Polypyrrole-glucose oxidase biosensor. Effect of enzyme encapsulation in multilamellar vesicles on analytical properties.

In this paper, we present the analytical properties of a new type of polypyrrole-based, enzymatic amperometric biosensor. It is produced by encapsulating the enzyme, glucose oxidase (GOx), into onion-type multilamellar vesicles (MLV). We compare its properties to those of a classical GOx-polypyrrole biosensor. When MLV are used to embed GOx in polypyrrole (PPy), GOx behaves as a Michaelis-Menten enzyme. Without MLV, a deviation to the Michaelis-Menten behaviour is observed for high glucose concentrations. Kinetics parameters of both types of biosensors are studied as a function of the surface charge synthesis: GOx encapsulation induces a 200-fold increase of the apparent maximal current (I(m)(app)) and a 10-fold increase of the apparent Michaelis constant (K(m)(app)). Sensitivity is improved by a factor of 5. GOx is also shown to be less sensitive to inhibiting ions (Cl(-)) when MLV are used. A residual amperometric response of 43% instead of 3% is measured. Finally, the long-term stability of biosensors is improved by the GOx encapsulation. All these results are partially explained by our previous study on the morphology of PPy films fabricated with GOx encapsulated into onion-type MLV (Olea et al., 2007).