Enzyme Entrapment in Reprecipitated Polyaniline Nano- and Microparticles

We introduce a novel method for fabricating nano- and microscale polyaniline particles containing an entrapped oxidoreductase enzyme for use in biosensing applications. This facile process utilizes the reprecipitation of the emeraldine base form of polyaniline from an aqueous-organic suspension, with hydrophobic collapse and subsequent cross-linking of the polymer induced by adjusting the ionic strength beyond a critical threshold. We present UV-vis spectroscopy data, including a quantitative treatment of the spectral line width, along with dynamic light scatting results, to explain the conformation changes in the polyaniline chains that accompany this transition. The resultant aggregated supermolecular polyaniline formations immobilize enzymes via gelation entrapment, augmented by electrostatic attraction, without the need for harsh reaction conditions or additional reagents. Because of its strong optical features at visible wavelengths that can serve as probes for chain conformation, oxidation state, and protonation level, polyaniline may act as a model system for the study of hydrophobic and ion screening effects in proteins and other foldamers.