Covalent immobilization of trypsin onto poly(2-hydroxyethyl methacrylate)/polystyrene composite microspheres by cyanogen bromide method and its enzymatic activity

Activation of Inert Supports for Enzyme(s) Immobilization Harnessing Biocatalytic Sustainability for Perennial Utilization

Although Nature's evolution and intelligence have gifted humankind with noteworthy enzyme candidates to simplify complex reactions with ultrafast, overselective, effortless, mild biological reactions for millions of years, their availability at minute-scale, short-range time-temperature stability, and purification costs hardly justify recycling/or reuse. Covalent immobilization, particularly via multipoint bonds, prevents denaturing, maintains activities for long-range time, pH, and temperature, and makes catalysts available for repetitive usages; which attracts researchers and industries to bring more immobilized enzyme contenders in science and commercial progressions. Inert-support activation, the most crucial step, needs appropriate activators; under mild conditions, the activator's functional group(s) still present on the activated support rapidly couples the enzyme, preventing unfolding and keeping the active site alive. This review summarizes exciting experimental advances, from the 1950s until today, in the activation strategies of various inert supports with five different surface activators, the cyanogen bromide, the isocyanate/isothiocyanate, the glutaraldehyde, the carbodiimide (with or without N-hydroxysuccinimide (NHS)), and the diazo group, for the immobilization of diverse enzymes for broader applications. These activators under mild pH (7.5 ± 0.5) and temperature (27 ± 3 °C) and ordinary stirring witnessed support activation and enzyme coupling and put off unfolding, harnessing addressable activities (CNBr: 40 ± 10%; -N═C═O/-N═C═S: 32 ± 7%; GA: 70 ± 15%; CDI: 60 ± 10%; -N+≡N: 80 ± 15%), while underprivileged stability, longevity, and reusabilities keep future investigations alive.

Control of protein immobilization: coupling immobilization and site-directed mutagenesis to improve biocatalyst or biosensor performance

Mutagenesis and immobilization are usually considered to be unrelated techniques with potential applications to improve protein properties. However, there are several reports showing that the use of site-directed mutagenesis to improve enzyme properties directly, but also how enzymes are immobilized on a support, can be a powerful tool to improve the properties of immobilized biomolecules for use as biosensors or biocatalysts. Standard immobilizations are not fully random processes, but the protein orientation may be difficult to alter. Initially, most efforts using this idea were addressed towards controlling the orientation of the enzyme on the immobilization support, in many cases to facilitate electron transfer from the support to the enzyme in redox biosensors. Usually, Cys residues are used to directly immobilize the protein on a support that contains disulfide groups or that is made from gold. There are also some examples using His in the target areas of the protein and using supports modified with immobilized metal chelates and other tags (e.g., using immobilized antibodies). Furthermore, site-directed mutagenesis to control immobilization is useful for improving the activity, the stability and even the selectivity of the immobilized protein, for example, via site-directed rigidification of selected areas of the protein. Initially, only Cys and disulfide supports were employed, but other supports with higher potential to give multipoint covalent attachment are being employed (e.g., glyoxyl or epoxy-disulfide supports). The advances in support design and the deeper knowledge of the mechanisms of enzyme-support interactions have permitted exploration of the possibilities of the coupled use of site-directed mutagenesis and immobilization in a new way. This paper intends to review some of the advances and possibilities that these coupled strategies permit.

Latex of immunodiagnosis for detecting the Chagas disease. I. Synthesis of the base carboxylated latex

This article investigates the synthesis of two (monodisperse, carboxylated, and core-shell) latexes, through a batch and a semibatch emulsion copolymerizations of styrene (St) and methacrylic acid (MAA) onto polystyrene latex seeds. A mathematical model of the process was developed that predicts conversion, average particle size, and surface density of carboxyl groups. The model was adjusted to the batch reaction measurements, and then it was used in the design of the semibatch experiment. The semibatch reaction involved an initial homopolymerization of St followed by instantaneous addition of MAA-St-initiator. Compared with the batch reaction results, the semibatch policy more than doubled the surface density of carboxyl groups. The second part of this series describes the development of an immunodiagnosis latex-protein complex for detecting the Chagas disease, by coupling an antigen of Trypanosoma cruzi onto the produced carboxylated latexes.

The Properties of Covalently Immobilized Trypsin on Soap-Free P(MMA-EA-AA) Latex Particles

The covalent immobilization of trypsin onto poly[(methyl methacrylate)-co-(ethyl acrylate)-co-(acrylic acid)] latex particles, produced by a soap-free emulsion polymerization technique, was carried out using the carbodiimide method. The catalytic properties and kinetic parameters, as well as the stability of the immobilized enzyme were compared to those of the free enzyme. Results showed that the optimum temperature and pH for the immobilized trypsin in the hydrolysis of casein were 55 degrees C and 8.5, both of which were higher than that of the free form. It was found that K(m) (Michaelis constant) was 45.7 mg . ml(-1) and V(max) (maximal reaction rate) was 793.0 microg . min(-1) for immobilized trypsin, compared to a K(m) of 30.0 mg . ml(-1) and a V(max) of 5 467.5 microg . min(-1) for free trypsin. The immobilized trypsin exhibited much better thermal and chemical stabilities than its free counterpart and maintained over 63% of its initial activity after reusing ten times.

Formation of Monodisperse Polyacrylamide Particles by Radiation-Induced Dispersion Polymerization: Particle Size and Size Distribution

Polyacrylamide microparticles were directly produced by radiation-induced dispersion polymerization in aqueous alcohol media using poly(N-vinylpyrrolidone) as a steric stabilizer at room temperature. The hydrodynamic diameter of a polymer particle and its distribution were measured on a dynamic laser light-scattering spectrometer. This method takes advantages of the specialties of radiation induction, and highly uniform polymer microspheres were obtained with high conversion. The number of the particle produced in the early stage of the polymerization was found to be constant during the remainder of the polymerization. The effects of various polymerization parameters, such as absorbed dose rate, monomer concentration, stabilizer content, medium polarity, and polymerization temperature on the particle size and size distribution were systematically investigated.

Effect of Lauryl Alcohol on Morphology of Uniform Polystyrene-Poly(methyl methacrylate) Composite Microspheres Prepared by Porous Glass Membrane Emulsification Technique

Fairly uniform poly(styrene)-poly(methyl methacrylate) (PST-PMMA) composite microspheres were prepared by employing an SPG (Shirasu Porous Glass) membrane emulsification technique. A mixture of PST, PMMA, and cosurfactant [lauryl alcohol (LOH)] dissolved in dichloromethane (DCM) was used as the dispersed phase, and an aqueous phase containing poly(vinyl alcohol) and sodium lauryl sulfate was used as the continuous phase. It is necessary to add LOH to obtain uniform particles with the SPG emulsification technique. The effects of the volume of LOH on the morphology of the final particles were investigated by varying the volume of LOH from 0 to 2 ml (per 1.2 g polymer). A three-component model was developed for different PMMA/PST ratios and LOH/polymer ratios, based on Sundberg's theory; and the calculation on morphology was carried out by using the three-component model. Agreement was obtained between experimental and calculated results. When 2 ml of LOH was added, it was found that LOH can engulf the polymer particles completely; a hemicore (HCP1P2P3) morphology, where PST and PMMA formed a hemisphere core inside a LOH shell, was observed when the PMMA/PST ratio was high, while core-shell-shell (CSP1P2P3) morphology, where PMMA formed a core and PST and LOH formed an inner shell and an outer shell, respectively, was observed when the PMMA/PST ratio was low. When the volume of LOH was below 1 ml (per 1.2 g polymer), however, LOH could not always engulf the inner polymer particles completely; cored hemisphere (CHSP3P2P1), core-shell-shell (CSP2P1P3), and hemicore (HCP1P2P3) morphologies were observed, depending on the PMMA/PST ratio and volume of LOH. Copyright 1999 Academic Press.

Study on Preparation and Morphology of Uniform Artificial Polystyrene-Poly(methyl methacrylate) Composite Microspheres by Employing the SPG (Shirasu Porous Glass) Membrane Emulsification Technique

Fairly uniform polystyrene-poly(methyl methacrylate) (PST-PMMA) composite microspheres were prepared by employing the SPG (Shirasu Porous Glass) membrane emulsification technique. PST, PMMA, and cosurfactant (lauryl alcohol, LOH) dissolved in dichloromethane (DCM) were used as a dispersed phase, and an aqueous phase containing poly(vinyl alcohol) and sodium lauryl sulfate was the continuous phase. The effects of LOH amount on the critical pressure of emulsification (Pcr), size distribution of droplets, and morphologies of final particles were investigated. It was found that Pcr decreased with increasing LOH amount because of preferential partition of LOH on the surface of the droplets in the initial stage of emulsification. When polymer concentration or PMMA/PST ratio was low, the size distribution of droplets decreased with increasing LOH amount, whereas an inverse trend was observed when both polymer concentration and PMMA/PST ratio were high. When polymer concentration was low, PST-PMMA core-shell particles always were obtained in the absence of LOH, irrespective of the PMMA/PST ratio. In the presence of LOH, however, microdomain, hemisphere, and inverted core-shell morphologies were formed as the PMMA/PST ratio decreased from 5/5 to 1/9 (g/g). When polymer concentration was high, different morphologies such as multiplet and inverted core-core-shell were observed. Theoretical calculations of morphologies were carried out, and agreement was obtained between experimental and calculated results. Copyright 1999 Academic Press.