In-situ-Investigation of Enzyme Immobilization on Polymer Brushes

Supra-biological performance of immobilized enzymes enabled by chaperone-like specific non-covalent interactions

Designing complex synthetic materials for enzyme immobilization could unlock the utility of biocatalysis in extreme environments. Inspired by biology, we investigate the use of random copolymer brushes as dynamic immobilization supports that enable supra-biological catalytic performance of immobilized enzymes. This is demonstrated by immobilizing Bacillus subtilis Lipase A on brushes doped with aromatic moieties, which can interact with the lipase through multiple non-covalent interactions. Incorporation of aromatic groups leads to a 50 °C increase in the optimal temperature of lipase, as well as a 50-fold enhancement in enzyme activity. Single-molecule FRET studies reveal that these supports act as biomimetic chaperones by promoting enzyme refolding and stabilizing the enzyme's folded and catalytically active state. This effect is diminished when aromatic residues are mutated out, suggesting the importance of π-stacking and π-cation interactions for stabilization. Our results underscore how unexplored enzyme-support interactions may enable uncharted opportunities for using enzymes in industrial biotransformations.

Surfaces Coated with Polymer Brushes Work as Carriers for Histidine Ammonia Lyase

The immobilization of enzymes on solid supports is an important challenge in biotechnology and biomedicine. In contrast to other methods, enzyme deposition in polymer brushes offers the benefit of high protein loading that preserves enzymatic activity in part due to the hydrated 3D environment that is available within the brush structure. The authors equipped planar and colloidal silica surfaces with poly(2-(diethylamino)ethyl methacrylate)-based brushes to immobilize Thermoplasma acidophilum histidine ammonia lyase, and analyzed the amount and activity of the immobilized enzyme. The poly(2-(diethylamino)ethyl methacrylate) brushes are attached to the solid silica supports either via a "grafting-to" or a "grafting-from" method. It is found that the grafting-from method results in higher amounts of deposited polymer and, consequently, higher amounts of Thermoplasma acidophilum histidine ammonia lyase. All polymer brush-modified surfaces show preserved catalytic activity of the deposited Thermoplasma acidophilum histidine ammonia lyase. However, immobilizing the enzyme in polymer brushes using the grafting-from method resulted in twice the enzymatic activity from the grafting-to approach, illustrating a successful enzyme deposition on a solid support.

High Adsorption of α-Glucosidase on Polymer Brush-Modified Anisotropic Particles Acquired by Electrospraying-A Combined Experimental and Simulation Study

In this particular contribution, we aim to immobilize a model enzyme such as α-glucosidase onto poly(DMAEMA) [poly(2-dimethyl amino ethyl methacrylate)] brush-modified anisotropic (cup- and disc-shaped) biocompatible polymeric particles. The anisotropic particles comprising a blend of PLA [poly(lactide)] and poly(MMA-co-BEMA) [poly((methyl methacrylate)-co-(2-(2-bromopropionyloxy) ethyl methacrylate)] were acquired by electrospraying, a scalable and convenient technique. We have also demonstrated the role of a swollen polymer brush grafted on the surface of cup-/disc-shaped particles via surface-initiated atom transfer radical polymerization in immobilizing an unprecedentedly high loading of enzyme [441 mg/g (cup)-589 mg/g (disc) of particles, 15-20 times higher than that of the literature-reported system] as compared to non-brush-modified particles. Circular dichroism spectroscopy was used to predict the structural changes of the enzyme upon immobilization onto the carrier particles. An enormously high amount of enzymes with preserved activity (∼85 ± 13% for cups and ∼78 ± 15% for discs) was found to adhere onto brush-modified particles at pH 7 via electrostatic adsorption. These findings were further explored at the atomistic level using a coarse-grained dissipative particle dynamics simulation approach, which exhibited excellent correlation with experimental results. In addition, accelerated particle separation was also achieved via magnetic force-induced aggregation within 20 min (without a centrifuge) by incorporating magnetic nanoparticles into disc-shaped particles while electrojetting. This further strengthens the technical feasibility of the process, which holds immense potential to be applied for various enzymes intended for several applications.

Reusable System for Phenol Detection in an Aqueous Medium Based on Nanodiamonds and Extracellular Oxidase from Basidiomycete Neonothopanus nambi

A reusable system for phenol determination in an aqueous medium was obtained by adsorption of extracellular oxidase from fungus Neonothopanus nambi onto modified nanodiamonds (MND) synthesized by detonation. It was found that the enzyme strongly binds to MND and exhibits catalytic activity in the reaction of co-oxidation of phenol with 4-aminoantipyrine without the addition of hydrogen peroxide. In the presence of the MND-oxidase complex, a significantly (by an order of magnitude) higher yield of the reaction product is recorded as compared to the yield in the presence of a free enzyme; the mechanism of the revealed effect is discussed. Model experiments have demonstrated the multiple use of the MND-oxidase complex for testing phenol in aqueous samples. The immobilized enzyme exhibits functional activity during long-term (2 months) storage of the MND-oxidase complex at 4°C. The data obtained create the prerequisites for using the created system in environmental monitoring of water pollution with phenol.

Extracellular Oxidase from the Neonothopanus nambi Fungus as a Promising Enzyme for Analytical Applications

The extracellular enzyme with oxidase function was extracted from the Neonothopanus nambi luminescent fungus by using mild processing of mycelium with β-glucosidase and then isolated by gel-filtration chromatography. The extracted enzyme is found to be a FAD-containing protein, catalyzing phenol co-oxidation with 4-aminoantipyrine without addition of H₂O₂, which distinguishes it from peroxidases. This fact allowed us to assume that this enzyme may be a mixed-function oxidase. According to gel-filtration chromatography and SDS-PAGE, the oxidase has molecular weight of 60 kDa. The enzyme exhibits maximum activity at 55-70 °C and pH 5.0. Kinetic parameters K_m and V_max of the oxidase for phenol were 0.21 mM and 0.40 µM min^-1. We suggest that the extracted enzyme can be useful to develop a simplified biosensor for colorimetric detection of phenol in aqueous media, which does not require using hydrogen peroxide.

Grafted polymer brush coatings for growth of cow granulosa cells and oocyte-cumulus cell complexes

In the present work, three types of grafted brush coatings [P4VP, POEGMA246, and P(4VP-co-POEGMA246)] were successfully fabricated using graft polymerization of monomers "from the surface." The composition, thickness, and morphology of the grafted brush coatings were analyzed by TOF-SIMS, ellipsometry, and AFM, respectively. The chemical nature of the polymer surface plays a crucial role in the growth and development of the cow granulosa cells and, therefore, also oocyte-cumulus complexes. In comparison with other coatings, the P(4VP-co-POEGMA246) copolymer coating enables the formation of dispersed and small but numerous cell conglomerates and high cumulus expansion in oocyte-cumulus complexes with highly homogeneous cumulus layers surrounding the oocytes. Moreover, the cellular oxygen uptake for this coating in the presence of NaF (inhibitor glycolysis) was stimulated. This new (4VP-co-POEGMA246) copolymer nanostructured coating is a promising material for granulosa cell and oocyte-cumulus complex cultivation and possibly will have great potential for applications in veterinary and reproductive medicine.