Efficient enzyme encapsulation inside sol-gel silica sheets prepared by poly-L-lysine as a catalyst

Abstract

High catalytic activities of enzymes are necessary for the enzyme immobilizing technology for the development of better biocatalysts and biosensors. Basic polypeptide (poly-L-lysine)-templated precipitation of silica synthesized by sol-gel chemistry produced a composite material that allows high enzyme activity. This study investigates the structural properties of the composite material that allow retaining the glucose oxidase (GOx) activity. Scanning (SEM) and transmission (TEM) electron microscopies reveal that the composite has plate- or sheet-type morphologies composed of hexagonal structures that are 0.2–2 µm in diameter. After the encapsulation in a sol-gel silica matrix, encapsulated GOx retained high activity (over 85% of oxidation activity compared with that of free GOx). The relative activity of GOx-encapsulated in SiO2@pLys remained approximately at 50–60% after eight cycles; in addition, the catalytic stability of encapsulated GOx improved under high temperature (60°C) and in several solvents (e.g., HCl, urea, and acetone). Moreover, D-glucose detection was performed in the linear range of 1–400 µM using SiO2@pLys-GOx composites. The obtained results show that SiO2@pLys-GOx composites can be used for enzyme encapsulation with high activity and stability and as biosensor materials with high sensitivity.

Keywords

• silica
• sheet
• poly-l-lysine
• enzyme
• encapsulation