Studies On Electrochemical Sensors Based On Metal-organic Framework

The impact of the biosensing technology is increasing in all major sectors such as pharmaceutical,healthcare,environment and food.Among various biosensors,the enzyme-based electrochemical biosensors are particularly attractive due to the possibility of performing rapid and on-spot analyses together with a high sensitivity,simplicity and ease of miniaturization.However,the enzyme-based electrochemical biosensors are susceptible to environments because the enzymes are easy to degenerate inactivation and aggregate after they are immobilized on the electrode surface,which have negative effects on the performance of enzyme-based biosensors.Therefore,the development of new host materials with improved immobilization efficiency and stability of enzymes is important for electrochemical biosensors.Metal-organic frameworks(MOFs)as a new class of organic-inorganic hybrid porous crystalline materials have received great attention in recent years.In comparison to other inorganic materials,MOFs have high porosities,very large surface area,tunable pore size and structural diversity.These impressive properties make MOFs as efficient matrices to immobilize various small molecules and proteins,which have shown the exciting applications in catalysis,sensors,drug delivery.Several reports on the encapsulate enzymes into mesoporous MOFs show higher loading of enzymes with superior stability compared to those incorporated into mesoporous silica.However,the investigation to utilize the pores of MOFs for encapsulating biomolecules to construct electrochemical biosensors is rarely explored so far.Especially,the stability of the biosensor based on the confinement of enzyme molecules within MOFs in harsh environments,to the best of our knowledge,has not been reported yet.Based on the enzyme loading of traditional material is small and unstable,we choose MOFs to immobilize enzyme,specific work content is as follows:1.A water-stable metal-organic framework(MOF)[(PCN-333(Fe)]with ultra-large cavities and ultra-high porosity was synthesized by hydrothermal methods.and employed to encapsulate horseradish peroxidases(HRP)for the fabrication of the electronic mediator hydrogen peroxide(H2O2)biosensors.Due to the size-match of a HRP and large cage of PCN-333(Fe),encapsulation of enzyme into the PCN-333(Fe)was achieved.The confinement of HRP in the cage of PCN-333(Fe),which not only essentially eliminated enzyme aggregation and leaching,improved the catalytic efficiency,but also effectively hindered the conformational change of immobilized HRP when continuously used.In addition,chosen Fe based-PCN-333 is possible to play a certain action in improving the activity of enzyme,and show a high stable in the heated or thermal condition.The specific surface area and pore size of PCN-333(Fe)before and after encapsulation of HRP were also investiaged with nitrogen sorption isotherms,we also study its electrochemical sensing performance,and H2O2 is selected as a target compound.The analysis of the substrate H2O2 has realized the wide linear range from 0.5 to 1472 μM,low detection limit(0.09μM),the result is satisfying.2.A stable MOF is prepared by hydrothermal method:ZIF-67(Co).On account of the MOFs have poor conditivity in general,we mixed the multiwalled carbon nanotube with the ZIF-67(Co)to form ZIF-67(Co)-MWCNT,and then fixed it on the glass carbon electrode(GCE)for immobilizing HRP.Nanoscale and good electrical conductivity of composites enhance the.ability of electronic transmission.The well-organized porous structure is beneficial for the analysis of the substrate and mass transfer in the channel and immobilizing enzyme.Building of hydrogen peroxide biosensor has the excellent anti-interference performance,a high sensitivity(22.05μA·mM-1).