Comparative behavior of glucose oxidase and oxalate oxidase immobilized in mucin/chitosan hydrogels for biosensors applications

The analytical response of amperometric glucose electrodes was explained in the framework of the properties of hydrogels with different muc/chit ratio at pH = 7.00 used as immobilization matrix for glucose oxidase. The continuous increase in the sensitivity of the electrodes with the amount of chitosan was attributed to a more efficient crosslinking without affecting the enzyme activity. The results were compared with those obtained using the same matrices to immobilize Oxalate Oxidase at pH = 2.85 where it has the highest activity. A maximum sensitivity at muc/chit 70/30 ratio for these oxalate electrodes was observed. Decrease in permeability of negatively charged oxalate with the chitosan content in the matrices, in spite of the high partition coefficient, explains the analytical differences with glucose electrodes. Swelling and viscoelasticity of the hydrogels allowed to asses the importance of a hydrophilic environment for the enzyme in both cases.