Modification Of Carboxyl Groups Research Articles

Porous Mn doped g-C3N4 photocatalysts for enhanced synergetic degradation under visible-light illumination

Photocatalytic degradation by semiconductors is an ideal way to solve the environmental problem. Here, the porous Mn doped g-C3N4 photocatalyst was synthesized by the calcination-refluxing method. The as-prepared g-C3N4 exhibits the high activity of photocatalytic degradation under visible light irradiation ( > 400nm) in the mixed system of Cr(VI) and organic pollutants. Especially, the photocatalytic activity of Cr(VI) reduction was increased from 9.5% to 76.5%, while that of Rhodamine B(RhB) degradation was enhanced from 15.3% to 88.9% after 60min irradiation. The porous Mn doped g-C3N4 still keeps the high degradation efficiency of mixed pollutants in the 7th running. Based on the computational modeling, the Mn doping and carboxyl modification affect the atomic arrangement and molecular orbital distribution of the g-C3N4 semiconductor, leading to the enhancement of photo-induced carrier separation. Additionally, the active oxygen species and intermediates in the photoreaction process were discovered by ESR measurement and UV–vis test. The RhB degradation in synergistic photocatalysis not only inhibits the reverse reaction of Cr(VI) reduction, but also validly supply the photogenerated electrons by the photosensitization effect. This work may be useful for rationally designing photocatalysts and providing illuminating insights into the photocatalytic mechanism.

Influence of Surface Chemistry on Adhesion and Osteo/Odontogenic Differentiation of Dental Pulp Stem Cells.

The complex interaction between extracellular matrix and cells makes the design of materials for dental regeneration challenging. Chemical composition is an important characteristic of biomaterial surfaces, which plays an essential role in modulating the adhesion and function of cells. The effect of different chemical groups on directing the fate of human dental pulp stem cells (hDPSCs) was thus explored in our study. A range of self-assembled monolayers (SAMs) with amino (-NH2), hydroxyl (-OH), carboxyl (-COOH), and methyl (-CH3) modifications were prepared. Proliferation, morphology, adhesion, and differentiation of hDPSCs were then analyzed to demonstrate the effects of surface chemical groups. The results showed that hDPSCs attached to the -NH2 surface displayed a highly branched osteocyte-like morphology with improved cell adhesion and proliferation abilities. Moreover, hDPSCs cultured on the -NH2 surface also tended to obtain an increased osteo/odontogenesis differentiation potential. However, the hDPSCs on the -COOH, -OH, and -CH3 surfaces preferred to maintain the mesenchymal stem cell-like phenotype. In summary, this study indicated the influence of chemical groups on hDPSCs in vitro and demonstrated that -NH2 might be a promising surface modification strategy to achieve improved biocompatibility, osteoconductivity/osteoinductivity, and osseointegration of dental implants, potentially facilitating dental tissue regeneration.

Surface decoration of polyimide fiber with carbon nanotubes and its application for mechanical enhancement of phosphoric acid-based geopolymers

A new methodology to decorate the surface of polyimide (PI) fiber with carbon nanotubes (CNTs) has been developed in this study. This surface decoration was carried out through a surface alkali treatment, a carboxylation modification, surface functionalization with acyl chloride groups and then with amino groups, and a surface graft of CNTs onto PI fiber. Fourier-transform infrared and X–ray photoelectron spectroscopic characterizations confirmed that CNTs were chemically grafted onto the surface of PI fiber, and scanning electron microscopic observation demonstrated the fiber surface was uniformly and densely covered with CNTs. The surface energy and wettability of PI fiber were improved in the presence of CNTs on the fiber surface, which made a contribution to enhance the interfacial adhesion of PI fiber with other inorganic matrices when used as a reinforcing fiber. The application of CNTs-decorated PI fiber for the reinforcement of phosphoric acid-based geopolymers was investigated, and the results indicated that the geopolymeric composites gained a noticeable reinforcement. Compared to unreinforced geopolymer, the geopolymeric composites achieved a remarkable increase in compressive strength by 120% and in flexural strength by 283%. Fractography investigation demonstrated that the interaction adhesion between the fibers and matrix was enhanced due to the surface decoration of PI fiber with CNTs, which contributed to an improvement in fracture-energy dissipation by fiber pullout and fiber debonding from the matrix. As a result, a significant reinforcement effect on geopolymeric composites was achieved through a fiber-bridging mechanism. This study provided an effective methodology to improve the interracial bonding force for PI fiber and also proves a highly efficient application of CNTs-decorated PI fiber for the mechanical enhancement of geopolymeric composites.

Synthesis and bioactivities of Phenazine-1-carboxylic acid derivatives based on the modification of PCA carboxyl group

Phenazine-1-carboxylic acid (PCA) as a natural product widely exists in microbial metabolites of Pseudomonads and Streptomycetes and has been registered for the fungicide against rice sheath blight in China. To find higher fungicidal activities compounds and study the effects on fungicidal activities after changing the carboxyl group of PCA, we synthesized a series of PCA derivatives by modifying the carboxyl group of PCA and their structures were confirmed by 1H NMR and HRMS. Most compounds exhibited significant fungicidal activities in vitro. In particular, compound 6 exhibited inhibition effect against Rhizoctonia solani with EC50 values of 4.35mg/L and compound 3b exhibited effect against Fusarium graminearum with EC50 values of 8.30mg/L, compared to the positive control PCA with its EC50 values of 7.88mg/L (Rhizoctonia solani) and 127.28mg/L (Fusarium graminearum), respectively. The results indicated that the carboxyl group of PCA could be modified to be amide group, acylhydrazine group, ester group, methyl, hydroxymethyl, chloromethyl and ether group etc. And appropriate modifications on carboxyl group of PCA were useful to extend the fungicidal scope.

Iron as a catalyst of human low-density lipoprotein oxidation: Critical factors involved in its oxidant properties

Iron-induced human LDL oxidation, which is relevant to atherosclerosis, has not yet been properly investigated. We addressed such issue using iron(II) and (III) basically in the presence of phosphates, which are present in vivo and influence iron oxidative properties, at pH 4.5 and 7.4, representative, respectively, of the lysosomal and plasma environment. In 10mM phosphate buffered saline (PBS), iron(II) induces substantial LDL oxidation at pH 4.5 at low micromolar concentrations, while at pH 7.4 has low oxidative effects; iron(III) promotes small LDL oxidation only at pH 4.5. In 10mM sodium acetate/NaCl buffer, pH 4.5, iron-induced LDL oxidation is far higher than in PBS, highlighting the relevance of phosphates in the inhibitory modulation of iron-induced LDL oxidation. LDL oxidation is related to iron binding to the protein and lipid moiety of LDL, and requires the presence of iron(II) bound to LDL together with iron(III). Chemical modification of LDL carboxyl groups, which could bind iron especially at pH 4.5, decreases significantly iron binding to LDL and iron-induced LDL oxidation. Hydroxyl radical scavengers are ineffective on iron-induced LDL oxidation, which is inhibited by metal chelation, scavengers of alkoxyl/peroxyl radicals, or removal of LDL lipid hydroperoxides (LOOH). Overall, substantial human LDL oxidation is induced LOOH-dependently by iron(II) at pH 4.5 even in the presence of phosphates, suggesting the occurrence of iron(II)-induced LDL oxidation in vivo within lysosomes, where pH is about 4.5, iron(II) and phosphates coexist, plasma with its antioxidants is absent, and glutathione peroxidase is poorly expressed resulting in LOOH accumulation.

Solid-Phase Synthesis of ɤ-Lactone and 1,2-Oxazine Derivatives and Their Efficient Chiral Analysis.

Derivatives of 3-methyl-3,6-dihydro-2H-1,2-oxazine-6-carboxylic acid prepared by regioselective hetero Diels-Alder reaction of arylnitroso compounds with sorbic acid were used for solid-phase synthesis of a library of derivatives that included modification of carboxylic group, dihydroxylation of double bond and cleavage of N-O bond. Derivatives of 2,3,4-trihydroxyhexanoic acid obtained from 3,6-dihydro-2H-1,2-oxazines after double bond dihydroxylation and N-O cleavage were used for simple and stereoselective formation of chiral lactones derived from 3,4-dihydroxydihydrofuran-2(3H)-one. The final compounds obtained as a mixture of stereoisomers were analyzed with use of chiral HPLC and SFC. HPLC analyses were not successful for all derivatives or required lengthy chromatography. On the other hand SFC afforded much shorter analyses and was effective for all studied derivatives. The method of synthesis and analysis is thus suitable for future study of stereoselective synthesis of lactones and other derivatives from single oxazine derivatives and application of high-throughput synthesis on solid-support and combinatorial chemistry.

In Vitro Antibacterial Activity of Rhodanine Derivatives against Pathogenic Clinical Isolates.

Bacterial infections present a serious challenge to healthcare practitioners due to the emergence of resistance to numerous conventional antibacterial drugs. Therefore, new bacterial targets and new antimicrobials are unmet medical needs. Rhodanine derivatives have been shown to possess potent antimicrobial activity via a novel mechanism. However, their potential use as antibacterials has not been fully examined. In this study, we determined the spectrum of activity of seven rhodanine derivatives (compounds Rh 1–7) against clinical isolates of Gram-positive and Gram-negative bacterial strains and Candida albicans. We also synthesized and tested three additional compounds, ethyl ester and amide of rhodanine 2 (Rh 8 and Rh 10, respectively) and ethyl ester of rhodanine 3 (Rh 9) to determine the significance of the carboxyl group modification towards antibacterial activity and human serum albumin binding. A broth microdilution assay confirmed Rh 1–7 exhibit bactericidal activity against Gram-positive pathogens. Rh 2 had significant activity against various vancomycin-resistant (MIC90 = 4 μM) and methicillin-resistant (MIC90 = 4 μM) Staphylococcus aureus (VRSA and MRSA), Staphylococcus epidermidis (MIC = 4 μM) and vancomycin-resistant Enterococcus (VRE) strains (MIC90 = 8 μM). The rhodanine compounds exhibited potent activity against Bacillus spp., including Bacillus anthracis, with MIC range of 2–8 μM. In addition, they had potent activity against Clostridium difficile. The most potent compound, Rh 2, at 4 and 8 times its MIC, significantly decreased S. epidermidis biofilm mass by more than 35% and 45%, respectively. None of the rhodanine compounds showed antimicrobial activity (MIC > 128 μM) against various 1) Gram-negative pathogens (Acinetobacter baumannii, Escherichia coli, Klebsiella pneumonia, Pseudomonas aeruginosa, and Salmonella Typhimurium) or 2) strains of Candida albicans (MIC > 64 μM). The MTS assay confirmed that rhodanines were not toxic to mouse murine macrophage (J774.1A) up to 64 μM, human keratinocytes (HaCat) up to 32 μM, and human ileocecal colorectal cell (HRT-18) up to 128 μM. Overall, these data suggest that certain rhodanine compounds may have potential use for the treatment of several multidrug-resistant Gram-positive bacterial infections.

Industrial waste derived biosorbent for toxic metal remediation: Mechanism studies and spent biosorbent management

The dried activated tannery industry sludge was used as complex biosorbent for removal of Ni(II), Co(II), Zn(II) and Cd(II) in single and multi-component system. The mechanism for toxic metals biosorption was analyzed along with equilibrium isotherm and kinetic study. The efficiency of the biosorbent was studied for real effluent treatment. Further, safe disposal of the spent biosorbent in glass form was established which is significant for commercial implementation of the biosorption technology. Zn(II) and Cd(II) showed 99% removal within 10 min while Ni(II) and Co(II) attained 98% removal at 20–24h. The biosorbent showed >96% removal efficiency for these metals in effluents from battery manufacturing industry with simultaneous removal of Pb, Cu and Fe ions. Chemical modification of hydroxyl, carboxyl, amino, phosphate, sulfonyl and carbonyl functional groups were undertaken and surface characterization of the biosorbent was done using zeta-potential, FTIR, FESEM-EDX and XPS technique to elucidate the biosorption mechanism. The biosorption efficiency was found to decrease significantly indicating involvement of functional groups in metal binding which was confirmed by FT-IR. Rapid removal of Zn(II) and Cd(II) was due to binding with functional groups. However, the gradual removal of Ni(II) and Co(II) was governed by ionic exchange mechanism, confirmed by ICP-AES. Deconvolution of N1s and C1s XPS spectra produced two and one additional peaks respectively, suggesting formation of amino-metal complexes. Increase in atomic concentration of total oxygen explained further the formation of different metal complexes on biosorbent surface. Upto 30% of metal laden biosorbent could be inertized in phosphate glass matrix as confirmed by the XRD-analysis. No leaching of heavy metals was observed on the glass with thermal cycle at 75°C for 8h/day up to 35 days.

Identification of dual ligands targeting angiotensin II type 1 receptor and peroxisome proliferator-activated receptor-γ by core hopping of telmisartan

It has been reported previously that some angiotensin II receptor blockers not only antagonize angiotensin II type 1 receptor (AT1R), but also exert stimulation in peroxisome proliferator-activated receptor γ (PPARγ) partial activation, among which telmisartan displays the best. Telmisartan has been tested as a bifunctional ligand with antihypertensive and hypoglycemic activity. Aiming at more potent leads with selective AT1R antagonism and PPARγ partial agonism, the three parts of telmisartan including the distal benzimidazole ring, the biphenyl moiety, and the carboxylic acid group experienced modification by core hopping method in our study. The central benzimidazole ring, however, remained intact considering its great affinity toward AT1R and PPARγ. We utilized computational techniques for the sake of details on the binding interactions and conformational stability. Standard precision docking analysis and absorption, distribution, metabolism, excretion, and toxicity prediction received 10 molecules with higher Glide scores, similar interactions, and improved pharmacokinetic profiles compared to telmisartan. Comp#91 with highest scores for AT1R (−11.92 kcal/mol) and PPARγ (−13.88 kcal/mol) exhibited excellent binding modes and pharmacokinetic parameters. Molecular dynamics trajectories on best docking pose of comp#91 confirmed the docking results and verified the conformational stability with both receptors throughout the course of 20-ns simulations. Thus, comp#91 could be identified as a promising lead in the development of dual AT1R antagonist and PPARγ partial agonist against hypertension and type 2 diabetes.

Contribution of carboxyl modified chiral mesoporous silica nanoparticles in delivering doxorubicin hydrochloride in vitro: pH-response controlled release, enhanced drug cellular uptake and cytotoxicity

In this study, dual functionalized mesoporous silica nanoparticle (Dual-MSN) with functions of carboxyl modification and chirality was successfully developed and its special contribution in delivering doxorubicin hydrochloride (DOX) in vitro was mainly studied. Characteristics of Dual-MSN and its application as DOX carrier were intensively explored by comparing with naked non-functionalized MSN (Naked MSN). The results indicated that both Naked MSN and Dual-MSN significantly controlled DOX release due to the release hindrance caused by mesopores. As expected, Dual-MSN exhibited obvious enhanced pH-response because of its negative charges of carboxyl groups. DOX loaded Naked MSN and DOX loaded Dual-MSN presented better cytotoxicity than DOX due to carrier-mediated endocytosis and the favorable intercalation of DOX into DNA in the nuclei. The cytotoxicity of DOX loaded Dual-MSN was better than DOX loaded Naked MSN owing to its enhanced cellular uptake induced by chirality of Dual-MSN, demonstrating that double functions of Dual-MSN had unique advantages in improving antitumor effect of DOX towards MCF-7 cells and thus confirming its special contribution in DOX delivery.

Two-photon polymerization of gelatin hydrogels: carboxylic acid modification as the key to success

Two-photon polymerization of gelatin hydrogels: carboxylic acid modification as the key to success

Preparation, Morphology and Properties of Acyl Azide-Functionalized Carbon Nanotubes

Multi-walled carbon nanotubes (MWNTs) functionalized with acyl azide groups were prepared via chemical modification of carboxyl groups introduced on the carbon nanotube surface. The acyl azides MWNTs have potential application in chemistry functionalization of MWNTs and energetic materials. The functionalizations of the MWNTs were characterized in detail using scanning electron microscope (SEM), transmission electron microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and thermogravimetry (TG). The results confirm the carboxylic acid groups converted to the desired acid azide functionalization of MWNTs.

CHARACTERIZATION ANDIN VITROEVALUATION OF POLY (L-LACTIC ACID) AND PURIFIED MULTIWALLED CARBON NANOTUBES NANOCOMPOSITES

Carbon nanotubes (CNT) have been studied for biomedical applications due to their unique properties. However, pristine CNT have structural features and impurities that can cause toxicity to biological systems. In this work, we describe a method to purify multiwalled carbon nanotubes (MWCNT) by chemical modification and subsequent attachment of hydroxyl and carboxyl groups to improve dispersion and to decrease toxic effects. Nanocomposites from poly (L-lactic acid) (PLLA) and nanotubes were produced by the solvent casting method and characterized and evaluated for cytocompatibility with Vero cells. The nanocomposite interactions with Vero cells demonstrated that the cells were able to adhere and sustain proliferation and showed favorable cytocompatibility. In vitro studies also revealed an increase in fibroblast cell viability in the nanocomposites, compared with neat PLLA.

De-Colorization Activity Enhancement of Degussa P25 TiO2 via the Formation of p-n Heterojunction by Carboxylic Modification

The visible-light-driven photocatalytic activity of Degussa P25 TiO2 is effectively promoted by modifiers containing carboxylic groups through impregnating cyclohexanol and a low-temperature heating treatment. The superficial TiO2 modified with the organic modifiers creates certain low band-gap states to enhance its visible-light activity. The carboxylic-modified TiO2 dispersed on the P25 surface shows the p-type semiconductor characteristics, confirmed by the photocurrent responses under the open-circuit state and blue-light irradiation. Accordingly, a p-n heterojunction between the superficial modified TiO2 and underneath P25 enhances the separation of photo-excited electron/hole pairs, resulting in the higher photocatalytic activity. During the photo-electrocatalytic de-colorization test, the photo-excited electrons are further withdrawn by the positive potential bias toward the graphite cathode through the electric circuit, which favors the oxygen reduction reaction (ORR) of two-electron transfer to effectively generates H2O2 for organic pollutants decomposition. Therefore, methylene blue (MB) can be efficiently de-colorized on the carboxylic-modified P25 under the visible-light irradiation meanwhile the de-colorization rate is enhanced under the photo-electrocatalytic mode.

Size and surface modification of amorphous silica particles determine their effects on the activity of human CYP3A4 in vitro

Because of their useful chemical and physical properties, nanomaterials are widely used around the world - for example, as additives in food and medicines - and such uses are expected to become more prevalent in the future. Therefore, collecting information about the effects of nanomaterials on metabolic enzymes is important. Here, we examined the effects of amorphous silica particles with various sizes and surface modifications on cytochrome P450 3A4 (CYP3A4) activity by means of two different in vitro assays. Silica nanoparticles with diameters of 30 and 70 nm (nSP30 and nSP70, respectively) tended to inhibit CYP3A4 activity in human liver microsomes (HLMs), but the inhibitory activity of both types of nanoparticles was decreased by carboxyl modification. In contrast, amine-modified nSP70 activated CYP3A4 activity. In HepG2 cells, nSP30 inhibited CYP3A4 activity more strongly than the larger silica particles did. Taken together, these results suggest that the size and surface characteristics of the silica particles determined their effects on CYP3A4 activity and that it may be possible to develop silica particles that do not have undesirable effects on metabolic enzymes by altering their size and surface characteristics.

Erratum to: Modifications of Diflunisal and Meclofenamate Carboxyl Groups Affect Their Allosteric Effects on GABAA Receptor Ligand Binding

Erratum to: Modifications of Diflunisal and Meclofenamate Carboxyl Groups Affect Their Allosteric Effects on GABAA Receptor Ligand Binding

Preparation and Adsorption Research of the Modification Macroporous Adsorption Resin (LX1180)

This work focused on the research of carboxylation modification of nonpolar macropolar adsorption resin (MAR) (LX1180) and its adsorption properties. Under optimization conditions a MAR with carboxylation degree of 23.10% (g/g, expressed as C7H6NO2) was obtained. After characterizing the structures of MAR LX1180, LX1180-Cl and LX1180-COO−, the adsorption mechanism (including isotherm kinetics) and influence of functional groups and functional degree of substrate on equilibrium adsorption capacity were also investigated systemically. The result showed the adsorption mechanism could be expressed well by an intra-particle diffusion model, and the four-parameter adsorption model was more appropriate to express the adsorption behavior of the MARs here. Moreover, it could be found that the introduction of a functional group could increase the equilibrium adsorption capacity, while the initial concentration related to the saturated adsorption capacity decreased.

Modifications of diflunisal and meclofenamate carboxyl groups affect their allosteric effects on GABAA receptor ligand binding.

Gamma-aminobutyric acid type A receptors (GABAAR) are allosterically modulated by the nonsteroidal anti-inflammatory drugs diflunisal and fenamates. The carboxyl group of these compounds is charged at physiological pH and therefore penetration of the compounds into the brain is low. In the present study we have transformed the carboxyl group of diflunisal and meclofenamate into non-ionizable functional groups and analyzed the effects of the modifications on stimulation of [(3)H]muscimol binding and on potentiation of γ-aminobutyric acid-induced displacement of 4'-ethenyl-4-n-[2,3-(3)H]propylbicycloorthobenzoate. N-Butylamide derivative of diflunisal modulated radioligand binding with equal or higher potency than the parent compound, while diflunisalamide showed reduced allosteric effect as compared to diflunisal. Amide derivative of meclofenamate equally affected radioligand binding parameters, while both diflunisal and meclofenamate methyl esters were less active than the parent compounds. Our study clearly demonstrates that an intact carboxyl group in diflunisal and meclofenamate is not indispensable for their positive GABAAR modulation. Further derivatization of the compound might yield compounds with higher selectivity for GABAARs that could be utilized in drug development.

A Comparable Study on the Effects of Pristine and Functionalized Single-Walled Carbon Nanotubes on Schwann Cells

A comparable study on the effects of pristine and functionalized single-walled carbon nanotubes on schwann cells were conducted. Schwann cells were co-cultured with three types of SWNTs, purified raw SWNTs (C), hydroxyl purified SWNTs (C-OH) and carboxyl purified SWNTs (C-COOH) at 25μg/mL. C-COOH promoted the cell viability after 72h exposure and sustained its redox states by enhancing GPx expression. On the contrary, C and C-OH weaken the antioxidant activity due to the inhibition in main antioxidant enzymes and further led to the decline in cell viability. Carboxyl modification of the SWNTs helps to improve the biocompatibility of the SWNTs by strengthening the antioxidant ability.

Carboxylic group modification as a method of intensification of diuretic properties of 7-hydroxy-5-oxo-2,3-dihydro-1h,5h-pyrido[3,2,1-ij]quinoline-6-carboxylic acid 2-carboxyanilide

The intensive and purposeful search of fundamentally new diuretics conducted by our research laboratory among the derivatives of 4-hydroxyquinolin-2-ones has found 7-hydroxy-5-oxo-2,3-dihydro-1H,5H-pyrido[3,2,1-ij] quinoline-6-carboxylic acid 2-carboxyanilide as an intermediate lead compound. The basis for it is a high diuretic activity and a low toxicity of this substance. However, a free carboxylic group, which is often conductive to appearance of an extremely undesirable ulcerogenic action in relation to the gastro-intestinal tract, can be a serious obstacle for using the given compound as a drug. That is why we attempted to block the carboxylic group of 2-carboxyanilide by one of the known methods. For this purpose the methodology of both classical and non-classical bioisosteric replacements has been used. When conducting the synthetic part of the research the alternative ways of close structural analogues of the basic molecule were considered. As a result the optimal method for their obtaining has been offered; it differs by the minimal time costs and preparative high yields and purity of the target products. The structure of all substituted 7-hydroxy-5-oxo-2,3-dihydro-1H,5H-pyrido[3,2,1-ij] quinoline-6-carboxanilides synthesized has been confirmed by the data of elemental analysis, counter synthesis and NMR 1Н spectra. The primary pharmacological screening in studying the effect of the compounds obtained on the excretory function of the kidneys has been carried out in white outbread rats using the standard method. The testing has been performed in parallel and in comparison with Hydrochlorothiazide, as well as the abovementioned 2-carboxyanilide. It has been determined that some compounds under study in the dose of 10 mg/kg when introduced orally exceed not only Hydrochlorothiazide, but the basic molecule as well. By the results of the experiments carried out the structural and biological regularities that are important for further research have been found. As a new lead compound 7-hydroxy-5-oxo-2,3-dihydro-1H,5H-pyrido[3,2,1-ij]quinoline-6-carboxylic acid 2-carbamoylanilide has been suggested. It has no free COOH-group and, therefore, is not capable of having an great effect on the gastro-intestinal tract.