realized by using AIE molecules as the fluorescent probes,specific aptamers as identification substances,and GO as the fluorescence quencher.Main Contents:1.Detection of ochratoxin AA label-free fluorescent aptasensor for specific and ultrasensitive monitoring ochratoxin A?OTA?was developed by using the specific aptamer of OTA?OSA?as the recognition element,an AIE molecule?a 9,10-distyrylanthracene with two ammonium groups,DSAI?as the fluorescent probe,and graphene oxide?GO?as a quencher.In the absence of OTA,the AIE probe DSAI and OSA complex?DSAI/OSA?are adsorbed on the GO surface,and the fluorescence of DSAI will be quenched efficiently via the fluorescence resonance energy transfer?FRET?from DSAI to GO.Upon OTA addition,a more stable complex?OSA-OTA?is formed and released from GO.Meanwhile,DSAI and OSA-OTA can form a new complex?DSAI/OSA-OTA?,then the fluorescent signal of DSAI recovers gradually.Therefore,by introducing GO and DSAI,the fluorescence signal of DSAI can be easily turned from“off”to“on”after the addition of OTA,and the ultrasensitive detection of OTA by monitoring the change of the fluorescence signal of DSAI can be readily realized.The detection limit of the assay can reach 0.324 nM with a linear detection range of 10 nM-200 nM.And the aptasensor exhibits high selectivity for OTA against other analogues.Moreover,it has been successfully applied for the detection of OTA in red wine samples.2.Detection of chloramphenicolWe developed a label-free and turn-on aptasensor for chloramphenicol?CAP?detection by using DSAC₂N as the fluorescent probe and GO as the fluorescence quencher.Before CAP addition,DSAC₂N and the specific aptamer of CAP?C-Apt?primarily form DSAC₂N/C-Apt complex and a bright fluorescence is present,then the fluorescence of the complex is quenched after the addition of GO.Upon CAP addition,C-Apt and CAP can form a more stable complex and release from GO,and the fluorescence of the complex recovers and enhances gradually due to the formation of DSAC₂N/C-Apt-CAP complex.The determination of CAP can be easily realized by comparing the fluorescence changes of DSAC₂N before and after the addition of CAP.The assay shows fantastic application prospect with simple design,easy operation and high sensitivity and selectivity characteristics with a detection limit of 1.26 pg/m L.