Physicochemical properties of a mucin/chitosan matrix used for the development of an oxalate biosensor

Immobilization conditions of biomolecules play an important role in a biosensor performance. In this paper the response of amperometric electrodes for oxalate is related with some physicochemical properties of the matrices where oxalate oxidase was immobilized. Swelling indexes, partition coefficients and permeability of oxalate in mucin/chitosan matrices in a pH = 2.85 succinic acid solution were measured. These properties were also determined in the 70/30 mucin/chitosan matrix in solutions containing succinic acid and sulfate or chloride anions at the same pH value. The results indicate that the sensitivity of the biosensors is mainly determined by the swelling index of the matrix. High slopes of the calibration curves of the electrodes were obtained with highly swollen matrices indicating the importance of a hydrophilic environment for a good enzymatic response.