Plasma surface modification of chitosan membranes: characterization and preliminary cell response studies

Surface modification of biomaterials is a way to tailor cell responses whilst retaining the bulk properties. In this work, chitosan membranes were prepared by solvent casting and treated with nitrogen or argon plasma at 20 W for 10-40 min. AFM indicated an increase in the surface roughness as a result of the ongoing etching process. XPS and contact angle measurements showed different surface elemental compositions and higher surface free energy. The MTS test and direct contact assays with an L929 fibroblast cell line indicated that the plasma treatment improved the cell adhesion and proliferation. Overall, the results demonstrated that such plasma treatments could significantly improve the biocompatibility of chitosan membranes and thus improve their potential in wound dressings and tissue engineering applications.     

磷酸化壳聚糖膜的仿生复合修饰

仿生构建羟基磷灰石/壳聚糖复合材料是制备骨修复材料的一条有效途径.以甲醛和磷酸为反应试剂,采用均相反应法制备出壳聚糖(CS)的磷酸化衍生物-甲基磷酸化壳聚糖(NPCS).红外光谱、X射线光电子能谱分析结果表明,改性后的CS分子结构和元素组成发生显著变化,偶合等离子体发射光谱测试显示NPCS的取代度可达到0.5左右.用模拟体液(SBF)处理CS和NPCS膜,扫描电镜(SEM)观察和能量色散X射线分析表明,NPCS膜表面沉积了磷酸钙盐.由X射线衍射分析得知,NPCS膜表面形成的是低结晶度的羟基磷灰石(HA).接触角测试结果表明,经改性或修饰后,材料表面的亲水性明显提高.     

Acid-Containing Tyrosine-Derived Polycarbonates: Wettability and Surface Reactivity

Tyrosine-derived polycarbonates having carboxylic acid pendant groups were characterized by water contact angle and X-ray photoelectron spectroscopy (XPS). A pronounce decrease of receding angle as well as contact angle hysteresis as a function of acid composition strongly indicated that the acid groups are more accessible at the water/polymer interface after hydration. pH dependent contact angle confirmed an existence of carboxylic acid groups in the surface region. The receding angle transition appearing in the pH range of 4-6 was a consequence of hydrophilicity change due to interconverting from carboxylic acid (-COOH) to carboxylate ion (-COO⁻). The surface compositions of imidazole-labeled polymers as analyzed by XPS were consistent with the bulk stoichiometry of the polymers. Reactivity of acid groups towards chemical reaction at the surface was also investigated. The acid groups at the surface of polymers were capable of adsorbing a significant amount of calcium ion from simulated body fluid and being activated by a reaction with N-hydroxysuccinimide.     

Investigation into the surface modification of aragonite whiskers

Aragonite whiskers (AWs) were treated with several fatty acid surfactants and silane coupling agent in order to determine the optimal modifier by using contact angle measurements. The results revealed that the AWs modified by fatty acids showed more remarkable increase in the contact angle than by silane, suggesting the former were preferentially applied in modifying AWs. While the samples coated with fatty acids exhibited hydrophobicity with contact angles ranging from 104.08° to 137.87° with increasing of carbon chain length. Therefore, the highest contact angle of AWs treated by oleic acid was discussed in detail as an example, which was characterized by field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), thermo‐gravimetry analyses (TGA), X‐ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR). FESEM and TEM results showed a thin layer coated on the modified sample surface. Both the results of TGA and XPS confirmed organic groups existed in the sample of AWs treated by oleic acid. FTIR demonstrated that calcium dioleate was formed in the modification process. Further, modification mechanism was proposed based on the obtained results. Copyright © 2016 John Wiley & Sons, Ltd.     

Corrosion resistant performances of alkanoic and phosphonic acids derived self-assembled monolayers on magnesium alloy AZ31 by vapor-phase method

Alkanoic and phosphonic acid derived self-assembled monolayers (SAMs) were formed on magnesium alloy by the vapor phase method. AFM and XPS studies showed that SAMs were formed on Mg alloy. The chemical and anticorrosive properties of the SAMs prepared on magnesium alloys were characterized using contact angle measurements, X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. Water contact angle measurements revealed that, although SA and ISA have the same headgroup to anchor to the magnesium alloy surface, the packing density on the magnesium alloy surface could be considerably different. The contact angle hysteresis of SAMs with a carboxylate headgroup is much larger than that of SAMs with a phosphonic acid group. The XPS O 1s peaks indicated more likely a mix of mono-, bi-, or tridentate binding of phosphonic acid SAM to the oxide or hydroxide surface of the Mg alloy. The electrochemical measurements showed that the phosphonic acid derived SAM had better corrosion resistance compared to alkanoic acid derived SAM. The chemical stability of SAMs modified magnesium alloy was investigated using water contact angle and XPS measurements. The water contact angle and XPS measurements revealed that the molecular density of OP and PFEP on magnesium alloy would be higher than those of SA and ISA on magnesium alloy.     

Bioinspired synthesis of superhydrophobic coatings

A superhydrophobic material prepared by precipitating calcium phosphate on TiO2 films under in vitro conditions is described. Crystalline calcium phosphate is very porous with octacalcium phosphate as the main phase. The films are made hydrophobic by the surface grafting of a perfluorophosphate surfactant (Zonyl FSE). The as-prepared coatings were strongly hydrophobic, with advancing contact angles exceeding 165 degrees and receding angles exceeding 150 degrees . The formation of the calcium phosphate layer is self-organizing, and the coating is easily functionalized. The material was characterized with dynamic contact angle measurements, SEM, XRD, and XPS. The strong water repellency is explained by the open porous morphology of the calcium phosphate coating together with the successful attachment of the hydrophobic function.     

Surface treatment of magnesium oxysulfate whiskers through plasma polymerization

The surface of magnesium oxysulfate (MOS) whiskers was treated through plasma polymerization to increase the compatibility between the MOS whiskers and a polymer matrix. Different plasma parameters were chosen to determine the most hydrophobic coating. The surface structure of the plasma-treated MOS whiskers was examined. The MOS whiskers retained their crystal structure after plasma treatment, as shown by X-ray powder diffraction (XRD) analyses. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) spectroscopy analyses revealed that a polymer sheath was formed on the surface of the MOS whiskers, and interfacial chemical bonds were generated between the polymer sheath and the MOS whiskers. The thin-layer polymer sheath was uniform around the entire surface of the MOS whiskers and exhibited a typical amorphous structure, as determined by transmission electron microscopy (TEM) combined with selected area electron diffraction (SAED) analyses. The possible reaction mechanism on the surface of the MOS whiskers under plasma treatment was then proposed. Finally, the effect of surface treatment was evaluated by scanning electron microscopy (SEM), measurement of the contact angle and contact angle hysteresis, and torque rheometer. Results showed that plasma treatment could markedly increase the hydrophobicity of the MOS whiskers' surface, effectively reducing the agglomeration and improving the dispersibility of the MOS whiskers in the matrix, which results in the improved compatibility between the MOS whiskers and the polyvinyl matrix, as well as the processability of the composites.     

Chitosan‐capped sulfur microparticles grafted on UV‐treated PET surface

Antimicrobial materials with immobilized particles are of considerable interest. Sulfur, as one of the abundant elements on earth, is cheap and environmentally friendly; therefore, sulfur particles (SPs) can be used as an effective, nontoxic and low‐cost alternative to metal particles. SPs were prepared by precipitation method using sodium thiosulfate and hydrochloric acid in the presence of chitosan as a stabilizer. Further, SPs were grafted on polyethylene terephthalate (PET) foil activated by ultraviolet radiation. The changes in surface properties of modified foils were characterized by contact angle measurement, electrokinetic analysis and X‐ray photoelectron spectroscopy (XPS). The contact angle decreased on the UV‐treated sample, owing to the formation of oxidized groups. The presence of nitrogen and sulfur on the polymer surface, revealed by XPS, showed that chitosan‐capped SPs were bound to this surface. The surface morphology of samples and particle sizes were examined by scanning electron microscopy. The size of SPs increased after grafting on surface to a few micrometres. The antibacterial activity of the PET samples was tested against Staphylococcus epidermidis and Escherichia coli bacteria strains. UV‐treated samples grafted with one of the tested chitosan‐capped SPs demonstrated antibacterial effect against both of the bacteria strains. This new nanocomposite has potential to be used in medical applications as an antibacterial agent or in food processing as an antimicrobial food packaging material. Food spoilage caused by microorganisms such as E. coli during distribution and storage has a major impact on food quality and shelf life.     

胆固醇接枝壳聚糖及其性能

以胆固醇琥珀酸单酯对壳聚糖进行仿生功能化改性, 并利用红外光谱和核磁共振波谱对改性后产物进行了表征. 通过接触角测试、 仿生矿化及细胞培养等方法研究了改性后产物的相关性能. 结果表明, 改性后的壳聚糖衍生物接触角有所增大. 在仿生矿化过程中, 随着时间的延长, 壳聚糖衍生物具有对沉积的钙磷盐的稳固作用. 在细胞培养过程中, 改性后的壳聚糖膜上细胞增殖明显. 噻唑蓝(MTT)比色法、 扫描电子显微镜(SEM)与激光共聚焦显微镜(CLSM)表征结果表明, 改性后的壳聚糖膜具有促进3T3细胞黏附、 伸展与增殖的效果.     

Preparation and properties of water‐soluble chitosan and polyvinyl alcohol blend films as potential bone tissue engineering matrix

The blend film was prepared by casting solutions of water‐soluble hydroxyethyacryl‐chitosan (HEA‐CS) and polyvinyl alcohol (PVA) and cross‐linked by glutaraldehyde. The structure and properties of the blend films were estimated by wide‐angle X‐ray diffraction (WXRD), contact angle measurements with water, and scanning electron microscopy (SEM). The tensile properties of the blend films were investigated and the tensile strength (TS) and the elongation increased with the increased amount of PVA. The thermal stability (thermogravimetric (TG) and derivative thermogravimetric (DTG)) was evaluated and HEA‐CS was more thermally‐stable than that of PVA. The water swelling properties analysis indicated that HEA‐CS in the blends promoted the water absorption owing to its porous structure and the antimicrobial ability of the blend films was retained. Indirect cytotoxicity assessment of the blend films with human bone sarcoma cell (SW1353) indicated that the biomaterials were non‐toxic and did not release substances harmful to living cells. Copyright © 2009 John Wiley & Sons, Ltd.     

Modelling of calcium sulphate solubility in concentrated multi-component sulphate solutions

The chemistry of several calcium sulphate systems was successfully modelled in multi-component acid-containing sulphate solutions using the mixed solvent electrolyte (MSE) model for calculating the mean activity coefficients of the electrolyte species. The modelling involved the fitting of binary mean activity, heat capacity and solubility data, as well as ternary solubility data. The developed model was shown to accurately predict the solubility of calcium sulphate from 25 to 95 °C in simulated zinc sulphate processing solutions containing MgSO₄, MnSO₄, Fe₂(SO₄)₃, Na₂SO₄, (NH₄)₂SO₄ and H₂SO₄. The addition of H₂SO₄ results in a significant increase in the calcium sulphate solubility compared to that in water. By increasing the acid concentration, gypsum, which is a metastable phase above 40 °C, dehydrates to anhydrite, and the conversion results in a decrease in the solubility of calcium sulphate. In ZnSO₄–H₂SO₄ solutions, it was found that increasing MgSO₄, Na₂SO₄, Fe₂(SO₄)₃ and (NH₄)₂SO₄ concentrations do not have a pronounced effect on the solubility of calcium sulphate. From a practical perspective, the model is valuable tool for assessing calcium sulphate solubilities over abroad temperature range and for dilute to concentrated multi-component solutions.     

Synthesis and surface properties of PDMS–acrylate emulsion with gemini surfactant as co-emulsifier

Composite latex particles of acrylate and polydimethylsiloxane (PDMS) with high PDMS content was prepared by emulsion copolymerization and characterized by particle size analyzer, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR). With gemini surfactant as the co-emulsifier in the system, the PDMS content in the system reached 50%, which was far higher than the other reported values. Through the characterization of the particle size analyzer, the particle size augmented with the increase of the amount of PDMS, which could be said that the polysiloxane had participated into the reaction and had been introduced into the colloid particle. The results of FTIR indicated that almost all the monomer had been exhausted in the reaction because there was no C=C and D₄ characteristic peaks in the spectrum. Besides the surface properties also were measured by surface tension analysis, water absorption, and the static contact angle, it could be found that with the increase of polysiloxane content, the excellent properties acquired by PDMS were clearly revealed by the findings, such as the decrease of surface tension and water absorption, and the increase of static contact angle. All the measurements were consistent with the conclusion that the composite latex particles of polysiloxane and acrylate with high siloxane content had been prepared successfully.     

Structure and properties of the nanocomposite films of chitosan reinforced with cellulose whiskers

Bio‐based nanocomposite films were successfully developed using cellulose whiskers as the reinforcing phase and chitosan as the matrix. Cellulose whiskers, with the lengths of 400 ± 92 nm and diameters of 24 ± 7.5 nm on average, were prepared by hydrolyzing cotton linter with sulfuric acid solution. The effects of whisker content on the structure, morphology and properties of the nanocomposite films were characterized by SEM, XRD, FTIR, UV‐vis spectroscopy, DMA, TG, tensile testing, and swelling experiment. The results indicated that the nanocomposites exhibited good miscibility, and strong interactions occurred between the whiskers and the matrix. With increasing whisker content from 0 to 15–20 wt %, the tensile strength of the composite films in dry and wet states increased from 85 to 120 MPa and 9.9 to 17.3 MPa, respectively. Furthermore, the nanocomposite films displayed excellent thermal stability and water resistance with the incorporation of cellulose whiskers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1069–1077, 2009     

Surface Characterization and Antimicrobial Activity of Chitosan-Deposited DBD Plasma-Modified Woven PET Surface

In this work, a woven PET with an antimicrobial activity was prepared by depositing chitosan on its surface. Firstly, the hydrophilic property of the PET surface was achieved by a plasma treatment using dielectric barrier discharge (DBD). The hydrophilic property of the PET surface was characterized by wickability and contact angle measurements. The XPS analysis revealed an increment of oxygen-containing polar groups, such as C–O and O–C=O, on the PET surface after the plasma treatment, resulting in an enhanced hydrophilic property. The plasma-treated PET specimen was further deposited with chitosan by immersing in a chitosan acetate aqueous solution. The effects of temperature, chitosan concentration, and number of rinses on the amount of deposited chitosan on the PET surface were investigated. The disappearance of the above-mentioned polar groups from the PET surface was clearly observed after the chitosan deposition, indicating the involvement of these functional groups in interacting with the chitosan. The chitosan-deposited plasma-treated woven PET possessed an exceptionally high antimicrobial activity against both E. coli (gram-negative bacteria) and S. aureus (gram-positive bacteria).     

Wetting of heterogeneous surfaces of block copolymers containing fluorinated segments

 The wetting of well-characterized heterogeneous surfaces of block copolymers has been studied by low-rate dynamic contact angle measurements using axisymmetric drop-shape analysis. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to investigate the roughness, the heterogeneity and the chemical composition of the surfaces. By changing the block length of polysulfone and semifluorinated polyester segments in the block copolymers, the surface heterogeneity of thin films prepared on silicon wafers could be controlled. Tapping-mode AFM measurements showed that soft, hydrophobic domains of varying size on the submicrometer length scale were obtained on these surfaces (60–250 nm). The mean roughness was of the order of several nanometers. The results of the contact angle measurements showed that neither roughness nor heterogeneity had a significant effect on the advancing contact angle of water, at the scale of the features present; however, the contact angle hysteresis increased with increasing percentage of the soft domains. We assume that liquid retention by the solid upon retraction of the three-phase line is the main cause for the observed increase in contact angle hysteresis. Concerning the molecular composition of these block copolymer surfaces, angle-resolved XPS analysis showed a surface segregation of fluorine within the surface region. A direct correlation was found between the fluorine content of the block copolymer surfaces and the advancing contact angle of water. Received: 26 May 2000 Accepted: 3 January 2001     

High Substitution Synthesis of Carboxymethyl Chitosan for Properties Improvement of Carboxymethyl Chitosan Films Depending on Particle Sizes

This study investigated the effect of chitosan particle sizes on the properties of carboxymethyl chitosan (CMCh) powders and films. Chitosan powders with different particle sizes (75, 125, 250, 450 and 850 µm) were used to synthesize the CMCh powders. The yield, degree of substitution (DS), and water solubility of the CMCh powders were then determined. The CMCh films prepared with CMCh based on chitosan with different particle sizes were fabricated by a solution casting technique. The water solubility, mechanical properties, and water vapor transmission rate (WVTR) of the CMCh films were measured. As the chitosan particle size decreased, the yield, DS, and water solubility of the synthesized CMCh powders increased. The increase in water solubility was due to an increase in the polarity of the CMCh powder, from a higher conversion of chitosan into CMCh. In addition, the higher conversion of chitosan was also related to a higher surface area in the substitution reaction provided by chitosan powder with a smaller particle size. As the particle size of chitosan decreased, the tensile strength, elongation at break, and WVTR of the CMCh films increased. This study demonstrated that a greater improvement in water solubility of the CMCh powders and films can be achieved by using chitosan powder with a smaller size.     

壳聚糖丝心蛋白包药微球的结构和释放性能研究

近年,高分子微球的研究与开发十分引人注目.将药物包裹于微球中,经主动和被动控制,进入预定靶器官或组织后缓慢释放出,不仅可降低其毒副作用,还可提高其生物活性利用度,壳聚糖(ＣＳ)可作牛血清白蛋白等药物缓释微球的载体[1～3].丝心蛋白(ＦＢ)含18种氨基酸,具有多孔性和良好的渗透性[4],也是一种理想的生物材料.壳聚糖和丝心蛋白共混可交联成半互穿聚合物网络(ＳｅｍｉＩＰＮ)结构.具有智能水凝胶的性能[5].本实验室已用纤维素铜氨液分别与干酪素、海藻酸钠及魔芋共混制得共混膜,两种分子间存在由次价键力引起的很强的相互作用,使其力学性…     

Preparation and Characterization of Chitosan Composite Membranes Crosslinked by Carboxyl-capped Poly（ethylene glycol）

In this study a series of chemically crosslinked chitosan/poly（ethylene glycol） （CS/PEG） composite membranes were prepared with PEG as a crosslinking reagent other than an additional blend. First, carboxyl-eapped poly（ethylene glycol） （HOOC-PEG-COOH） was synthesized. Dense CS/PEG composite membranes were then prepared by casting/evaporation of CS and HOOC-PEG-COOH mixture in acetic acid solution. Chitosan was chemically crosslinked due to the amidation between the carboxyl in HOOC-PEG-COOH and the amino in chitosan under heating, as confirmed by FTIR analysis. The hydrophilicity, water-resistance and mechanical properties of pure and crosslinked chitosan membranes were characterized, respectively. The results of water contact angle and water absorption showed that the hydrophilicity of chitosan membranes could be significantly improved, while no significant difference of weight loss between pure chitosan membranes and crosslinked ones was detected, indicating that composite membranes with amidation crosslinking possess excellent water resistanance ability. Moreover, the tensile strength of chitosan membranes could be significantly enhanced with the addition of certain amount of HOOC-PEG-COOH crosslinker, while the elongation at break didn＇t degrade at the same time. Additionally, the results of swelling behaviors in water at different pH suggested that the composite membranes were pH sensitive.     

硫酸钙晶须改性双马来酰亚胺树脂摩擦磨损性能的研究

研究了载荷、偶联剂及硫酸钙晶须用量对双马来酰亚胺树脂摩擦磨损性能的影响及材料的磨损机制.结果表明,当摩擦载荷较大时,树脂基体在摩擦过程中出现明显的塑性变形和裂纹,而经过硫酸钙晶须改性的复合材料体系则塑性变形和裂纹情况得到明显的改善,并且磨损量显著降低.载荷从200 N增大到300 N后,树脂基体的磨损机制从粘着磨损过渡为严重的疲劳磨损,添加晶须体系仍以粘着磨损为主.晶须添加量较小时,复合材料的磨损机理主要为粘着磨损,晶须添加量较高时,磨粒磨损占主导地位.     

A facile method for fabrication of superhydrophobic coating on aluminum alloy

A superhydrophobic coating applied in corrosion protection was successfully fabricated on the surface of aluminum alloy by chemical etching and surface modification. The water contact angle on the surface was measured to be 161.2° ± 1.7° with sliding angle smaller than 8°, and the superhydrophobic coating showed a long service life. The surface structure and composition were then characterized by means of SEM and XPS. The electrochemical measurements showed that the superhydrophobic coating significantly improved the corrosion resistance of aluminum alloy. The superhydrophobic phenomenon of the prepared surface was analyzed with Cassie theory, and it was found that only about 6% of the water surface is in contact with the metal substrate and 94% is in contact with the air cushion. Copyright © 2011 John Wiley & Sons, Ltd.