Bioactive monetite‐containing whisker‐like fibers reinforced chitosan scaffolds

The aim of this work was to develop bioactive chitosan scaffolds reinforced with monetite‐containing whisker‐like fibers. The fibers synthesized by homogeneous precipitation were characterized as monetite/hydroxyapatite short fibers (MAFs), using XRD, FTIR and SEM. The pure chitosan and MAFs/chitosan composite scaffolds were produced by freeze‐drying, and characterized with respect to porosity, pore size, swelling behavior, compressive strength and modulus, and in vitro bioactivity. The incorporation of MAFs in chitosan matrices led to increase the pore size, according to the evaluation by FE‐SEM, and decrease the porosity of composite scaffolds. The swelling ratio decreased as MAFs content of scaffolds increased. The compressive strength and modulus of scaffolds were improved by an increase in MAFs content. The noncross‐linked scaffolds with a chitosan: MAFs weight ratio of 1:1 (CW3) showed a porosity of 75.5%, and the strength and modulus of 259 kPa and 2.8 MPa in dry state, respectively. The crosslinking by glutaraldehyde resulted in improved mechanical properties. The strength and modulus of cross‐linked CW3 scaffolds in wet state reached to 345 kPa and 1.8 MPa, respectively. The in vitro bioactivity of the reinforced scaffolds, evaluated by FE‐SEM/EDS, XRD, and ATR‐FTIR, was confirmed by the formation of a carbonated apatite layer on their surfaces when they soaked in simulated body fluid (SBF). The results of this initial study indicate that the monetite‐containing whisker‐like fibers may be an appropriate reinforcement of chitosan scaffolds.     

Packaging‐related properties of alkyd‐coated,wax‐coated,and buffered chitosan and whey protein films

Packaging‐related properties of coated films of chitosan–acetic acid salt and whey protein concentrate (WPC) were studied. Chitosan (84.7% degree of deacetylation) and WPC (65–67% protein) were solution cast to films. These films are potential oxygen barriers for use in packaging. Coatings of wax or alkyds were used to enhance the water‐barrier properties. The packaging‐related properties of chitosan films treated in a buffering solution, with a pH of 7.8, were also investigated. The coated films were characterized with respect to Cobb absorbency, overall migration to water, water vapor transmission rate, and oxygen permeability. The creasability and bending toughness were determined. The wax was a more efficient barrier to liquid water and 90–95% relative humidity than the alkyd. However, the alkyd‐coated material had superior packaging‐converting properties. The alkyd‐coated WPC and chitosan–salt films were readily folded through 180° without any visible cracks or delamination. The overall migration from the alkyd‐coated materials was below the safety limit, provided the coat weight was higher than 7.5 mg/cm² on WPC and 2.1 mg/cm² on chitosan–salt. The barrier properties of chitosan film under moist conditions were improved by the buffer treatment. However, the buffering also resulted in shrinkage of the film. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 60–67, 2004     

Alginate‐coated chitosan membrane for guided tissue regeneration

Chitosan membranes were first prepared by a thermally induced phase separation method and then alginate was coated on one side of the membranes by a modified dialysis apparatus to prepare alginate/chitosan membranes (A/C membranes). Electron spectroscopy for chemical analysis (ESCA), scanning electron microscope, and contact angle measurements were conducted to evaluate the surface characteristics. The mechanical strength, degradation behavior, and cell adhesion test were performed to evaluate the feasibility of using A/C membrane in guided tissue regeneration applications. The results revealed that alginates could effectively be coated onto the chitosan membrane. As observed in ESCA results, the N‐atomic emission peak was decreased from originally 6.2% on the untreated chitosan surface to 2% on the alginate‐treated surface. The contact angle decreased on the alginate‐modified side substantially, compared with the untreated side (from 88.4° to 34.2°). The A/C membrane had a higher water content of 71.8% in comparison to the chitosan membrane of 61.8%. Consequently, A/C membrane became stiffer and had a higher Young's modulus and strength. After a 30‐day in vitro shaking test, the weight of membranes was degraded to about 75% from the original. The 3T3 fibroblast cells showed less adhesion to alginate‐modified side as compared to the untreated chitosan‐side in cell adhesion test. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4528–4534, 2006     

Physical and mechanical properties of the fully interconnected chitosan ice‐templated scaffolds

Porous chitosan scaffolds were prepared with a freeze‐casting technique with different concentrations, 1.5 and 3 wt %, and also different cooling rates, 1 and 4°C/min. The pore morphology, porosity, pore size, mechanical properties, and water absorption characteristics of the scaffolds were studied. Scanning electron microscopy images showed that the freeze‐cast scaffolds were fully interconnected because of the existence of pores on the chitosan walls in addition to many unidirectionally elongated pores. Increases in the chitosan concentration and freezing rate led to elevations in the thickness of the chitosan walls and reductions in the pores size, respectively. These two results led to the enhancement of the compressive strength from 34 to 110 kPa for the scaffolds that had 96–98% porosity. Also, augmentation of the chitosan concentration and decreases in the freezing rate led to the reduction of the number of pores on the chitosan walls. Furthermore, the volume of water absorption increased with a reduction in the chitosan concentration and cooling rate from 690 to 1020%. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41476.     

Pore collapse during the fabrication process of rubber‐like polymer scaffolds

Rubbery polymer scaffolds for tissue engineering were produced using templates of the pore structure. The last step in the fabrication process consists of dissolving the template using a solvent that, at the same time, swells the scaffolding matrix that was a polymer network. Sometimes the polymer matrix is stretched so strongly that when the solvent is eliminated, i.e., the network is dried, it shrinks and is not able to recover its original shape and, consequently, the porous structure collapses. In this work we prepared, using the same fabrication process (the same template and the same solvent), a series of polymer scaffolds that results in collapsed or noncollapsed porous structures, depending on the polymer network composition. We explain the collapse process as a consequence of the huge volume increase in the swelling process during the template extraction due to the large distance between crosslinking points in the scaffolding matrix. By systematically increasing the crosslinking density the porous structure remains after network drying and the final interconnected pores were observed. It is shown that this problem does not take place when the scaffolding matrix consists of a glassy polymer network. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1475–1481, 2007     

Collagen‐based scaffolds reinforced by chitosan fibres for bone tissue engineering

In this paper, porous bone scaffolds reinforced with chitosan fibres were prepared. The porosity and pore size of the reinforced scaffolds were both satisfactory. The reinforced scaffolds resembled natural bone in both components and crystal size. Only if the length of the fibres was no shorter than the critical length, could the fibres reinforce the material. We have proposed an empirical formula to calculate the critical length of the fibres for the porous materials and determined the modifying factor (F_l) for the porous bone scaffold investigated in this work. Along with the increase of the fibres' volume content, the compressive strength of the scaffold also increased. We have proposed a further empirical formula for calculating the compressive strength of the porous reinforced materials and determined the modifying factor (F_σ) for the porous reinforced bone scaffold examined in these studies. Along with the degradation in vitro, the decrease in strength of the reinforced scaffold was less than that of the unreinforced scaffold. The growth rate of osteoblast cells on the reinforced scaffold was higher than that on the unreinforced scaffold. These results suggest that the reinforced scaffold may be a promising candidate matrix for repairing large bone defects. Copyright © 2005 Society of Chemical Industry     

Preparation and efficacy of tumor vasculature‐targeted doxorubicin cationic liposomes coated by N‐trimethyl chitosan

Cationic liposomes (CLs) can accumulate in tumor vascular endothelial cells (VECs) to show high selective targeting ability. Therefore, chemotherapeutic agent‐loaded CLs are considered as new therapeutic vehicles to enhance the treatment efficacy. This study investigated the effect of N‐trimethyl chitosan (TMC), one of derivatives of chitosan with positive charge determined by its degree of quaternization (DQ), on preparing doxorubicin (DOX)‐loaded CLs. TMCs with various DQ, i.e., 20% (TMC20), 40% (TMC40), and 60% (TMC60) were synthesized and characterized by ¹HNMR. DOX‐loaded liposomes (DOXL) were prepared by ammonium sulfate gradients followed by TMC‐coating to obtain TMC‐coated DOXL with various positive surface charges. The morphology, size, ζ‐potential and drug release in vitro of TMC‐coated DOXL were studied compared with those of DOXL. Human umbilical vein endothelial cells (HUVECs) as cell model, the vascular targeting ability of TMC‐coated DOXL was evaluated in vitro. A solid tumor, formed by implantationmurine hepatoma cells (H₂₂) into mice, as tumor model, the tumor inhibition rate and tumor histological sections stained by HE of TMC‐coated DOXL group were researched compared with those of free DOX and DOXL group. It was found that with the increase of TMC's DQ, the positive surface charge of TMC‐coated DOXL was enhanced accordingly, which had little effect on DOX release in vitro while led to the significant increase of DOX uptake by HUVECs in vitro and the treatment effect on solid tumor in vivo. Especially, TMC‐coated DOXL showed better targeting ability to the nuclei compared with free DOX and DOXL, which could further enhance the efficacy of DOX in vivo. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Characterization of bagasse‐rind particleboard bonded with chitosan

The development of high‐performance non‐wood lignocellulosic board without using synthetic adhesives derived from fossils resources is very important for the future. In this study, the characterization of bagasse particleboard bonded with chitosan was investigated. The 4 wt % chitosan‐acetic acid solution was sprayed onto bagasse rind particles at a 2–10 wt % chitosan solid content based on the dry particles. Particleboards with target densities of 0.75 and 0.9 g/cm³ were manufactured using a steam‐injection press. The steam pressure and total pressing time were 1 MPa (180°C) and 7 min, respectively. The addition of 2–4 wt % of chitosan was the most effective in the bending properties. The high‐density board bonded with a 4 wt % addition of chitosan showed a good result in the internal bond strength test. Furthermore, the board had favorable dimensional stability in dilute acetic acid as well as in a cyclic accelerated aging test. Judging from the analysis of bagasse extract‐added chitosan films, it was suggested that chitosan reacted with extract from bagasse during steam‐injection pressing. The reaction seemed to contribute to the board's good resistance to dilute acid. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Characterization of the morphology and hydrophilicity of chitosan/caffeic acid hybrid scaffolds

The morphology and affinity of a scaffold influence the attachment of cells to its surfaces. In this study, the morphology and hydrophilicity of chitosan/caffeic acid hybrid scaffolds were investigated. Grafting caffeic acid onto chitosan hybrid scaffolds by using high levels of potassium persulfate produced scaffolds with looser morphology and higher porosity, as indicated by scanning electron microscopy (SEM) and porosity analysis. SEM analysis showed that the prepared scaffolds had a macroporous morphology with interconnected pores. Differential scanning calorimetry (DSC) revealed that the scaffolds’ hydrophilicity decreased after caffeic acid grafting. The scaffolds were cultured with human osteosarcoma UMR-106 cells, but SEM analysis showed that cell attachment was poor. However, calcification of the scaffolds promoted the attachment of UMR-106 cells onto the scaffold. This study shows that calcified chitosan/caffeic acid hybrid scaffolds could be suitable for use in hard-tissue engineering.     

Polysaccharide‐based artificial extracellular matrix: Preparation and characterization of three‐dimensional,macroporous chitosan and chondroitin sulfate composite scaffolds

Scaffold‐guided tissue engineering based on synthetic and natural occurring polymers has gained much interest in recent years. In this article, the development of a polysaccharide‐based artificial extracellular matrix (AECM) is reported. Three‐dimensional, macroporous composite AECMs composed of chondroitin sulfate (ChS) and chitosan (Chito) were prepared by an interpolyelectrolyte complex/lyophilization method. The ChS–Chito composite AECMs were crosslinked with glutaraldehyde and calcium ions (Ca²⁺) and cocrosslinked with N,N‐(3‐dimethylaminopropyl)‐N′‐ethyl carbodiimide (EDC) and N‐hydroxysuccinimide (NHS). The crosslinking reactions were examined with Fourier transform infrared analysis. Glutaraldehyde and Ca²⁺ crosslinked with Chito and ChS, respectively, to produce different types of ChS–Chito semi‐interpenetrated networks. In contrast, EDC/NHS crosslinked with both Chito and ChS to produce ChS–Chito connected networks. In physiological buffer solutions, the Ca²⁺‐crosslinked ChS–Chito composite AECMs showed a lower swelling ratio than their EDC/NHS‐ and glutaraldehyde‐crosslinked counterparts. The ChS–Chito composite AECMs showed excellent antibacterial capability and biocompatibility according to the results of the in vitro antibacterial test and cytotoxic assay. This result suggested that the ChS–Chito composite AECMs might be a potential biomaterial for scaffold‐guided tissue‐engineering applications. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Synthesis and Characterization of TiN‐coated Cubic Boron Nitride Powders

Titanium nitride‐coated cubic boron nitride (TiN/cBN) composite powders were prepared by nitridizing TiO₂/cBN powders in a NH₃ flow at 950°C. The TiO₂/cBN powders were synthesized via a sol‐gel process using tetra‐butyl titanate and concentrated‐HNO₃‐treated BN powders as starting materials. The techniques of XRD, SEM, TEM, FT‐IR, and TG‐DTA were used to characterize the products and their intermediates. The cBN powders were uniformly coated with TiN nanoparticles. During the nitridization, the morphology of the TiO₂/cBN powders is unchanged. The TiN/cBN powders can be used as starting materials to prepare polycrystalline cBN compacts, or as reinforcements to strengthen metal‐matrix composites.     

Synthesis and magnetorheological characteristics of ribbon‐like,polypyrrole‐coated carbonyl iron suspensions under oscillatory shear

One of the crucial problems of classical magnetorheological (MR) fluids is their high rate of sedimentation. This disadvantage may be substantially eliminated using core‐shell particles. The aim of this study is to prepare spherical carbonyl iron (CI) particles coated with conducing polymer polypyrrole (PPy) with ribbon‐like morphology. Scanning electron microscopy proved the formation of the ribbon‐like layer onto CI particles while Fourier transform infrared spectroscopy confirmed the chemical structure of PPy. The magnetic properties observed via vibrating sample magnetometer showed decreased magnetization saturation of core‐shell‐structured particles due to the existence of non‐magnetic surface layer. MR measurements performed under oscillatory shear flow as a function of the applied magnetic flux density, temperature, and particle concentration showed that core‐shell particle‐based MR suspension exhibits sufficient MR performance for practical applications. Moreover, the suspension stability is promoted significantly when core‐shell particles are used as a dispersed phase. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation and anti‐TMV activity of guanidinylated chitosan hydrochloride

In this study, guanidinylated chitosan hydrochloride (GCH) was synthesized and its structure was characterized by UV–vis and FTIR. The degree of substitution of guanidinylated chitosan was confirmed by elemental analysis. In vitro antiviral activity of guanidinium derivative on local infection and systemic infection of tobacco mosaic virus (TMV) inoculated were evaluated by semileaf method using different modes of GCH application and antiserum assay. Meanwhile, the morphological characteristic of virus treated by GCH was performed by transmission electron microscope. The results showed that GCH had better antiviral activity than chitosan. The average inhibitory rate of GCH on local infection was 84%, which was much higher than that of chitosan hydrochloride. It was shown that the guanidinylated chitosan was an efficient passivator, and its antiviral effect decreased after mechanical inoculation. The guanidinylated chitosan increased the resistance of plant against TMV and decreased the infection of the virus. The electron microscope photograph exhibited that GCH not only directly altered the configuration of TMV but also congregated and reduced the virus. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Polyaniline coated on aluminum (Al‐2024‐T3): Characterization and electrochemical studies

A polyaniline coating was deposited onto an Al‐2024‐T3 substrate using oxalic acid as electrolyte. Both galvanostatic and potentiostatic techniques were used to deposit polyaniline on aluminum under aqueous conditions. The dc polarization studies showed that polyaniline coatings reduced the corrosion rate of Al‐2024‐T3 significantly by about threefold compared to that of the control. The passivation of the polyaniline‐coated aluminum was characterized by reflection absorption infrared spectroscopy and cyclic voltametry. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1669–1675, 2002     

Composite membranes of chitosan and titania‐coated carbon nanotubes as promising materials for new proton‐exchange membranes

Titania‐coated carbon nanotubes (TCNTs) were obtained by a simple sol–gel method. Then chitosan/TCNT (CS/TCNT) composite membranes were prepared by stirring chitosan/acetic acid and a TCNT/ethanol suspension. The morphology, thermal and oxidative stabilities, water uptake and proton conductivity, and mechanical properties of CS/TCNT composite membranes were investigated. The CNTs coated with an insulated and hydrophilic titania layer eliminated the risk of electronic short‐circuiting. Moreover, the titania layer enhanced the interaction between TCNTs and chitosan to ensure the homogenous dispersion of TCNTs in the chitosan matrix. The water uptake of CS/TCNT composite membranes was reduced owing to the decrease of the effective number of the ? NH₂ functional groups of chitosan. However, the CS/TCNT composite membranes exhibited better performance than a pure CS membrane in thermal and oxidative stability, proton conductivity, and mechanical properties. These results suggest that CS/TCNT composite membranes are promising materials for new proton‐exchange membranes. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43365.     

三苯基锡壳聚糖羧酸酯的表征与杀螺活性研究

以羧甲基壳聚糖(CMC-Na)为接枝骨架、三苯基氯化锡(Ph_3SnCl)为接枝单体,用80%的甲醇水溶液作溶剂在20℃反应2 d,合成了三苯基锡壳聚糖羧酸酯(CMC-SnPh_3),借助红外光谱、热重分析、差热分析、X射线衍射等分析手段对CMC-SnPh_3的结构进行了表征,并进行杀钉螺活性实验。结果表明:分析的谱图数据与CMC-SnPh_3的结构相符,证明CMC-SnPh_3接枝共聚物的生成;CMC-SnPh_3的浓度大于10 mg/L时,能抑制钉螺七爬,CMC-SnPh_3的浓度大于1 mg/L,室温浸泡3 d后,钉螺的死亡率达100%,该接枝共聚物具有高效杀钉螺活性。     

Free radical scavenging activity of cellulase‐treated chitosan

Partially N‐acetylated chitosan was hydrolyzed by the cheap, commercially available, and efficient cellulase. The products, with different molecular weight, were comparatively investigated by GPC, FT‐IR, XRD, and NMR. The results show that the decrease of molecular weight led to transformation of crystal structure and increase of water‐solubility, but the chemical structures of residues were not modified. Superoxide anion radical and hydroxyl radical quenching assay were used for the evaluation of free radical scavenging activity of cellulase‐treated chitosan in vitro. Low molecular weight chitosan (LMWC3, M_w 1.7 × 10³) exhibited high scavenging activity against free radical. It scavenged 79.3% superoxide radical at 0.1 mg mL^?1. At 2.0 mg mL^?1, scavenging percentage of initial chitiosan, LMWC1 (M_w 27.3 × 10³), LMWC2 (M_w 5.9 × 10³), and LMWC3 (M_w 1.7 × 10³) against hydroxyl radical was 14.3%, 33.1%, 47.4%, and 65.9%, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Vinculin focal adhesion of osteoblast‐like cells on PEEK coated with ultra‐thin polymer nano films

PEEK is the polymer of choice to replace metal encapsulants and other parts in active medical implants fixated into bone. The current challenge is to improve its biocompatibility with bone tissue to ultimately achieve osseointegration. PEEK sheets surfaces coated with plasma deposited nano thin polymer films using CH₄, (CH₄ + O₂) and (CH₄ + N₂) gases. PEEK samples plasma treated with nonpolymerizing gases (O₂) were also used for comparison. The adhesion performance of osteoblast like cells on the plasma‐treated PEEK surfaces and the presence of Vinculin in these cells were evaluated after long culturing period (12 days). X‐ray photoelectron spectroscopy and Auger spectroscopy were used to provide surface molecular information, surface hardness and molecular density. All plasma‐treated surfaces retained functionality after the sterilization process. PEEK surfaces with high number of oxygen functional groups and particularly oxygen rich thin polymer coating (plasma deposition using CH₄+O₂ gas mixture) resulted in strong cellular adhesion strength and large Vinculin amount. Further, osteoblast‐like cells responded better to surfaces with lower molecular density acting like another signal for cell adhesion. The osteoblast‐like cells response was weaker for surfaces with both thin films with nitrogen functional groups and nonfunctional (nonpolar) films. Furthermore, thin films rich in nitrogen functional groups repelled the cells, showed abnormal cells shape, smaller Vinculin amount and induced thicker cellular clusters with poor spread. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42181.     

Preparation of CEL2 glass-ceramic porous scaffolds coated with chitosan microspheres that have a drug delivery function

The present work focused on the preparation of CEL2 bioactive glass (SiO₂–P₂O₅–CaO–MgO–K₂O–Na₂O) scaffolds loaded with chitosan microspheres. Chitosan microspheres, with a mean particle size of 0.55 μm ± 0.25 μm and loaded with acetaminophen, were obtained through the water-in-oil single emulsion solvent evaporation method and were adhered to the surface of the scaffolds by a simple dip-coating technique. The characterization of the microsphere-loaded scaffolds, before and after immersion in simulated body fluid (SBF), was performed by scanning electron microscopy, X-ray diffraction, and infrared spectroscopy. In vitro bioactivity was performed for 21 days. The glass-ceramic microsphere-loaded scaffolds showed more than 70% interconnected porosity and an average compressive strength of 1.2 ± 0.43 MPa after immersion in SBF. They also showed the formation of a hydroxyapatite layer from the first day of immersion in SBF, demonstrating their high bioactivity. The microspheres were shown to be homogeneously dispersed on the scaffold surfaces. After 120 hours, the biologic tests showed good fibroblast cell proliferation onto the scaffolds. The encapsulated drug in the microspheres was released by diffusion in a sustained manner (90% and 99% in 200 hours). The results suggest that scaffolds have a promising role in applications of bone tissue engineering.