Amperometric Enzyme Biosensors Based On Nanocomposites

Since the development of the first biosensor in 1962 based on the biology sensing technologies, biosensor has been received considerable attention and widely applied in various fields including clinical diagnosis, environment monitoring, food industry, and so on. Up to now, it is a field combining several subjects such as biology, physics, chemistry, medicine, pharmaceutical and electro technology.Recently, with rapid development of nano technique, nano material including nanoparticles, nanolines and nanotubes etc have been extensively utilized in biosensor. It not only brings special characteristics, but also developed a wide prospect in biosensor. If the nonmaterial used in preparing of biological sensors, due to its size effect, surface effect, the modified electrodes will exhibit high electro catalyze, reduce the over potential, the possible interference and the background current. Simultaneously, if the nonmaterial modified onto the electrode, it will improve a micro environments with high biological active and stability, enhance the volume of immobilized enzyme, as well as accelerate the electron transfer rate. Based on this, the main research works in this paper had constructed several biosensors based on the nanomaterial, there have a great improvement on the performance such as sensitivity and service life.The main works are included as follows:1. Hydrogen peroxide sensor based on horseradish peroxidase immobilized on an electrode modified with DNA-L-cysteine-gold-platinum nanoparticles in polypyrrole filmA third-generation mediator-free hydrogen peroxide biosensor was fabricated by combining electrodeposition and self-assembly techniques. In this strategy, Au-Pt hybrid nanoparticles were electrodeposited on a film of polypyrrole, and L-cysteine was assembled to their surface by exploiting the strong affinity between mercapto groups and nanoparticles. Then, DNA and horseradish peroxidase were respectively self-assembled on the surface of the electrode. The resulting electrode was characterized by impedance spectroscopy, and the electrode surface (without enzyme) was characterized by scanning electron microscopy. The response of the sensor towards hydrogen peroxide, as investigated by cyclic voltammetry and chronoamperometry, is linear between 4.9μmol·L-1 to 4.8 mmol·L-1, with a detection limit of 1.3μmol·L-1(at an S/N of 3). The apparent Michaelis-Menten constant(KMapp) is 0.69 mmol·L-1.2. Amperometric glucose biosensor based on Prussian blue@multi-wall carbon nanotubes composite and hollow PtCo nanochainsA new glucose biosensor was developed based on immobilizing glucose oxidase (GOD) on prussian blue@multi-wall carbon nanotubes (PB@MWNTs) composite and hollow PtCo (H-PtCo) nanochains modified electrode. The successful fabrication of the PB@MWNTs composite which were synthesized with MWNTs as a template and Fe(Ⅲ)-reducer was characterized by UV-vis absorption spectroscopy, Fourier transform infrared (FTIR) spectrometry and transmission electron microscopy (TEM). The hollow PtCo nanochains were also characterized by TEM and X-ray photoelectron spectroscopy (XPS). The response of the biosensor towards glucose under the optimized conditions, as investigated by chronoamperometry. is linear from 3.0μmol·L-1 to 3.6 mmol·L-1,with a low detection limit of 0.85μmol·L-1 (S/N=3) and a high sensitivity 21 mAmol·L-1cm-2. The apparent Michaelis-Menten constant (KMapp) is 2.36 mmol·L-1. Moreover, the biosensor exhibits strong anti-interferent ability, good reproducibility and excellent stability.3. A glucose biosensor based on chitosan-Prussian blue-multiwall carbon nanotubes-hollow PtCo nanochains formed by one-step electrodepositionA simple one-step electrodeposition method is described to fabricate chitosan-Prussian blue-multiwall carbon nanotubes-hollow PtCo nanochains (CS-PB-MWNTs-H-PtCo) film onto the gold electrode surface, then glucose oxidase (GOD) and Nafion were modified onto the film subsequently to fabricate a glucose biosensor. The morphologies and electrochemistry of the composite were investigated by using Fourier transform infrared (FTIR) spectrometry, scanning electron microscopy (SEM) and electrochemical techniques including cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), respectively. The specific surface area and electroconductivity have improved after introduce the MWNTs and H-PtCo. And the same time, evaluated the electrocatalytic activity of the hollow and solid PtCo nanoparticle, the result revealed that the biosensor applied hollow PtCo had a better chronoamperometric response for glucose oxidation than using solid PtCo nanoparticles. The performances of the biosensor have been investigated by chronoamperometry method under the optimized conditions. This biosensor showed a linear response to glucose range from 1.5μmol·L-1 to 1.12 mmol·L-1 with a detection limit of 0.47μmol·L-1 (S/N=3), a high sensitivity of 23.4μAmmol·L-1cm-2, and a fast response time. The apparent Michaelis-Menten constant (KMapp) was 1.89 mmol·L-1. Since electrodeposition method can control the film thickness through the deposition time, and it very quick and simple, the sensor has good stability and reproducibility.