The Electrochemical Biosensor Based On MOFs

As a new type of biosensor,the electrochemical biosensor has the important application in the fields of disease diagnosis,drug analysis and environmental monitoring.The electrode materials,as one of the core components of electrochemical sensors,play a key role in the progress of various electrochemical sensors because the electrochemical properties and signal conversion on the electrode surface can directly affect the performance of the sensor.In addition,metal organic frameworks?MOFs?can be utilized as good electrocatalyst for electrochemical reactions due to its large surface area,highly porosity,rich and controllable framework structure,together with the electrochemical activity of metal ions.However,in order to make up for the poor stability of MOFs in aqueous solution and enhance its electrocatalytic ability,other active materials were usually applied for combining with MOFs to achieve synergistic effects.In this work,a variety of electrochemical biosensors based on MOFs were prepared and successfully used to determine some biomolecules.The important parts in this work are as follows:?I?In this part,Cu-MOF-199 was used as the basic modification material.In order to improve the stability of Cu-MOF-199 in aqueous solution and further enhance the electronic conductivity,we introduced single walled carbon nanotubes?SWCNTs?as auxiliary material.Cyclic voltammetry?CV?and differential pulse voltammetry?DPV?were carried out for the simultaneous determination of ascorbic acid?AA?,dopamine?DA?and uric acid?UA?at Cu-MOF-199/SWCNTs/GCE.The experimental results showed that the modified electrode possessed excellent electrocatalytic activity for detecting AA,DA and UA simultaneously.The linear ranges of AA,DA and UA were obtained as 1.0-909?mol·L^-1,1.0-741?mol·L^-1 and5.0-99?mol·L^-1 with corresponding detection limits of 0.59?mol·L^-1,0.06?mol·L^-1and 0.21?mol·L^-1,respectively.?II?In view of the characteristic of the peroxidase-like acticity for hemin and the electrochemical activity for porous MOFs,the composite named Hemin@MOF,which consisted of hemin and Cu-MOF-199,was synthesized.CV,DPV and orther electrochemical methods were applied for investigating the electrochemical behavior of H₂O₂ on Hemin@MOF/GCE.The as-prepared Hemin@MOF/GCE showed the high sensitivity and good selectivity for H₂O₂.In order to expand the application of the composite,the electrocatalytic activity of Hemin@MOF toward H₂O₂ was used as an electrochemical signal in DNA electrochemcial sensor.In addition,the carboxyl functionalized graphene?CFGR-COOH?was used to immobilize the probe DNA.And finally the quantitative analysis of sequence-specific DNA was carried out at the designed electrochemical DNA biosensor.The biosensor showed an excellent performance with the wide range from 1.0×10^-15 mol·L^-1 to 1.0×10^-6 mol·L^-1 and the lower detection limit down to 6.9×10^-16 mol·L^-1.?III?In order to explore the impacts of different organic ligands or framework structures on the performance of electrochemical sensors based on MOFs,a series of electrochemical sensors based on MIL-53/GCE,MIL-100/GCE and MIL-101/GCE were prepared.CV and DPV were used to test the electrocatalytic performance of those electrochemical sensors toward the redox reaction of H₂O₂.The results showed that the three electrochemical sensors possessed excellent electrocatalytic activity.The stability of the MIL-53/GCE is the best with 99.9%oxidation current of H₂O₂ retained after 30 days;the detection limit of MIL-100/GCE is the lowest with0.01?mol·L^-1;while the linear range of the MIL-101/GCE for H₂O₂ is the widest from 1.0?mol·L^-1 to 3707?mol·L^-1.In conclusion,the as-prepared modified electrodes have good prospects in the pratical application of H₂O₂.?IV?In order to take advantage of the significant electrocatalytic effect of metals and their oxides toward glucose,the composite Cu/Ni-BTC was synthesized by using1,3,5-benzenetricarboxylic?H₃BTC?as the ligand.Then,the Cu/Ni-BTC was carbonized at high tempreature to obtained Cu-Ni@C_T and further used for quantitative analysis of glucose under alkaline conditions.The results indicated that the constructed Cu-Ni@CT/GCE exhibited good linear relationship with the glucose concentration in the range of 0.1-2200?mol·L^-1 and the detection limit was 0.06?mol·L^-1.