Enzymatic Catalysis at Nanoscale: Enzyme-Coated Nanoparticles as Colloidal Biocatalysts for Polymerization Reactions

Abstract

Enzyme-catalyzed controlled radical polymerization represents a powerful approach for the polymerization of a wide variety of water-soluble monomers. However, in such an enzyme-based polymerization system, the macromolecular catalyst (i.e., enzyme) has to be separated from the polymer product. Here, we present a compelling approach for the separation of the two macromolecular species, by taking the catalyst out of the molecular domain and locating it in the colloidal domain, ensuring quasi-homogeneous catalysis as well as easy separation of precious biocatalysts. We report on gold nanoparticles coated with horseradish peroxidase that can catalyze the polymerization of various monomers (e.g., N-isopropylacrylamide), yielding thermoresponsive polymers. Strikingly, these biocatalyst-coated nanoparticles can be recovered completely and reused in more than three independent polymerization cycles, without significant loss of their catalytic activity.

Nanoparticle‐Mediated Enzyme Immobilization on Cellulose Fibers: Reusable Biocatalytic Systems for Cascade Reactions

“…Leaching of the enzymes was not observed due to their strong interactions to the gold surface. This was demonstrated by the absence of enzymatic activity in the supernatant after multiple centrifugation and redispersion cycles . The enzymes can catalyze chemical reactions in aqueous solutions, after they have been immobilized to the nanocarriers.…”

“…The enzyme is then robustly attached to the scaffold and remains catalytically active. This is in accordance with prior studies, where we showed the robust binding of enzymes and other proteins to metal nanoparticles (gold, iron oxide) via a simple ligand exchange reaction. The reaction is mainly driven by the displacement of small molecules (citrate) by the macromolecular proteins on the particle surface.…”

“…Recently, however, it could be shown that gold nanoparticles (NPs) provide a good support for enzyme immobilization via physisorption. Various enzymes, as well as other proteins, could be easily and robustly immobilized on the particle surface in a ligand exchange process . Leaching of the enzymes was not observed due to their strong interactions to the gold surface.…”

“…In this work, we overcome the disadvantages of the colloidal (quasi‐homogeneous) approach by transferring the enzymatically active colloids to the next level of hierarchy. By immobilizing the colloids onto a macroscopic scaffold, we yield a heterogeneous biocatalytic system, based on simple physisorption of enzymes and nanoparticles.…”

Functionalized gold nanoparticles for sample preparation: A review

“…GNPs are a popular support for enzyme immobilization due to its easy size‐controlled preparation and good biocompatibility. Besides, various flexible bioconjugation strategies of GNPs with enzymes have been proposed and sample processing is straightforward . A variety of strategies has been used for enzyme immobilization such as adsorption ionic binding , affinity binding and covalent binding.…”