Construction Of NMOF-based Fluorescence Ratiometric Sensor For Rapid Detection Of Toxin In Food

In recent years,more and more people pay attention to food safety.Biotoxin is a important topic in the field of food safety.Marine toxins and mycotoxins are common,distibutive and toxic biotoxins in daily life.High performance liquid chromatography（HPLC）,liquid chromatographytandem mass spectrometry（LC-MS）and enzyme-linked immunosorbent assay method（ELISA）are the traditional methods for detection of biotoxins in food.However,these methods suffered from some shortcomings,such as complicate procedure,reqirement of expensive equipments and time-consuming.It’s important to develop new method to facile and efficent detection of biotoxins.Metal organic frameworks（MOFs）are a class of porous cystal material based on metal nodes and organic ligands.And the major advantage of MOFs are high surface area and tuneable stucture.Moreover,nano-scale MOFs（NMOFs）is greatly soluble and stable.This papre reports ratio fluorescence sensors based on NMOFs and dye-modified aptamers,and upgrades fluroescence sensors twice through optimizing synthesis method of NMOFs and FRET pairs.Different fluorescence sensors are used to detect tetrodotoxin（TTX）,saxitoxin（STX）and aflatoxin B1（AFB1）,respectively.At the same time,the sensing ability and practicability in real samples of sensors are also evaluated.The detection mechanism of the sensors are discussed finally.This paper is mainly consisted of the following parts:1.NMOF 1 with blue fluorescence was constructed using Zr Cl₄ and 1,2,4,5-Tetrakis（4-carboxyphenyl）benzene,and NMOFs-Aptasensor 1 was constructed using NMOF 1 and TAMRA-modified aptamer.Then,NMOFs-Aptasensor was firstly upgraded via optimalizing FRET pairs.NMOF 2 with green fluorescence was constructed using Zr Cl₄ and 4,4’-（1,2-Diphenylethene-1,2-diyl）dibenzoic acid,and NMOFs-Aptasensor 2 was constructed using NMOF 2 and TAMRA-modified aptamer.NMOFs-Aptasensor was upgraded again via furthermore optimalizing FRET pairs and synthesis method.Optimalized NMOF 3 with green fluorescence was constructed using Zr Cl₄ and 4,4’-（1,2-Diphenylethene-1,2-diyl）dibenzoic acid,the size of NMOFs were reduced from 37.53 nm（NMOF 2）to 21.71 nm（NMOF 3）.NMOFs-Aptasensor 3 was constructed using NMOF 3 and Cy3-modified aptamer.After that,SEM anlysis,TEM analysis,DLS analysis,XRD spectra,EDS spectra,FT-IR spectrum were used to verify the successful construction of NMOFs-Aptasensors and characterize NMOFs and NMOFs-Aptasensors.2.NMOFs-Aptasensor 1 was used for detection of TTX.The sensitivity,selectivity and stability of NMOFs-Aptasensor 1 were measured.The LOD of NMOFs-Aptasensor 1 was 3.07n M for TTX.Moreover,domoic acid（DA）,okadaic acid（OA）and dinophysistoxin（DTX）can barely change the fluroescnece intensity ratio of the fluorescence sensor,indicating great selectivity.During the stroage at 4°C,the fluorescence ratio values of NMOFs-Aptasensor 1decreased no more than 8%,indicating good stability.NMOFs-Aptasensor 1 was successfully used to detect TTX in shellfish samples,the mean recoveries ranged from 84.79%to 100.73%.3.NMOFs-Aptasensor 2 was used for detection of STX.The sensitivity,selectivity and stability of NMOFs-Aptasensor 2 were measured.The LOD of NMOFs-Aptasensor 2 was 1.17n M for STX.Moreover,DA,OA and DTX can barely change the fluroescnece intensity ratio of the sensor.During the stroage at 4°C,the fluorescence ratio values of NMOFs-Aptasensor 2decreased no more than 5%,indicating excellent optical stability.NMOFs-Aptasensor 2 was successfully used to detect STX in shellfish samples,the mean recoveries ranged from 89.96%to 103.31%.4.NMOFs-Aptasensor 3 was used for detection of AFB1.The sensitivity,selectivity and stability of NMOFs-Aptasensor 3 were measured.The LOD of NMOFs-Aptasensor 3 was 0.08ng m L^-1 for AFB1.Moreover,aflatoxin G1,aflatoxin G2,fumonisin B1 and fumonisin B2 can barely change the fluroescnece intensity ratio or effect the sensing results for AFB1 of the sensor.NMOFs-Aptasensor 3 was successfully used to detect AFB1 in fresh corn samples,the mean recoveries ranged from 89.11%to 102.40%.Due to the smaller size of NMOFs-Aptasensor 3,the sensitivity and selectivity was enhanced.Flurescence lifetime,CD spectra analysis,Zeta potential analsis and agarose gel electrophoresis analysis were used to verify FRET effect and structure change of aptamer.Through various analysis methods the detection mechanism of NMOFs-Aptasensor was discussed and verified.