Modeling of a cationic glucose-sensitive membrane with consideration of oxygen limitation

A theoretical model concerning simultaneous diffusion and reaction was developed to describe the steady state behavior of a cationic glucose-sensitive membrane with consideration of oxygen limitation and swelling-dependent diffusivities of involved species inside the membrane. Donnan equilibrium was used to find concentrations of buffer ions inside the membrane. The profiles of species concentrations, pH, polymer volume fraction and solute diffusivity inside the membrane were predicted by the model in response to step changes of glucose concentration in the external solution. The influence of various factors on the responsiveness of the membrane was analyzed using the model. The results indicated that the membrane response could be amplified by optimizing loading of glucose oxidase or increasing the density of charged groups in the polymer. The glucose sensitivity of the membrane in a citrate buffer was found to be higher than that in a phosphate buffer.