Real-time monitoring of invertase activity immobilized in nanoporous aluminum oxide.

In this work, we demonstrate the activity of enzyme invertase immobilized in the pores of nanoporous anodized 3 μm thick aluminum oxide (AA). The porous anodic alumina has uniform nanosized pores with an interpore distance of p = 100 nm, with pore diameters on the order of 60-65 nm. The pores trap the enzyme and continuous monitoring of the activity is carried out in a flow cell where the substrate is made to flow and the product is detected. The activity of the immobilized enzyme has been determined for the different concentrations of sucrose and for pH ranging from 3 to 6.5. Maximum activity was found for pH 4.5. Adsorption of the enzyme followed by its interaction with the substrate have been analyzed using confocal laser scanning microscopy (CLSM) and surface plasmon spectroscopy (SPR) and the results obtained show excellent correlation. SPR results show a biphasic kinetics for the adsorption of the enzyme as well as its interaction with the substrate with rates of adsorption for the enzyme at k = 2.9 × 10(5) M(-1) s(-1) and 1.17 × 10(5) M(-1) s(-1). The rate of interaction of the substrate with the invertase is initially rapid with k = 4.49 × 10(5) M(-1) s(-1) followed by a slower rate 1.43 × 10(4) M(-1) s(-1).