Structural Insight into Stabilization of Pickering Emulsions with Fe₃O₄@SiO₂ Nanoparticles for Enzyme Catalysis in Organic Media

Abstract

Encapsulation of enzymes with enhanced activity and recyclability in water‐in‐oil Pickering emulsions is a simple and efficient method for their immobilization; however, the effect produced by the structure of colloidal particles on the stabilization of the Pickering emulsion for enzyme catalysis has not been investigated in detail. In this study, four types of hydrophobic Fe3O4@SiO2 nanoparticles (NPs) with similar chemical compositions, particle diameters, but different surface characteristics have been prepared and utilized for enzyme encapsulation in various water‐in‐oil magnetic Pickering emulsions, after which the relationship between NPs structure, size of emulsions droplets, and enzyme activity is examined. The obtained results indicate that (i) the more hydrophobic Fe3O4@SiO2 NPs cause the higher enzyme activity; (ii) the higher hydrophobicity of oil phase also increases the enzyme activity, especially for Fe3O4@w‐SiO2 NPs which form in the solvent of water. The results are mainly attributed to the higher specific surface area of emulsion droplets and interfacial mass transfer of substrates through the interfaces of droplets. The reported data provide new insights into the mechanism of stabilization of Pickering emulsions for enhancing enzyme activity and demonstrate efficient theoretical references for enzyme immobilization and synthesis of stable and active biocatalysts with high recyclability.

Catalysis in Pickering emulsions

“…In general, examples of PAC are widely found in the field of biocatalysis, where the enzyme (catalyst) is dissolved in the aqueous phase and the solid particles are located at the liquidliquid interface. 15,22,24,47,[54][55][56][57] In most of these examples, silica particles were selected as the emulsifier for the preparation of w/o emulsions to study hydrolysis and esterification reactions using lipase enzymes as the biocatalyst dissolves in water. However, in ref.…”

Submicron Inverse Pickering Emulsions for Highly Efficient and Recyclable Enzymatic Catalysis

“…Therefore, although micron‐sized Pickering emulsions have been extensively studied over the past decade, there have been no reports of submicron Pickering emulsions that are solely stabilized by colloidal particles in biphasic enzyme catalysis. The increase in interfacial area between the organic and aqueous phases is a crucial reason for increasing the reaction efficiency in biphasic enzymatic transformations based on Pickering emulsions . The smaller size of the dispersion phase typically leads to a larger interfacial area between the two phases for increasing mass transfer in biphasic enzymatic reactions and, thus, the catalytic efficiency.…”

Armored Droplets as Soft Nanocarriers for Encapsulation and Release under Flow Conditions

“…NP-coated droplets have been intensively used as drug-delivery vehicles in topical medication, where their surfactant-free character makes them attractive for different applications since surfactants often produce adverse effects, such as irritation and hemolytic disturbances. , They can serve as ideal compartments for reactions catalyzed by NPs attached at the oil–water interfaces − and can be used in bacterial recognition technologies. , Another important and useful advantage of NP-coated droplets over conventional surfactant-stabilized systems is their enhanced stabilization against coalescence and their smaller environmental footprint…”