Synthesis and evaluation of carboxymethyl chitosan for glycopeptide enrichment

Glycans are known to be involved in a variety of biological processes throughout human physiology. Mass spectrometry has demonstrated itself as powerful analytical tool for quantitative and structural characterization of glycans. Studying these molecules at the glycopeptide level however, offers distinct advantages, namely the ability to characterize both the glycan and peptide fragments simultaneously, and moreover the ability to assign site specific heterogeneity. In light of this, peptides often dominate the spectrum and hinder the ionization efficiency of glycopeptides. For this reason, enrichment protocols prior to downstream MS analysis need to be developed. Here, we discuss the synthesis and use of carboxymethyl chitosan (CMCH) to enrich glycopeptides from a 12 protein mixture for MS analysis. This protocol was compared to a commercially available glycopeptide enrichment kit offered by EMD Millipore through the use of tandem mass tags (TMT) for relative quantification. Using this approach, we identified 98 unique N-linked glycopeptides and observed, that CMCH was able to enrich more sialylation than the commercial kit. In addition, we observed a trend based on TMT reporter ratios with respect to increasing sialylation. This corroborated that this stationary phase was exhibiting a mixed-mode enrichment through both hydrophilic interaction liquid chromatography (HILIC) and weak anion exchange (WAX) principles.     

Synthesis, characterization and metal uptake capacity of a new carboxymethyl chitosan derivative

Chemical modification of chitosan (Cs) and its derivatives via graft copolymerization can enhance their properties and consequently expands their potential applications. Carboxymethyl chitosan (CMCs) was prepared and characterized by FTIR spectroscopy, elemental analysis and X-ray diffraction. Graft copolymerization of N-acryloylglycine (NAGly) onto CMCs using 2,2-dimethoxy-2-phenyl acetophenone (PI) as photoinitiator was carried out under nitrogen atmosphere in aqueous solution. Evidence of grafting was confirmed by comparison of FTIR spectra of CMCs and the graft copolymers as well as the 2D-X-ray diffraction patterns, elemental analysis and the difference in solubility profiles before and after grafting. The effects of concentration of NAGly, PI and reaction time on the extent of grafting were investigated by determining the grafting percentage and grafting efficiency. With other conditions kept constant, the obtained optimum grafting conditions were: CMCs = 0.1 g, NAGly = 0.4 g, PI = 0.02 g and reaction time = 1 h. A preliminary study was then carried out to evaluate the capacity of the prepared new graft copolymer to uptake copper ions from aqueous systems. This preliminary investigation of the prepared graft copolymers showed that they may be tailored and exploited to expand the utilization of these systems in metal ions uptake and treatment of wastewater.     

Synthesis and characterization of antibacterial semi-interpenetrating carboxymethyl chitosan/poly (acrylonitrile) hydrogels

Blend hydrogels composed of carboxymethyl chitosan (CMCh) and poly (acrylonitrile) (PAN) were synthesized via crosslinking method. Several analyses were made to investigate both physical and thermal properties of CMCh/PAN hydrogels like; FTIR, scanning electron microscope, XRD and thermogravimetric analysis (TGA). TGA results showed that CMCh/PAN hydrogels are thermally more stable than CMCh and their thermal stability increases as PAN content increases in the hydrogel. Moreover, the swelling behavior of CMCh/PAN hydrogels was studied in different buffer solutions. It was found that CMCh/PAN hydrogels swell much more than PAN especially at pH 9. The hydrogels sorption for different dyestuff and various metal ions like; Cu²⁺, Cd²⁺ and Co²⁺ were also studied. In this work, antibacterial characteristic of hydrogels was mainly investigated towards Escherichia coli (E. coli) as a serious disease-leading bacterium. All tested hydrogels have clearly presented good antibacterial activity as CMCh content increases in the hydrogels.     

Synthesis and characterisation of advanced UHMWPE/silver nanocomposites for biomedical applications

A supercritical fluid (SCF) route for facile and homogeneous introduction of silver nanoparticles into polymer hosts is described. Our focus is on ultra-high molecular weight polyethylene (UHMWPE). We demonstrate that the metallic nanoparticles have a substantial effect upon the wear and tribochemical properties of the polymer substrate.     

Self-aggregated nanoparticles from linoleic acid modified carboxymethyl chitosan: Synthesis, characterization and application in vitro

The purpose of the present research work was to study the formation of linoleic acid (LA) modified carboxymethyl chitosan (LCC). Another objective was to evaluate effect of linoleic acid degree of substitution on loading capacity (LC), ADR loading efficiency (LE) and in vitro release profile of LCC nanoparticles. The hydrogel nanoparticles can be prepared using linoleic acid modified carboxymethyl chitosan (LACMCS) after the sonication. The critical aggregation concentration (CAC) of the self-aggregate of LA modified CMCS (LCC) was determined by measuring the fluorescence intensity of the pyrene as a fluorescent probe. The CAC values were in the range of 0.061–0.081 mg/mL. Self-aggregated nanoparticles exhibited an increased LC and LE, decreased sustained release with an increasing ratio of the hydrophobic LA to hydrophilic CMCS. LCC nanoparticles loaded with ADR exerted in vitro anticancer activity against Hela cells that was comparable to the activity of free (non-entrapped in nanoparticles) ADR.     

Metal adsorption of carboxymethyl cellulose/carboxymethyl chitosan blend hydrogels prepared by Gamma irradiation

Blend hydrogels based on the carboxymethyl cellulose (CMC) and carboxymethyl chitosan (CMCts) were prepared by γ-irradiation of a high concentrated CMC/CMCts aqueous solution. Properties of the hydrogels, such as gel fraction, swelling ratio, gel strength, and metal adsorption for Pb and Au were investigated. The gel fraction increased with increasing dose, while the swelling ratio decreased with increasing it. The obtained blend hydrogels had high adsorption performance which was controlled by adjusting the composition of CMC/CMCts.     

Radiation synthesis and characterization of nanosilver/gelatin/carboxymethyl chitosan hydrogel

A series of antibacterial hydrogels were fabricated from an aqueous solution of AgNO₃, gelatin and carboxymethyl chitosan (CM-chitosan) by radiation-induced reduction and crosslinking at ambient temperature. The nanosilver particles were in situ synthesized accompanying with the formation of gelatin/CM-chitosan hydrogel. Transmission Electron Microscope and UV–vis analysis have verified the formation and homogeneous distribution of nanosilver particles in the hydrogel matrix. The nanosilver/gelatin/CM-chitosan hydrogels possessed interconnected porous structure, had a compressive modulus of 44 to 56 kPa, and could absorb 62 to 108 times of deionized water to its dry weight. Furthermore, the hydrogels were found to have sound antibacterial effect on Escherichia coli (E. coli), and their antibacterial ability could be significantly enhanced by the increasing of AgNO₃ content. The comprehensive results of this study suggest that nanosilver/gelatin/CM-chitosan hydrogels have potential as an antibacterial wound dressing.     

Physico-chemical characterisation of chitosan/halloysite composite membranes

Chitosan membranes reinforced by halloysite nanotubes (HNTs) at concentrations from 2 to 15 (w/w%) have been prepared by solution casting to investigate the optimal physico-chemical properties for biomedical applications. Tensile test data revealed that the membranes reinforced with 5 (w/w%) HNTs yielded the highest Young's modulus (0.52 ± 0.01 GPa) and strength (81.6 ± 4.4 MPa). Electron micrographs of the fractured surfaces implicated the interplay between individual HNTs and agglomerates of HNTs in the stress transfer mechanism. Infrared spectra revealed interaction between the HNT siloxane and chitosan functional groups. Thermogravimetric results demonstrated that the thermal stability of the membranes increased with HNT concentration.     

Synthesis and characterization of novel carboxymethyl chitosan grafted polylactide hydrogels for controlled drug delivery

Novel carboxymethyl chitosan‐polylactide (CMCS‐g‐PLA) hydrogels were prepared by using 1‐(3‐dimethylaminopropyl)‐3‐ethylcarbodiimide hydrochloride/N‐hydroxysuccinimide (EDC/NHS) as crosslinking agent and catalyst at room temperature. Solid‐state ¹³C‐NMR, SEM, and FT‐IR measurements showed that PLA blocks are successfully grafted onto the CMCS main chains. DSC measurements confirmed the effective crosslinking of carboxymethyl chitosan. With increasing the amount of EDC/NHS, the crosslink destiny of CMCS‐g‐PLA copolymers is improved. The swelling ratio of CMCS‐g‐PLA hydrogels is pH dependent, showing a minimum in the pH range of 3 to 5. Rheological studies confirmed the formation of hydrogels. The higher the crosslinking density, the higher the storage modulus of hydrogels. CMCS‐g‐PLA hydrogels only slightly degrade in PBS for 10 days. In the presence of lysozyme, however, hydrogels with low crosslink density are totally degraded in 10 days. Drug release studies show that after 96 h, 95% of thymopentin is released under in vitro conditions. Copyright © 2015 John Wiley & Sons, Ltd.     

Physicochemical properties and sensing ability of metallophthalocyanines/chitosan nanocomposites

Electroactive nanostructured films of chitosan (Ch) and tetrasulfonated metallophthalocyanines containing nickel (NiTsPc), copper (CuTsPc), and iron (FeTsPc) were produced via the electrostatic layer-by-layer (LbL) technique. The multilayer formation was monitored with UV-vis spectroscopy by measuring the increase of the Q-band absorption from metallophthalocyanines. Results from transmission and reflection infrared spectroscopy suggested specific interactions between SO(3)(-) groups from metallophthalocyanines and NH(3)(+) from chitosan. The electroactive multilayered films assembled onto an ITO electrode were characterized by cyclic voltammetry, with Ch/NiTsPc films showing higher stability and well-defined voltammograms displaying reversible redox peaks at 0.80 and 0.75 V. These films could be used to detect dopamine (DA) in the concentration range from 5.0 x 10(-6) to 1.5 x 10(-4) mol L(-1). Also, ITO-(Ch/NiTsPc)(n)() electrodes showed higher electrocatalytic activity for DA oxidation when compared with a bare ITO electrode. On the other hand, only the Ch/FeTsPc and Ch/CuTsPc modified electrodes could distinguish between DA and ascorbic acid. These results demonstrate that versatile electrodes can be prepared by incorporation of different metallophthalocyanine molecules in LbL films, which may be used in bioanalytical applications.     

Synthesis and antitumoral activity of gelatin/polyoxometalate hybrid nanoparticles

Surfactant-free gelatin/heptamolybdate (HM) hybrid nanoparticles are prepared by a simple and environmentally friendly approach utilizing the electrostatic interaction between anionic HM and the zwitterionic gelatin. The obtained nanoparticles have a tunable size and very high HM loading content up to about 70%. In vitro and in vivo experiments prove that the gelatin/HM hybrid nanoparticles exhibit significantly better antitumor activity than plain ammonium heptamolybdate solution. Therefore, the gelatin/HM hybrid nanoparticles reported here may serve as a prototype platform for polymer/polyoxometalate (POM) hybrid nanoparticles as cancer treatment agents and hence open up more opportunities to maximize the potential of POM-based pharmaceutical agents.     

pH and ionic sensitive chitosan/carboxymethyl chitosan IPN complex films for the controlled release of coenzyme A

pH and ionic sensitive interpenetrating polymer network (IPN) complex films based on chitosan (CS) and carboxymethyl chitosan (CM-CS) were prepared by using glutaraldehyde as crosslinking agent. Its structure was characterized by FT-IR, which indicated that the IPN was formed. The films were studied by swelling, weight loss with time, and release of coenzyme A (CoA). It was found that the IPN films were sensitive to pH and ionic strength of the medium. The cumulative release rate of CoA decreased with CoA loading content, ionic strength or crosslinking agent increasing. The composition of the IPN films and pH of release medium also had significant effect on the release of CoA. The differences in the rates and amounts of released CoA may be attributed to the swelling behavior, the degradation of films, and interaction between drug molecule and polymer matrix. These results suggested CS/CM-CS IPN films could be used as drug delivery carrier.     

Synthesis, photoluminescence, and adsorption of CdS/dendrimer nanocomposites

CdS/dendrimer nanocomposites can be synthesized from methanolic Cd(2+) and S(2-) with amine-terminated polyamidoamine dendrimers of generation 8 (G8NH(2)) as stabilizers. By controlling the preparation conditions, nanoparticles with diameters < or = 2 nm can be obtained with a narrow size distribution. They show blue photoluminescence at approximately 450 nm. We studied the effects of various additives on the photoluminescence and elucidated its mechanism. Stable aggregates of two to three G8NH(2) molecules with several CdS nanoparticles form; the particles are located at the surface of the G8NH(2) molecules. The adsorption of the CdS/G8NH(2) nanocomposites on flat substrate surfaces is determined by the substrate chemistry. The hydrophilic nature of G8NH(2) results in weak affinity to graphite but strong affinity to hydroxy-terminated substrates such as mica, oxidized silicon wafers, and carboxylate-terminated monolayers. Patterning of nanocomposites on these hydrophilic substrates is achieved by the microcontact printing method. We propose to use only one molecule, a large dendrimer, to control the nanoparticle formation and also the immobilization of the synthesized nanoparticle/dendrimer composites.     

Characterization and biocompatibility of chitosan nanocomposites

Chitosan nanocomposites were prepared from chitosan and gold nanoparticles (AuNPs) or silver nanoparticles (AgNPs) of ～5 nm size. Transmission electron microscopy (TEM) showed the NPs in chitosan did not aggregate until higher concentrations (120-240 ppm). Atomic force microscopy (AFM) demonstrated that the nanocrystalline domains on chitosan surface were more evident upon addition of AuNPs (60 ppm) or AgNPs (120 ppm). Both nanocomposites showed greater elastic modulus, higher glass transition temperature (T(g)) and better cell proliferation than the pristine chitosan. Additionally, chitosan-Ag nanocomposites had antibacterial ability against Staphylococcus aureus. The potential of chitosan-Au nanocomposites as hemostatic wound dressings was evaluated in animal (rat) studies. Chitosan-Au was found to promote the repair of skin wound and hemostasis of severed hepatic portal vein. This study indicated that a small amount of NPs could induce significant changes in the physicochemical properties of chitosan, which may increase its biocompatibility and potential in wound management.     

Buildup mechanism of carboxymethyl cellulose and chitosan self-assembled films

Films with different numbers of layers have been built by alternating the adsorption of carboxymethyl cellulose (CMC) and chitosan (CHI) at different pH levels. The adsorption process was recorded by quartz crystal microbalance (QCM). The results showed that under all pH conditions considered, the growth of the films is nonlinear. The film construction performed at pH 4.0 (preferred assembly pH) with different numbers of bilayers (CMC/CHI as one bilayer) was also observed step by step by atomic force microscopy (AFM). Comparing the growth process from QCM with the surface morphological changes from AFM shows the existence of an inhomogeneous structure for the first nine bilayers, and, after a coalescence of islands, an increase in the number of bilayers was demonstrated. The possible growth mechanism was also evaluated.     

Synthesis of Keggin-type polyoxometalate crystals

Vanadium-containing polyoxometalates (POM) were synthesized under acidic conditions and characterized by XRD, FT-IR, ⁵¹V MAS-NMR, EXAFS-XANES and SEM.POM crystals were successfully grown under acidic atmosphere, thus forming a self-assembled structure. This self-organized structure was constituted by cubic crystals having between 20 and 80 μm in size.Both ⁵¹V MAS-NMR, EXAFS-XANES and PM6 calculations suggest that non-covalent interactions, such as hydrogen bonding, or shared vanadium atoms of non-complete coordination are the driving force of the self-assembly process.     

一例Wells-Dawson型铌钨混配多酸的合成及光催化性质

在双氧水存在条件下,合成了一例Wells-Dawson型铌钨混配多酸K3.5Na4[H4.5（NbO2）6P2W12O56]·12.5H2O（1）,X射线单晶结构分析表明,化合物1的多阴离子是一个六过氧铌基团取代的P2W12衍生物.六个铌原子分别与五个来自多酸框架上的氧原子和一个端位的过氧单元配位.另外,对化合物1的光催化产氢性能进行了初步研究.     

Graft copolymerization of methacrylic acid onto carboxymethyl chitosan

Carboxymethyl chitosan (CMCTS) was prepared and characterized by FTIR, ¹H NMR, and elemental analysis. The graft copolymerization of methacrylic acid (MAA) onto CMCTS using ammonium persulfate (APS) as an initiator was carried out in an aqueous solution. Evidence of grafting was obtained by comparison of FTIR spectra of CMCTS and the grafted copolymer as well as solubility characteristics of the products. The effects of APS, MAA, reaction temperature and time on graft copolymerization were studied by determining the grafting parameters such as grafting percentage and grafting efficiency. With keeping other conditions constant, the optimum conditions were shown as following: [APS]=8 mmol/l, [MAA]=2.4 mol/l, reaction temperature=60-70 °C, reaction time=120 min.