The Fabrication Of Fluorescence MOF Composite And Its Application In Biosensing

Metal organic framework?MOF?has been widely used in many fields,such as gas storage,catalysis,sensing,separation and biomedicine,which is due to their unique features,such as large specific surface area,high porosity,unique pore structure,controllable structures and variable chemical components.However,the low mechanical strength and poor chemical stability of MOF themselves limit their further application.MOF composite is material composed of MOF and guest materials,which combines the excellent properties of MOF and guest materials.In this paper,a series of fluorescent MOF complexes were fabricated for bioanalysis.The main works are as follows:?1?ZIF-8 composed of 2-methimidazole and zinc nitrate was selected as a host to prepare a fluorescent composite,EuPS@AnC/ZIF-8,for ratiometric sensing of singlet oxygen?¹O₂?.AnC is a specific capture molecule of ¹O₂,which can be oxidized by¹O₂,leading to fluorescence quenching.However,the fluorescence of Eu³⁺remains unchanged in the presence of ¹O₂.Inspired by this fact,EuPS@AnC/ZIF-8 was used a ratiometric sensor to detect ¹O₂.Benefiting from the confinement effect of ZIF-8 host,this sensor showed high sensitivity toward ¹O₂ with a detection limit of 43 nM.Furthermore,the target responsive fluorescent color change of EuPS@AnC/ZIF-8allowed ¹O₂ to be easily identified by the naked eye under a UV lamp.?2?By self-adaptive assembly,a fluorescent composite was fabricated by using MOF composed of Tb³⁺and adenosine monophosphate?AMP?as a host for the encapsulation of glucose oxidase?GOx?and carbon dots?CDs?.Owing to the confinement effect,the GOx&CDs@AMP/Tb exhibited about 2-fold higher catalytic activity than free GOx.Meanwhile,significantly enhanced storage stability and negligible leakage of GOx were also achieved.On this basis,by considering the advantages of carboxyphenylboronic acid?CPBA?in the sensitization of Tb³⁺fluorescence and specific recognition of hydrogen peroxide?H₂O₂?,a dual-emissive GOx&CDs@AMP/Tb-CPBA composite was further fabricated for the ratiometric sensing of glucose.The ratio of F₅₄₅/F₄₁₅ of GOx&CDs@AMP/Tb-CPBA showed a good linearity with the glucose concentration ranged from 0.5 to 300?M.The detection limit was calculated to be 80 nM.Meanwhile,the level of glucose in serum can be determined with good accuracy and recovery by using this sensor.?3?By using Ce-MOF with peroxidase activity as a host,a fluorescent composite that was encapsulated with cholesterol oxidase?ChOx?was fabricated,which was denoted as ChOx@Ce-MOF.Ce-MOF is formed from the self-assembly of Ce³⁺and adenosine triphosphate?ATP?under mild conditions.Compared with Ce-MOF and free ChOx,ChOx@Ce-MOF not only possesses higher catalytic efficiency?2.5 times?,but also shows a better storage stability.Inspired by the fact that Ce³⁺can sensitize Tb³⁺fluoresence by a process of energy transfer,a fluoresence composite with green emission,ChOx@Ce/Tb-MOF was further fabricated.Benefiting from the long lifetime of Tb³⁺?ms?,ChOx@Ce/Tb-MOF as a cholesterol sensor can effectively eliminate the interference of nonspecific fluorescence,resulting in a improved detection sensitivity.There is good linear relationship between Tb³⁺fluoresence and cholesterol concentration in the range of 0.7 to 100?M.The detection limit of ChOx@Ce/Tb-MOF to cholesterol was calculated to be 700 nM.