Studies On Electrochemical Biosensors Based On Functionalized Nanoparticles As Enhanced Sensitivity Strategy

Electrochemically biosensor is a inter-discipline based on electrochemical analysis and biological technology, which consist of a biological recognition element (such as enzyme, antibody, etc) in intimate contact with a suitable transducer. In the fabricated process of biosensors, it is very important to choice the immobilized methods and materials of biomolecules. Therefore, a series of research focuses on the preparation of multi-functionalized nanomaterials, the construction of the electrochemical sensing interface and biomolecules immobilization. The detaij contents are as follows:1. Amine-terminated organosilica nanosphere functionalized prussian blue for the electrochemical detection of glucose.The mediated-enzyme biosensors have attracted much attention. However, there are still several challenges concerning immobilization of electron-shuttling mediators on the electrode surface since low molecular weight soluble mediators can easily diffuse away from the electrode surface into the bulk solution when the biosensor is used continuously, which would lead to significant signal loss and greatly affect the performance and lifetime of the biosensor. To circumvent this problem, the monomeric mediators are linked directly with the organic polymer or proteins system. First of all, we adopted a facile and bottom-up method to synthesize organosilica nanospheres. which contain rich amino-group. Then prussian blue was prepared in organosilica nanospheres suspension, which is donated as amine-terminated organosilica nanosphere functionalized prussian blue (OSiFPB). The OSiFPB compound could not only effectively prevent the leakage of the PB mediator during measurements, but also easily form stable film on the electrode surface with efficient redox-activity and excellent conductivity. Furthermore. with the negatively charged surface of OSiFPB. this film could be used as an interface to adsorb the positively charged gold nanoparticles (PGNs). which were prepared in organic solvents at relatively high concentrations with improved monodispersity compared to those prepared in aqueous solution. The presence of PGNs provided a congenial microenvironment for adsorbed biomolecules and decreased the electron transfer impedance. Finally, with glucose oxidase as a model biomolecular, the proposed sensor showed rapid and highly sensitive amperometric response to glucose and this immobilization approach effectively improved the stability of the electron transfer mediator. This work would be promising for construction of biosensor and bioelectronic devices.2. Determination of glucose using pseud o-bienzyme channeling based on sugar-lectin biospecific interactions in a novel organic-inorganic composite matrix.It is effective method to prevent the leakage of the mediate through chemical linking, but the step is complexity. A porous organic conducting polymer containing abundant amino groups (PTC-NH2) was coated on the surface of PB film, which could not only avoid the leakage of the PB efficiently, but also provide an interface of abundant amino-groups to further modifiability. At the same time, gold/platinum hybrid nanostructure supported on silica nanofibers (GP-SNFs) were synthesize to enhance the sensitivity. Finally, the glucose oxidase (GOD) was attached on the electrode surface through the strong biological affinity links between Con A and sugar chains intrinsically. The proposed biosensor possessed high sensitivity and stability for the detection of glucose. Several advantages of the obtained sensors should be highlighted. Firstly, it was found that this resulting nanomaterial exhibited a high electrocatalytic activity toward glucose, and a necessary pathway of electron transfer. Secondly, with the use of porous PTC-NH2, overcame the defect of mediator leakage successfully, which enhanced the stability and sensitivity of the bioassay. Thirdly, the pseudo-bienzymatic sensors could be operated at low working potentials, and interferences from other electroactive compounds are minimal in biological samples. The proposed method can be extended to a large group of enzymes to provide great promise platforms for biosensor and bioelectronics applications.3. Study of the biosensor based on Pt nanoparticles supported on carbon nanotubes and sugar-lectin biospecific interactions for the determination of glucose.The third generation biosensor is based on the direct electrochemistry of the enzyme without the introduction of the redox-mediator, so it is unnecessary to consider that its leakage caused pollution problem of the sample. However, the redox center of the majority of the enzymes is buried inside the protein matrix, which results in a slow process of direct electron transfer between the electrode and enzyme. To facilitate superior electron transport, the nanomaterial may be selectively placed in an optimum position between the redox center and the enzyme periphery. In this concept, Pt nanoparticles supported on carbon nanotubes (Ptnano-CNTs) were prepared in the presence of carbon nanotubes (CNTs), as "molecular wires" to enhance the electronic transfer. Thereafter, concanavalin A (Con A) was adsorbed onto the precursor film by the electrostatic force between positively charged chitosan and the negatively charged Con A. Finally, the multilayers of Con A/GOD films were prepared based on biospecific affinity of Con A and GOD via layer-by-layer (LBL) self-assembly technique. The results shows the proposed biosensor provides a remarkable synergistic action of the response current toward glucose. It also exhibits high sensitivity, low detection limit, excellent reproducibility. good and anti-interfering capability. Thus, the electrode has good application potential in glucose detection.4. Reagentless amperometric cancer antigen 15-3 immunosensor based on enzyme-mediated direct electrochemistry.A novel strategy was proposed for the construction of reagentless and mediatorless immunosensors based on the direct electrochemistry of glucose oxidase (GOD). Firstly, a composite material containing carbon nanotubes (CNTs) and core-shell organosilica@chitosan nanospheres was successfully prepared and cast on the glassy carbon electrode surface directly. Then. Pt nanoclusters (Pt NCs) as an electron relay were deposited on it to form the interface of biocompatibility and huge surface free energy for the adsorption of the first GOD layer. Subsequently, the second Pt NCs layer was deposited on the surface of GOD to capture CA 15-3 antibodies (anti-CA 15-3). Finally. GOD. as a blocking reagent instead of bovine serum albumin, was employed to block the possible remaining active sites of the Pt NCs and avoid the nonspecific adsorption. The immunosensor with the double layer GOD membranes as tracer performed excellent biocompatible and avoided the pollution of mediator molecules, as well as amplify the response of the antigen-antibody reaction was proposed. Such a detection of immunointeraction provided a new promising platform for clinical immunoassay.5. A new immobilized glucose oxidase approach on magnetic gold nanoshell surface via click chemistry and its direct electrochemistry.Immobilizing biomolecular on the sensing electrode surface is one of the most important points to be considered in the construction of amperometric biosensors. The reported methods have exhibited their own advantage and disadvantage. In this concept, we devoted to the method study of enzyme immobilization. In this study, a novel glucose biosensor was developed based on click reaction. Firstly, alkynyl-terminated multifunctional magnetic gold nanoparticles (alkynyl-Mag-GNSs) consisting of gold nanoshells, carboxymethylated chitosan inner layer, and magnetic core were synthesized, then were grafted on the synergistic beneficial characteristics interface of carboxyl-modified graphene oxide, ionic liquids and chitosan modified electrodes. Finally, azido-glucose oxidase (azido-GOD) was covalent immobilized onto the formed films by click reaction. Compared to the conventional methods, the biosensor exhibited more sensitivity, a lower detection limit, and a wider linear range to glucose detection. Overall, this work provided a new avenue for electrochemical investigation of enzyme immobilization.