Preparation Of Chitosan And Nanocomposites And Their Application To Biosensor

1. In order to avoid mass transport limitation of analytes in films based biosensors, micro/macroporous films are usually employed. In this paper, a simple and controllable electrodeposition method was described to fabricate a homogeneous porous chitosan/single-walled carbon nanotubes (CS/SWCNTs) nanocomposite film. The thickness of the nanocomposite film can be controlled through the change of concentration of SWCNTs, SiO₂ nanoparticles, chitosan solution and deposition time. Glucose oxidase (GOD) served as a model enzyme to demonstrate the potential application of the macroporous structured films in fabrication of amperometric glucose sensor with negligible mass transport limitation. The glucose biosensor was constructed by entrapping GOD molecules to the porous SWCNTs/CS nanocomposite film using glutaraldehyde as a cross-linker. The fabricated biosensor with three-dimension porous structures can provide biocompatible microenvironment for maintaining the bioactivity of the immobilized enzyme, enhance mass transport of glucose substrate, and increase the enzyme loading. Therefore, the present biosensor exhibits a rapid response (＜5s), a wide linear range (10μM to 35mM) and a low detection limit of 2.5μM for the detection of glucose.2. A composite film via sequential deposition of Prussian Blue and chitosan/silicon dioxide nanoparticle was constructed on a bare glass carbon electrode using electrochemical methods. After etching silicon dioxide nanoparticle, an three-dimensional porous chitosan film with homogeneous pore size provides a suitable biosensing matrix due to its good biocompatible microenvironment, high real surface area and porosity which is propitious to load more glucose oxidase. The resulting glucose biosensor under optimal conditions showed high sensitivity, long-term operational stability, fast response time and wide-range detection.3. It was reported that single walled carbon nanotube (SWCNTs) was functionalized with the Ferrocene (Fc) by a noncovalent method to form Fc/SWCNTs nanocomposite, The Fc/SWCNTs was characterized by transform infrared (FTIR) and the results show that Fc can rapidly and effectively be adsorbed to the surface of SWCNTs with high stability. Moreover, it is shown that the dispersion ability of Fc and SWCNTs in aqueous solution has a significantly improvement after SWCNTs functionalized with Fc. Glucose oxidase (GOD) was selected as a model enzyme to fabricate a biosensor based on the CS/Fc/SWCNTs composites. The presence of CS/Fc/SWCNTs can provide suitable microenviroment for GOD and also retain its activity. The fabricated glucose biosensor presents a linear range from 0.1mM to 2.6mM (glucose). The response time of stable current was less 3 S and the detection limit was 6.8μM.The apparent Michaelis-Menten constant (K_M^app) for the biosensor was 2.28mM.4. Ferrocene molecular was successfully adsorbed on the surface of the SWCNTs by a noncovalent method to form Fc/SWCNTs nanocomposite, The Fc/SWCNTs was characterized by UV-Vis and the results show that Fc can rapidly and effectively be adsorbed to the surface of SWCNTs with high stability. The composite film was used to immobiliz horseradish peroxidase (HRP) on a grass carbon electrode. The effect of experiment variables such as the nanocomposites concentration, the enzyme loading, the working potential and pH of the measured solution were investigated for the optimum analytical performance by an amperometric method. The presence of the SWCNTs improved the conductivity of the composite, the matrix showed a biocompatible microenviroment for retaining the native activity of the entrapped HRP and a very fast mass transport to the substrate. The biosensor provided a linear response to hydrogen peroxide over a concentration range of 1μM to 2.3mM with a detection limit of 0.68μM and a K_M^app value of 0.9mM. The sensor effectively eliminated the interference from most of coexistent substances such as ascorbic acid. This biosensor possessed good analytical performance and storage stability.