Enzyme Immobilization in Polyelectrolyte Brushes: High Loading and Enhanced Activity Compared to Monolayers
- 11 February 2019
- journal article
- research article
- Published by American Chemical Society (ACS) in Langmuir
- Vol. 35 (9), 3479-3489
- https://doi.org/10.1021/acs.langmuir.9b00056
Abstract
Catalysis by enzymes on surfaces has many applications. However, strategies for efficient enzyme immobilization with preserved activity are still in need of further development. In this work we investigate polyelectrolyte brushes prepared by both grafting-to and grafting-from with the aim to achieve high catalytic activity. For comparison, self-assembled monolayers that bind enzymes with the same chemical interactions are included. We use the model enzyme glucose oxidase and two kinds of polymers: anionic poly(acrylic acid) and cationic poly(diethylamino)methyl methacrylate. Surface plasmon resonance and spectroscopic ellipsometry are used for accurate quantification of surface coverage. Besides binding more enzymes, the “3D-like” brush environment enhances the specific activity compared to immobilization on self-assembled monolayers. For grafting-from brushes, multilayers of enzymes were spontaneously and irreversibly immobilized without conjugation chemistry. When the pH was between the pI of the enzyme and the pKa of the polymer, binding was considerable (thousands of ng/cm2 or up to 50% of the polymer mass), even at physiological ionic strength. However, binding was observed also when the brushes were neutrally charged. For acidic brushes (both grafting-to and grafting-from), the activity was higher for covalent immobilization compared to non-covalent. For grafting-from brushes, a fully preserved specific activity compared to enzymes in the liquid bulk was achieved, both with covalent (acidic brush) and non-covalent (basic brush) immobilization. Catalytic activity of hundreds of pmol cm-2 s-1 were easily obtained for polybasic brushes only tens of nm in dry thickness. This study provides new insights for designing functional interfaces based on enzymatic catalysis.Funding Information
- Vetenskapsr??det (2016-03319)
- Deutsche Forschungsgemeinschaft (STA 324/49-1, EI 317/6-1, STA 324/37-1)
- Knut och Alice Wallenbergs Stiftelse (2015.0161)
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