Water-soluble Cross-linking Agent Research Articles

Dual dynamic network system constructed by waterborne polyurethane for improved and recoverable performances

The implementation of the dynamic crosslinking network toward the commodity polymers such as polyurethane has been much highlighted for resource conservation and environmental protection. This work demonstrates a feasible dual dynamic network (DDN) construction of waterborne polyurethane (WPU) by using a biobased trifunctional ketose, 1,3-dihydroxyacetone (DHA) serving as the chain extender. The WPU dispersion was compatible well with the post-added adipic acid hydrazide (ADH) as the water soluble crosslinking agent. When the one-pot system of WPU-ADH was cast into films, covalent adaptive network (CAN) was formed through the condensation of ketohydrazine and carbonyl groups driven by the evaporation of water. The produced acylhydrazone groups would also contribute to the strengthen on the H-bonding crosslinking network. The synergism of the two sets of the networks provided not only the improved mechanical performances, but their > 95% recovery efficiencies on the 28 MPa of strength and 750% fracture elongation in the self-healing, reprocessing and welding tests under moderate heating. In addition, the WPU exhibited as an effective adhesive to metal with the adhesive strength sustained after four times of deconstruction-rebonding circles. The all commercially available components, feasible preparation together with the excellent and recoverable performances suggest an industrializable resolution for the sustainability of environmental friendly WPU materials.

E-Beam Processing of Collagen-Poly(N-vinyl-2-pyrrolidone) Double-Network Superabsorbent Hydrogels: Structural and Rheological Investigations

Collagen (C)-poly(N-vinyl-2-pyrrolidone) (PVP) double-network superabsorbent hydrogels were synthesized by e-beam (electron beam) radiation processing, both with the addition of water-soluble cross-linking agents (CA), as well as without CA. The aim of the study was to develop a hydrogel for future application as wound dressings via e-beam radiation cross-linking of two biocompatible polymers. The formation of C-PVP hydrogels was confirmed by Fourier transform infrared (FTIR) spectroscopy and their performance was determined from morphological and rheological experiments, such as sol-gel analysis, swelling capacity, storage (G′) and viscous (G″) moduli, cross-linking density, and pore size. Sol-gel analysis was performed in order to determine the gel properties as function of absorbed dose and it was found that the degradation density (p0)/cross-linking density (q0) ratio indicates a negligible contribution of chain scission processes. The rheological data confirmed that the elastic properties were predominant: G′ moduli were larger than G″ moduli, as is specific to elastic solids and indicate the formation of a permanent hydrogel network were cross-links are present. Moreover, the swelling studies indicated that the hydrogels have good stability both in deionized water and phosphate-buffered saline (PBS) solution at 37 °C, and superabsorbent properties. The hydrogels network parameters obtained with lower content of CA, could be controlled by changing the absorbed dose.

Effects of EDC-PEI heparinization on allogeneic vascular antigens and inflammation levels via a rat abdominal aorta transplantation model.

The objective of this study was to investigate the possibility of increasing the remote patency rate of allogeneic vessel transplantation through studying the effects of N-ethyl-N-(3-dimethylaminopropyl)-carbodiimide and polyethyleneimine (EDC-PEI) heparinization on allogeneic vascular antigens and inflammation levels. Forty rats were randomly divided into the control group, the EDC group, the PEI group and the EDC-PEI group. The rat abdominal aorta was used as the object of study, and the transplanted blood vessels were pretreated with EDC as the water-soluble cross-linking agent and PEI as the heparin-coated carrier. A rat abdominal aorta allogeneic transplantation model was established. Ultrasonic examination was used for observation of patency of proximal and distal anastomosis in each group. The tissue repair after abdominal aorta transplantation in each group was examined by H&E staining. The biomechanics, denaturation temperature and blasting strength of each group were compared. The levels of IL-1, IL-6 and TNF-α in serum of rats were measured by ELISA method, and the expression of MHC-II and α-GAL antigens in blood vessels were detected by immunohistochemistry. There were different degrees of thickening and inflammatory cell aggregation in the abdominal aorta of rats in the control, EDC and PEI groups, but there was no obvious lesion in the EDC-PEI group. Compared with the four groups, the mechanical characteristics of the EDC group decreased significantly, and the stenosis rate of anastomotic stoma in the EDC group was higher than that in the EDC-PEI and PEI groups (P<0.05). The denaturation temperature of the PEI group was lower than that of the EDC and EDC-PEI groups (P<0.05). The mechanical property and vascular bursting strength in the EDC-PEI group were similar to those in the control group. At the same time, it has more significant advantages than the other three groups in removing the vascular antigens MHC-II and α-GAL and reducing the level of inflammatory reaction, thus increasing the remote patency rate of allogeneic vascular transplantation. The inflammatory response and vascular antigenicity after transplantation are effectively reduced via the rat abdominal aorta transplantation model treated with allogeneic EDC-PEI heparinization, which has a higher remote patency rate.

Genipin Reverses HFD-Induced Liver Damage and Inhibits UCP2-Mediated Pyroptosis in Mice

Background/Aims: Liver damage is a typical manifestation of nonalcoholic fatty liver disease (NAFLD). It originates from excessive fat accumulation, leading to hepatocyte death, inflammation, and fibrosis. Nonalcoholic steatohepatitis (NASH) is a type of NAFLD with a prevalence of 49% in morbidly obese patients. Pyroptosis plays an important role in the development of NASH; thus, it is important to elucidate the effect of lipid accumulation on pyroptosis. Genipin (GNP), a natural water-soluble cross-linking agent, has hepatoprotective effects and decreases lipid accumulation in the liver; however, the mechanisms underlying these effects are unknown. Methods: In this study, qPCR and Western blot were used to examine pyroptotic gene expression in high-fat diet (HFD) induced obese mice and free fatty acids (FFAs) treated hepatocytes. At the same time, relative lactate dehydrogenase (LDH) release and Hoechst & propidium iodide (PI) staining were done to verify cell death. To explore the molecular mechanism, cell transfection were constructed with siRNA or plasmid to obtain knockdown or overexpression hepatocytes. Results: We found that HFD-fed mice and FFAs-treated hepatocytes had obvious pyroptosis, and addition of GNP reversed liver damage and inhibited pyroptosis both in vitro and in vivo. Besides, UCP2 knockdown cells showed suppressed FFAs-mediated pyroptosis, as determined by decreased pyroptotic gene expression, reduced lactate dehydrogenase (LDH) release, and reduced cell death. Consistent with this, cells transfected with UCP2 had upregulated pyroptotic gene expression, increased LDH release, and increased cell death. Conclusion: GNP reverses HFD-induced liver damage and inhibits UCP2-mediated pyroptosis. Thus, GNP may serve as a potential therapeutic candidate for NAFLD.

Effect of pH on dentin protease inactivation by carbodiimide.

A water-soluble crosslinking agent, 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC), has been used as a pretreatment of acid-etched dentin to inactivate matrix-bound endogenous dentin proteases. The aim of this study was to evaluate the effect of pH on the inactivation capacity of EDC. Demineralized dentin beams (1×2×6mm) were divided into six groups (n=8 per group). Then, EDC (0.3M) was solubilized in distilled water with pH of 2, 4, 6, 7, 9, or 11. Control EDC was solubilized in 0.1M 2-(N-morpholino) ethanesulfonic acid (MES) buffer and its pH was adjusted to 6. The dentin beams were pretreated for 1min with EDC at each pH or with EDC in MES buffer at pH6.0 and then incubated in 1ml of simulated body fluid (pH7.2) for 1, 3, 7, or 14d. Untreated beams served as controls. At each study time-point, the dry mass of dentin beams was assessed and the incubation media were analyzed for carboxyterminal telopeptide of type-I collagen (ICTP) and C-terminal telopeptide of type I collagen (CTX) using specific ELISAs. Data were subjected to repeat-measures anova. The results of the study indicated that specimens pretreated with EDC in MES buffer showed the lowest collagen degradation in terms of mass loss and release of telopeptides, while specimens pretreated in alkaline media showed the highest collagen degradation. This study indicates that the pH of the EDC solution plays an important role in the stability of dentin protease inactivation.

Novel Polymer Monolithic Column for Hydrophilic Compounds

A hydrophilic polymer-based monolithic column was prepared from water-soluble crosslinking agents for liquid chromatography. The column media were prepared with a diacrylate monomer, aqueous polyethylene glycol, methanol, and a water-soluble radical initiator. A fused silica capillary column, which was significantly modified by vinyl groups, was utilized as the outer column in order to control polymer shrinkage. We optimized the modification of the capillary column, composition of the monomer and porogen, and polymerization condition. The optimized column exhibited high hydrophilicity and achieved the baseline separation of nucleobases by using only a buffered solution as the mobile phase. Additionally, another column prepared from binary water-soluble crosslinking agents exhibited lower nonspecific adsorption of several proteins. Basically, we would show the possibility of a new type of polymer monolith prepared from water-soluble crosslinker and water-soluble porogenic solvent, and they can be used for chromatographic separation without non-specific hydrophobic interaction.

Structural Requirements for Multimerization of the Pathogen Receptor Dendritic Cell-specific ICAM3-grabbing Non-integrin (CD209) on the Cell Surface

The myeloid C-type lectin dendritic cell-specific ICAM3-grabbing non-integrin (DC-SIGN, CD209) recognizes oligosaccharide ligands on clinically relevant pathogens (HIV, Mycobacterium, and Aspergillus). Alternative splicing and genomic polymorphism generate DC-SIGN mRNA variants, which have been detected at sites of pathogen entrance and transmission. We present evidence that DC-SIGN neck variants are expressed on dendritic and myeloid cells at the RNA and protein levels. Structural analysis revealed that multimerization of DC-SIGN within a cellular context depends on the lectin domain and the number and arrangement of the repeats within the neck region, whose glycosylation negatively affects oligomer formation. Naturally occurring DC-SIGN neck variants differ in multimerization competence in the cell membrane, exhibit altered sugar binding ability, and retain pathogen-interacting capacity, implying that pathogen-induced cluster formation predominates over the basal multimerization capability. Analysis of DC-SIGN neck polymorphisms indicated that the number of allelic variants is higher than previously thought and that multimerization of the prototypic molecule is modulated in the presence of allelic variants with a different neck structure. Our results demonstrate that the presence of allelic variants or a high level of expression of neck domain splicing isoforms might influence the presence and stability of DC-SIGN multimers on the cell surface, thus providing a molecular explanation for the correlation between DC-SIGN polymorphisms and altered susceptibility to HIV-1 and other pathogens.

Preparation of a novel molecularly imprinted polymer using a water-soluble crosslinking agent

A molecularly imprinted polymer was prepared using a water-soluble crosslinking agent. An ionic complex was utilized as the assembly for the template molecule and the functional monomer, and water as porogenic solvent during preparation of the imprinted polymer. The results of chromatographic evaluations for the prepared polymer suggested that the polymer had much lower hydrophobicity compared with usual octadecyl group bonded silica or the usual molecular imprinted polymer prepared from ethyleneglycol dimethacrylate, and the selective recognition ability for template molecule in the completely aqueous condition.

Naturally Occurring Mutations in the Largest Extracellular Loops of ABCA1 Can Disrupt Its Direct Interaction with Apolipoprotein A-I

The ABCA1 transporter contains two large domains into which many of the genetic mutations in individuals with Tangier disease fall. To investigate the structural requirements for the cellular cholesterol efflux mediated by ABCA1, we have determined the topology of these two domains and generated transporters harboring five naturally occurring missense mutations in them. These mutants, unlike wild type ABCA1, produced little or no apoA-I-stimulated cholesterol efflux when transfected into 293 cells, establishing their causality in Tangier disease. Because all five mutant proteins were well expressed and detectable on the plasma membrane, their interaction with the ABCA1 ligand, apolipoprotein (apo) A-I, was measured using bifunctional cross-linking agents. Four of five mutants had a marked decline in cross-linking to apoA-I, whereas one (W590S) retained full cross-linking activity. Cross-linking of apoA-I was temperature-dependent, rapid in onset, and detectable with both lipid- and water-soluble cross-linking agents. These results suggest that apoA-I-stimulated cholesterol efflux cannot occur without a direct interaction between the apoprotein and critical residues in two extracellular loops of ABCA1. The behavior of the W590S mutant indicates that although binding of apoA-I by ABCA1 may be necessary, it is not sufficient for stimulation of cholesterol efflux.

Association of membrane-bound amyloid precursor protein APP with the apolipoprotein E receptor LRP

In order to identify cell surface proteins that interact with the amyloid precursor protein (APP), we biotinylated H4 human neuroglioma cells in culture with a water soluble biotinylating agent, immunoprecipitated APP with an antibody specific to the intracellular domain, and probed the precipitated proteins with anti-biotin. In human neuroglioma cells overexpressing APP751, we found a high molecular weight protein that immunoprecipitated with APP. This band was identified as the low density lipoprotein receptor-related protein (LRP) by three criteria: first, the band immunolabeled with anti-LRP antibodies; second, the band bound the LRP receptor associated protein, RAP; and third, this band was present in LRP-expressing fibroblasts, but not LRP-deficient fibroblasts. In complementary experiments, we found that APP co-precipitated with LRP, with a preference for an isoform of APP containing the Kunitz protease inhibitor domain. Interaction of APP and LRP on the surface of living cells was demonstrated by crosslinking APP and LRP with the water-soluble cross-linking agent BS 3. APP and LRP were shown by confocal microscopy to colocalize in perinuclear structures, but to primarily remain separate in vesicles and on the cell surface. We propose that full-length APP can transiently interact with the receptor LRP on the cell surface, affecting the processing and intracellular transport of APP.

Microencapsulation of water‐soluble herbicide by interfacial reaction. I. Characterization of microencapsulation

A new microencapsulation was established in which small microcapsules with a hydrophilic polymeric wall could be fabricated, capsulizing the water-soluble content. The new microencapsulation is based on an emulsion interfacial reaction technique that combines the characteristics of an interfacial reaction and conventional emulsion processes. In this technique, hydrophilic polymers [poly(vinyl alcohol) and chitosan] were used as the wall material of the microcapsules. The microencapsulation process was composed mainly of the following steps: preparation of a water/oil (w/o) emulsion 1 containing hydrophilic polymers and a water-soluble core material and w/o emulsion 2 containing a water-soluble crosslinking agent and catalyst; the formation of microcapsules by mixing emulsion 1 and emulsion 2; and washing and drying the formed microcapsules. In the new technique an insoluble polymer film was formed easily by the fast crosslinking reaction on the surface of tiny emulsified polymer solution particles in contact with the emulsified crosslinking agent solution particles under mixing with high speed agitation. Thereby, small stable microcapsules were formed. The emphasis in this study was on the establishment of the microencapsulation process by which microcapsules were formed and controlled. The microencapsulation was characterized by analysis of the size distribution of microcapsules fabricated with process conditions. The clarification of the effect of the preparation conditions was also made on the morphology and diameter of the microcapsules. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1645–1655, 2000

POLYCATIONIC SALTS. 3. SYNTHESIS, STYRENE BASED TRIALKYLAMMONIUM SALTS AND THEIR POLYMERIZATION1-2 1, 2

A number of styrene-based vinylbenzyltrialkylammonium chloride salts were prepared via the Menshutkin reaction of vinylbenzylchloride with selected tert. amines. The vinylbenzyltrinalkylammonium salts were obtained in most cases in nearly quantitative yields. The lower members of the vinyl-benzyltrialkylammonium salts, such as vinylbenzyltrimethyl-ammoniumchloride, vinylbenzyl-triethylammonium chloride are highly water soluble. Vinylbenzyldimethyl(n-octyl or n-dodecyl) ammonium chloride were insoluble in water, but soluble in methanol. These monomers were polymerized and copolymerized in water using water-soluble azo initiators for water soluble monomers or in methanol with 2,2-azobisisobutyronitrile to polyelectrolytes of extremely high molecular weights. Vinylbenzyltri-n-alkylammonium chlorides were also copolymerized and crosslinked with the water soluble crosslinking agent: N,N'di(vinylbenzyl)-N,N,N',N′-tetramethylethylene diammonium dichloride. Monomers and polymers were characterized by 15N NMR spectroscopy. With N,N'-di(vinylbenzyl)-N,N,N',N'-tetramethylethylene-diammonium dichloride, vinylbenzyltri-n-alkylammonium chlorides were polymerized to randomly crosslinked polycations with unusual properties. The polymers were evaluated for their effectiveness a bile acid sequestering agents. 1 Polycationic Salts 1: P. Zarras and O. Vogl, Polymer Preprints, ACS Division of Polymer Chemistry, 34(2), 424 (1993). 2 Polycationic Salts 2: P. Zarras and O. Vogl, Prog. Polym. Sci., 24(3), 485 (1999).

Microencapsulation of water-soluble herbicide by interfacial reaction. I. Characterization of microencapsulation

A new microencapsulation was established in which small microcapsules with a hydrophilic polymeric wall could be fabricated, capsulizing the water-soluble content. The new microencapsulation is based on an emulsion interfacial reaction technique that combines the characteristics of an interfacial reaction and conventional emulsion processes. In this technique, hydrophilic polymers [poly(vinyl alcohol) and chitosan] were used as the wall material of the microcapsules. The microencapsulation process was composed mainly of the following steps: preparation of a water/oil (w/o) emulsion 1 containing hydrophilic polymers and a water-soluble core material and w/o emulsion 2 containing a water-soluble crosslinking agent and catalyst; the formation of microcapsules by mixing emulsion 1 and emulsion 2; and washing and drying the formed microcapsules. In the new technique an insoluble polymer film was formed easily by the fast crosslinking reaction on the surface of tiny emulsified polymer solution particles in contact with the emulsified crosslinking agent solution particles under mixing with high speed agitation. Thereby, small stable microcapsules were formed. The emphasis in this study was on the establishment of the microencapsulation process by which microcapsules were formed and controlled. The microencapsulation was characterized by analysis of the size distribution of microcapsules fabricated with process conditions. The clarification of the effect of the preparation conditions was also made on the morphology and diameter of the microcapsules. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1645–1655, 2000

A Nonhydrolyzable-Water Soluble Crosslinker: Tetrallylpiperazinium Dichloride and its Copolymers with Acrylic Acid and Acrylamide

A versatile crosslinking agent, tetraallyl piperazinium dichloride (TAP) has been prepared and demonstrated to be useful in copolymerization with water soluble monomers such as acrylic acid and acrylamide. Although the crosslinker itself does not readily homopolymerize in water, it forms transparent rigid hydrogels within a reasonable period of time when copolymerized with acrylic acid. Being nonhydrolysable, the crosslinker presented is superior to other common water soluble crosslinking agents such as methylene or ethylene bis(acrylamides). Since this crosslinker has a low toxicity, it may be used for bioapplications such as gel electrophoresis etc.

Species-specific differences in covalently crosslinked complexes of yeast cytochrome C peroxidase with horse and yeast ISO-1 ferricytochromes C

1. 1. The results of chemically crosslinking yeast cytochrome c peroxidase with both horse and yeast iso-1 ferricytochromes c have been studied by a combination of gel electrophoresis and proton NMR spectroscopy. 2. 2. The complexes were formed at a variety of potassium phosphate concentrations ranging from 10 to 300 mM using the water soluble crosslinking agent, EDC (l-ethyl-3-[3-(dimethylamino)propyl]-carbodiimide). 3. 3. The primary crosslinking product in both cases is the 1:1 covalent complex, but, for each pair of partner proteins the yield of the 1:1 crosslinked complex varies with the salt concentration. 4. 4. Furthermore, at low salt concentrations the yield of the 1:1 covalent complex involving horse cytochrome c is much larger than the yield of the 1:1 covalent complex formed with yeast iso-1 cytochrome c, whereas at high salt concentrations the situation is reversed. 5. 5. Proton NMR spectroscopy, in combination with gel electrophoresis, provides evidence for the formation of different types of 1:1 complexes for the peroxidase/yeast cytochrome c pair and has been used to study the effect of changes in the solution ionic strength upon both the peroxidases/horse cytochrome c and the peroxidase/yeast cytochrome c complexes. 6. 6. This work indicates that electrostatic interactions between proteins play a dominant role in formation of complexes between cytochrome c peroxidase and horse ferricytochrome c, whereas the hydrophobic effect plays a comparatively larger role in stabilizing complexes between cytochrome c peroxidase and yeast iso-1 ferricytochrome c.

Chemical cross-linking study of complex formation between methylamine dehydrogenase and amicyanin from Paracoccus denitrificans

Two soluble periplasmic redox proteins from Paracoccus denitrificans, the quinoprotein methylamine dehydrogenase and the copper protein amicyanin, form a weakly associated complex that is critical to their physiological function in electron transport [Gray, K. A., Davidson, V. L., & Knaff, D. B. (1988) J. Biol. Chem. 263, 13987-13990]. The specific interactions between methylamine dehydrogenase and amicyanin have been studied by using the water-soluble cross-linking agent 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC). Treatment of methylamine dehydrogenase alone with EDC caused no intermolecular cross-linking but did cause intramolecular cross-linking of this alpha 2 beta 2 oligomeric enzyme. The primary product that was formed contained one large and one small subunit. Methylamine dehydrogenase and amicyanin were covalently cross-linked in the presence of EDC to form at least two distinct species, which were identified by nondenaturing polyacrylamide gel electrophoresis (PAGE). The formation of these cross-linked species was dependent on ionic strength, and the ionic strength dependence was much greater at pH 6.5 than at pH 7.5. The effects of pH and ionic strength were different for the different cross-linked products. SDS-PAGE and Western blot analysis of these cross-linked species indicated that the primary site of interaction for amicyanin was the large subunit of methylamine dehydrogenase and that this association could be stabilized by hydrophobic interactions. In light of these results a scheme is proposed for the interaction of amicyanin with methylamine dehydrogenase that is consistent with previous data on the physical, kinetic, and redox properties of this complex.