Bicarboxylic Acids Research Articles

Anti-adhesive membranes based on crosslinked carboxymethyl cellulose

In recent times, new anti-adhesion devices including devices based on carboxymethyl cellulose (CMC), which have “barrier” effect are being developed and actively introduced into surgical practice. The “barrier” should be completely resorbed after the time required to healing the morphofunctional integrity of the injured peritoneum, be economically available and easy to use (including laparoscopic technologies). But the time when the CMC is in the body is insufficient to prevent the formation of adhesions, particularly in the presence of non-absorbable rigid implants. The reactive functional groups in CMC allow to transform the CMC-macromolecule into a spatial structure. For this are required the using of bifunctional (bicarboxylic or aminocarboxylic) acids and the transform of a part of the carboxyl groups from the Na-form to the hardly soluble H-form, i.e., it is necessary to crosslink CMC-macromolecules. Adipic acid and glutaric acid, aminoacetic acid and amino capronic acid used are linking agents. The influence of modification parameters on the degree of polymers swelling in water is studied. As a result, to obtain membranes designed for the treatment of adhesive disease, it is recommended to use additives in CMC of bifunctional compounds.

Aqueous phase reforming of the residual waters derived from lignin-rich hydrothermal liquefaction: investigation of representative organic compounds and actual biorefinery streams

Abstract Secondary streams in biorefineries need to be valorized to improve the economic and environmental sustainability of the plants. Representative model compounds of the water fraction from the hydrothermal liquefaction (HTL) of biomass were subjected to aqueous phase reforming (APR) to produce hydrogen. Carboxylic and bicarboxylic acids, hydroxyacids, alcohols, cycloketones and aromatics were identified as model compounds and tested for APR. The tests were performed with a Pt/C catalyst and the influence of the carbon concentration (0.3–1.8 wt. C%) was investigated. Typically, the increase of the concentration negatively affected the conversion of the feed toward gaseous products, without influencing the selectivity toward hydrogen production. A synthetic ternary mixture (glycolic acid, acetic acid, lactic acid) was subjected to APR to evaluate any differences in performance compared to the tests with single compounds. Indeed, glycolic acid reacted faster in the mixture than in the corresponding single compound test, while acetic acid remained almost unconverted. The influence of the reaction time, temperature and carbon concentration was also evaluated. Finally, residual water resulting from the HTL of a lignin-rich stream originating from an industrial-scale lignocellulosic ethanol process was tested for the first time, after a thorough characterization. In this framework, the stability of the catalyst was studied and found to be correlated to the presence of aromatics in the aqueous feedstock. For this reason, the influence of an extraction procedure for the selective removal of these compounds was explored, leading to an improvement in the APR performance.

Modified Polymer Matrix in Pharmaceutical Hot Melt Extrusion by Molecular Interactions with a Carboxylic Coformer.

Hot melt extrusion (HME) has become an essential technology to cope with an increasing number of poorly soluble drug candidates. However, there is only a limited choice of pharmaceutical polymers for obtaining suitable amorphous solid dispersions (ASD). Considerations of miscibility, stability, and biopharmaceutical performance narrow the selection of excipients, and further technical constraints arise from needed pharmaceutical processing. The present work introduces the concept of molecularly targeted interactions of a coformer with a polymer to design a new matrix for HME. Model systems of dimethylaminoethyl methacrylate copolymer, Eudragit E (EE), and bicarboxylic acids were studied, and pronounced molecular interactions were demonstrated by 1H, 13C NMR, FTIR spectroscopy, as well as by different techniques of microscopic imaging. A difference was shown between new formulations exploiting specifically the targeted molecular interactions and a common drug-polymer formulation. More specifically, a modified matrix with malic acid exhibited a technical extrusion advantage over polymer alone, and there was a benefit of improved physical stability revealed for the drug fenofibrate. This model compound displayed greatly enhanced dissolution kinetics from the ASD formulations. It can be concluded that harnessing molecularly designed polymer modifications by coformers has much potential in solid dispersion technology and in particular regarding HME processing.

In Vivo and in Situ Activated Aggregation-Induced Emission Probes for Sensitive Tumor Imaging Using Tetraphenylethene-Functionalized Trimethincyanines-Encapsulated Liposomes

The design and exploration of fluorescent probes with high-sensitivity and low-background are essential for noninvasive optical molecular imaging. The in vivo and in situ activated aggregation-induced emission (AIE) probes were found to be ideal for achieving higher signal-to-background ratios for tumor detections. We herein developed novel tetraphenylethene-encapsulated liposomes (TPE-LPs) constructed by loading TPE-trimethincyanine into liposomes for the first time, and the probes were applied to tumor bioimaging in vivo. TPE-functionalized trimethincyanines were synthesized with a new and efficient one-pot reaction. In TPE-LPs, TPE-functionalized bicarboxylic acids benzoindole trimethinecyanine (TPE-BICOOH) fluorophores were found to be well dispersed in lipid bilayers (with non-restricted rotation) during the blood circulation, and then aggregated (with restriction of intramolecular rotation) upon liposome rupture in the tumor tissue, achieving a low-background and high-target signal for tumor imaging. The in situ activated AIE probes not only had great accumulation at the tumor site after intravenous injection in 4T1 tumor-bearing mice but also demonstrated excellent signal-to-background ratios, as well as low cytotoxicity and excellent biocompatibility. The proposed strategy is believed to be a simple and powerful tool for the sensitive detection of tumors.

Effect of organic bicarboxylates on the structures of cobalt(II) coordination polymers derived from a semi-rigid bis(benzimidazole) derivative

Two new Co(II) coordination polymers, [Co(L)(glu)] (1) and [Co(L)(npht)]·H2O (2) (H2glu = glutaric acid, H2npht = 3-nitrophthalic acid, L = 1,4-bis(5,6-dimethylbenzimidazol-1-ylmethyl)benzene), have been hydrothermally synthesized by self-assembly of cobalt chloride with a semi-rigid bis(benzimidazole) derivative and different organic bicarboxylic acids. Single crystal X-ray diffraction analysis reveals that complex 1 is a one-dimensional tube-like coordination polymer containing one helical [Co-L] and two linear [Co-glu] chains. In complex 2, two npht ligands connect two Co(II) atoms to form a binuclear [Co(npht)]2 subunit, which is further linked by L ligands with two kinds of conformations to form a 3-D CdSO4-like framework. In addition, the electrochemical behaviors of the title complexes in bulk-modified carbon paste electrodes, and their thermal stabilities and fluorescent properties were investigated in this paper.

Effects of organic acids as reducing agents in the synthesis of LiFePO 4

In this work, several organic acids are evaluated as reductants in the synthesis of LiFePO 4, where FePO 4 is one of the starting materials. The investigated acids include formic, glycolic, oxalic, maleic, and malonic acids, which have minimal carbon content. Mono-carboxylic acids have favorable decomposition mechanisms as reductants compared to bi-carboxylic acids. On the other hand, bi-carboxylic acids follow a more complicated path to produce H 2 and H 2O. Only one of the two carbonyl groups in bi-carboxylic acids is involved in producing CO, although there are slight variations among bi-carboxylic acids. When a reductant is not sufficiently strong to reduce all of the Fe(III)PO 4, Fe 2O 3 and Li 3PO 4 are formed through ion exchange reactions between un-reacted Fe(III)PO 4 and LiOH. It is believed that the volatility of organic acids and the ion exchange reactivity of LiOH produce impurities. The replacement of organic acids and LiOH with less volatile mono-carboxylic acids and LiR (R = alkyl) may improve the purity of the LiFePO 4 obtained.

A new polythiophene derivative with highly sensitive and selective affinitychromism properties

A new poly(3-alkyl)thiophene bearing a piperidinic moiety in the side chain was synthesized in different ways with satisfactory yields in soluble fractions at high molecular weights. The chromic behaviors of the different polymeric samples were studied by UV–vis spectroscopy in different solvent/non-solvent mixtures and in the presence of some analytes; a strong affinitychromism toward bicarboxylic acids was observed. The good chromic response and its independence from the structural parameters of the polymer indicate the development of a very useful and easily obtainable colorimetric tool for the quick, sensitive and selective detection of diacid molecules in organic solvents.

PEG-epirubicin Conjugates with High Drug Loading

PEG is used as a polymeric carrier for low molecular weight drugs, but limitations arise from the fact that only one or two hydroxyl residues are on each polymer. Therefore, the synthesis of dendrimeric structures, based on amino adipic acid or beta-glutamic acid, as a branching molecule, built on a PEG diol of Mw 10,000Da was investigated. The large polycyclic drug epirubicin molecule was chosen as a model to investigate the influence of structure branching and drug steric hindrance during coupling reactions. Several derivatives with increased numbers of drug molecules linked to each PEG chain were synthesized and their physical, chemical and biological properties were studied. The use of specific amino bicarboxylic acids (amino adipic acid or -glutamic acid), as the branching moiety for the dendrimer synthesis, allowed linking the hindered molecule epirubicin to multibranched PEG. Most drug loaded conjugates only dissolve in water following dissolution in DMSO. This solubility problem was solved by adding a hydrophilic peptide linker between the drug and the polymer. The conjugates, synthesized in good yield and purity, showed better stability than free epirubicin in different pH buffers and in plasma as well as prolonged residence time in blood. Dynamic light scattering investigation showed that these products have a high tendency to aggregate forming stable micelles.

Inhibition and regulation of rat liver L-threonine dehydrogenase by different fatty acids and their derivatives

Rat liver L-threonine dehydrogenase is a mitochondrial enzyme which transforms L-threonine either into aminoacetone or into acetyl-CoA. We show that it is inhibited by several fatty acids and their derivatives: short chain fatty acids, L-2-hydroxybutyrate and D-3-hydroxybutyrate, long chain fatty acids, such as lauric acid, myristic acid, palmitic and stearic acids, bicarboxylic acids such as malonic acid and its derivatives methyl- and hydroxymalonic acids. The inhibition occurs at low and physiological concentrations of such compounds, which are normally present and metabolized in mitochondria. It presumably plays a role in the physiology of acetyl-CoA-dependent formation of fatty acids and ketobodies, in L-threonine-dependent gluconeogenesis, and in the regulation of L-threonine metabolism by L-threonine dehydrogenase and L-threonine deaminase.

The formation of ice between hydrotalcite particles measured by thermoporometry

AbstractThermoporometry (TPM) was applied to hydrotalcite precipitates prepared with carbonate, bicarboxylic acids and chloride. It was used to measure the formation of an ice body between the hydrotalcite particles. Before TPM could be applied, the dried hydrotalcite precipitate had to be soaked for two weeks in water. The mean value of a factor F measured by TPM, which described the shape of the ice body in hydrotalcite, was 1.7. This value was between those of a purely cylindrical (F = 2) and a purely spherical ice body (F = 1), indicating the formation of ice lenses. From the radius of the ice body, Rn, ice volume, Vn and shape factor F, the corresponding specific surface area of the hydrotalcite particles could be assessed. The TPM indicated that the distance between the separate hydrotalcite crystals in water, which is equal to 2(Rn+0.9) nm, was a function of the type of anion incorporated at the interlayer, such as chloride and bicarboxylic acid. The pore volume and surface area of the hydrotalcite particles measured by TPM were compared with those determined by the traditional nitrogen sorption technique on dried hydrotalcite. It appeared that sorption of N2 yielded much lower values than TPM. This difference was interpreted as being due to slow penetration of N2 through the dried hydrotalcite samples to the interparticle voids.

Acetazolamide-like carbonic anhydrase inhibitors with topical ocular hypotensive activity

New carbonic anhydrase (EC 4.2.1.1) inhibitors were synthesized as potential drugs for the topical treatment of glaucoma. They were obtained by substituting the acetyl group of acetazolamide and methazolamide with bicarboxylic acids of different chain length (C4-C6). The terminal carboxyl was either kept free or esterified with alcohols of different size (C1-C12). A gamma-aminovaleric derivative was also prepared. All compounds proved active as carbonic anhydrase inhibitors in vitro, with an average IC50 of about 0.5 microM. Some proved also to be topically active in vivo in lowering the artificially elevated intraocular pressure in rabbits. The most active compound, carrying a succinic acid side chain, is the most soluble in aqueous buffers. Its duration of action is about 8 h and it is under evaluation as a topical antiglaucoma drug. It is hypothesized that the duration of action could be longer in compounds having both the same high water solubility and partition coefficient.

Homogeneous catalytic hydrogenation of the esters of bicarboxylic acids: Part III . Ethylene glycol from dimethyl oxalate

Dimethyl oxalate may readily be hydrogenated in the presence of Ru(CO) 2(CH 3COO) 2(PBu 3) 2 to methyl glycolate, which is subsequently reduced at a much slower rate to ethylene glycol. The reduction to ethylene glycol is favourably affected by a high hydrogen pressure and the pre-treatment of the catalytic system with a hydroxylated reactant such as methyl glycolate or ethylene glycol itself. The catalytic system under reaction conditions seems to evolve towards less reactive species. Under optimum conditions a 95% conversion of dimethyl oxalate to the corresponding glycol has been achieved.

Crosslinked PVA-PS thin-film composite membrane for reverse osmosis

With bicarboxylic acids as crosslinking agents and H 2SO 4 as catalyst, polyvinyl alcohol (PVA) was crosslinked in the temperature range of 90–120°C, resulting in thin-film composite membranes with polysulphone as substrate. IR analysis showed that crosslinking changes the chemical structure of PVA, involving H 2SO 4 in the reaction. Besides oxalic acid, other bicarboxylic acids, such as malonic acid, succinic acid and citric acid can also crosslink PVA in the temperature range given above. RO tests showed that the salt rejection of membranes using oxalic acid as crosslinking agent was higher than that of membranes using other bicarboxylic acids.

Le potentiel chimique d'excès dans des systèmes binaires: acides dicarboxyliques –acides monocarboxyliques ou esters. L'énergie libre d'interéchange entre groupes aliphatiques et carboxyliques

We report experimental data concerning the solid–liquid and liquid–liquid equilibrium temperatures for some binary systems composed of ethyl hexadecanoate and some bicarboxylic aliphatic acids. The crystallization curves of these systems and of others, previously published only in a graphical form, are used in order to obtain the excess chemical potential of the bicarboxylic acid along its crystallization curve. This thermodynamic quantity is compared with that calculated from the theory of group interaction, by means of the areas of the contact surfaces and of three interchange energy parameters.

Homogeneous catalytic hydrogenation of free carboxylic acids in the presence of cluster ruthenium carbonyl hydrides

Saturated monocarboxylic acids up to C 6, several bicarboxylic acids and some of the corresponding anhydrides are hydrogenated in the homogeneous phase with H 4Ru 4(CO) 8(PBu 3) 4 as catalyst to give the corresponding alcohols (present among the reaction products as esters) or lactones at 100–200°C under a pressure of 100–200 atm of hydrogen. Anhydrides react at temperatures lower than those needed for acids. Esters are not reduced. Only δ-valerolactone is hydrogenated to 1,5-pentanediol. Ruthenium carbonyl carboxylates have been recovered at the end of the reaction and appear to be catalytically active intermediates.

New polymer materials for reverse osmosis membranes

The results of investigations on new polymer materials suitable for reverse osmosis are reported. The studies particularly concerned polypiperazinamides derived from differently structured bicarboxylic acids. Such polyamides show a water permeability that may vary from 0.09 μg cm −1 sec −1 to 2.3 μg cm −1 sec −1 depending on the structure. The results obtained from reverse osmosis tests on dense and homogeneous films are described. Anisotropic membranes were prepared from poly( trans-2,5-dimethyl-piperazin-thiofurazanamide). Their properties very closely approach those of the corresponding cellulose acetate membranes. The anisotropic structure of the membranes has been evidenced by stereoscan electron microscope analysis.