Electrostatic immobilization of glucose oxidase in a weak acid, polyelectrolyte hyperbranched ultrathin film on gold: Fabrication, characterization, and enzymatic activity

In this paper we show that hyperbranched polymers can be used as a host mat rix for electrostatic entrapment of enzymes, Specifically, amine-functional ized glucose oxidase (GOx(+)) and horseradish peroxidase, as well as poly(a midoamine) 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(+) entrapp ed within the PAA(-) films depends on the nature of film preparation but is typically on the order of 0.06 unit/cm(2). The extent to which entrapped G Ox(+) retains its activity depends on the film history, but for PAA(-)/GOx( +) composites not exposed to glucose and stored at 4 degrees C, the origina l activity is retained for up to 68 days and perhaps longer.