The Application And Study Of Electrochemical Biosensors Based On Nanomaterials

Nanomaterials have special structure, which results in serials of interesting chemical and physical properties. In our work, the nanomaterials are used to construct the electrochemical biosensors by means of the combination of biochemistry and electrochemical methods and we aim to develop new types of biosensors based on nanomaterials for the purpose of improving the long-term stability and the higher sensitivity of biosensors. The details are summarized as follows:(1) A new porous sorbent for waste water treatment of meta lions was synthesized by covalent grafting of molecularly imprinted organic-inorganic hybrid on silica gel. With sucrose and polyethylene glycol 4000 (PEG 4000) being synergic imprinting molecules, covalent surface coating on silica gel was achieved by using polysaccharide-incorporated sol–gel process starting from the functional biopolymer, chitosan and an inorganic epoxy-precursor, gamma-glycid oxypropyltrimethoxy siloxane (GPTMS) at room temperature. The prepared porous sorbent was characterized by using simultaneous thermogravimetry and differential scanning calorimeter (TG/DSC), scanning electronmicroscopy (SEM), nitrogen adsorption porosimetry measurement and X-ray diffraction (XRD). Copper ion, Cu2+, was chosen as the model metal ion to evaluate the effectiveness of the new biosorbent in wastewater treatment. The influence of epoxy-siloxane dose, buffer pH and co-existed ions on Cu2+ adsorption was assessed through batch experiments. The imprinted composite sorbent offered a fast kinetics for the adsorption of Cu2+. The uptake capacity of the sorbent imprinted by two pore-building components was higher than those imprinted with only a single component. The dynamic adsorption in column underwent a good elimination of Cu2+ in treating electric plating wastewater. The prepared composite sorbent exhibited high reusability. Easy preparation of the described porous composite sorbent, absence of organic solvents, cost-effectiveness and high stability make this approach attractive in biosorption.(2) A feasible approach modified nanoSiO2 particles on the Au electrode surface to construct a novel DNA biosensor is described. On the basis of Schiff base reaction between the -CHO groups and -NH2 groups, cysteamine and glutaraldehyde was used as covelent attachment cross-linkers. The covalent attachment processes were followed and confirmed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The hybridized dsDNA biosensor was studied by Different Pulse Voltammetry (DPV). From the analysis of voltammetric signals, the linear response range of the biosensor is 6×10-8 M ~ 8×10-10 M, the detection limit is 3×10-10 M. In addition, the sensitivity biosensor is easily manipulated and exhibited good stability and long-term life.(3) In this article, colloidal gold nanoparticles (Au NPs) and carboxyl group-functionalized CdS Nanoparticles (CdS NPs) were immobilized on the Au electrode surface to fabricate a novel electrochemical DNA biosensor. Both Au NPs and CdS NPs, well known to be good biocompatibile and conductive materials, could provide larger surface area and sufficient amount of binding points for DNA immobilization. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) experiments were performed to follow the whole electrode fabrication process. DNA immobilization and hybridization were characterized with differential pulse voltammetry (DPV) by using [Co(phen)2(Cl)(H2O)]Cl?2H2O as an electrochemical hybridization indicator. With this approach, the target DNA could be quantified at a linear range from 2.0×10-10 to 1.0×10-8 M, with a detection limit of 2.0×10-11 M by 3σ. In addition, the biosensor exhibited a good repeatability and stability for the determination of DNA sequences.(4) A novel and sensitive sandwich electrochemical biosensor based on the amplification of magnetic microbeads and Au nanoparticles (NPs) modified with bio bar code and PbS nanoparticals was constructed in the present work. In this method, the magnetic microspheres were coated with 4 layers polyelectrolytes in order to increase carboxyl groups on the surface of the magnetic microbeads, which enhanced the amount of the capture DNA. The amino-functionalized capture DNA on the surface of magnetic microbeads hybridized with one end of target DNA, the other end of which was hybridized with signal DNA probe labelled with Au NPs on the terminus. The Au NPs was modified with bio bar code and the PbS NPs was used as a marker for identifying the target oligoncleotide. The modification of magnetic microbeads could immobilize more amino-group terminal capture DNA, and the bio bar code could increase the amount of Au NPs that combined with the target DNA. The detection of lead ions performed by anodic stripping voltammetry (ASV) technology further improved the sensitivity of the biosensor. As a result, the present DNA biosensor showed good selectivity and sensitivity by the combined amplification. Under the optimum conditions, the linear relationship with the concentration of the target DNA was ranging from 2.0×10?14 M to 1.0×10?12 M and a detection limit as low as 5.0×10?15 M were obtained.(5) A novel nanocomposite material of muti-walled carbon nanotubes (MWCNTs) and room-temperature ionic liquid (RTIL) N-butylpyridinium hexafluorophosphate (BPPF6) was explored and was used to construct a novel Microperoxidase-11 (MP-11) biosensor for the determination of H2O2. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to characterize the performance of the biosensor. Under the optimized experimental conditions, H2O2 could be detected in a linear calibration range of 0.5×10-7 ~ 7.0×10-7 M with a correlation coefficient of 0.9949 (n = 9) and a detection limit of 3.8×10-9 M at 3σ. The modified electrodes displayed excellent electrochemical response, high sensitivity, long-term stability, good bioactivity and selectivity.