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1.
Epidermal growth factor (EGF, 5900 Da) has been reported to have the high efficiency of wound repair. However, the half‐life of EGF in the body is too short to exert the biological activity effectively when applied in free forms. Conjugation of the low molecular weight chitosan (LMC) to EGF was carried out to enhance its stability. EGF was conjugated with LMC activated by water‐soluble carbodiimide. The formation of EGF–LMC was quantitatively measured by indirect enzyme‐linked immunosorbent assay (ELISA). In a study of the thermal and the proteolytic stability of free EGF and EGF–LMC, EGF covalently attached to LMC was found to be more stable than free EGF in thermal and proteolytic stabilities. In animal experiments of which free EGF (control), EGF–LMC (test) and LMC (carrier) diluted in viscous carboxymethyl cellulose (CMC) solution (vesicle) were applied to the incisional wounds in rats, the EGF–LMC conjugates are considered to be potent wound healing agent with mitogenicity and wound‐healing property. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5072–5082, 2006 相似文献
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Influence of physicochemical and structural characteristics of chitosan flakes on molybdate sorption
This study investigates the effect of deacetylation degree and molecular weight of chitosan on molybdate sorption on both raw and glutaraldehyde crosslinked samples. It appears that the physicochemical parameters affect the crystallinity of the samples: a high crystallinity reduces the accessibility of both water and metal ions to the amine binding sites. Both equilibrium and kinetic performances are thus influenced. The crosslinking by glutaraldehyde decreases sorption performances for large size particles while it does not influence sorption for the smallest. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 571–580, 1998 相似文献
3.
Justyna Kozlowska Alina Sionkowska Anna Maria Osyczka Marta Dubiel 《Polymer International》2017,66(8):1164-1172
This paper reports the effect of the combined technique of dehydrothermal treatment (DHT) and a mixture of 1‐ethyl‐3(3‐dimethylaminopropyl) carbodiimide (EDC) and N‐hydroxysuccinimide (NHS) crosslinking on the physicochemical properties of collagen/hydroxyapatite materials. Collagen and collagen/hydroxyapatite porous scaffolds containing different amounts of collagen and hydroxyapatite were prepared with use of the freeze‐drying technique. All samples were capable of absorbing a large quantity of phosphate buffered saline. Samples crosslinked by DHT+EDC/NHS presented higher resistance to collagenase degradation (with slightly reduced degradation in DHT+EDC/NHS crosslinked scaffolds prepared from 2% collagen solution), whereas DHT scaffolds exhibited faster degradation. Mechanical testing results suggested that scaffolds crosslinked by DHT+EDC/NHS treatment have an improved compressive modulus compared with EDC/NHS crosslinking. The qualitative analysis of colour intensity resulting from the CellTiter 96 Aqueous One Solution Cell Proliferation Assay (MTS) led to the conclusion that all samples, regardless of the crosslinking method, were well tolerated by cells. However, DHT and EDC/NHS crosslinked scaffolds seem to support better cell viability, in contrast to DHT+EDC/NHS crosslinked scaffolds that support cell differentiation instead. DHT+EDC/NHS crosslinked scaffolds markedly increase the specific alkaline phosphatase activity of cells, which may be of benefit in bone tissue engineering. © 2017 Society of Chemical Industry 相似文献
4.
Neutral protease was immobilized on glutaraldehyde‐pretreated N‐succinyl chitosan hydrogel beads and the biocatalyst obtained was used for the preparation of low molecular weight chitosan and chito‐oligomers with molecular weight of 1.9–23.5 kDa from commercial chitosan. Factors affecting the chitinolytic hydrolysis were described. The degradation was monitored by gel permeation chromatography. The structure of degraded chitosan was characterized by Fourier transform infrared, X‐ray diffraction and liquid chromatography‐mass spectrometry. Immobilized neutral protease showed optimal depolymerization at pH 5.7 and 50°C. The degree of deacetylation of the hydrolysates did not change compared to that of the initial chitosan. The decrease of molecular weight led to transformation of crystal structure but the chemical structures of residues were not modified. The degree of polymerization of chito‐oligomers was mainly from 3 to 8. The method allows cyclic procedures of immobilized enzyme and N‐succinyl chitosan support utilization, and is suitable for a large‐scale production of the low molecular weight chitosan and chito‐oligomers free of protein admixtures. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:4185–4193, 2006 相似文献
5.
Sung‐Pei Tsai Chien‐Yang Hsieh Chung‐Yu Hsieh Da‐Ming Wang Lynn Ling‐Huei Huang Juin‐Yih Lai Hsyue‐Jen Hsieh 《应用聚合物科学杂志》2007,105(4):1774-1785
In this study, a novel freeze‐gelation method instead of the conventional freeze‐drying method was used to fabricate porous chitosan/collagen‐based composite scaffolds for skin‐related tissue engineering applications. To improve the performance of chitosan/collagen composite scaffolds, we added 1‐ethyl‐3‐(3‐dimethylaminopropyl)‐carbodiimide (EDC) and amino acids (including alanine, glycine, and glutamic acid) in the fabrication procedure of the composite scaffolds, in which amino acid molecules act as crosslinking bridges to enhance the EDC‐mediated crosslinking. This novel combination enhanced the tensile strength of the scaffolds from 0.70 N/g for uncrosslinked scaffolds to 2.2 N/g for crosslinked ones; the crosslinked scaffolds also exhibited slower degradation rates. The hydrophilicity of the scaffolds was also significantly enhanced by the addition of amino acids to the scaffolds. Cell compatibility was demonstrated by the in vitro culture of human skin fibroblasts on the scaffolds. The fibroblasts attached and proliferated well on the chitosan/collagen composite scaffolds, especially the one with glutamic acid molecules as crosslinking bridges, whereas cells did not grow on the chitosan scaffolds. Our results suggest that the collagen‐modified chitosan scaffolds with glutamic acid molecules as crosslinking bridges are very promising biomaterials for skin‐related tissue engineering applications because of their enhanced tensile strength and improved cell compatibility with skin fibroblasts. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 相似文献
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The objective of this study is to explore the effect of using different recovery methods and conditions on the yield, solubility, molecular weight, and creep compliance of the regenerated chitosan. The results show that yields obtained by dialysis were higher than those using recovery medium of alkali solutions, organic solvents, or alkali–alcohol–water mixtures. For those chitosans employing alkali solutions as the recovery medium, the higher the alkali concentration used, the higher the yields obtained, although the total quantity of alkali in the solution were the same. Solubilities of regenerated chitosans were similar and independent at the methods of using alkali solution, organic solvent or alkali–alcohol–water mixture or at different concentrations of alkali solution. The molecular weight of regenerated chitosan decreased from 2.37 × 107 to 1.68 × 107 Da proportionally with the concentration of the alkali solution of the recovery medium from 1N to 8N. Creep compliance of regenerated chitosan gel obtained from 65% degree of deacetylation (DD) chitosan was lower than that of either 72 or 89% DD chitosan gel. Of the same DD chitosan, compliance of regenerated chitosan gels obtained by using a higher concentration of alkali solution was lower than that of a lower concentration ones. Hydrogels regenerated from different DD chitosans and/or different recovery mediums have different structure and tactile properties. Therefore, they can be used as wound dressings suited to different applications. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 193–202, 2002; DOI 10.1002/app.10296 相似文献
8.
Chitosan/gelatin porous bone scaffolds made by crosslinking treatment and freeze‐drying technology: Effects of crosslinking durations on the porous structure,compressive strength,and in vitro cytotoxicity
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In this study, freezing was used to separate a solute (polymer) and solvent (deionized water). The polymer in the ice crystals was then crosslinked with solvents, and this diminished the linear pores to form a porous structure. Gelatin and chitosan were blended and frozen, after which crosslinking agents were added, and the whole was frozen again and then freeze‐dried to form chitosan/gelatin porous bone scaffolds. Stereomicroscopy, scanning electron microscopy, compressive strength testing, porosity testing, in vitro biocompatibility, and cytotoxicity were used to evaluate the properties of the bone scaffolds. The test results show that both crosslinking agents, glutaraldehyde (GA) and 1‐ethyl‐3‐(3‐dimethylaminopropyl) carbodiimide, were able to form a porous structure. In addition, the compressive strength increased as a result of the increased crosslinking time. However, the porosity and cell viability were not correlated with the crosslinking times. The optimal porous and interconnected pore structure occurred when the bone scaffolds were crosslinked with GA for 20 min. It was proven that crosslinking the frozen polymers successfully resulted in a division of the linear pores, and this resulted in interconnected multiple pores and a compressively strong structure. The 48‐h cytotoxicity did not affect the cell viability. This study successfully produced chitosan/gelatin porous materials for biomaterials application. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41851. 相似文献
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Encapsulation of salicylic acid in acylated low molecular weight chitosan for sustained release topical application
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Acylated low molecular weight chitosan was used to encapsulate salicylic acid (SA) for sustained release in topical delivery. Chitosan nanoparticles were prepared from the depolymerization of commercial chitosan and further acylated with short alkyl chains. The successful acylation of butyryl chitosan [low molecular weight chitosan (LMWC)‐B] were proved by Fourier transform infrared (FTIR) and 1H‐NMR. Successful encapsulation of SA was observed by the shift of amide I band from 1648 cm?1 in LMWC‐B to 1641–1633 cm?1 in SA‐loaded LMWC‐B in FTIR analysis, which further confirmed with the size increment from dynamic light scattering and transmission electron microscopy analyses by comparing its unencapsulated LMWC‐B. SA release from LMWC‐B studied by Franz diffusion experiment followed Korsmeyer–Peppas model where the release component n value (0.502) indicated diffusion and polymer swelling were involved in release mechanism. The slow release study of SA showed the acylated chitosan exhibited sustained release property toward SA. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45273. 相似文献
11.
Control of swelling properties of polyvinyl alcohol/hyaluronic acid hydrogels for the encapsulation of chondrocyte cells
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Hydrogel scaffolds for tissue engineering are important biomaterials. The target in this study was to prepare polyvinyl alcohol/hyaluronic acid hydrogels for the encapsulation of chondrocyte cells by a simple cross‐linking reaction. Control of the swelling properties and morphology of the hydrogels for cultivation of chondrocytes was studied. The hydrogels were prepared from polyvinyl alcohol and hyaluronic acid derivatives bearing primary amine and aldehyde functionalities, respectively. The formation of the hydrogel upon mixing the aqueous solutions of the polymer derivatives took place at room temperature in a few seconds. The swelling properties of the hydrogels were found to depend on the polymer concentration and degree of substitution of the modified polymers. Scanning electron microscopy studies showed that the hydrogels had a suitable porous morphology for cell encapsulation. Furthermore, in vitro cell viability tests with the hydrogels showed no cytotoxicity for chondrocytes and that the cells grew well in the hydrogel scaffolds. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42272. 相似文献
12.
The molecular weights of the industrial-grade isotactic polypropylene (i-PP) homopolymers samples were determined by the melt-state rheological method and effects of molecular weight and molecular weight distribution on solid and melt state creep properties were investigated in detail. The melt-state creep test results showed that the creep resistance of the samples increased by Mw due to the increased chain entanglements, while variations in the polydispersity index (PDI) values did not cause a considerable change in the creep strain values. Moreover, the solid-state creep test results showed that creep strain values increased by Mw and PDI due to the decreasing amount of crystalline structure in the polymer. The results also showed that the amount of crystalline segment was more effective than chain entanglements that were caused by long polymer chains on the creep resistance of the polymers. Modeling the solid-state viscoelastic structure of the samples by the Burger model revealed that the weight of the viscous strain in the total creep strain increased with Mw and PDI, which meant that the differences in the creep strain values of the samples would be more pronounced at extended periods of time. 相似文献
13.
Effects of the degree of deacetylation (DDA) and the molecular mass of chitosan oligosaccharides (CTS-OS), obtained from the enzymatic hydrolysis of high molecular weight chitosan (HMWC), on antitumor activity was explored. The DDA and molecular weights of CTS-OS were determined by matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-TOF MS) analysis. The CTS-OS were found to be a mixture of mainly dimers (18.8%), trimers (24.8%), tetramers (24.9%), pentamers (17.7%), hexamers (7.1%), heptamers (3.3%), and octamers (3.4%). The CTS-OS were further fractionated by gel-filtration chromatography into two major fractions: (1) COS, consisting of glucosamine (GlcN)(n), n = 3-5 with DDA 100%; and (2) HOS, consisting of (GlcN)(5) as the minimum residues and varying number of N-acetylglucosamine (GlcNAc)(n), n = 1-2 with DDA about 87.5% in random order. The cytotoxicities, expressed as the concentration needed for 50% cell death (CC(50)), of CTS-OS, COS, and HOS against PC3 (prostate cancer cell), A549 (lung cancer cell), and HepG2 (hepatoma cell), were determined to be 25 μg·mL(-1), 25 μg·mL(-1), and 50 μg·mL(-1), respectively. The HMWC was approximately 50% less effective than both CTS-OS and COS. These results demonstrate that the molecular weight and DDA of chitosan oligosaccharides are important factors for suppressing cancer cell growth. 相似文献
14.
Functionalized multiwall carbon nanotubes (f-MWCNTs) were used to reinforce the freeze-dried gelatin (G)/chitosan (Ch) scaffolds for bone graft substitution. Two types of G/Ch scaffolds at a ratio of 2:1 and 3:1 by weight incorporated with 0.025, 0.05, or 0.1 and 0.2 or 0.4?wt% f-MWCNT, respectively, were prepared by freeze drying, and their structure, morphology, and physicochemical and compressive mechanical properties were evaluated. The scaffolds exhibited porous structure with pore size of 80–300 and 120–140?µm for the reinforced scaffolds of G/Ch 2:1 and 3:1, respectively, and porosity 90–93% which slightly decreased with an increase in f-MWCNTs content for both types. Incorporation of f-MWCNTs led to 11- and 9.6-fold increase in modulus, with respect to their pure biopolymer blend scaffolds at a level of 0.05?wt% for G/Ch 2:1 and 0.2?wt% for G/Ch 3:1, respectively. The higher content of f-MWCNTs resulted in loss of mechanical properties due to agglomeration. The highest value of compressive strength and modulus was obtained for G/Ch 2:1 with 0.05?wt% f-MWCNT as 411?kPa and 18.7?MPa, respectively. Improvement of in vitro bioactivity as a result of f-MWCNTs incorporation was proved by formation of a bone-like apatite layer on the surface of scaffolds upon immersion in simulated body fluid. The findings indicate that the f-MWCNT-reinforced gelatin/chitosan scaffolds may be a suitable candidate for bone tissue engineering. 相似文献
15.
Juthamas Ratanavaraporn Nathaon Chuma Sorada Kanokpanont Siriporn Damrongsakkul 《应用聚合物科学杂志》2019,136(1):46893
The alginate/hyaluronic acid (AL/HA) blended beads at different ratios (AL70HA30, AL50HA50, and AL30HA70) were formed by ionic crosslinking technique. The layer-by-layer coating of the beads with two opposite charged molecules, positive-charged type A gelatin (GA), and negative-charged AL, using alternate soaking technique was introduced to stabilize the beads. The AL70HA30, AL50HA50 beads showed high stability because of high ionic crosslinked AL component. Two-layer coating resulted in an appropriate layer that maximized the stability of the AL/HA beads. The higher ratio of HA resulted in the higher water absorption ability but degradation rate was accelerated. An antibiotic gentamicin was loaded into the beads with the entrapment efficiency of 69–89%. The beads containing 30% and 50% HA and coated with two layers showed a sustained release of gentamicin while the release behavior was governed by the diffusion and degradation of the beads. The gentamicin released from all beads also potentially inhibited the growth of Staphylococcus aureus (gram-positive) and Escherichia coli (gram-negative) bacteria up to at least 48 h. These beads with antibacterial activity can be further explored for the application as bone void filling material for treatment of infection in bone diseases such as osteoarthritis or rheumatoid. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46893. 相似文献
16.
High molecular weight polybenzoxazine precursors have been synthesized from aromatic or aliphatic diamine and bisphenol-A with paraformaldehyde. The precursors were obtained as soluble white powder. Molecular weight was estimated from the size exclusion chromatography to be several thousands. The structure of the precursors was confirmed by IR, 1H NMR and elemental analysis, indicating the presence of cyclic benzoxazine structure. The ratio of the ring-closed benzoxazine structure and the ring-opened structure in the high molecular weight precursor was estimated from 1H NMR spectrum and also from the exotherm of DSC, showing that the ratio of the ring-closed benzoxazine structure was 77–98%. The precursor solution was cast on glass plate, giving transparent and self-standing precursor films, which was thermally cured up to 240 °C to give brown transparent polybenzoxazine films. The toughness of the crosslinked polybenzoxazine films from the high molecular weight precursors was greatly enhanced compared with the cured film from the typical low molecular weight monomer. Tensile measurement of the polybenzoxazine films revealed that polybenzoxazine from aromatic diamine exhibited the highest strength and modulus. While, polybenzoxazine from longer aliphatic diamine had higher elongation at break. The viscoelastic analyses showed that the glass transition temperature of the polybenzoxazines derived from the high molecular weight precursors were as high as 238–260 °C. Additionally, these novel polybenzoxazine thermosets showed excellent thermal stability. 相似文献
17.
In this study, a series of chitosan‐graft‐poly(N‐isopropylacrylamide) (CTS‐g‐PNIPAAm) copolymers based on different molecular weight (Mw) of CTS and NIPAAm were synthesized through the polymerization of NIPAAm in an acid aqueous solution. The structures were verified by Fourier transform infrared and nuclear magnetic resonance. The influence of the CTS Mw on the properties of the resulting copolymers and self‐assembled nanoparticles was fully examined. The grafting ratio and grafting efficiency of the copolymers increased with the CTS Mw. All the copolymers have a similar low critical solution temperature of 33.5°C, which was independent of the CTS Mw. Furthermore, the copolymers were less temperature sensitive, when CTS Mw increased to 200 kDa. Besides, once the CTS Mw increased to 700 kDa, the copolymers were less pH sensitive near the tumor site (from pH 7.4 to 6.8). The copolymers could form uniform nanoparticles once the temperature increased to 34°C, which was reversible. After crosslinking by N,N‐methylenebisacrylamide (MBA), structurally stable nanoparticles could be obtained. The results from Transmission electron microscope (TEM) and Atomic force microscopy (AFM) showed that the MBA crosslinked nanoparticles were uniformly spherical with a loose structure. Surface tension method indicated that the critical aggregate concentrations were 0.045, 0.042, 0.037, and 0.036 mg mL?1 prepared from CTS 50, 100, 200, and 700 kDa, respectively. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
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The capillary flow properties and morphologies of ultrahigh molecular weight polyethylene/polypropylene (UHMWPE/PP) blends were studied. The results show that UHMWPE is difficult to process. The melts flowed unsteadily at lower shear rate. With 10 wt % PP contained in the UHMWPE/PP blends, the apparent melt viscosity was much lower than that of UHMWPE. When the PP content increased to 20 and 30 wt %, no pressure vibration occurred throughout the whole shear rate range. Microstructure analysis showed that PP prefers to locate in the amorphous or low crystallinity zones of the UHMWPE matrix. The flowability of UHMWPE increased substantially with the addition of PP. The addition of PE could not effectively reduce the chain entanglement density of UHMWPE. The improvement of processability of UHMWPE by the addition of PE was rather limited. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3894–3900, 2004 相似文献
19.
Effect of CaO in the thermal crosslinking of maltodextrin and citric acid: A cooperative action of condensation and ionic interactions
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The study of the effect of CaO in the thermal crosslinking of maltodextrin with citric acid demonstrates that the addition of small amount of this compound enhances the crosslinking of the cured system under processing conditions. This enhancement of the crosslinking leads to a noticeable improvement of the mechanical properties. The mechanism of the enhanced crosslinking reaction has been deeply analyzed by rheology, FT‐IR, and TGA. The rheological results show that CaO contributes to the crosslinking. This contribution would allow decreasing 10 °C the temperature of curing process. The enhancement of the crosslinking and consequent improvement of mechanical properties is explained by the contribution of the interactions between the Ca2+ and citric acid and the polycondensate network formed between maltodextrin and citric acid. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44203. 相似文献
20.
The effects of molecular weight (MW) and the degree of deacetylation (DD) of chitosan (CS) on the physicochemical properties, antibacterial activity, and cytotoxicity of CS/2‐glycerophosphate (GP)/nanosilver hydrogel in the development of a thermosensitive in situ formed wound dressing are examined herein. The gelation temperatures for the hydrogels were measured in the range of 32–37°C by manipulating the MW and DD of CS and the GP concentration. The structure of 88% DD CS hydrogel was more porous, uniform, and connective than that of the 80% DD CS hydrogel. The superior water vapor transmission rates of hydrogels with 80% and 88% DD CS were 7150 ± 52 and 9044 ± 221 gm?2 d?1, respectively. The skin permeations of nanosilver by the 80% and 88% DD CS hydrogels were 3.82 and 4.99 μg cm?2, respectively, in 24 h tests. Both the hydrogels with 6 and 12 ppm nanosilver showed cytotoxicity for HS68 cells. The diameters of the hydrogel's inhibition zones for Pseudomonas aeruginosa and Staphylococcus aureus increased when the concentration of nanosilver increased and the MW of the CS decreased. Therefore, the hydrogel could be prepared with lower MW CS and lower concentration of nanosilver in order to reduce the cytotoxicity of nanosilver, while maintaining similar antibacterial activity for a hydrogel prepared with higher concentration nanosilver and higher MW CS. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献