Carboxymethyl Groups Research Articles

Thermal stability of cellulose and their nanoparticles: Effect of incremental increases in carboxyl and aldehyde groups

Oxidized cellulose containing carboxyl and aldehyde functional groups represent an important class of cellulose derivatives. In this study effect of incrementally increasing COOH and CHO groups at C2, C3, and C6 positions of cellulose and nanocellulose has been investigated, with a view to understanding their effect on thermal treatment of cellulose. The results show that 2,3-dialdehyde cellulose (DAC) is the most thermally stable oxidized product of cellulose while the most unstable derivatives contain carboxyl group at the C6 position (6CC). Carboxymethylcellulose (CMC), with carboxymethyl group on C6 position, is more stable than 6CC. Multi-functionalized celluloses 2,3,6-tricarboxycellulose and 6-carboxy-2,3-dialdehyde, have the same level of thermal stability as 6CC, showing that the presence of carboxyl at the C6 is a key destabilizing factor in the thermal stability of oxidized cellulose products. More the number of reducing end groups on the polymer chain, lower the thermal stability of the cellulose, as proved by comparing the TGA/DTG of monomeric analogs dextrose, cellobiose and glucuronic acid with the oxidized celluloses. The thermal stability trend observed for oxidized celluloses was DAC>DCC>nanoparticles>dextrose>glucuronic acid, caused by extent of reducing ends and COOH groups.

The influence of the substituent position in monocarboxymethyl-γ-cyclodextrins on enantioselectivity in capillary electrophoresis.

Three newly synthesized chiral selectors, namely, 2(I)-O-, 3(I)-O-, and 6(I)-O-carboxymethyl-γ-cyclodextrin, native γ-cyclodextrin, and commercially available carboxymethylated γ-cyclodextrin with degree of substitution of 3-6 were used as additives in a background electrolyte composed of phosphate buffer at 20 mmol/L concentration and pH 2.5. This system was used for the analysis of several biologically significant low-molecular-mass chiral compounds by capillary electrophoresis. The results confirmed that the position of carboxymethyl group influences the enantioseparation efficiency of all the studied analytes. The 2(I)-O- and 3(I)-O- regioisomers provide a significantly better resolution than native γ-cyclodextrin, while the 6(I)-O-regioisomer gives only a slightly better enantioseparation than native γ-cyclodextrin. The application of γ-cyclodextrin possessing higher number of carboxymethyl groups led to the best resolution for the majority of the compounds analyzed.

Carboxymethylation of an exopolysaccharide from Lachnum and effect of its derivatives on experimental chronic renal failure

Carboxymethylated polysaccharide CLEP-1b was prepared from a single component (LEP-1b) of Lachnum YM281 exopolysaccharides by molecular modification with a degree of substitution (DS) of 0.286. Infrared result proved that the carboxymethylation of LEP-1b succeeded and 13C NMR result showed that the carboxymethyl group (CH2COOH) was chemically linked to an oxygen (O) atom of the hydroxyl on C-3 of LEP-1b. LEP-1b could improve the histopathological status of kidney and significantly reduce the contents of serum creatinine (Scr) and blood urea nitrogen (BUN), and increase the contents of total protein and albumin. It could also enhance the activity of SOD, GSH-PX, CAT, GSH and decrease MDA contents in the nephridial and hepatic tissues. What's more, CLEP-1b showed more significant effects than LEP-1b at the same dosage. The research indicated that LEP-1b and CLEP-1b could mitigate the chronic renal failure of mice and the effects were closely associated with antioxidant activity.

Synthesis and characterization of water soluble O-carboxymethyl chitosan Schiff bases and Cu(II) complexes

In this study, mono-imine was synthesized (3a and 4a) via a condensation reaction between 2,4-pentadion and aminobenzoic acid (meta or para) in alcohol (1:1). The second-imine (CS-3a and CS-4a) was obtained as a result of the reaction of the free oxo groups of mono-imine (3a and 4a) with the amino groups on the chitosan (CS). Their structures were characterized with FTIR and 13C CP-MAS. Then, the water soluble forms of CS-3a and CS-4a were obtained through oxidation of the hydroxide groups on the chitosan to carboxymethyl groups using monochloracetic acid ([O-CMCS-3a]·2H2O and [O-CMCS-4a]·2H2O). Thus, the solubility problem of chitosan in an aqueous media was overcome and Cu(II) complexes could be synthesized more easily. Characterization of the synthesized O-carboxymethyl chitosan Schiff base derivatives and their metal complexes, [O-CMCS-3a-Cu(OAc)2]·2H2O and [O-CMCS-4a-Cu(OAc)2]·2H2O, was conducted using FTIR, UV–Vis, TG/DTA, XRD, SEM, elemental analysis, conductivities and magnetic susceptibility measurements.

Conversion of agricultural residues to carboxymethylcellulose and carboxymethylcellulose acetate

In view of continuing interest in the utilization of agricultural by-products, we have converted cellulose, wheat straw, barley straw, and rice hull into carboxymethylcellulose (CMC), using both conventional heat and microwave-assisted synthesis. The application of microwave technology has enabled an improved synthesis of CMC to be conducted, with similar degrees of substitution as conventional heat (3h) but reduced reactions times (30min). The CMC obtained can be acetylated to form carboxymethylcellulose acetate (CMC acetate). The FT-IR and solid state 13C NMR spectra of these materials have been characterized. With variations in the degrees of substitution of carboxymethyl and acetyl groups, a family of CMC acetate products can be made. The polymer may perhaps find applications as filtration membranes, functional fillers in polymers, and additives in commercial formulations.

Highly diluted solutions of amphiphilic derivatives of calix[4]resorcinols: self-organization and physicochemical properties

Self-organization and physicochemical properties of highly diluted solutions (10−11–10−2 mol L−1) in aqueous DMF (30 vol.% DMF) of a series of octasubstituted amphiphilic calix[4]resorcinols (CRs 1–4, where 1 is CR with carboxymethyl groups, 2 is its potassium salt, and 3 and 4 are CRs with acetylhydrazide and tris(hydroxymethyl)methylamide fragments) stored both under natural conditions and in the absence of external physical fields (geomagnetic and low-frequency electromagnetic) were studied by a complex of methods (dynamic light scattering, electrophoresis, tensiometry, conductometry, and pH metry). The studied solutions of CRs 1–4 are dispersed systems in which micelles (for CRs 1, 2, and 4), supramolecular domains (for CRs 1–4), and nanoassociates (for CRs 2–4) are formed, depending on hydrophilicity and nature of functional groups of CRs in various concentration ranges. The new approach to studying highly diluted solutions made it possible to explain for the first time the reasons for the nonmonotonic changes in the physicochemical properties and surface activity of aqueous-dimethylformamide highly diluted solutions of amphiphilic calix[4]resorcinols (10−4–10−7 mol L−1) from the viewpoint of the formation and rearrangement of supramolecular domains and nanoassociates.

Preparation of keratin hydrogel/hydroxyapatite composite and its evaluation as a controlled drug release carrier

Infection after artificial joint replacement is a serious problem, which requires the re-implantation of prosthesis. To aim at developing bone filling materials having both osteoconductivity and ability as a sustained drug release carrier, composites of wool keratin or carboxymethylated (CM) keratin hydrogels with hydroxyapatite were prepared and evaluated as a sustained drug release carrier. CM-keratin was prepared by the reaction of keratin extracted from wool with iodoacetic acid. Hydrogels were obtained by dropping keratin or CM-keratin solution into CaCl2 solution. The composites were obtained by immersing hydrogels in simulated body fluid (SBF). The introduction of carboxymethyl groups to keratin facilitated the deposition of hydroxyapatite on hydrogel. After 7days of immersion in SBF, a 4–5 times higher amount of hydroxyapatite was accumulated on CM-keratin hydrogel than that on keratin hydrogel. When salicylic acid was loaded on keratin and CM-keratin hydrogels, a good sustained release was observed; that is, 90% of a drug was released up to 14days after 60 and 45% of the initial burst in 1day. On the other hand, initial release within 1day was suppressed by forming a composite with hydroxyapatite and the release was almost ceased at 3days when 60% of the drug was released.Although further improvement to prolong drug release might be necessary, CaKHA and CaCMKHA are expected to be a promising novel type of bone filling materials which has both osteoconductivity and sustained drug release ability.

Folic acid-conjugated Fe3O4 magnetic nanoparticles for hyperthermia and MRI in vitro and in vivo

Abstract The folic acid (FA)-conjugated Fe 3 O 4 magnetic nanoparticles (MNPs) were synthesized by co-precipitation of Fe 3+ and Fe 2+ solution followed by surface modification with carboxymethyl dextran (CMD) to form carboxymethyl group terminated MNPs, then FA was conjugated with the carboxyl group functionalized MNPs. The morphology and properties of obtained nanoparticles were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), UV–visible spectra (UV–vis), transmission electron microscopy (TEM), dynamic light scattering (DLS), vibrating sample magnetometer (VSM) and thermogravimetric analysis (TGA). The FA-conjugated MNPs exhibited relatively high saturation magnetization and fast magneto-temperature response which could be applied to hyperthermia therapy. To determine the accurate targeting effect of FA, we chose FA-conjugated MNPs as MRI contrast enhancement agent for detection of KB cells with folate receptor over-expression in vitro and in vivo . The results show that these magnetic nanoparticles appear to be the promising materials for local hyperthermia and MRI.

Preparation of carboxymethyl cellulose superabsorbents from waste textiles

Production of superabsorbent polymers from cotton and viscose waste textiles was investigated. The cellulose wastes were carboxymethylated, crosslinked by divinylsulfone, and then converted to superabsorbent material using air-drying, freeze-drying, or air-drying after phase inversion. The separation of cellulose from synthetic polymers in the textile (polyester) was carried out by direct dissolution of cellulose in N-methylmorpholine-N-oxide (NMMO), or separation by dissolution in water after carboxymethylation of the textiles. The progress of the carboxymethylation reaction was evaluated by measurement of the degree of substitution (DS) of carboxymethyl cellulose (CMC). The DS values of 0.50–0.86 confirmed the prosperous substitution of hydrophilic carboxymethyl groups into the cellulosic chains. The water binding capacity and the swelling rate of the superabsorbents prepared under different conditions were measured. Under the best condition the superabsorbent obtained from waste textiles showed an ultimate water binding capacity of 541 g/g which was notably higher than that of the reference superabsorbent derived from cotton linter (470 g/g). The amount of absorbed water by this product exceeded that of the reference sample after 60 min immersion.

Biodegradable and injectable in situ cross-linking chitosan-hyaluronic acid based hydrogels for postoperative adhesion prevention

Postsurgical peritoneal adhesions are very common and serious complication after surgery. Biodegradable and injectable hydrogels derived from natural polysaccharides are ideal biomaterials for prevention of postoperative adhesion. In this work, we report a class of injectable, biodegradable, and non-toxic hydrogel derived from N, O-carboxymethyl chitosan (NOCC) and aldehyde hyaluronic acid (A-HA), without requirement of any chemical linkers or radiant light sources. NOCC was prepared by introducing carboxymethyl groups to the N-position and the O-position of chitosan, and A-HA was prepared using periodate oxidation method. The gelation is attributed to the Schiff base between the amino groups of NOCC and aldehyde groups in A-HA, and the hydrogel precursors cross-linked to form a flexible hydrogel. NOCC, A-HA, and NOCC/A-HA hydrogel extract exhibited very low cytotoxicity and hemolysis, and the acute toxicity tests showed that the hydrogel was non-toxic. Besides, the highly porous three-dimensional hydrogel can supported the growth and proliferation of the cells encapsulated in the hydrogels, but was not favorable for the attachment of fibroblasts to the surface, suggesting that the NOCC/A-HA hydrogel can be developed for adhesion prevention. The hydrogel was susceptible to the lysozyme and can be degraded within 2 weeks in vivo. Furthermore, we employed a rat model of sidewall defect-cecum abrasion to investigate the efficacy of NOCC/A-HA hydrogel in preventing post-operative peritoneal adhesions. A significant reduction of peritoneal adhesion formation was found in the NOCC/A-HA-treated group, compared with commercial hyaluronic acid (HA) hydrogel group and normal saline group. In addition, the potential anti-adhesion mechanism of NOCC/A-HA hydrogel was discussed, which may attribute to the combination of barrier function and bioactivity of NOCC and A-HA.

Adsorption of Hg2+ and Ni2+ from Aqueous Solutions Using Unmodified and Carboxymethylated Granular Activated Carbon (GAC)

The use of unmodified and carboxymethylated granular activated carbon (GAC) for adsorption of Hg2+ and Ni2+ from aqueous solutions was assessed in this work. The effect of concentration and modification by carboxymethyl group on the adsorption of these metal ions was studied in batch process. The adsorption data were correlated with Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherm models. Results show that Freundlich model gave the best description for the adsorption process followed by the Langmuir model. Langmuir adsorption capacity corresponding to sites saturation was found to be 20.83 mg g-1 and 19.05 mg g-1 for adsorption of the Hg2+ and Ni2+ respectively onto the unmodified adsorbent and 19.72 mg g-1 and 17.01 mg g-1 for adsorption onto the carboxymethylated substrate. The apparent energy values obtained from the Dubinin-Radushvich model further indicates that the forces of the adsorption follow physical mode. Modification by carboxymethyl group generally caused a decline in the adsorption capacity by the adsorbent. Results obtained generally showed that Hg (II) ions were better adsorbed onto both adsorbents as compared to Nickel (II).

Formation and thermodynamic stability of novel methyl–vinyl derivatives of PtIV as possible intermediates for Csp3–Csp2 cross-coupling

Methyl–vinyl derivatives of PtIV were obtained in a sequence of the reactions of methyl iodide oxidative addition to PtII iodo complexes followed by iodoplatination of C–C triple bond of R1CCR2 (R1 = Ph, R2 = C(O)OC2H5; R1 = R2 = C(O)OCH3) in acetone solution under excess of I−. In the reaction of the ethyl phenylpropiolate equilibrium formation of PtIV methyl–vinyl derivative ▪ occurs. The reaction is highly exothermic, ΔH = –(81 ± 7) kJ/mol, and this provides a favorable thermodynamics even though a significant decrease in entropy, ΔS = −(249 ± 23) J/(K mol). In the reaction of dimethyl acetylenedicarboxylate the chelate metallocycle ▪ is quantitatively formed. The quantitative yield of the organometallic product is explained by more favorable thermodynamics of the reaction: chelation of the metal center by the oxygen atom of the carboxymethyl group in the σ-vinyl ligand forming metallocycle provides an additional stabilization of the product. In the formed organoplatinum compounds vinyl and methyl ligands are located in the mutual cis-positions, which is essential for further accomplishment of Csp3–Csp2 coupling reaction.

Carboxymethylation of pine wood subjected to microwave irradiation after pretreatment in an “acetic acid-hydrogen peroxide-water-catalyst” system

Pretreatment of pine wood in a mixture containing acetic acid, hydrogen peroxide, water, and catalyst has been performed in order to minimize wood component destruction and analyze the behavior of the principal components of pine wood upon carboxymethylation. The effects of catalysts (sulfuric acid or ammonium molybdate) and the characteristics of the microwave radiation on the composition of the solid residue have been investigated. The reaction of pine wood carboxymethylation after pretreatment in a mixture of acetic acid, hydrogen peroxide, water, and catalyst has been studied. Formation of highly substituted carboxymethylated derivatives containing 17–29% carboxymethyl groups has been demonstrated for pine wood. Solubility of carboxymethylated pine wood depended on the nature of the catalyst used during pretreatment. Carboxymethylation products obtained with sulfuric acid as catalyst had the highest solubility.

Gelation of Vesicles and Nanoparticles Using Water-Soluble Hydrophobically Modified Chitosan

Hydrophobically modified chitosan (hmC) is a self-assembling polymer that has attracted recent attention for many applications, including as a hemostatic agent. One limitation with chitosan and its derivatives like hmC is that these polymers are soluble in water only under acidic conditions (because the pKa of chitosan is about 6.5), which could be undesirable for biomedical applications. To circumvent this limitation, we have synthesized a derivative of a C12-tailed hmC that is soluble in water at neutral pH. This water-soluble hmC (ws-hmC) is obtained by grafting O-carboxymethyl groups onto some of the primary hydroxyls on hmC. The solubility of ws-hmC at neutral pH is shown to be the result of a net anionic character for the polymer due to ionization of the carboxymethyl groups (in comparison, hmC is cationic). We also demonstrate that ws-hmC retains the self-assembling properties of hmC. Specifically, ws-hmC is able to induce gelation at neutral pH in dispersions of anionic surfactant vesicles as well as polymethylmethacrylate latex nanoparticles. Gelation is attributed to hydrophobic interactions between the hydrophobes on ws-hmC with vesicle bilayers and nanoparticle surfaces. In each case, gelation can be reversed by the addition of α-cyclodextrin, a supramolecule with a hydrophobic cavity that sequesters the hydrophobes on the polymer.

Synthesis and pH‐responsive assembly of methoxy poly(ethylene glycol)‐b‐poly(ε‐caprolactone) with pendant carboxyl groups

ABSTRACTpH‐responsive methoxy poly(ethylene glycol)‐b‐poly(ε‐caprolactone) bearing pendant carboxyl groups mPEG‐b‐P(2‐CCL‐co‐6‐CCL) was synthesized based on our newly monomer benzyloxycarbonylmethly functionalized ε‐caprolactone. Their structure was confirmed by 1H NMR, 13C NMR, and Fourier transform infrared spectrum spectra. In addition, SEC results indicated that the copolymers had a relatively narrow polydispersity. WXRD and DSC demonstrated that the introduction of carboxymethyl groups had significant effect on the crystallinity of the copolymers. Furthermore, the solution behavior of mPEG‐b‐P(2‐CCL‐co‐6‐CCL) has been studied by various methods. The results indicated that mPEG‐b‐P(2‐CCL‐co‐6‐CCL) had a rich pH‐responsive behavior and the micelles could be formed by pH induction, and the mPEG‐b‐P(2‐CCL‐co‐6‐CCL) could existed as unimers, micelles or large aggregates in different pH range accordingly. The mechanism of which was supposed to depend on the counteraction between the hydrophobic interaction from PCL and the ionization of the carboxyl groups along the polymer chain. Moreover, the mPEG‐b‐P(2‐CCL‐co‐6‐CCL) copolymers displayed good biocompatibility according to the preliminary cytotoxicity study. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 188–199

ONO Dianionic Pincer-Type Ligand Precursors for the Synthesis of σ,π-Cyclooctenyl Iridium(III) Complexes: Formation Mechanism and Coordination Chemistry

The σ,π-cyclooctenyl iridium(III) pincer compounds [Ir(κ3-pydc-X)(1-κ-4,5-η-C8H13)] (X = H (1), Cl, Br) have been prepared from [Ir(μ-OMe)(cod)]2 and the corresponding 4-substituted pyridine-2,6-dicarboxylic acids (H2pydc-X) or, alternatively, from their lithium salts (X = H) and [Ir(cod)(CH3CN)2]PF6. Deuterium labeling studies in combination with theoretical calculations have shown that formation of 1 involves a metal-mediated proton transfer in the reactive intermediate [Ir(κ2-Hpydc)(cod)], through the solvent-stabilized hydrido complex [IrH(κ3-pydc)(cod)(CH3OH)], followed by olefin insertion. The formation of this hydrido intermediate results from solvent-assisted proton transfer through a hydrogen-bonding network, forming an eight-membered metallacycle. In contrast, reaction of [Ir(μ-OMe)(cod)]2 with iminodiacetic acid derivatives, RN(CH2COOH)2, gave the stable iridium(I) mononuclear [Ir{κ2-MeN(CH2COOH)(CH2COO)}(cod)] (R = Me) complex having a free carboxymethyl group and the tetranuclear complex [Ir4...

Carboxymethyl inulin: A novel flocculant for wastewater treatment

Carboxymethyl inulin (CMI) has been synthesized by incorporation of carboxymethyl groups in the inulin framework; by reacting inulin with sodium salt of monochloro acetic acid (SMCA) in presence of sodium hydroxide. The resulting carboxymethylated product, with different degrees of substitution, has been confirmed through various physicochemical characterization techniques, such as intrinsic viscosity measurement, elemental analysis (C, H, N and O), FTIR spectroscopy, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) studies. Flocculation efficacy of various grades of CMI, have been studied in kaolin suspension and then in municipal wastewater, in relation to inulin (parent polysaccharide). This has been done utilizing jar-test procedure towards possible application as a flocculant for waste water treatment.

Synthesis, characterization, and drug‐release behavior of amphiphilic quaternary ammonium chitosan derivatives

ABSTRACTA new type of amphiphilic quaternary ammonium chitosan derivative, 2‐N‐carboxymethyl‐6‐O‐diethylaminoethyl chitosan (DEAE–CMC), was synthesized through a two‐step Schiff base reaction process and applied to drug delivery. In the first step, benzaldehyde was used as a protective agent for the incorporation of diethylaminoethyl groups to form the intermediate (6‐O‐diethylaminoethyl chitosan). On the other hand, NaBH4 was used as a reducing agent to reduce the Schiff base, which was generated by glyoxylic acid, for the further incorporation of carboxymethyl groups to produce DEAE–CMC. The structure, thermal properties, surface morphology, and diameter distribution of the resulting chitosan graft copolymers were characterized by Fourier transform infrared spectroscopy, 1H‐NMR, thermogravimetric analysis, differential scanning calorimetry, X‐ray powder diffraction, scanning electron microscopy, and laser particle size analysis. Benefiting from the amphiphilic structure, DEAE–CMC was able to be formed into microspheres in aqueous solution with an average diameter of 4.52 ± 1.21 μm. An in vitro evaluation of these microspheres demonstrated their efficient controlled release behavior of a drug. The accumulated release ratio of vitamin B12 loaded DEAE–CMC microspheres were up to 93%, and the duration was up to 15 h. The grafted polymers of DEAE–CMC were found to be blood‐compatible, and no cytotoxic effect was shown in human SiHa cells in an MTT [3‐(4, 5‐dimethyl‐thiazol‐2‐yl)‐2, 5‐diphenyltetrazolium bromide] cytotoxicity assay. These results indicate that the DEAE–CMC microspheres could be used as safe, promising drug‐delivery systems. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39890.

Composite films of N,O‐carboxymethyl chitosan and bamboo fiber

ABSTRACTTo obtain an antibacterial chitosan derivative, composite films of N,O‐Carboxymethyl Chitosan (N,O‐CMCS) and bamboo fiber were prepared. A water‐soluble chitosan derivative‐N,O‐CMCS was synthesized from chitosan with chloroacetic acid in alkaline solution. Composite films with 1–5 wt % N,O‐CMCS content were prepared in NaOH/urea/thiourea solution. The DS of N,O‐CMCS reached 1.70 and the water solubility increased with the increasing of DS. The carboxymethyl group was introduced into chitosan, which led to the decrease of thermal stability and crystallinity. The structural characterization confirmed that N,O‐CMCS was adsorbed on the surface of bamboo fiber. The antibacterial performance of the composite films were enhanced with the increasing of N,O‐CMCS content. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39851.

Synthesis and evaluation of a novel β-cyclodextrin derivative for oral insulin delivery and absorption

In this paper, we describe the synthesis and testing of a novel β-cyclodextrin derivative, carboxymethy-hydroxypropyl-β-cyclodextrin (CM-HP-β-CD). After synthesis, we verified that carboxymethyl and hydroxypropyl groups were successfully substituted onto β-cyclodextrin to form CM-HP-β-CD. Then, we performed in vitro experiments to investigate (1) the ability of CM-HP-β-CD to bind insulin, (2) the transportation of insulin-CM-HP-β-CD complexes across a Caco-2 cell monolayer, and (3) the cytotoxicity of CM-HP-β-CD. CM-HP-β-CD showed the strongest insulin-binding ability and the best transport properties compared with the other β-cyclodextrin derivatives we evaluated. In addition, CM-HP-β-CD showed no cytotoxicity up to 200mM (IC50>200mM). To examine the effectiveness of the cyclodextrin complexes in delivering insulin in vivo, we administered different insulin-cyclodextrin complexes to diabetic rats. In these studies, we found that the insulin-CM-HP-β-CD complex provided a significant and sustained (5h) reduction in the blood glucose levels of diabetic rats. Overall, our study showed that CM-HP-β-CD may be a promising protein carrier for use in oral protein drug delivery.