An amperometric glucose biosensor based on the oxygen electrode principle has been developed. Polycarbonate membranes (pore size from 0.01 μm to 0.4 μm) were used as external glucose diffusion membranes in order to obtain direct proportionality of the amperometric signal to the substrate concentration in the entire physiological range. The commercially available membranes - standard (hydrophilic, treated with Polyvinylpyrrolidone/(PVP)) and PVP-free membranes were compared with membranes coated with a silicone elastomer (silastic). Spindrop coating technique was used to create stable, adhesive coatings over the polycarbonate membranes. These coated membranes achieved diffusion control of the glucose flux such that the amperometric signal of the biosensor was linearly proportional to the substrate concentration up to 16 mM glucose. The membrane parameters were optimized by varying the parameters of the coating process-spin rate of the membrane rotation and the silastic/water ratio in the coating emulsion.