Enzyme-mediated synthesis and post-modification of aqueous microgels

• Enzym-vermittelte Synthese und Post-Modifikation von wässrigen Mikrogelen

Gau, Elisabeth; Pich, Andrij (Thesis advisor); Schwaneberg, Ulrich (Thesis advisor)

Aachen (2019)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2019

Abstract

Enzyme-Mediated Synthesis and Post-Modification of Aqueous Microgels. Aqueous Microgels have been the research focus of polymer scientists during the last decades since they offer a broad field of application possibilities due to their fascinating stimuli-responsive properties. Especially temperature-responsive microgels based on N-vinylcaprolactam (VCL) are interesting candidates for many biomedical applications, since they exhibit a volume phase transition temperature (VPTT) close to body temperature and a high biocompatibility. To further expand the application possibilities in this area, special attention has been paid to the development of methods to combine microgels and biomolecules, especially enzymes, since they can serve as natural alternatives to chemical catalysts and open up ways to a more sustainable chemistry. Therefore, the focus of this work is to establish different methods to combine these two interesting systems, microgels and enzymes with the aim to design new materials with outstanding properties benefitting from both, the highly porous and adaptive synthetic polymer network and the natural, highly selective biocatalyst.This work includes three different attempts to combine enzymes and microgels. Firstly, two different methods to synthesize microgels by employing enzymes instead of conventional thermal initiators are investigated. Glucose oxidase and laccase are used to produce radicals which then initiate the free radical precipitation polymerization of VCL and short oligo ethylene glycol acrylates (OEGAs) in the presence of a crosslinker to form microgels. Secondly, approaches to post-modify microgels enzymatically are investigated. A general applicable, highly selective method to covalently attach biomacromolecules to microgels by employing the transpeptidase enzyme sortase A is established by using the enhanced Green Fluorescent Protein (eGFP) as model protein. Besides, in another approach, the saccharide containing monomer ethylmethacrylate-β-ᴅ-galactopyranoside (Gal-EMA), which was enzymatically synthesized by transglycosylation using a galactosidase, is copolymerized with VCL to achieve sugar-containing microgels. The third part of this work deals with finding the most suitable way to immobilize two different enzymes, namely phosphorylase b and hyaluronan synthase, into microgels. Immobilization via diffusion, covalent attachment and electrostatic interactions is investigated to integrate the enzymes into PVCL-based microgels. Both enzymes are able to catalyze the grafting-from polymerization of a certain monomer and should be therefore employed to catalyze the formation of a polymer layer around the microgels.