Synthesis Of Metal Organic Framework Nanocomposites And Their Applications In Electrochemiluminescence Biosensing

Metal Organic Frameworks（MOFs）are a new class of organic-inorganic hybrid crystalline materials formed by self-assembly of metal ions and organic ligands through coordination bonds.Due to its high specific surface area,functional pores,stable and diverse structure,it has great potential applications in gas adsorption,selective catalysis,drug release and biosensing.However,the MOF prepared by the traditional methods are mostly crystals with particle sizes on the micrometer or submicron scale,and the particle morphology is irregular,resulting in the MOF and the sensor surface are not bonded together and the conductivity is poor,which limits its wide applications in the sensor field.Therefore,preparation of MOF composites is an effective measure to make up for the inherent defects of MOF.Taking advantage of superior properties of each component in the composite MOF material,this article aims to build highly sensitive and highly selective sensors,thus broadening the application of MOF composites in biosensing field.Electrochemiluminescence（ECL）biosensor is an analytical method developed by combining ECL technology with biosensors.It not only has the characteristics of ECL,but also has the versatility of biosensors.At present,ECL biosensors have been widely used to determine chemical and biochemical analytes,including clinical diagnostics,food and water safety,environmental monitoring,and pharmaceutical research.In this study,MOF nanocomposites were used in the construction of ECL sensors.The main research contents and innovations of two ECL sensors designed to detect thrombin（TB）and prostate specific antigen（PSA）were as follows:1.An ECL sensor based on MOF-Ag-aptamer probe was designed and constructed for the detection of thrombin.Ag NPs-modified Fe-MIL-88 MOF material was prepared,and a thrombin aptamer was modified on the surface of this material to form a MOF-Ag-aptamer probe.The electrode surface modified with signal probe of Au-g-C₃N₄nanosheets,attaching the complementary strand of the aptamer,the MOF-Ag-aptamer probe is bound to the electrode surface to quench the ECL signal of Au-g-C₃N₄ by DNA base complementation.The competitive reaction of the test substance TB with DNA resulted in the separation of the probe from the electrode surface and the ECL signal was enhanced.The TB concentration was quantified by the recovery of ECL signal and achieving the purpose of detecting TB.The linear range of the sensor is 10^-1110^-6 g/mL,and the detection limit is 3×10^-13 g/mL.2.A ratiometric ECL sensor based on MOF-Au-G-quadruplex cooperative amplification was designed and constructed for to detect the prostate specific antigen.Fe-MIL-88 MOF was used as a carrier platform to package a large number of Hemin molecules and to further modify the nanoparticles and G-quadruplexes.The prepared DNA-MOF/Au/G-4 probe worked as a dual-signal label for catalysis of Luminol and quenching of quantum dots.When the target PSA and its aptamer recognize and combine to each other,the binding of the probe DNA was destroyed,the ECL double signal switches from the"off-on"state to the"on-off"state.Under the optimal detection conditions,the change of the ECL double signal ratio and the linear range of the PSA concentration for the sensor were 0.5 ng/mL to 500 ng/mL.The detection limit was 5.8×10^-5 ng/mL.