Analysis Methods Using Metal-organic Frameworks NH₂-MIL-53?Al? As The Fluorescent Probes

MOFs are a group of framework materials composed of organic ligands and metal nodes,which possess periodic network structures connected by coordination bonds between organic ligands and metal ions.MOFs show many attractive characteristics,such as diverse structure and composition,tunable pore size,high surface area,tunable active sites,and facile modification on both metal nodes and ligands.In the recent years,they have been extensively employed in various areas including gas adsorption and storage,biomedical imaging,catalysis,drug delivery and chemical separation because of their attractive physicochemical properties.In addition,MOFs have achieved remarkable results in the field of optical sensing due to their superior loading performance,strong colorimetric and FL responses.In our works,MOFs NH₂-MIL-53?Al?were synthesized by a facile hydrothermal method.Utilizing the FL properties of MOFs NH₂-MIL-53?Al?,a sensitive immunoassay method and a double-site-recognition-based FL assay method were developed for the detection of mycotoxin and pathogenic bacteria,respectively.1.Alkaline hydrolysis behavior of MOFs NH₂-MIL-53?Al?employed for sensitive immunoassay via releasing fluorescent moleculesMOFs NH₂-MIL-53?Al?were synthesized from NH₂-H₂BDC and AlCl₃ by a facile hydrothermal method.The synthesized MOFs displayed good stability and uniform particle size in netural medium,and hydrolyzed in alkaline medium to release a large amount of fluorescent ligand NH₂-H₂BDC.Therefore they can act as large-capability nanovehicles to load signal molecules for investigating various biorecognition events.In this work,based on the alkaline hydrolysis behavior of MOFs NH₂-MIL-53?Al?,a sensitive immunoassay method was developed for the detection of AFB₁ by employing they as the fluorescent signal probes.With a competitive immunoassay mode on microplate,AFB₁ can be detected within a linear range of 0.05 ng m L^-1-25 ng mL^-1,and the limit of detection was 0.03 ng m L^-1?3??.The method was specific for AFB₁detection.Other mycotoxins showed minor interference.The method was successfully employed to detect AFB₁ spiked in Job Tears,Polygala Tenuifolia and with acceptable recovery values of 83.00%-114.00%.The detection results for moldy Fructus Xanthii displayed acceptable agreement with those by HPLC method,with relative errors of-14.21%-3.49%.With the merits of high sensitivity,facile manipulation and ideal reliability,the approach have good analytical performance in practical applications.2.Double-site recognition-based method for florescent detection of S.aureus employing alkaline hydrolysis behavior of MOFs NH₂-MIL-53?Al?With the previously synthesized MOFs NH₂-MIL-53?Al?,a double-site recognition-based FL method was established to detect S.aureus employing their alkaline hydrolysis behavior.In this work,MOFs NH₂-MIL-53?Al?-labeled TEI were used as FL signal probes for tracing the target analyte,and magenetic beads coated with pig IgG were adopted to isolate S.aureus utilizing the strong affinity between pig IgG and protein A on S.aureus.Thus a FL method for detecting S.aureus was established on a magnetic separation platform.S.aureus can be detected within a linear range of 3.3×10³-3.3×10⁷ CFU mL^-1,with a limit of detection of 5.3×10²CFU mL^-1?3??.The method was specific for viable Gram-positive bacteria detection.Gram-negative bacteria and other Gram-positive bacteria showed minor interference.The method was successfully employed to detect S.aureus spiked in saliva,pomegranate green tea and glucose injection with acceptable recovery values of 97.70%-115.10%.With the merits of high sensitivity,facile manipulation and short detection time,the approach can also be extended to other areas and shows great application potential.In summary,utilizing the unique FL property of MOFs NH2-MIL-53?Al?,FIA and double-site recognition-based FL method was constructed for the detection of AFB₁ and S.aureus,respectively.They show the advantages of high sensitivity,strong specificity and facile operation,and demonstrate the good application prospects in food safety and drug quality control.