THE CHARACTERIZATION OF LIPOSOMAL GLUCOSE-OXIDASE ELECTRODES FOR THE MEASUREMENT OF GLUCOSE

Many biosensors have been described for the measurement of glucose in order to monitor diabetic patients. Glucose oxidase has been used comm only in the construction of glucose sensors but the performance of thi s enzyme is limited by enzyme saturation kinetics, which restrict the measurement of clinically relevant glucose concentrations (0 to 25 mM) . Diffusion limiting membranes have been described that result in the exposure of the enzyme to lower concentrations of glucose than are pre sent in the bulk test solution. Recently a liposomal enzyme electrode was reported whereby glucose oxidase was encapsulated within liposomes so that the lipid bilayer was the diffusion limiting membrane. It was shown that the electrode response was defined by the lipid constituen ts of the liposome, and that a linear response to glucose could be ach ieved up to 40 mM. This paper describes research undertaken to improve the methods of production of a liposomal enzyme electrode. Improved i mmobilization of liposomes is demonstrated with the use of poly-L-lysi ne solution. The variation in electrode response with respect to the a mount of glucose oxidase liposomally encapsulated is reported. The new method allows a greater number of sensors to be produced from a singl e batch of liposomes. Studies also show the biofouling effects of the lipid constituents of ruptured liposomes on the response of the electr ode to glucose over time.