Electrostatic Immobilization of Glucose Oxidase in a Weak Acid, Polyelectrolyte Hyperbranched Ultrathin Film on Gold: Fabrication, Characterization, and Enzymatic Activity

Abstract

In this paper we show that hyperbranched polymers can be used as a host matrix for electrostatic entrapment of enzymes. Specifically, amine-functionalized glucose oxidase (GOx⁺) and horseradish peroxidase, as well as poly(amidoamine) dendrimer-modified horseradish peroxidase, reversibly sorb into polyanionic, hyperbranched poly(sodium acrylate) (PAA^-) films that are on the order of a few hundred angstroms thick. The quantity of GOx⁺ entrapped within the PAA^- films depends on the nature of film preparation but is typically on the order of 0.06 unit/cm². The extent to which entrapped GOx⁺ retains its activity depends on the film history, but for PAA^-/GOx⁺ composites not exposed to glucose and stored at 4 °C, the original activity is retained for up to 68 days and perhaps longer.