The Preparation And Application Of Electrochemical Biosensors Modified With Novel Nanocomposite Materials

Biosensors have wide applications in clinical,environmental,food and other fields,and the researches on biosensors are ongoing very active in recent years.The development of suitable materials to realize the efficient immobilization of the biomolecules on the surface of the electrode is very important for the wide application of biomolecules in biochemical analysis.Therefore,the biocompatibility and stability of the loaded materials great impact on the performance of the resultant sensor.Nanomaterials have unique catalytic activity and good biocompatibility,which provide a better prospect for the development of sensors.The application of nanomaterials in the construction of biosensors can significantly improve the performance of the prepared sensor.With the high catalytic activity of various nanomaterials,a series of new enzyme sensors were explored.Nanomaterials with different morphologies were synthesized and assembled on the electrode surface to develop novel glucose biosensors and phenol biosensors.The main contents are as follows:(1)Tyrosinase(Tyr)/gold nanoparticles(Au)-Zinc Oxide films(ZnO)/multi-walled carbon nanotubes(MWCNTs)composites(Tyr/Au-ZnO/MWCNTs)were prepared and utilized in the sensing of Tyr substrates(phenol and catechol)and Tyr inhibitor(atrazine)sensing applications.Au-ZnO/MWCNTs composites was synthesized by one-step electrochemical reduction of HAuCl4 and Zn(NO3)2 with MWCNTs as substrate material.The electrochemical behavior of phenol,catechol and atrazine on modified electrode was studied.The prepared Tyr/Au-ZnO/MWCNTs sensor exhibits a sensitivity up to 49.4 mA mM-1 cm-2 in the linear range(LR)of 0.01-2.22 ?M for the sensing of phenol,with a limit of detection(LOD)as 1.3 nM observed,the detection sensitivity for catechol is 40.5 mA mM-1 cm-2 in the LR of 0.01-3.27 ?M,and the LOD was 2.6 nM.The sensitivity of the resultant sensors to phenol and catechol was significantly higher than most of reported sensors.At the same time,based on the inhibitive effect of atrazine on Tyr activity,the prepared sensor can also realize the rapid and sensitive detection of atrazine.The results show that atrazine has a good current response on the modified electrode,with the LR of 0.5?50 nM and a LOD as low as 0.5 nM observed.In addition,the enzyme sensor has good anti-interference ability and stability,and is expected to be more widely used in the detection of environmental pollutants.(2)Poly dimethyl diallyl ammonium chloride(PDDA)is a kind of cationic water-soluble quaternary ammonium salt electrolyte.With the combination of the reduction effect of PDDA and the high conductivtity and high specific surface area of 3D graphite network(Co-N-GNWs),novel PDDA-Au-Co-N-GNWs nanocomposites were prepared for the first time with one-step hydrothermal method.The Pt/PDDA-Au-Co-N-GNWs/Au electrode was obtained by casting the prepared PDDA-Au-Co-N-GNWs on Au electrode surface,and then the modified electrode was immersed in 1 mM H2PtCl6 solution and potentialstated at-0.2 V for 300 s.Glucose oxidase(GOx)was adsorbed on the resultant Pt/PDDA-Au-Co-N-GNWs/Au electrode surface to construct GOx-based sensor.The experimental results show that the sensor exhibiting a glucose detection sensitivity up to 149 ?A mM-1 cm-2 in the LR of 0.01v16 mM,and a LOD of 1 ?M.The enzyme electrode also has a good second generation biosensor performance,so it exhibits excellent performance when it is used as a biological anode in developing biofuel battery.Consequently,the monopole glucose biofuel cell(BFC)constructed with the GOx/Pt/PDDA-Au-Co-N-GNWs/Au electrode as the biological anode was demonstrated experimentally to be of good performance in biofuel cell.(3)Enzyme immobilization was carried out by combining physical adsorption and covalent crosslinking techniques.Tyr was firstly adsorbed on MWCNTs-Au-Fe304-NH2 composite by electrostatic interaction.Then,another film of Tyr is firmly fixed on the composites via the covalent crosslinking effect of GA.In order to obtain the highest sensitivity for the resultant biosensor,the optimization of the enzyme concentration,the pH of adsorption solution,adsorption time,GA and Fe304-NH2 concentration and the immobilization conditions were studied.Tyr-based biosensor was successfully prepared and used for the detection of phenolic pollutants and heavy metal ions.The sensitivity of the prepared sensor for phenol detection is as high as 1883 ?A mM-1 cm-2 in the LR of 0.2?24 ?M,and the LOD is 0.03 ?M.The sensitivity of the resultant sensor to catechol is 1643 ?A mM-1 cm-2 in the LR of 0.2?26 ?M,and the LOD is 0.05 ?M.