Development Of Nanoparticle Mimic Enzyme-based Biomimetic Sensor And Applications

Due to the high catalytic efficiency and substrate specificity of natural enzymes, they were widely used in the medicine, chemical industry, food processing and agriculture. Unfortunately, the catalytic activity of the natural enzymes is sensitive to environmental conditions. Furthermore, the preparation and purification of natural enzymes are usually expensive. It has a great significance to exploit a new material, which shows the enzymes catalytic activity similar to natural enzymes. With the development of nanotechnology, nanomaterials are widely applied in several fields owing to their surface effect, quantum size effect. Their catalytic activity has been neglected for a long time. Since Yan report the magnetic iron oxide nanoparticles possess peroxidase-like catalytic activity in 2007, some oxide nanomaterials, carbon nanometerials, noble metal nanomaterials displayed intrinsic mimetic activity. Compared with natural enzyme, enzyme mimetics have several advantages such as controlled synthesis in low-cost, high stability against stringent conditions. This study concentrated on the construction of new nanomaterials peroxidase mimetics, development of composite nanomaterials for further enhancing the catalytic activity and analytical applications of peroxidase mimetics. The main research is as follows:(1) The Zn Fe2O4@MWNTs was synthesized by a simple method, Which could catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine to produce blue color in the presence of H2O2. That demonstrated Zn Fe2O4@MWNTs possessed peroxidase-like catalytic activity. The catalytic performance of Zn Fe2O4@MWNTs was higher than Zn Fe2O4 due to the high electrical conductance of MWNTs. A new paper-based colorimetric immunosensor for the detection of carcinoembryonic antigen(CEA) was developed based on the intrinsic peroxidase activity of Zn Fe2O4@MWNTs. The immunosensor platform was based on the assembly approach formed by depositing of chitosan and porous gold onto filter paper and entrapping the primary antibodies on the layers. Secondary antibodies were assembled on the surface of functionalized Zn Fe2O4@MWNTs. Detection was achieved by measuring the color change when the concentrations of CEA were different. This method was simple for CEA detection with a linear range from 0.005 to 30 ng×m L-1 and a detection limit of 2.6 pg×m L-1. Such an equipment-free immunoassay had great potential in resource-limited environments.(2) The nanohybrid Zn Fe2O4-Graphene quantum dots(Zn Fe2O4/GQDs) was developed by assembling the GQDs on the Zn Fe2O4 through a photo-Fenton reaction. Compared with traditional enzyme labels, the mimic enzyme Zn Fe2O4/GQDs exhibited many advantages such as environment friendly and better stability. Zn Fe2O4/GQDs could produce a large current towards the reduction of H2O2 for signal amplification. To fabricate a high-performance protocol, the glassy carbon electrode was successively modified with aminated graphene and Pd nanowires, which improved the electronic transfer rate. Under the optimal conditions, the approach provided a wide linear range from 10-16 to 5×10-9 M and low detection limit of 6.2×10-17 M. The remarkable high catalytic capability could allow the nanohybrid to replace conventional peroxidase-based assay systems. The new, robust and convenient assay systems can be widely utilized for the identification of other target molecules.(3) In this paper, Pt Pd alloy decorated reduced graphene oxide(RGO/Pt Pd) was synthesized by a simple and green method. The RGO/Pt Pd could catalytic oxidation of H2O2 to form O2 and O2 acted as the coreactant of peroxydisulfate, could greatly amplify the ECL signal. Moreover, the RGO/Pt Pd exhibited higher catalytic activity compared to the RGO/Pt or RGO/Pd catalyst because of the synergetic effects of Pt and Pd and the enhanced electron transfer of RGO. Based on this, a highly sensitive and selective label-free elect use rochemiluminescence aptasensor for detection of adenosine triphosphate was designed.(4) One-dimensional Pt Pd porous nanorods(Pt Pd PNRs) were successfully synthesized through a bromide-induced galvanic replacement reaction between Pd nanowires and K2 Pt Cl6. The Pt Pd PNRs were porous and alloy-structured with Pt/Pd atomic ratio up to 1:1 which demonstrated by spectroscopic methods. We had also proved that the nanorods could function as peroxidase mimetics that exhibited much higher affinity to H2O2 over other peroxidase mimetics. On the basis of the peroxidase-like activity, we used the Pt Pd PNRs as a signal transducer to develop a novel and simple colorimetric method for the study of the flux of H2O2 release from living cell. The method developed a new platform for a reliable collection of information on cellular reactive oxygen species release. And the nanomaterial could bed as a power tool for a wide range of potential applications in biotechnology and medicine.