Immobilized horseradish peroxidase as a reusable catalyst for emulsion polymerization

Facile preparation of MOF-derived MHCo3O4&Co/C with a hierarchical porous structure for entrapping enzymes: having both high stability and catalytic activity

MHCo3O4&Co/C with hierarchical porous structure are functionally modified with “polydopamine (PDA)” bionic membrane for entrapping horseradate peroxidase (HRP).

Hierarchically porous magnetic Fe3O4/Fe-MOF used as an effective platform for enzyme immobilization: a kinetic and thermodynamic study of structure–activity

Fe₃O₄/Fe-MOF integrate magnetic characteristics and hierarchical porous structure for supporting chloroperoxidase (CPO) or horseradish peroxidase (HRP).

Nano-in-Nano Approach for Enzyme Immobilization Based on Block Copolymers

We set up a facile approach for fabrication of supports with tailored nanoporosity for immobilization of enzymes. To this aim block copolymers (BCPs) self-assembly has been used to prepare nanostructured thin films with well-defined architecture containing pores of tailorable size delimited by walls with tailorable degree of hydrophilicity. In particular, we employed a mixture of polystyrene-block-poly(l-lactide) (PS-PLLA) and polystyrene-block-poly(ethylene oxide) (PS-PEO) diblock copolymers to generate thin films with a lamellar morphology consisting of PS lamellar domains alternating with mixed PEO/PLLA blocks lamellar domains. Selective basic hydrolysis of the PLLA blocks generates thin films, patterned with nanometric channels containing hydrophilic PEO chains pending from PS walls. The shape and size of the channels and the degree of hydrophilicity of the pores depend on the relative length of the blocks, the molecular mass of the BCPs, and the composition of the mixture. The strength of our approach is demonstrated in the case of physical adsorption of the hemoprotein peroxidase from horseradish (HRP) using 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) with H₂O₂ as substrate. The large surface area, the tailored pore sizes, and the functionalization with hydrophilic PEO blocks make the designed nanostructured materials suitable supports for the nanoconfinement of HRP biomolecules endowed with high catalytic performance, no mass-transfer limitations, and long-term stability.

Radical-Mediated Enzymatic Polymerizations

Polymerization reactions are commonly effected by exposing monomer formulations to some initiation stimulus such as elevated temperature, light, or a chemical reactant. Increasingly, these polymerization reactions are mediated by enzymes--catalytic proteins--owing to their reaction efficiency under mild conditions as well as their environmental friendliness. The utilization of enzymes, particularly oxidases and peroxidases, for generating radicals via reduction-oxidation mechanisms is especially common for initiating radical-mediated polymerization reactions, including vinyl chain-growth polymerization, atom transfer radical polymerization, thiol-ene step-growth polymerization, and polymerization via oxidative coupling. While enzyme-mediated polymerization is useful for the production of materials intended for subsequent use, it is especially well-suited for in situ polymerizations, where the polymer is formed in the place where it will be utilized. Such polymerizations are especially useful for biomedical adhesives and for sensing applications.

Nanostructures for peroxidases

Peroxidases are enzymes catalyzing redox reactions that cleave peroxides. Their active redox centers have heme, cysteine thiols, selenium, manganese, and other chemical moieties. Peroxidases and their mimetic systems have several technological and biomedical applications such as environment protection, energy production, bioremediation, sensors and immunoassays design, and drug delivery devices. The combination of peroxidases or systems with peroxidase-like activity with nanostructures such as nanoparticles, nanotubes, thin films, liposomes, micelles, nanoflowers, nanorods and others is often an efficient strategy to improve catalytic activity, targeting, and reusability.

Novel formulations for antimicrobial peptides

Peptides in general hold much promise as a major ingredient in novel supramolecular assemblies. They may become essential in vaccine design, antimicrobial chemotherapy, cancer immunotherapy, food preservation, organs transplants, design of novel materials for dentistry, formulations against diabetes and other important strategical applications. This review discusses how novel formulations may improve the therapeutic index of antimicrobial peptides by protecting their activity and improving their bioavailability. The diversity of novel formulations using lipids, liposomes, nanoparticles, polymers, micelles, etc., within the limits of nanotechnology may also provide novel applications going beyond antimicrobial chemotherapy.

In situ formation of enzyme-free hydrogels via ferromagnetic microbead-assisted enzymatic cross-linking

This work reports a new in situ enzymatic crosslinking method to prepare mechanically tunable hydrogels not possessing an enzyme.

Assembly of horseradish peroxidase within supported cationic bilayers

The interaction between horseradish peroxidase (HRP) and dioctadecyldimethylammonium bromide (DODAB) bilayers supported on polystyrene microspheres (PSS) or on flat silicon wafers was evaluated from the following techniques: (1) dynamic light-scattering for determining size distributions, zeta-potentials and polydispersities for dispersions; (2) spectrophotometric determination of HRP concentration in supernatants of centrifuged mixtures; (3) in situ ellipsometry for mean thickness of deposited layers on wafers; (4) kinetics of product appearance for oxidation of 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid by H(2) O(2) in presence of free or immobilized enzyme. HRP incorporation (3.0 mg/m(2)) did not alter mean diameter and zeta-potential of PSS/DODAB particles but reduced enzyme activity by 50%, though activity persisted after several rinsing steps. In situ ellipsometry could not detect any HRP layer on top of the DODAB bilayer. HRP insertion in the bilayer core explained all results for both systems. Useful biotechnological applications are anticipated for such assemblies.

Determination of a setup correction function to obtain adsorption kinetic data at stagnation point flow conditions

This paper is the first report on the characterization of the hydrodynamic conditions in a flow cell designed to study adsorption processes by spectroscopic ellipsometry. The resulting cell enables combining the advantages of in situ spectroscopic ellipsometry with stagnation point flow conditions. An additional advantage is that the proposed cell features a fixed position of the "inlet tube" with respect to the substrate, thus facilitating the alignment of multiple substrates. Theoretical calculations were performed by computational fluid dynamics and compared with experimental data (adsorption kinetics) obtained for the adsorption of polyethylene glycol to silica under a variety of experimental conditions. Additionally, a simple methodology to correct experimental data for errors associated with the size of the measured spot and for variations of mass transfer in the vicinity of the stagnation point is herein introduced. The proposed correction method would allow researchers to reasonably estimate the adsorption kinetics at the stagnation point and quantitatively compare their results, even when using different experimental setups. The applicability of the proposed correction function was verified by evaluating the kinetics of protein adsorption under different experimental conditions.

Hydrolytic activity of free and immobilized cellulase

Cellulase is an enzymatic complex which synergically promotes the degradation of cellulose to glucose. The adsorption behavior of cellulase from Trichoderma reesei onto Si wafers or amino-terminated surfaces was investigated by means of ellipsometry and atomic force microscopy (AFM) as a function of temperature. Upon increasing temperature from (24 +/- 1) to (60 +/- 1) degrees C, adsorption of cellulase became faster and more pronounced and the mean roughness of cellulase adsorbed layers increased. In the case of cellulase adsorbed onto Si wafers, Arrhenius's plot allowed us to estimate the adsorption energy as 24.2 kJ mol(-1). The hydrolytic activity of free cellulase and cellulase immobilized onto Si wafers was tested using cellulose dispersions as substrates. The incubation temperature ranged from (37 +/- 1) to (60 +/- 1) degrees C. The highest efficiency was observed at (60 +/- 1) degrees C. The amount of glucose produced by free cellulase was approximately 20% higher than that obtained from immobilized cellulase. However, immobilizing cellulase onto Si wafers proved to be advantageous because they could be reused six times while retaining their original activity level. Such an effect was attributed to surface hydration, which prevents enzyme denaturation. The hydrolytic activity of cellulase immobilized onto amino-terminated surfaces was slightly lower than that observed for cellulase adsorbed onto Si wafers, and reuse was not possible.

Adsorption behavior and activity of horseradish peroxidase onto polysaccharide-decorated particles

The adsorption behavior of horseradish peroxidase (HRP) onto hybrid particles of poly(methylmethacrylate) (PMMA) and carboxymethylcellulose (CMC) was investigated by means of spectrophotometry. Dispersions of PMMA/CMC particles were characterized by light scattering, zeta potential measurements and scanning electron microscopy before and after HRP adsorption. HRP adsorbed irreversibly onto PMMA/CMC particles; the adsorption isotherm showed an initial step and an adsorption plateau. The enzymatic activity of free HRP and immobilized HRP (plateau region) was monitored by means of spectrophotometry as a function of storing time. Upon adsorbing HRP there is little (up to 20%) or no reduction of enzymatic activity in comparison to that observed for free HRP in solution. After storing free HRP and HRP-covered PMMA/CMC particles for 18 days the level of enzymatic activity is kept. HRP-covered PMMA/CMC particles dispersions, which were dried and re-dispersed, retained 50% of their catalytic properties. These interesting findings were discussed in the light of a beneficial effect of a hydrated microenvironment for maintenance of enzyme conformation and activity.