Dextran aldehyde coating of glucose oxidase immobilized on magnetic nanoparticles prevents its inactivation by gas bubbles

Glucose oxidase (GOX) was readily inactivated in stirred systems by the interaction between the enzyme and the hydrophobic interfaces of gas bubbles. Immobilization of the enzyme on glutaraldehyde-agarose (a porous support) under very mild conditions yielded preparations with similar thermostability as the soluble GOX. However, this immobilization permitted the enzyme to retain full stability in stirred systems due to lack of undesired interaction of the gas bubbles with the enzyme. Similar immobilization of the enzyme on magnetic nanoparticles, a non-porous support, presented very different results: here GOX was inactivated by the gas bubbles in a similar way to the soluble enzyme. This could be due to the fact that the enzyme is now immobilized on the external surface of the particles, and, therefore, it is fully exposed to the gas bubbles. The coating of the enzyme molecules with aldehyde dextran, while maintaining the enzyme thermostability, permitted to avoid enzyme inactivation by gas bubbles. (C) 2004 Elsevier B.V. All rights reserved.