丝素褐藻糖胶共混膜的结构与热性能

丝素是蚕丝的主要成分，是人类最早应用的天然蛋白质之一，作为性能优良的天然纤维一直用于纺织行业．近年来，丝素膜由于具有良好的透气透氧性和较少的炎症反应，尤其是对活体组织具有良好的生物相容性的特点，在生物工程和生物医学领域得到广泛地研究，被用作酶的固定化材料和哺乳动物细胞培养的基质、体外组织工程支架和抗凝血材料等．     

PH effects in the complex formation and blending of poly(acrylic acid) with poly(ethylene oxide)

The effect of pH on the complex formation between poly(acrylic acid) (PAA) and poly(ethylene oxide) (PEO) has been studied in aqueous solutions by turbidimetric and fluorescent methods. It was shown that the formation of insoluble interpolymer complexes is observed below a certain critical pH of complexation (pH(crit1)). The formation of hydrophilic interpolymer associates is possible above pH(crit1) and below a certain pH(crit2). The effects of polymer concentrations in solution and PEO molecular weight as well as inorganic salt addition on these critical pH values were studied. The polymeric films based on blends of PAA and PEO were prepared by casting from aqueous solutions with different pHs. These films were characterized by light transmittance measurements and differential scanning calorimetry. The existence of the pH value above which the polymers form an immiscible blend was demonstrated. The transitions between the interpolymer complex, miscible blend, and immiscible blend caused by pH changes are discussed. The recommendations for preparation of homogeneous miscible films based on compositions of poly(carboxylic acids) and various nonionic water-soluble polymers are presented.     

甲醇-水混合溶剂后处理制备丝素蛋白膜及其药物释放研究

采用溶液浇注法制备丝素蛋白薄膜, 应用傅里叶红外光谱(FTIR)和X 射线衍射(XRD)研究了浓度不同的甲醇-水混合溶剂处理后丝素蛋白薄膜的结构变化, 并以罗丹明B 为模型药物与丝素蛋白构建药物缓释体系, 考察了丝素蛋白膜的结晶结构对药物释放动力学的影响. 结果显示, 在甲醇体积比浓度Φ_MeOH＝50%～90%的范围内, 丝素蛋白材料中以β-折叠为主的silk Ⅱ 结晶含量随着混合溶剂中甲醇浓度的增加而先增加后下降, 在Φ_MeOH＝80%附近出现最大值. 罗丹明B 从丝素蛋白膜的释放属于Fickian 扩散机理, 其扩散指数n 随着丝素蛋白膜中β-折叠含量的增加而增加, silk Ⅱ结晶是丝素蛋白材料药物释放的天然调节器.     

Mineralization of HA crystals regulated by terephthaloyl chloride-modified silk fibroin films

Terephthaloyl chloride(DB)-modified silk fibroin(SF) films were immersed into 1.5 times simulated body fluid(1.5 SBF) to regulate the mineralization of hydroxyapatite(HA) crystals at about 36.5℃for 24 h.UV was used to prove that the new bonds form between the DB and SF.The structure and morphology of the SF/HA were investigated by FTIR,ICP,XRD and SEM.The results showed that the apatite deposited on the matrix of SF mainly was HA.HA was self-assembled on the matrix of SF and formed three-dimensional framework when the weight ratio of DB/SF was 0.30.The content of DB affected the structure and morphology of the apatite composites deposited on the SF films.     

Effects of sol-gel processing parameters on the phases and microstructures of HA films

Bioactive hydroxyapatite (HA) films were fabricated by a sol–gel method and triethylphosphate and calcium nitrate were used as the phosphorus and calcium precursors, respectively. The effects of the heat treatment temperature, pH level and substrate materials on the phases and microstructures of HA films were studied by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and electronic probe microanalysis (EPMA) and so on. The results show that all the sol–gel films are composed of the phases of HA, CaO, TiO₂ and CaTiO₃. With increasing the calcining temperature, the crystallinity of the films increases, the structure becomes more compact and changes from granular and lamellar to cellular structure, and the Ca/P ratio increases slightly because of the loss of P in the films. The addition of ammonia (adjusting the pH level to be about 7.5) can increase the HA content in the films, and the difference of substrate materials only has a little influence on the microstructure of the sol–gel films.     

Crosslinking of hyaluronic acid with glutaraldehyde

Hyaluronic acid (HA) was chemically crosslinked with glutaraldehyde (GA) to produce water-insoluble films having low water contents when brought into contact with water. The crosslinking reaction was performed using uncrosslinked HA films in acetone–water mixtures. This method could produce water-insoluble HA films with water contents as low as 60 wt % when subjected to swelling with phosphate-buffered saline of pH 7.4 at 37°C. This 60 wt % water content was lower than any values for HA ever reported. There was an optimal HCl concentration around 0.01N for the HA crosslinking with GA in acetone—water mixtures. To get information on the crosslinking mechanism, alginic acid, which possesses hydroxyl and carboxyl groups in one molecule, similar to HA, and poly(vinyl alcohol) (PVA) and amylopectin, which possess only hydroxyl groups, were subjected to crosslinking with GA. PVA and amylopectin were also found to become water-insoluble after reaction with GA. On the basis of the infrared spectra of these crosslinked films, it was concluded that intermolecular formation of hemiacetal bonds with GA between the hydroxyl groups belonging to different HA molecules led to crosslinking. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 3553–3559, 1997     

Effects of Paraffin Emulsion on the Structure and Properties of Soy Protein Films

In this work, the water-repellent capacity of the paraffin emulsion?covered soy flour (SF) substrate has been studied. Effect of paraffin emulsion content on the structure and properties of the resulting films were studied using laser particle size distribution analyzer, water absorption test, x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and tensile testing. Study on the emulsion particle size and stability revealed that the particle size distribution and stability were strongly dependent on the pH of the system. And the optimum pH was 9.9. The incorporation of paraffin emulsion produced at pH 9.9 could markedly enhance the water resistance of films. However, the improvement was realized at the expense of decreased thermal stability and tensile strength of SF?paraffin emulsion films. The addition of paraffin emulsion could destroy the crystalline domains of soy protein and change the protein secondary structure.     

Interaction between myoglobin and hyaluronic acid in their layer-by-layer assembly: quartz crystal microbalance and cyclic voltammetry studies

Myoglobin (Mb), with different net surface charges at different pH in buffers and negatively charged hyaluronic acid (HA) at pH 5.0 in solutions were alternately adsorbed onto various solid surfaces and successfully assembled into {Mb/HA}(n) layer-by-layer films. The Mb in {Mb/HA}(n) films showed a quasi-reversible cyclic voltammetry (CV) response for its heme Fe(III)/Fe(II) redox couple. Quartz crystal microbalance (QCM) and CV were used to confirm the film growth and characterize the films. The interaction between Mb and HA and the influencing factors for Mb adsorption on HA surface, such as pH, Mb concentration, and ionic strength, were investigated in detail. The assembly driving force for {Mb/HA}(n) films, especially for the films assembled with like-charged Mb and HA, was found to be of electrostatic origin, while the secondary interaction such as hydrophobic interaction also plays an important role in some circumstances. Although the growth of {Mb(pH 7.0)/HA}(n) and {Mb(pH 9.0)/HA}(n) films was linear with the adsorption step, the exponential growth of {Mb(pH 5.0)/HA}(n) films was observed, especially when the films became thick. This exponential increase of mass and thickness with deposition step for {Mb(pH 5.0)/HA}(n) films was most probably attributed to the diffusion mechanism in which some HA molecules could diffuse in to and out of the whole films during the film assembly. Atomic force microscopy (AFM) results supported this speculation. UV-vis and IR spectroscopies of {Mb/HA}(n) films, combined with the comparative CV experiments of {Mb/HA}(n) and {catalase/HA}(n) films, suggest that Mb in the {Mb/HA}(n) multilayer films retains its near-native structure.     

Compression-inhibited pore formation of polyelectrolyte multilayers containing weak polyanions: a scanning force microscopy study.

Morphological changes of poly(acrylic acid)/poly(diallyldimethylammonium chloride) multilayers induced by low pH were investigated by scanning force microscopy. The weakened interaction between the charged polymer chains in the protonation process is believed to be the reason for this variation. Kinetic studies have shown that during protonation phase separation and dissociation of the multilayers took place successively. The compression of the multilayers, however, caused a transition of the multilayers from a rubbery state to a glassy state. As a result, the closely compacted multilayers lost their sensitivity to pH change. An increase of electrostatic and hydrophobic interactions, can decrease the free energy of the multilayers, and stabilize the films. By compression of the multilayers with a rubber stamp having geometric patterns, films with spatially localized pores were produced.     

Multicomponent acid-base titration by principal component-artificial neural network calibration

In this study, a three-layered feed-forward artificial neural network (ANN) trained by back-propagation learning was used to model the complex non-linear relationship between the concentration of anthranilic acid (HA), nicotinic acid (HN), picolinic acid (HP) and sulfanilic acid (HS) in their quaternary mixtures and the pH of solutions at different volumes of the added titrant. The principal components of the pH matrix were used as the input of the network. The network architecture and parameters were optimized to give low prediction error. The optimized networks predicted the concentrations of acids in synthetic mixtures. The results showed that the ANN used can proceed the titration data with low percent relative error of prediction (i.e.<4%). A comparison between the ANN and PLS methods revealed the superiority of the results obtained by the former method.     

Structure evolution of α′‐phase poly(lactic acid)

Poly(lactic acid) films consisting of α′‐forms were prepared and uniaxially drawn. The effects of the draw rate at temperatures above the glass transition temperature on chain conformation, degree of crystallinity, and crystalline phase transformation were investigated by a combination of vibrational spectroscopy (infrared and Raman), differential scanning calorimetry, and wide‐angle X‐ray diffraction (WAXD). It was established that the α′‐crystal's phase of poly(lactic acid) films does not transform into either an α or β crystals on uniaxial drawing at a fixed draw ratio of 4. However, the degree of crystallinity was significantly increased on deformation. The structural change as a function of deformation also promotes an increase in the strain‐induced enthalpic relaxation endothermic peak appearing near the glass transition region. While the overall changes in physical properties can be attributed to the changes in the degree of crystallinity as a function of strain rate, polarized Raman spectra, and WAXD clearly illustrated changes and the differences in the amorphous and crystalline orientation as a function of processing conditions. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1446–1454, 2011     

HA/PDM自组装复合胶体粒子及其乳化性能

以阴离子天然大分子透明质酸(HA)和阳离子单体甲基丙烯酸二甲氨基乙酯(DM)组成带相反电荷的聚合物/单体复合体系, DM通过水相原位聚合可制备荷正电的聚甲基丙烯酸二甲氨基乙酯(PDM), PDM与HA间的静电作用可诱导两者在水溶液中进行自组装, 得到HA/PDM复合胶体粒子. 用傅里叶变换红外(FTIR)光谱仪对HA/PDM复合物结构进行了表征. 用动态激光光散射(DLS)研究了HA与PDM复合体系在水溶液中的自组装行为, 并表征了反应时间对HA/PDM复合胶体粒子粒径的影响. 利用透射电镜(TEM)表征了胶体粒子的形貌. 考察了溶液pH 对胶体粒子粒径及zeta 电位的影响, 并对胶体粒子的乳化性能进行初步探索. 结果表明:DM单体聚合前, 无HA/DM复合物聚集体形成; 而随着DM的逐步聚合, HA与PDM可通过静电作用逐渐组装形成球状HA/PDM复合胶体粒子, 其粒径随反应时间延长逐渐减小并趋于稳定. 同时, 该复合胶体粒子具有pH敏感性和乳化性, 乳化性能较纯HA和PDM有较大提高.     

pH impact on the sol-gel preparation of calcium hydroxyapatite, Ca10(PO4)6(OH)2, using a novel complexing agent, DCTA

Aqueous sol-gel chemistry routes — based on ammonium hydrogen phosphate as the phosphorus precursor, calcium acetate monohydrate as the source of calcium ions, and 1,2-diaminocyclohexanetetraacetic acid monohydrate (DCTA) as the complexing agent — have been used to prepare calcium hydroxyapatite (HA). The sol-gel process was performed in aqueous solution at different pH values followed by calcination of the dry precursor gels for 5 h at 1000°C. Phase transformations, composition, and structural changes in the polycrystalline samples were studied by thermoanalytical methods (TG/DTA), infrared spectroscopy (IR), X-ray powder diffraction analysis (XRD), and scanning electron microscopy (SEM). It was shown that pH adjustment has significant impact on the apatite formation process and on the morphology and phase purity of the ceramic samples.     

Loading behavior of {chitosan/hyaluronic acid}n layer-by-layer assembly films toward myoglobin: an electrochemical study

When {CS/HA}n layer-by-layer films assembled by oppositely charged chitosan (CS) and hyaluronic acid (HA) were immersed in myoglobin (Mb) solution at pH 5.0, Mb was gradually loaded into the {CS/HA}n films, designated as {CS/HA}n-Mb. The cyclic voltammetric (CV) peak pair of Mb FeIII/FeII redox couple for {CS/HA}n-Mb films on pyrolytic graphite (PG) electrodes was used to investigate the loading behavior of {CS/HA}n films toward Mb. The various influencing factors, such as the number of bilayers (n), the pH of Mb loading solution, and the ionic strength of solution, were investigated by different electrochemical methods and other techniques. The results showed that the main driving force for the bulk loading of Mb was most probably the electrostatic interaction between oppositely charged Mb in solution and HA in the films, while other interactions such as hydrogen bonding and hydrophobic interaction may also play an important role. Other polyelectrolyte multilayer (PEM) films with different components were compared with {CS/HA}n films in permeability and Mb loading, and electroactive probes with different size and surface charge were compared in their incorporation into PEM films. The results suggest that due to the unique structure of CS and HA, {CS/HA}n films with relatively low charge density are packed more loosely and more easily swelled by water, and have better permeability, which may lead to the higher loading amount and shorter loading time for Mb. The protein-loaded PEM films provide a new route to immobilize redox proteins on electrodes and realize the direct electrochemistry of the proteins.     

The effect of morphological changes on the coprecipitation of strontium by calcium phosphate

The coprecipitation of strontium by a calcium phosphate phase formed at an elevated pH 10.8 was investigated. The first phase obtained under these conditions in the amorphous calcium phosphate (ACP) which is transformed into crystalline hydroxyapatite (HA) after the induction period. Is has been shown that this transformation together with morphological changes of the precipitated solid phase, influences the amount of the sorbed strontium significantly. The possible consequences of this finding on practical application of coprecipitation of strontium by calcium phosphate have been discussed.     

Potential of capillary zone electrophoresis for estimation of humate acid-base properties

Capillary zone electrophoresis (CZE) has been applied for fractionation and characterization of soil-derived humic acids (HAs). Humic acids from soddy-podzolic (HA(s)) and chernozem (HA(ch)) soils were studied as well as hydrophobic high-molecular-weight (HMW) and hydrophilic low-molecular-weight (LMW) HA(s) fractions obtained by salting-out with ammonium sulfate at a saturation of 0-40% and >70%, respectively. The possibility of CZE partial fractionation of HAs has been demonstrated. The shape of "humic hump" was shown to depend on the pH of running electrolyte. Almost the whole peak overlapping occurred if alkaline solutions were used for fractionation, but the peak resolution was improved at pH 5-7. Under appropriate fractionation conditions (pH 7), at least three humic acid subfractions with different electrophoretic mobilities were distinguished in the electropherograms of initial HA and HA(s) fractions. Such a high peak resolution has never been achieved for humic acids before. The presence of three subfractions in the HA is in agreement with gel-filtration analysis and was confirmed by comparison of the electrophoretic behavior of HA(s) with those of its HMW (hydrophobic) and the LMW (hydrophilic) fractions. The potentiometric titration of HA and its fractions was performed and the pK(a) of the functional groups were calculated. An attempt was made for the first time to relate the variation of electrophoretic mobility values with acid-base properties of humic acids. It was shown that changes in the humate charge resulting from the variation of the ionization degree of its functional groups as a function of pH can be estimated on the basis of electrophoretic mobility values. Potential of CZE in estimation of HA isoelectric point was demonstrated. The pH value corresponding to the lowest absolute electrophoretic mobility value of about 20 x 10(-5) cm(2) V(-1) s(-1) can be used for approximate estimation of HA isoelectric point. The data were discussed and agreement with the random coil structural model has been shown.     

Electrodeposition of mesoporous semimetal and magnetic metal films from lyotropic liquid crystalline phases

Mesoporous semimetal bismuth film and magnetic metal nickel and cobalt thin films have been electrodeposited from hexagonal or lamellar structured lyotropic liquid crystalline phases with polyoxyethylene surfactant. The liquid crystalline templates are characterized by low-angle X-ray diffraction (XRD) and polarized-light optical microscopy (POM). The metal films are characterized by low-angle and wide-angle XRD, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The magnetic measurements on the mesoporous nickel and cobalt films are shown to have higher coercivity (Hc) than the nonporous polycrystalline films.     

Associative and segregative phase separations of gelatin/kappa-carrageenan aqueous mixtures

The effects of ionic strength, temperature, and pH on the phase separation behavior of type B pigskin gelatin/sodium-type kappa-carrageenan aqueous mixtures were investigated. Depending on the different combinations of temperature and sodium chloride (NaCl) concentration, the mixtures showed compatible, associative, and segregative phase separation behaviors. Additionally, a coexistence of associative and segregative (associative-co-segregative) phase separations was expected at low temperature and low NaCl concentration. These different phase separation events were observed using confocal scanning laser microscopy. Moreover, it was found that the segregative phase separation when alone is induced by the ordering of kappa-carrageenan chains, while that in the coexistence region is induced by the ordering of gelatin chains. pH had a significant effect on the associative phase separation, resulting in morphologies changing from compatible solution to liquid coacervate and further to solid precipitate with decreasing pH. These were attributed to the dramatic changes of the charge density of amphoteric gelatin during the pH decrease.     

Adsorption of chlorhexidine on synthetic hydroxyapatite and in vitro biological activity

The kinetic of chlorhexidine digluconate (CHXDG) uptake from aqueous solution by hydroxyapatite (HA) was investigated by ultraviolet (UV) analysis performed in HA powder (UV-solid) after the CHX adsorption. Adsorption isotherm of chlorhexidine (CHX) uptake was modeled by a combination of Languimir and Langmuir-Freundlich mechanisms. Strong molecule-molecule interactions and positive cooperativity predominated in the surface when CHX concentration was above 8.6 μg(CHX)/mg(HA). UV-solid spectra (shape, intensity and band position) of CHX bound to HA revealed that long-range molecular structures, such as aggregates or micelles, started to be formed at low CHX concentrations (1.52 μg(CHX)/mg(HA)) and predominated at high concentrations. Grazing-incidence X-ray diffraction (GIXRD) analysis from synchrotron radiation discarded the formation of crystalline structures on HA surface or precipitation of CHX crystalline salts, as suggested in previous works. The effect of the HA/CHX association on HA in vitro bioactivity, cytotoxicity and CHX antimicrobial activity was evaluated. It was shown that CHX did not inhibit the precipitation of a poorly crystalline apatite at HA/CHX surface after soaking in simulating body fluid (SBF). Cell viability studies after exposure to extracts of HA and HA/CHX showed that both biomaterials did not present significant in vitro toxicity. Moreover, HA/CHX inhibited Enterococcus faecalis growth for up to 6 days, revealing that binding to HA did not affect antimicrobial activity of CHX and reduced bacterial adhesion. These results suggested that HA/CHX association could result in a potential adjuvant antimicrobial system for clinical use.     

Effects of oxygen plasma on cellulose surface

These studies aimed to investigate in detail changes on cellulose surfaces treated with low pressure oxygen plasma at various exposure times. Modifications of cellulose films were studied in respect to topography effects by means of atomic force microscopy and scanning electron microscopy. Chemical effects of plasma treatment were studied using X-ray photoelectron spectroscopy and X-ray diffractometry. Results show that the topographical evolution of the surfaces to rougher ones is not at all gradual. Local maxima of fractionation and the surface size regularity were investigated using surface fractal analysis and Wenzel roughness factors, respectively. It was shown, that plasma treatments decompose the cellulose material by formation of highly functionalized molecules. Such plasma-initiated and supported reactions taking place on the sample surface. The bulk phase and in particular, the crystalline domains are not influenced by plasma treatments. The studies provide useful information to understand the plasma reaction on amorphous and crystalline regions of cellulose surfaces and allow to predict effects of the plasma treatment on physical and chemical properties of much more complex cellulose systems such as cotton fibres and fabrics.