High activity of enzymes immobilized in colloidal nanoreactors.

We present a novel type of nanoreactor suitable for the immobilization of enzymes. The particles used consist of a polystyrene core onto which long chains of poly(acrylic acid) are grafted ("spherical polyelectrolyte brush"). Proteins adsorbed spontaneously onto these particles from aqueous solutions if the ionic strength is low. We immobilized glucoamylase on these particles and showed that this enzyme keeps nearly its full activity. This is shown by analyzing the enzymatic activity in terms of the Michaelis-Menten kinetics. No leaching out of the enzyme takes place during the reaction and the colloidal stability is not impeded by the adsorbed biomolecules. The data presented here suggest that the principle of immobilizing enzymes on these particles may be of general use.The Figure shows a schematic representation of the colloidal nanoreactors.