Ultrasound-Assisted Enantioselective Esterification of Ibuprofen Catalyzed by a Flower-Like Nanobioreactor

A flower-like nanobioreactor was prepared for resolution of ibuprofen in organic solvents. Ultrasound irradiation has been used to improve the enzyme performance of APE1547 (a thermophilic esterase from the archaeon Aeropyrum pernix K1) in the enantioselective esterification. Under optimum reaction conditions (ultrasound power, 225 W; temperature, 45 °C; water activity, 0.21), the immobilized APE1547 showed an excellent catalytic performance (enzyme activity, 13.26 μmol/h/mg; E value, 147.1). After ten repeated reaction batches, the nanobioreactor retained almost 100% of its initial enzyme activity and enantioselectivity. These results indicated that the combination of the immobilization method and ultrasound irradiation can enhance the enzyme performance dramatically.

Synthesis of Fe3O4/P(St-AA) nanoparticles for enhancement of stability of the immobilized lipases

Core–shell Fe₃O₄/P(St-AA) nanoparticles were synthesized and employed as a magnetic carrier for lipase immobilization, and the properties of the immobilized lipase were studied.

Biomimetic catalysis of metal–organic frameworks

Recent advances in biomimetic catalysis of MOFs have been summarized and reviewed.

Robust glucose oxidase with a Fe3O4@C-silica nanohybrid structure

An enzyme-material hybrid, biomineralization-based method has been developed for glucose oxidase immobilization with high thermal stability, operational stability and recyclability.

Facile synthesis of enzyme-embedded magnetic metal-organic frameworks as a reusable mimic multi-enzyme system: mimetic peroxidase properties and colorimetric sensor

This work reports a facile and easily-achieved approach for enzyme immobilization by embedding glucose oxidase (GOx) in magnetic zeolitic imidazolate framework 8 (mZIF-8) via a de novo approach. As a demonstration of the power of such materials, the resulting GOx embedded mZIF-8 (mZIF-8@GOx) was utilized as a colorimetric sensor for rapid detection of glucose. This method was constructed on the basis of metal-organic frameworks (MOFs), which possessed very fascinating peroxidase-like properties, and the cascade reaction for the visual detection of glucose was combined into one step through the mZIF-8@GOx based mimic multi-enzyme system. After characterization by electron microscopy, X-ray diffraction, nitrogen sorption, fourier transform infrared spectroscopy and vibrating sample magnetometry, the as-prepared mZIF-8@GOx was confirmed with the robust core-shell structure, the monodisperse nanoparticle had an average diameter of about 200 nm and displayed superparamagnetism with a saturation magnetization value of 40.5 emu g(-1), it also exhibited a large surface area of 396.10 m(2) g(-1). As a peroxidase mimic, mZIF-8 was verified to be highly stable and of low cost, and showed a strong affinity towards H2O2. Meanwhile, the mZIF-8 embedded GOx also exhibited improved activity, stability and greatly enhanced selectivity in glucose detection. Moreover, the mZIF-8@GOx had excellent recyclability with high activity (88.7% residual activity after 12 times reuse).

Protein Analysis by Ambient Ionization Mass Spectrometry Using Trypsin-Immobilized Organosiloxane Polymer Surfaces

In the growing field of proteomic research, rapid and simple protein analysis is a crucial component of protein identification. We report the use of immobilized trypsin on hybrid organic-inorganic organosiloxane (T-OSX) polymers for the on-surface, in situ digestion of four model proteins: melittin, cytochrome c, myoglobin, and bovine serum albumin. Tryptic digestion products were sampled, detected, and identified using desorption electrospray ionization mass spectrometry (DESI-MS) and nanoDESI-MS. These novel, reusable T-OSX arrays on glass slides allow for protein digestion in methanol:water solvents (1:1, v/v) and analysis directly from the same polymer surface without the need for sample preparation, high temperature, and pH conditions typically required for in-solution trypsin digestions. Digestion reactions were conducted with 2 μL protein sample droplets (0.35 mM) at incubation temperatures of 4, 25, 37, and 65 °C and digestion reaction times between 2 and 24 h. Sequence coverages were dependent on the hydrophobicity of the OSX polymer support and varied by temperature and digestion time. Under the best conditions, the sequence coverages, determined by DESI-MS, were 100% for melittin, 100% for cytochrome c, 90% for myoglobin, and 65% for bovine serum albumin.

A general protein purification and immobilization method on controlled porosity glass: biocatalytic applications

A general combined purification and immobilization method to facilitate biocatalytic process development is presented. The support material, EziG™, is based on controlled porosity glass (CPG) or polymer-coated versions thereof (HybCPG) and binds protein affinity tags. Biocatalytic reactions in aqueous and organic media with seven enzymes of biocatalytic interest are shown.

Influence of the hydrophilic-hydrophobic contrast of porous surfaces on the enzymatic performance

Herein we report the dependency of the performance (uptake, activity, stability) of hydrophilic glucose-6-phosphate dehydrogenase (G6PDH) onto mesoporous cellular foams (MCF) grafted with aminosilanes of different chain length. The resulting hydrophobic-hydrophilic contrast was carefully evaluated by combined argon and water sorption and quantified with a newly developed hydrophilicity index suitable for the characterization of large-pore materials. The enzymatic behaviour was influenced by electrostatic and hydrophobic interactions between both reaction partners due to the creation of specific microenvironments inside the pore system. The microenvironment created by the materials with high hydrophobicity did not contribute to the beneficial electrostatic interactions of the charged amine groups by increased hydrophobic forces instead a competition of both forces was present. Thus an improved biocatalytic performance was not observed for materials with high hydrophobicity but short-chain functionalized MCFs led to highly stable and active biocatalysts.

Nanostructured microfluidic digestion system for rapid high-performance proteolysis

A novel microfluidic protein digestion system with a nanostructured and bioactive inner surface was constructed by an easy biomimetic self-assembly strategy for rapid and effective proteolysis in 2 minutes, which is faster than the conventional overnight digestion methods. It is expected that this work would contribute to rapid online digestion in future high-throughput proteomics.

Insights into mesoporous metal phosphonate hybrid materials for catalysis

Mesoporous metal phosphonates have received increasing attention as promising heterogeneous catalysts due to their abundant framework compositions and controllable porosity.

Lipase immobilized in microemulsion based organogels (MBGs) as an efficient catalyst for continuous-flow esterification of protected fructose

Sugar-based surfactants are important esters for the cosmetic, food and pharmaceutical industries due to their intrinsic properties.

One-pot synthesis of (R)-2-acetoxy-1-indanone from 1,2-indanedione combining metal catalyzed hydrogenation and chemoenzymatic dynamic kinetic resolution

A heterogeneously catalyzed one-pot reaction for synthesis of (R)-2-acetoxy-1-indanone is described.

Design of metal organic framework–enzyme based bioelectrodes as a novel and highly sensitive biosensing platform

The mesoporous iron(iii) trimesate MIL-100(Fe) based biosensor presents very interesting electrocatalytic performances for glucose detection.

Co-immobilization of enzymes with the help of a dendronized polymer and mesoporous silica nanoparticles

Two enzymes were immobilized in close proximity to each other using enzyme-containing mesoporous nanoparticles and a dendronized polymer–enzyme hybrid structure.

Immobilizing and de-immobilizing enzymes on mesoporous silica

β-Glucosidase was immobilised as a model enzyme within silica mesocellular foam (MCF) at a high loading, further entrapped to achieve higher stability and released unharmed upon need by applying fluoride buffered solutions.

The performance of mesoporous organosilicas with phenyl groups in Heme protein immobilization

We demonstrate the influence of phenyl groups in the pore structure of mesoporous organosilicas, on the quantity of absorbed enzyme and the activity of immobilized enzyme.

Glucose oxidase adsorption performance of carbonaceous mesocellular foams prepared with different carbon sources

Several carbonaceous mesocellular foams (C-MCFs) were prepared with MCF-silica as template using the carbon precursors of sucrose, furfuryl alcohol and lab-made phenolic resin, and the corresponding C-MCFs were named as C-MCF-Suc, C-MCF-FA and C-MCF-PR, respectively. The results of SEM, transmission electron microscopy, N2 adsorption-desorption and energy-dispersive X-ray measurements indicated that the C-MCFs prepared from different carbon source appeared morphologically with different degree of order and different pore distribution. The C-MCF-FA exhibited the highest ordered structure and the smallest pore distribution among the foams. The optimum conditions for adsorption of C-MCFs on glucose oxidase (GOD) were also studied, and the maximum adsorbance was determined. The adsorption of GOD on C-MCF-FA was performed at different pH with different GOD concentrations. The maximum adsorption (423.3 mg g(-1)) was observed near the isoelectric point of the GOD (pI ≈ 5.0) with a GOD concentration of 6.0 mg mL(-1), suggesting that the GOD adsorption on C-MCFs might be affected strongly by the electric repulsion between the GOD molecules. Moreover, GOD adsorption performances on different C-MCFs revealed that both the pore size and the pore volume played important roles in the adsorption process, and the window size of C-MCFs dominated the residual immobilized amounts of GOD. Compared to the other two C-MCFs, the C-MCF-FA with a smaller window pore (10 nm) and higher volume (1.40 cm(3) g(-1)) exhibited the highest GOD adsorption and catalytic activity. Furthermore, the immobilized GOD exhibited improved thermal and storable stabilities. Thus the C-MCF-FA could be served as the prospective GOD carrier material used in enzymatic fuel cells.

Construction of a high-performance magnetic enzyme nanosystem for rapid tryptic digestion

A magnetic enzyme nanosystem have been designed and constructed by a polydopamine (PDA)-modification strategy. The magnetic enzyme nanosystem has well defined core-shell structure and a relatively high saturation magnetization (Ms) value of 48.3 emu g(-1). The magnetic enzyme system can realize rapid, efficient and reusable tryptic digestion of proteins by taking advantage of its magnetic core and biofunctional shell. Various standard proteins (e.g. cytochrome C (Cyt-C), myoglobin (MYO) and bovine serum albumin (BSA)) have been used to evaluate the effectiveness of the magnetic enzyme nanosystem. The results show that the magnetic enzyme nanosystem can digest the proteins in 30 minutes, and the results are comparable to conventional 12 hours in-solution digestion. Furthermore, the magnetic enzyme nanosystem is also effective in the digestion of low-concentration proteins, even at as low as 5 ng μL(-1) substrate concentration. Importantly, the system can be reused several times, and has excellent stability for storage. Therefore, this work will be highly beneficial for the rapid digestion and identification of proteins in future proteomics.

Lipase immobilized catalytically active membrane for synthesis of lauryl stearate in a pervaporation membrane reactor

A composite catalytically active membrane immobilized with Candida rugosa lipase has been prepared by immersion phase inversion technique for enzymatic synthesis of lauryl stearate in a pervaporation membrane reactor. SEM images showed that a "sandwich-like" membrane structure with a porous lipase-PVA catalytic layer uniformly coated on a polyvinyl alcohol (PVA)/polyethersulfone (PES) bilayer was obtained. Optimum conditions for lipase immobilization in the catalytic layer were determined. The membrane was proved to exhibit superior thermal stability, pH stability and reusability than free lipase under similar conditions. In the case of pervaporation coupled synthesis of lauryl stearate, benefited from in-situ water removal by the membrane, a conversion enhancement of approximately 40% was achieved in comparison to the equilibrium conversion obtained in batch reactors. In addition to conversion enhancement, it was also found that excess water removal by the catalytically active membrane appears to improve activity of the lipase immobilized.

"Active surfaces" formed by immobilization of enzymes on solid-supported polymer membranes

In various domains ranging from catalysis to medical and environmental sciences, there is currently much focus on the design of surfaces that present active compounds at the interface with their environments. Here, we describe the design of "active surfaces" based on solid-supported monolayers of asymmetric triblock copolymers, which serve as templates for the attachment of enzymes. A group of poly(ethylene glycol)-block-poly(γ-methyl-ε-caprolactone)-block-poly[(2-dimethylamino) ethyl methacrylate] amphiphilic copolymers, with different hydrophilic and hydrophobic domains (PEG45-b-PMCLx-b-PDMAEMAy) was selected to generate solid-supported polymer membranes. The behavior of the copolymers in terms of their molecular arrangements at the air-water interface was established by a combination of Langmuir isotherms and Brewster angle microscopy. Uniform thin layers of copolymers were obtained by transferring films onto silica solid supports at optimal surface pressure. These solid-supported polymer membranes were characterized by assessing various properties, such as monolayer thickness, hydrophilic/hydrophobic balance, topography, and roughness. Laccase, used as an enzyme model, was successfully attached to copolymer membranes by stable interactions as followed by quartz crystal microbalance with dissipation measurements, and its activity was preserved, as indicated by activity assays. The interaction between the amphiphilic triblock copolymer films and immobilized enzymes represents a straightforward approach to engineer "active surfaces", with biomolecules playing the active role by their intrinsic bioactivity.

Inorganic materials as supports for covalent enzyme immobilization: methods and mechanisms

Several inorganic materials are potentially suitable for enzymatic covalent immobilization, by means of several different techniques. Such materials must meet stringent criteria to be suitable as solid matrices: complete insolubility in water, reasonable mechanical strength and chemical resistance under the operational conditions, the capability to form manageable particles with high surface area, reactivity towards derivatizing/functionalizing agents. Non-specific protein adsorption should be always considered when planning covalent immobilization on inorganic solids. A huge mass of experimental work has shown that silica, silicates, borosilicates and aluminosilicates, alumina, titania, and other oxides, are the materials of choice when attempting enzyme immobilizations on inorganic supports. More recently, some forms of elemental carbon, silicon, and certain metals have been also proposed for certain applications. With regard to the derivatization/functionalization techniques, the use of organosilanes through silanization is undoubtedly the most studied and the most applied, although inorganic bridge formation and acylation with selected acyl halides have been deeply studied. In the present article, the most common inorganic supports for covalent immobilization of the enzymes are reviewed, with particular focus on their advantages and disadvantages in terms of enzyme loadings, operational stability, undesired adsorption, and costs. Mechanisms and methods for covalent immobilization are also discussed, focusing on the most widespread activating approaches (such as glutaraldehyde, cyanogen bromide, divinylsulfone, carbodiimides, carbonyldiimidazole, sulfonyl chlorides, chlorocarbonates, N-hydroxysuccinimides).

Radiofrequency treatment enhances the catalytic function of an immobilized nanobiohybrid catalyst

Biocatalysis, the use of enzymes in chemical transformation, has undergone intensive development for a wide range of applications. As such, maximizing the functionality of enzymes for biocatalysis is a major priority to enable industrial use. To date, many innovative technologies have been developed to address the future demand of enzymes for these purposes, but maximizing the catalytic activity of enzymes remains a challenge. In this study, we demonstrated that the functionality of a nanobiocatalyst could be enhanced by combining immobilization and radiofrequency (RF) treatment. Aminopeptidase PepA-encapsulating 2 nm platinum nanoparticles (PepA-PtNPs) with the catalytic activities of hydrolysis and hydrogenation were employed as multifunctional nanobiocatalysts. Immobilizing the nanobiocatalysts in a hydrogel using metal chelation significantly enhanced their functionalities, including catalytic power, thermal-stability, pH tolerance, organic solvent tolerance, and reusability. Most importantly, RF treatment of the hydrogel-immobilized PepA-PtNPs increased their catalytic power by 2.5 fold greater than the immobilized PepA. Our findings indicate that the catalytic activities and functionalities of PepA-PtNPs are greatly enhanced by the combination of hydrogel-immobilization and RF treatment. Based on our findings, we propose that RF treatment of nanobiohybrid catalysts immobilized on the bulk hydrogel represents a new strategy for achieving efficient biocatalysis.

Nanoscale roughness affects the activity of enzymes adsorbed on cluster-assembled titania films

In this study, we investigated how the adsorption properties governed by the nanometer-scale surface morphology of cluster-assembled titanium oxide films influence the catalytic activity of immobilized serine-protease trypsin. We developed an activity assay for the parallel detection of physisorbed enzyme activity and mass density of the adsorbed proteins in microarray format. The method combines a microarray-based technique and advanced quantitative confocal microscopy approaches based on fluorescent labeling of enzymes and covalent labeling of active sites of surface-bound enzymes. The observed diminishing trypsin binding affinity with increasing roughness, as opposed to the steep rise in its saturation uptake, was interpreted as heterogeneous nucleation-driven adsorption of trypsin at the rough nanoporous titania surface. The increase in relative activity of adsorbed trypsin is proportional to the fractional saturation of titania surfaces, expressed as percentage of saturation uptake. In turn, the specific activity, that is, the ratio of active proteins to the absolute number of adsorbed proteins, drops with growing saturation uptake and surface roughness, witnessing a reduction in the accessibility of enzyme active sites. Both geometrical constraints of titania nanopores and the clusterwise adsorption of trypsin were identified as the key factors underpinning the steric hindrance of the immobilized enzyme. These findings are relevant for the optimization of rough nanoporous surfaces as carriers of immobilized enzymes. The proposed activity assay is particularly advantageous in the screening of candidate materials for enzyme immobilization.

Thin-layer polymer wrapped enzymes encapsulated in hierarchically mesoporous silica with high activity and enhanced stability

A novel soft-hard cooperative approach was developed to synthesize bioactive mesoporous composite by pre-wrapping Penicillin G amidase with poly(acrylaimde) nanogel skin and subsequently incorporating such Penicillin G amidase nanocapsules into hierarchically mesoporous silica. The as-received bioactive mesoporous composite exhibited comparable activity and extraordinarily high stability in comparison with native Penicillin G amidase and could be used repetitively in the water-medium hydrolysis of penicillin G potassium salt. Furthermore, this strategy could be extended to the synthesis of multifunctional bioactive mesoporous composite by simultaneously introducing glucose oxidase nanocapsules and horseradish peroxidase nanocapsules into hierarchically mesoporous silica, which demonstrated a synergic effect in one-pot tandem oxidation reaction. Improvements in the catalytic performances were attributed to the combinational unique structure from soft polymer skin and hard inorganic mesoporous silica shell, which cooperatively helped enzyme molecules to retain their appropriate geometry and simultaneously decreased the enzyme-support negative interaction and mass transfer limitation under heterogeneous conditions.