Microgel Supported Bioinorganic Catalysts

  Schematic view of a microgel Copyright: © F. Fink

Colloids are generally divided into three major subclasses: flexible macromolecules, rigid particles, and surfactants. Over the last decades, new colloidal particles have moved into the focus of academic research. These so-called microgels combine properties of all three colloidal subclasses and therefore resist categorization into a single subclass. Microgels are crosslinked polymer chains consisting of specific monomers like N-isopropylacrylamide (NIPAM) or N-vinylcaprolactam (VCL), which result in nanometer-sized polymer globules. Depending on the used monomers, microgel particles can exhibit stimuli responsiveness by reacting to an external stimulus, e.g. a change in temperature, pH, or ionic strength. Thus, microgels are often referred to as “smart” particles. Their smartness is, in fact, the key feature that enables them to be employed in diverse fields of application such as tissue engineering, bio-sensor technology, and catalysis.

Our working group investigates the use of microgels as catalysts by combining them with molecular, bioinspired metal complexes within the framework of the collaborative research center “Functional Microgels and Microgel Systems” (SFB 985). Here, we collaborate with academic partners in two subprojects: in Project A1 “Microgel-engineered chemoenzymatic cascades employing whole cells” and Project C6 “Modular colloidal catalysts based on responsive microgels (microgelzymes)”.

Project A1 concentrates on cascade reactions in cooperation with the working group of Prof. Schwaneberg (Institute of Biotechnology). Herein, we aim to combine fungal peroxygenases, bioinorganic copper complexes, and microgels on whole yeast cells to convert polycyclic aromatic compounds into phenazines. Recently, we published a one-pot two-step cascade reaction combining a copper-catalyzed cross-coupling followed by an enzyme-catalyzed hydroxylation to produce a bis-benzofuran derivative. This publication highlights the advantages of chemoenzymatic cascades.

Project C6 is a cooperation between the working groups of Prof. Pich (Institute of Technical and Macromolecular Chemistry), Prof. Hecht (Institute of Technical and Macromolecular Chemistry), and our working group. We aim at generating microreactors by incorporating photoswitches and plasmonic nanoparticles together with bioinorganic zinc complexes into tailor-made microgels. These microreactors are designed to enable a light-triggered, zinc-catalyzed ring-opening polymerization of cyclic esters. This allows controlling the morphology of the produced polymers. In our latest publication, we showed an enhanced catalytic activity of a bioinspired complex by immobilizing it into a microgel (doi.org/10.1039/D0CC02433C). Based on this knowledge, we gained valuable insights and were able to devise useful tools for microgel functionalization.

For further information on the collaborative research center “Functional Microgels and Microgel Systems” (SFB 985) please visit the website.