The immobilization of trypsin onto polyaniline for protein digestion

Purification and Glutaraldehyde Activation Study on HCl-Doped PVA⁻PANI Copolymers with Different Aniline Concentrations

In this work, we report the synthesis and purification of polyvinyl alcohol-polyaniline (PVA⁻PANI) copolymers at different aniline concentrations, and their molecular (¹H-NMR and FTIR), thermal (TGA/DTG/DSC), optical (UV⁻Vis-NIR), and microstructural (XRD and SEM) properties before and after activation with glutaraldehyde (GA) in order to obtain an active membrane. The PVA⁻PANI copolymers were synthesized by chemical oxidation of aniline using ammonium persulfate (APS) in an acidified (HCl) polyvinyl alcohol matrix. The obtained copolymers were purified by dialysis and the precipitation⁻redispersion method in order to eliminate undesired products and compare changes due to purification. PVA⁻PANI products were analyzed as gels, colloidal dispersions, and thin films. ¹H-NMR confirmed the molecular structure of PVA⁻PANI as the proposed skeletal formula, and FTIR of the obtained purified gels showed the characteristic functional groups of PVA gels with PANI nanoparticles. After exposing the material to a GA solution, the presence of the FTIR absorption bands at 1595 cm^-1, 1650 cm^-1, and 1717 cm^-1 confirmed the activation of the material. FTIR and UV⁻Vis-NIR characterization showed an increase of the benzenoid section of PANI with GA exposure, which can be interpreted as a reduction of the polymer with the time of activation and concentration of the solution.

Surface-Engineered Biocatalytic Composite Membranes for Reduced Protein Fouling and Self-Cleaning

A new biocatalytic nanofibrous composite ultrafiltration membrane was developed to reduce protein fouling interactions and self-clean the membrane surface. The dual-layer poly(vinylidenefluoride)/nylon-6,6/chitosan composite membrane contains a hydrophobic poly(vinylidenefluoride) cast support layer and a hydrophilic functional nylon-6,6/chitosan nanofibrous surface layer where enzymes were chemically attached. The intrinsic surface chemistry and high surface area of the nanofibers allowed optimal and stable immobilization of trypsin (TR) and α-chymotrypsin enzymes via direct covalent binding. The enzyme immobilization was confirmed by X-ray photoelectron spectroscopy and visualized by confocal microscopy analysis. The prepared biocatalytic composite membranes were nanoporous with superior permeability offering stable protein antiadhesion and self-cleaning properties owing to the repulsive mechanism and digestion of proteins into peptides and amino acids, which was quantified by the gel electrophoresis technique. The TR-immobilized composite membranes exhibited 2.7-fold higher permeance and lower surface protein contamination with 3-fold greater permeance recovery, when compared to the pristine membrane after two ultrafiltration cycles with the model feed solution containing bovine serum albumin/NaCl/CaCl₂. The biocatalytic membranes retained about 50% of the enzyme activity after six reuse cycles but were regenerated to 100% activity after enzyme reloading, leading to a simple and cost-effective water remediation operation. Such surface- and pore-engineered membranes with self-cleaning properties offer a viable solution for severe surface protein contamination in food and water applications.

A bioactive film based on cashew gum polysaccharide for wound dressing applications

This work presents the development of a new bioactive material for wound therapeutics which may play a dual role of modulate metallo proteinases activity while prevents infection blocking out pathogenic microorganisms and foreign materials. A CGP/PVA film was activated by covalent immobilization of trypsin. Results from biocompatibility test revealed that PDL fibroblasts grown on the surface of CGP/PVA and the high amount of viable cells proved absence of cytotoxicity. Trypsin immobilized onto CGP/PVA film remained 100% active after 28 days stored dried at room temperature. In addition, CGP/PVA-trypsin film could be used for 9 cycles of storage/use without loss of activity. After immobilization, trypsin retained its collagenolytic activity, indicating this material as a promising material for wound dressing applications.

Immobilization of trypsin on plasma prepared Ag/PPAni nanocomposite film for efficient digestion of protein

This work demonstrates the efficacy of a support matrix prepared by plasma process for trypsin immobilization without any surface activator. Plasma polymerization cum sputtering process is used to prepare the nanocomposite support matrix. Plasma sputtered silver nanoparticles (AgNPs) are uniformly embedded into plasma polymerized aniline (PPAni) film. Various characterization tools are employed to study the surface morphology, microstructure and chemical composition of the support matrices. Trypsin is immobilized onto the support matrix via the formation of covalent bond between them. Plasma generated free radicals on composite films activate the support matrix and make it efficient for increasing the tertiary enzyme stability via multipoint covalent attachment. Trypsin immobilized onto Ag/PPAni matrix has more hydrolyzing capacity of bovine serum albumin (BSA) than free trypsin as well as trypsin immobilized onto PPAni films.

Effects of organic and conventional management of sugar cane crop on soil physicochemical characteristics and phosphomonoesterase activity

Soil enzymes play an important role in agriculture and particularly in nutrient cycling. They are also involved in the degradation, transformation, and mineralization of organic matter and availability of nutrients in soil. It is believed that organic agriculture causes fewer losses to soil quality and is less aggressive to the environment than conventional management. In this study, the effects of conventional (CM) and organic management (OM) on phosphomonoesterases, an important enzyme for soil fertility, were evaluated and compared to those results from native Cerrado (Brazilian Savanna) soil (NS), because they are the most common phosphatases in soils. The results showed that there were both acid (AcP) and alkaline (AkP) phosphatases in all soils tested and that AcP activity was higher than that of AkP. In contrast to AkP, AcP had its activity affected by land use. In the cultivated areas there was a reduction of almost 50% of AcP activity respect to native unexploited soils and there was no significant difference between organic and CM, demonstrating that independent of the management chosen, there was an impact of land use on AcP activity. Principal component analysis indicated that characteristics related to pH such as alkali saturation (V%), aluminum saturation (M%), Al(3+), soil total acidity (H+Al), and Ca(2+) are the main factors that permit distinguishing NS from OM and CM.

Development of glutaraldehyde-crosslinked chymotrypsin and an in situ immobilized enzyme microreactor with peptide mapping by capillary electrophoresis

Immobilized proteolytic enzymes present several advantages over their soluble form, not the least of which is suppression of autoproteolysis peaks even at high enzyme-to-substrate ratios. We have made immobilized chymotrypsin by directly crosslinking it with glutaraldehyde to produce polymeric particles. Digestion of two model substrates using the particles was followed by CE peptide mapping with detection by UV absorbance or LIF. Results showed that autoproteolysis was highly suppressed and that different storage conditions of the particles in the short term (24 h) did not affect digestion of denatured BSA. As well, the chymotrypsin particles were indifferent to the presence of fluorescein groups on a casein substrate. Glutaraldehyde crosslinking of chymotrypsin inside a fused silica capillary column to make an immobilized enzyme reactor (IMER) was achieved in a series of reagent addition and washing steps, entirely automated using a commercial CE instrument. Digestion of myoglobin in the IMER for 30 min at 37°C followed by peptide mapping by CE-MS of the collected digest allowed identification of 17 chymotryptic peptides of myoglobin, or 83% primary sequence coverage.

Investigation of the binding of dioxin selective pentapeptides to a polyaniline matrix

Polyaniline in form of emeraldine salt and emeraldine base was used as a matrix to attach several labeled and non-labeled dioxin selective pentapeptides both directly to the polymer and using glutaraldehyde as a linker. The peptides have been selected as a model to study the binding process due to their smaller size, lower sensitivity to the environment and potential application as solid state extraction reagents for chlorinated toxins. The composition and the properties of the compounds were investigated by means of elemental analysis, XPS, FTIR, UV/vis, and fluorescence spectroscopy. The results have shown that 3.30-7.76% peptides were attached to the emeraldine base both with and without a linker. Glutaraldehyde and the peptides were connected to the matrix via chemical bond resulting in formation of compounds whit similar composition and stability in a broad pH range. The influence of the linker and the peptides on the electronic properties and composition of the polymer have been investigated by principal component analysis.

Immobilization of peroxidase onto magnetite modified polyaniline

The present study describes the immobilization of horseradish peroxidase (HRP) on magnetite-modified polyaniline (PANImG) activated with glutaraldehyde. After the optimization of the methodology, the immobilization of HRP on PANImG produced the same yield (25%) obtained for PANIG with an efficiency of 100% (active protein). The optimum pH for immobilization was displaced by the effect of the partition of protons produced in the microenvironment by the magnetite. The tests of repeated use have shown that PANImG-HRP can be used for 13 cycles with maintenance of 50% of the initial activity.

Trypsin-enabled construction of anti-fouling and self-cleaning polyethersulfone membrane

Constructing anti-fouling and self-cleaning membrane surfaces based on covalent attachment of trypsin on poly(methacrylic acid)-graft-polyethersulfone (PMAA-g-PES) membrane was reported. The carboxylic acid groups enriched on asymmetric PMAA-g-PES membrane surface were activated with 1-ethyl-(3-3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC)/N-hydroxysuccinimide (NHS) and employed as chemical anchors for the conjugation with amino groups of trypsin. Activity assays showed that such chemically immobilized trypsin was much more active and stable than that of the physically adsorbed counterpart. Trypsin covalently attached on membrane surface could substantially resist protein fouling in dynamic flow process. The considerable enhancement of protein solution permeation flux was observed as a consequence of rapid enzymatic degradation of protein deposited onto membrane surface. The permeation flux of the membrane could be recovered upon simple hydraulic flush after protein filtration, suggesting superior self-cleaning property. After multi-cycle BSA filtration over 15-day period, the active self-cleaning membrane maintained more than 95.0% of its initial flux.