Baoyan Wu

Preparation of chitosan/glucose oxidase nanolayered films for electrode modification by the technique of layer-by-layer self-assembly

Enzyme immobilization onto the electrode surface is a critical step in assembling amperometric biosensors. Recently, layer-by-layer (LBL) techniques have been developed for the immobilization of enzyme on various matrices [1, 2]. The multilayer films of various proteins alternating with synthetic or natural polyanions and polycations were prepared to fabricate biosensors by this novel technique [3–10]. The glucose oxidase is widely used for the detection of glucose in body fluids and in removing residual glucose and oxygen from beverages and foodstuffs. The glucose oxidase (β-D-glucose: oxygen 1-oxidoreductase, EC1.1.3.4) catalyses the oxidation of β-D-glucose to D-glucono1,5-lactone and hydrogen peroxide, using molecular oxygen as the electron acceptor (as Fig. 1 shows). The chitosan, an N-deacetylated derivative of chitin, is a naturally occurring biopolymer found in the exoskeleton of crustaceans, in fungal cell walls, and in other biological materials [11]. It has an unusual combination of properties [12], which includes excellent membrane-forming ability towards water, good adhesion, nontoxicity, high mechanical strength, especially good biocompatibility and susceptibility to chemical modification due to the presence of reactive amino and hydroxyl functional groups. In recent years, the artificial polyelectrolytes have mainly been used to immobilize various enzymes by LBL techniques [13]. Chitosan was generally used to immobilize various enzymes by techniques such as sol-gel [14], crosslinking [15] etc. The LBL techniques could control the enzyme loading by changing the adsorption cycles with fewer side effects on glucose oxidase while the chitosan was used for preparing LBL films, which was expected to be an alternative method for the chitosan to immobilize glucose oxidase. In this paper, we report the first attempt to prepare chitosan/GOx nanolayered films for electrode modification by the technique of layer-by-layer selfassembly. In situ gravimetric measurement of quartz crystal microbalance (QCM, QCA917, EG&G) was applied to investigate the assembly process. An AFM (Nanoscope IIIa, Digital Instruments) was used to characterize the surface morphology. The electrochemical

An optical biosensor for kinetic analysis of soluble Interleukin-1 receptor I binding to immobilized Interleukin-1α

We report here the development of an optical biosensor based on the resonant mirror for kinetic analysis of soluble Interleukin-1 receptor I (sIL-1R I) in solution binding to immobilized Interleukin-1alpha (IL-1alpha). IL-1alpha was immobilized through its surface amine groups via amide bonds with the carboxyl groups of the carboxymethyl dextran (CMD) on cuvette surface. The interaction of sIL-1R I and IL-1alpha was monitored in real time. Evaluation of the binding curves allowed the analysis of the binding kinetics. The linear range of sIL-1R I in solution was over a range of 100-1600nM (R=0.9962). Equilibrium dissociation constant (K(D)) was derived by Scatchard plot analysis for sIL-1R I binding to immobilized IL-1alpha. For this assay, the K(D) was 2.6x10(-6)M. The CMD cuvette modified by IL-1alpha was successfully regenerated using 10mM HCl, and the same sensing surface was used repeatedly for the interaction analysis.

Effects of propyl gallate on interaction between TNF-alpha and sTNFR-I using an affinity biosensor

AbstractAim:To study the effects of propyl gallate on the interaction of tumor necrosis factor-α (TNF-α) with its soluble receptor, sTNFR-I.Methods:Interactions between TNF-α and sTNFR-I were analyzed using an IAsys biosensor. sTNFR-I was immobilized on the carboxymethyl dextran (CMD) surface of the IAsys biosensor cuvettes, and TNF-α preincubated with different concentrations of propyl gallate was added to the cuvettes. The resonant angle shift caused by the binding between TNF-α and sTNFR-I was then recorded.Results:sTNFR-I was immobilized on the CMD surface at a density of 2.76 ng/mm2. TNF-α then bound the immobilized sTNFR-I specifically, and propyl gallate was able to enhance the binding between TNF-α and sTNFR-I in a dose-dependent manner.Conclusion:The binding between TNF-α and sTNFR-I is one of the targets that propyl gallate can act on in vivo. The IAsys biosensor offers a new clue as to the study on the mechanisms of action of propyl gallate.