Label-free Biosensor Based On Electrochemical/Electrocatalytic Activity Of MOFs

Metal-Organic Frameworks?MOFs?have greater porosity and specific surface area,special topological structure,high internal structural regularity,high electrochemical activity and high electrocatalytic activity compared to traditional porous materials such as carbon,zeolite,and molecular sieves.In this paper,Prussian blue?PB?,Cu-MOF-74 and MIL-101?Fe?were modified on the surface of the electrode by electrochemical method or covalent bond,and its electrochemical activity or electrocatalytic activity was used for detection of biomarkers such as liver cancer and heart damage.Three new types of electrochemical biosensors were constructed.The main contents were as follows:?1?Prussian blue?PB?and gold nanoparticles?AuNPs?,were deposited on bare glassy carbon electrode by cyclic voltammetry?CV?and amperometric I-t curve?I-t?,respectively.The modified electrodes were characterized by scanning electron microscopy?SEM?and fourier transform infrared spectroscopy?FT-IR?for confirming that PB and AuNPs were successfully synthesized on the electrode surface.HS-5'-DNA probe and 6-mercaptohexanol?MCH?were immobilized on AuNPs/PB/GCE by Au-S bond to construct MCH/Pro-DNA/AuNPs/PB/GCE and atomic force microscopy?AFM?was used to confirm the layer by layer modification of the electrode surface.The sensitive detection of liver cancer marker microRNA-122?miRNA-122?was examined by differential pulse voltammetry?DPV?using the high electrochemical activity of PB.The detection linear range is 0.1 fM to 1.0 nM and the detection limit is 0.021 fM.It has been successfully applied to the detection of serum samples and the recovery rate was 98%?108%.?2?Electrochemically active Cu-MOF-74 materials were prepared on-site by NH₂-reduced graphene oxide?NH₂-rGO?modified glassy carbon electrode by CV,and different modified electrodes were characterized by SEM and FT-IR.The carboxyl groups on the surface of the MOF material were bonded with the amino groups on the anti-cTnI to form an amide bond to realize the immobilization of the antibody on the electrode,and then the superfluous active sites were blocked by bovine serum albumin?BSA?.A novel label-free immunosensor BSA/anti-cTnI/Cu-MOF-74/NH₂-rGO/GCE,was constructed to detect cardiac troponin I?cTnI?sensitively by DPV using the high electrochemical activity of Cu-MOF-74.The detection linear range is 10 fg/mL to 1.0 ng/mL,and the detection limit is 4.5 fg/mL.The method has been successfully applied to the detection of serum samples and and the recovery rate was 95%?104%.?3?Hydrothermal synthesis of hydrogen peroxide mimic enzyme MIL-101?Fe?was characterized by SEM,X-ray energy spectroscopy?EDS?,FT-IR and X-ray diffraction?XRD?.The immobilization of anti-cTnI and BSA in the same way as in?2?by immobilizing MOF on NH₂-rGO/GCE by covalent bond,and obtaining new BSA/anti-cTnI/MIL-101?Fe?/NH₂-rGO/GCE.The sensing platform utilizes MIL-101?Fe?to catalyze hydrogen peroxide and utilizesMIL-101?Fe?highelectrocatalyticactivityforthefirsttime touse chronoamperometry for the detection and analysis of cTnI.The linear range was measured from 10 fg/mL to 0.1?g/mL with a detection limit of 3.1 fg/mL.And successfully used for the detection of serum samples and the recovery rate was 96%?103%.