Catalytically Active Protein Coatings: Toward Enzymatic Cascade Reactions at the Intercolloidal Level

Abstract

In this work, we show that different enzymes, such as horseradish peroxidase (HRP), glucose oxidase, laccase, and catalase, can be directly immobilized onto plasmonic gold nanoparticles (NPs) and superparamagnetic iron oxide NPs simply via unspecific physical adsorption, yielding catalytically active and colloidally stable NP systems. The enzyme coating on the NP surface is highly robust and enzymatically active. The colloidal stability and the enzymatic performance (V max and K m) of the enzyme-coated NPs (Au@enzyme) are strongly dependent on the pH of the dispersion and physicochemical properties of the respective enzyme. In particular, we observe that the colloidal stability of the enzyme-coated NPs does not necessarily lie in the pH range of the optimal catalytic performance of the enzymes (Au@HRP is unstable at pH 3, but k cat is the highest, 7.4 × 103 min–1). Understanding the relationship between the colloidal stability of the different enzyme-coated NPs at different pH values and the optimal catalytic performance of enzyme-coated NPs will allow us to perform enzymatic reactions at the colloidal level, ensuring quasi-homogeneous catalysis. We also demonstrate that the immobilization of different enzymes on different NP systems allows for the design of enzymatic cascade reactions at an intercolloidal level, with selective catalyst separation.

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

“…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.…”

“…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.…”

“…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.…”

“…One approach is to covalently bind enzymes to GNPs using proper linkers or spacers with bifunctional reactive groups (e.g., thiol group at one end, carboxyl or amino group at the other end) via the formation of SAM . Kinetic and thermodynamic behaviors and catalytic activities of the heterogeneous catalysis have been investigated in detail in some studies . It was found that assembling enzymes onto nanoparticle surfaces could accelerate or improve catalysis in comparison with freely diffusing enzyme in bulk solution .…”