Enzyme Entrapped in Polymer‐Modified Nanopores: The Effects of Macromolecular Crowding and Surface Hydrophobicity

Abstract

Macromolecular crowding is an ubiquitous phenomenon in living cells that significantly affects the function of enzymes in vivo. However, this effect has not been paid much attention in the research of the immobilization of enzymes onto mesoporous silica. Herein, we report the combined effects of macromolecular crowding and surface hydrophobicity on the performance of an immobilized enzyme by accommodating lipase molecules into a series of mesoporous silicas with different amounts of inert poly(methacrylate) (PMA) covalently anchored inside the nanopores. The incorporation of the PMA polymer into the nanopores of mesoporous silica enables the fabrication of a crowded and hydrophobic microenvironment for the immobilized enzyme and the variation in polymer content facilitates an adjustment of the degree of crowding and surface properties of this environment. Based on this system, the catalytic features of immobilized lipase were investigated as a function of polymer content in nanopores and the results indicated that the catalytic efficiency, thermostability, and reusability of immobilized lipase could all be improved by taking advantage of the macromolecular crowding effect and surface hydrophobicity. These findings provide insight into the possible functions of the macromolecular crowding effect, which should be considered and integrated into the fabrication of suitable mesoporous silicas to improve enzyme immobilization.

Effect of crowding by Dextrans in enzymatic reactions

“…Well-mixed dilute solutions, with less than 1 mg/mL macromolecules content, represent the typical environment for in vitro experiments [2]. Various crowding effects have been put into evidence over the last decades related to changes of diffusion rate [3][4][5][6][7][8][9], protein folding, self-association and protein binding enhancement [10][11][12][13][14][15][16][17][18][19][20][21][22][23], enzymatic activity alteration [24][25][26][27] and reaction kinetics modification [28][29].…”

Engineering of Supported Nanomaterials

“…Selection of support material is made by the size of enzyme to be confined in the pore; but also the possible interaction between support and supported material have to be taken into account. Large particle supports will immobilize more proteins, but this will reduce the number of enzymes that have access to the reagent because of the distance between each other or due to macromolecular crowding 18 .…”

Engineering aspects of immobilized lipases on esterification: A special emphasis of crowding, confinement and diffusion effects

“…Once lipase interacts with inert support, the conformation will be changed due to the folding/unfolding phenomenon in a crowded and/or confined environment. The free volume space of the lipase is limited either by the dense surrounding biomolecules, or by the small confinements which eventually affect the protein stability in terms of thermal stability, and chemical reactivity . Hence, the knowledge of crowding and confinement of proteins on immobilization drive the researcher for better understanding the folding and its stability in crowding and/or confinement conditions.…”