Metabolism and biochemical/physiological roles of chondroitin sulfates: analysis of endogenous and supplemental chondroitin sulfates in blood circulation

Chondroitin sulfate (CS) is a linear heteropolysaccharide consisting of repeating disaccharide units of glucuronic acid and galactosamine, which is commonly sulfated at C-4 and/or C-6 of galactosamine. The administration of CS as a supplement or a drug for the treatment of osteoarthrosis, the prevention of subsequent coronary events, treatment of psoriasis and ophthalmic diseases has been suggested. Much debate on the metabolism of CS and therefore the effectiveness of these treatments, especially after oral administration, has arisen due to the macromolecular nature of CS. Difficulties in analysing CS in blood due to the low endogenous concentrations and the covalent and anionic complexes with proteins have hampered the resolution of these issues. In this review, the information on the pharmacokinetics of CS obtained from studies in experimental animals and in humans is presented. Emphasis has been given to the analytical methods used for the determination of glycosaminoglycans, intact CS and CS-derived disaccharides in blood serum and plasma.     

An Expansion of Crystalline Sponge X-ray Analysis to Elucidate the Molecular Structure of Reactive Compounds via Ion Pair Formation

The crystalline sponge (CS) method allows structural elucidation of a target compound (guest) in solution by single crystal X-ray diffraction through trapping the guest into the CS framework. In principle, the CS method is inapplicable to reactive compounds that break the CS framework, such as acidic, basic, or nucleophilic ones. Here, a solution to this problem is disclosed wherein an ion pair of the guest compound is formed during the guest-soaking step by adding a suitable reagent. The ion pair can be observed and does not damage the CS framework. Using the developed method, amino, guanidino, and amidino compounds have been successfully analyzed as ion pairs with sulfonic acids. Practical utility has been shown because the absolute configurations of optically resolved amine derivatives were revealed with only a few micrograms. This demonstrates that the ion-pair-soaking method is simple and expands the range of compounds applicable to the CS method.     

Polyacrylamide gel electrophoresis of fluorophore-labeled hyaluronan and chondroitin sulfate disaccharides: application to the analysis in cells and tissues

This report describes a new formulation of polyacrylamide gel electrophoresis of fluorophore-labeled saccharides (PAGEFS) for the analysis of hyaluronan (HA) and chondroitin sulfate (CS) Delta-disaccharides. PAGEFS relies on derivatization of reducing ends of HA- and the variously sulfated CS-derived Delta-disaccharides with 2-aminoacridone (AMAC), followed by electrophoresis under optimized buffer conditions (Tris-borate and Tris-HCl) and on polyacrylamide gels (25% T/3.75% C). The method was applied to the analysis of glycosaminoglycans (GAGs) from the human umbilical cord tissue and GAGs isolated from human aortic smooth muscle cell cultures. The obtained results were in agreement with those obtained after an analysis with high-performance liquid chromatography (HPLC). On the basis of these results, PAGEFS is a rapid and sensitive method for the analysis of the total amount of HA- and CS-derived disaccharides, as it allows analyzing 20 samples in minigels in one run and provides quantitation with relatively high sensitivity (less than 25 pmol per disaccharide). In addition, PAGEFS overcomes the lack of commercial gels described previously for the separation of AMAC-labeled disaccharides. Therefore, the method proposed here is an economic and useful tool for a fast screening of GAGs in biological samples, particularly when a high number of samples should be analyzed.     

The Taste-Masking Mechanism of Chitosan at the Molecular Level on Bitter Drugs of Alkaloids and Flavonoid Glycosides from Traditional Chinese Medicine

Taste masking of traditional Chinese medicines (TCMs) containing multiple bitter components remains an important challenge. In this study, berberine (BER) in alkaloids and phillyrin (PHI) in flavonoid glycosides, which are common bitter components in traditional Chinese medicines, were selected as model drugs. Chitosan (CS) was used to mask their unfriendly taste. Firstly, from the molecular level, we explained the taste-masking mechanism of CS on those two bitter components in detail. Based on those taste-masking mechanisms, the bitter taste of a mixture of BER and PHI was easily masked by CS in this work. The physicochemical characterization results showed the taste-masking compounds formed by CS with BER (named as BER/CS) and PHI (named as PHI/CS) were uneven in appearance. The drug binding efficiency of BER/CS and PHI/CS was 50.15 ± 2.63% and 67.10 ± 2.52%, respectively. The results of DSC, XRD, FTIR and molecular simulation further indicated that CS mainly masks the bitter taste by disturbing the binding site of bitter drugs and bitter receptors in the oral cavity via forming hydrogen bonds between its hydroxyl or amine groups and the nucleophilic groups of BER and PHI. The taste-masking evaluation results by the electronic tongue test confirmed the excellent taste-masking effects on alkaloids, flavonoid glycosides or a mixture of the two kinds of bitter components. The in vitro release as well as in vivo pharmacokinetic results suggested that the taste-masked compounds in this work could achieve rapid drug release in the gastric acid environment and did not influence the in vivo pharmacokinetic results of the drug. The taste-masking method in this work may have potential for the taste masking of traditional Chinese medicine compounds containing multiple bitter components.     

壳聚糖大分子链的形态调控及其在微悬浮聚合中的分散稳定作用

以易去除可回用的壳聚糖(CS)为分散剂,通过微悬浮聚合制备微米级的软硬质聚合物胶粒.考察不同酸碱度下水相介质中CS大分子链的质子化程度、亲疏水性和形态结构,及其对油水界面处CS存在形态的影响,进而评估其对剪切均质化所制单体液滴的分散稳定作用.发现通过调节体系pH值可较容易地控制CS大分子链的质子化程度、亲疏水性以及在单体液滴表面的吸附效率和铺展程度,进而可在弱酸性环境下调控微悬浮聚合体系中CS的分散能力和稳定效果.特别是当pH值在6.0左右时,CS大分子链质子化程度和亲疏水性适中,链内易形成具有一定内聚密度的高分子链收缩构象、链间易形成由多根CS链缠结而成的疏松聚集状态.在此状态下的CS链对苯丙单体液滴具有较强的分散能力和稳定作用,因而通过微悬浮聚合可制得形态结构规整、分散状态良好的聚合物粒子.进一步与微悬浮聚合常用的无机粉末类和高分子类分散剂进行应用效果比较,发现CS具有形态调控性好、分散稳定效率高、易去除能回用、特别适合制备软质微米胶粒等优点,是一种有别于无机粉末类和高分子类分散剂的新型微悬浮聚合分散剂.     

Improved cellular response on multiwalled carbon nanotube-incorporated electrospun polyvinyl alcohol/chitosan nanofibrous scaffolds

We report the fabrication of multiwalled carbon nanotube (MWCNT)-incorporated electrospun polyvinyl alcohol (PVA)/chitosan (CS) nanofibers with improved cellular response for potential tissue engineering applications. In this study, smooth and uniform PVA/CS and PVA/CS/MWCNTs nanofibers with water stability were formed by electrospinning, followed by crosslinking with glutaraldehyde vapor. The morphology, structure, and mechanical properties of the formed electrospun fibrous mats were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, and mechanical testing, respectively. We showed that the incorporation of MWCNTs did not appreciably affect the morphology of the PVA/CS nanofibers; importantly the protein adsorption ability of the nanofibers was significantly improved. In vitro cell culture of mouse fibroblasts (L929) seeded onto the electrospun scaffolds showed that the incorporation of MWCNTs into the PVA/CS nanofibers significantly promoted cell proliferation. Results from this study hence suggest that MWCNT-incorporated PVA/CS nanofibrous scaffolds with small diameters (around 160 nm) and high porosity can mimic the natural extracellular matrix well, and potentially provide many possibilities for applications in the fields of tissue engineering and regenerative medicine.     

Mechanically reinforced chitosan/cellulose nanocrystals composites with good transparency and biocompatibility

Chitosan/cellulose nanocrystals(CS/CNCs) composites were prepared with different contents of CNCs. Due to the homogeneous dispersion of CNCs and the strong interfacial interactions resulting from hydrogen bonding between CS chains and CNCs, the transparency of CS is well retained and the overall mechanical properties of CS are significantly improved. Furthermore, because both CS and CNCs are biocompatible materials, cell proliferation test shows that the obtained composites are noncytotoxic and can potentially meet safety requirements of biomedical applications. These advantages pave the way of potential applications of CS in the field of commercial plastics and encourage the use of CS as environmentfriendly material and biomedical material.     

Sedimentation and drying dissipative patterns of colloidal silica (560 nm in diameter) suspensions in a glass dish and a watch glass

The sedimentation and drying dissipative structural patterns formed during the course of drying colloidal silica spheres (CS550, 560 nm in diameter) in an aqueous suspension have been studied in a glass dish and a watch glass. Broad ring patterns were formed within 20 min in the suspension state by the convectional flow of the colloidal spheres and water. The sedimentary spheres always moved by the convectional flow of water, and the broad ring patterns became sharp with time. The sharpness of the broad rings was sensitive to the change in the room temperature and/or humidity. Colorful macroscopic structures were composed of the broad ring and wave-like patterns, and further colorful and beautiful microscopic fine patterns formed during the solidification processes based on the convectional and sedimentation structures. The drying patterns of the colloidal suspensions containing sodium chloride were different from the structures of CS550 or sodium chloride individuals, which support the synchronous cooperative interactions between the colloidal spheres and the salts.     

The controlled release of a drug from biodegradable chitosan gel beads

Chitosan (CS) forms a gel in solutions with a pH above 12, and the gelation occurs at pH of about 9 in 10% amino acid solutions. In this paper, we investigated the enzymatic degradation and the drug release profile of this novel CS gel beads. The degradability of the CS gel beads was affected by the CS properties, e.g. the degree of deacetylation. The release of prednisolone (PS), as a model drug, from the CS gel beads was sustained significantly compared with the gel prepared with NaOH only. However, the release was not able to be sustained by the increment of NaOH concentration in the solution employed for the preparation of CS gel beads. We also investigated the control of drug release from CS gel beads by application of a complex formed between chondroitin sulfate (Cho) and CS. The release of PS from the CS gel beads treated with Cho was prolonged, and the release pattern was not affected by the treatment time. The time to 50% drug release was about 5 min with PS powder, about 200 min in CS gel beads with 10% glycine (Gly) (pH 9.0), and about 330 min in the CS gel beads with 10% Gly (pH 9.0) treated with Cho. Thus CS gel beads appear promising as a vehicle for sustained drug delivery, and the degradation of CS gel beads may be controlled by the degree of deacetylation of CS.     

The structural motifs of the crystals of some thiocyanato compounds of divalent nickel and copper

Conclusions Comparison of the structural motifs of nickel and copper tetrathiocyanatomercurates and the dithiocyanatotetrammine complexes of nickel and copper shows that the analogy which is observed in the structure of the crystals for many compounds of divalent nickel and copper and which follows from the similarity in the typical coordination polyhedra for Ni and Cu is broken down to a considerable extent when the compounds contain thiocyanato groups. The general reason for this is the sensitivity of the thiocyanato groups to slight differences in the nature of the complex-forming elements and in the composition of the complexes. The dispersion of the six bonds in copper to four principal bonds and two supplementary bonds is accompanied in this case by changes in the composition of the partners reacting directly with the metal atoms. The supplementary bonds, unlike the principal bonds, are more readily formed by the sulfur atoms of the thiocyanato groups. On going from Ni to Cu in the tetrathiocyanatomercurates, we find that this leads to a displacement of water molecules; in the dithiocyanatotetrammine compounds it leads to reversal of the thiocyanato groups, accompanied by a change in the Cu–S–CN valence angle (compared with the Ni–N=CS angle) by almost 90° and hence to a complete change in the structural motif.Translated from Zhurnal Strukturnoi Khimii, Vol. 4, No. 4, pp. 584–593, July–August, 1963     

Enzyme:nanoparticle bioconjugates with two sequential enzymes: stoichiometry and activity of malate dehydrogenase and citrate synthase on Au nanoparticles

We report the synthesis and characterization of bioconjugates in which the enzymes malate dehydrogenase (MDH) and/or citrate synthase (CS) were adsorbed to 30 nm diameter Au nanoparticles. Enzyme:Au stoichiometry and kinetic parameters (specific activity, k(cat), K(M), and activity per particle) were determined for MDH:Au, CS:Au, and three types of dual-activity MDH/CS:Au bioconjugates. For single-activity bioconjugates (MDH:Au and CS:Au), the number of enzyme molecules adsorbed per particle was dependent upon the enzyme concentration in solution, with multilayers forming at high enzyme:Au solution ratios. The specific activity of adsorbed enzyme increased with increasing number adsorbed per particle for CS:Au, but was less sensitive to stoichiometry for MDH:Au. Dual activity bioconjugates were prepared in three ways: (1) by adsorption of MDH followed by CS, (2) by adsorption of CS followed by MDH, and (3) by coadsorption of both enzymes from the same solution. The resulting bioconjugates differed substantially in the number of enzyme molecules adsorbed per particle, the specific activity of the adsorbed enzymes, and also the enzymatic activity per particle. Bioconjugates formed by adding CS to the Au nanoparticles before MDH was added exhibited higher specific activities for both enzymes than those formed by adding the enzymes in the reverse order. These bioconjugates also had 3-fold higher per-particle sequential activity for conversion of malate to citrate, despite substantially fewer copies of both enzymes present.     

Effect of Butyl Methacrylate on Properties of Regenerated Cellulose Coconut Shell Biocomposite Films

In this study, butyl methacrylate acid (BMA) is used as chemical modifier of regenerated cellulose (RC) coconut shell (CS) biocomposite films. The effect of CS content and BMA on tensile properties and crystallinity index (CrI) of RCCSbiocomposite films were investigated. It is found that the increasing of CS content up to 3 wt% increased the tensile strength and modulus of elasticity but decreased at higher content of CS. Elongation at break decreased with increasing of CS content and increased at 4 wt% of CS. Cystallinity index (CrI) of biocomposite films also increased with increasing CS up to 3 wt% content. At similar CS content, treated RC CS biocomposite films with BMA were found to have higher tensile properties and crystallinity index (CrI) than the untreated biocomposite films. The modification by BMA improved interfacial interaction and dispersion of CS in RC biocomposite films.     

Indirect determination of thionic compounds by nephelometric determination of barium sulfate

The indirect determination of thionic compounds by nephelometric determination of barium sulfate, formed after treatment of the compounds containing the group CS with potassium permanganate in neutral aqueous solutions, has been studied. Allylthiourea, thiourea, thioacetamide and thiosemicarbazide have been tested. The determination limit was 0.05 g/ml and the RSD less than 10%.     

Chitosan‐based composite membranes containing chitosan‐coated carbon nanotubes for polymer electrolyte membranes

Considering the poor dispersion and inert ionic conduction ability of carbon nanotubes (CNTs), functionalization of CNTs is a critical issue for their application in polymer electrolyte membranes. Herein, CNTs were functionalized by the polyelectrolyte, chitosan (CS), via a facile noncovalent surface‐deposition method. The obtained CS‐coated CNTs (CS@CNTs) were then incorporated into the CS matrix and fabricated composite membranes. The CS coating can enhance the compatibility between CNTs and the matrix, thus ensuring the homogenous dispersion of CS@CNTs and effectively improved the mechanical properties of the composites. Moreover, the CS coating can make CS@CNTs act as an additional proton‐conducting pathway through the membranes. The CS/CS@CNTs‐1 composite shows the highest proton conductivity of 3.46 × 10⁻² S cm⁻¹ at 80°C, which is about 1.5‐fold of the conductivity of pure CS membrane. Consequently, the single cell equipped with CS/CS@CNTs‐1 membrane exhibits a peak power density of 47.5 mW cm⁻², which is higher than that of pure CS (36.1 mW cm⁻²).     

In situ conductance measurements for alignments of silica particles under alternating electric fields

The alignments of silica particles formed in sinusoidal electrical fields of 1 kHz were assessed using an optical microscope with measuring the electric conductance of a silica dispersion between two Pt electrodes in a vitreous silica glass cell. We confirmed that the electric conductance of the silica dispersion between the two electrodes in the cell reflected the surface conductance of the silica particles settling at the bottom of the cell. More interestingly, we observed that the electric conductance of the silica dispersion in the cell increased when pearl chains of the silica particle were formed along the direction of the electric field. However, no clear change in the electric conductance of the dispersion was observed at higher electric field strengths where a transition from pearl chains to zigzag band patterns and circulating movements of the silica particles in the zigzag bands formed.     

几种烟煤CS2萃取物的GC/MS分析

利用气相色谱－质谱联用（GC／MS）技术测定了平朔、大同和神府三种烟煤中CS2萃取物的成分，对其化学组成及结构特征进行了对比研究。结果表明，萃取物主要由脂肪烃、芳烃和含杂原子化合物三类成分组成。芳烃在萃取物整体中占绝对优势，以苯系、萘系、菲系和芘系的烷基取代芳烃为主要成分：脂肪烃除主要成份正构烷烃外，还有少量的类异戊二烯烃和萜烷；含杂原子化合物所占的比例很小，以含氧、氮和硫的化合物为主，在平朔和大同煤的CS2萃取还发现少量邻二氯苯。     

大豆分离蛋白与壳聚糖复合材料的制备

蛋白质与多糖的静电作用是生物体内一个基本医学-化学现象,是实现自组装的主要驱动力,可利用这种非共价作用设计和构筑理想的微结构。 以大豆分离蛋白(Soybean Protein Isolates,SPI)和壳聚糖(Chitosan,CS)为原料,采用浊度法考察了配比、溶液pH值、离子强度和温度对SPI与CS在溶液中相互作用的影响。 结果显示,由于pH值影响静电作用强度,从而成为影响SPI与CS相互作用的主要因素,其中,当pH值为5.5~6.6时,SPI与CS可以实现有效结合。在较低的离子强度下,有利于形成具有紧凑结构的CS/SPI聚集体,较高离子强度下聚集体发生解离。 蛋白质受热发生变性,多肽链上的疏水氨基酸残基暴露在溶液中,导致与壳聚糖链的疏水作用增强。 DLS结果显示,CS与SPI自组装形成了分布均一的纳米粒子,变性后的SPI与CS形成的纳米粒子粒径有所增大,分布均一;经戊二醛交联,粒径有所减小。 SEM显示,壳聚糖单层膜表面存在龟裂现象,与SPI形成双层膜后龟裂消失;同时,单层膜厚度约为300 nm,双层膜厚度约为500 nm。     

The morphology of zinc dimethacrylate reinforced elastomers investigated by SEM and TEM

The morphologies of various ZDMA-reinforced elastomers, including styrene butadiene rubber (SBR), ethylene-propylene-diene monomer (EPDM), nitrile-butadiene rubber (NBR), ethylene-propylene monomer (EPM), poly(α-octylene-co-ethylene) elastomer (POE) and hydrogenated nitrile-butadiene rubber (HNBR), were studied by using SEM and TEM. The observation on the compounds showed that during the compounding process, the dimension of ZDMA particles reduced, and could even form dispersion structures with nanometer size (<100 nm). It is shear stress of compounds during mixing rather than polarity of matrix rubber that plays the most important role to determine dispersion state of ZDMA in compounds. High shear stress facilitates dispersion of ZDMA. Only in elastomers having the lower shear stress such as POE and EPM, original dimension features of ZDMA particles make considerable effects on dispersion level of ZDMA in compounds. The observation on cured composites displayed that there are two kinds of micro-dispersed structures: micron dispersion—residual ZDMA particles and nano-dispersion—the aggregate of poly-ZDMA. The higher saturation and polarity of rubbers and the better dispersion level of ZDMA in compounds benefit in situ polymerization of ZDMA, resulting in the lower amount of residual ZDMA particles (micron dispersion). In the elastomer with higher saturation such as POE, EPM, EPDM and HNBR, the dimensions of nano-dispersions are slightly larger. For the ZDMA/POE, formula effect on morphology of the composite was also discussed. It was found that the loading of ZDMA and peroxide impact remarkably on the amount and dimension of nano-particles in the composite.