Studies on a potentiometric urea biosensor based on an ammonia electrode and urease, immobilized on a γ-aluminum oxide matrix

A potentiometric biosensor for urea is developed, based on the immobilization of urease on a γ-Al2O3 substrate without using bovine serum albumin-glutaraldehyde as usual. The large specific surface area and porous structure of the γ-Al2O3 particle result in high enzyme loading, and the urease entrapped in this matrix is stable. FT-IR spectra were employed to give insight into the intermolecular interaction between the substrate and urease. The point of zero charge calculated from mass titration was used to explain the influence of pH on immobilization. The developed biosensor is sensitive to urea in the linear range 3.0 × 10−5-1.4 × 10−2 M, with a detection limit of 10 μM. Some studies on γ-Al2O3-urease were reported and the characteristics of the sensor were examined. The novel urea sensor was also successfully applied for the actual measurement of urea in urine.