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1.
Chem Commun (Camb) ; 57(59): 7284-7287, 2021 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-34212953

RESUMO

Natural DNA was employed for the first time as a phosphorization agent and carbon source to controllably synthesize a RuP2/N,P-codoped carbon composite by a simple "mix-and-pyrolyze" strategy, which displays higher activity for alkaline and acidic HER and neutral activity compared to Pt/C together with outstanding durability.


Assuntos
DNA de Cadeia Simples/química , Grafite/química , Hidrogênio/química , Rutênio/química , Animais , Catálise , Concentração de Íons de Hidrogênio , Nitrogênio/química , Fósforo/química , Espectroscopia Fotoeletrônica , Salmão/genética
2.
Molecules ; 26(13)2021 Jun 24.
Artigo em Inglês | MEDLINE | ID: mdl-34202843

RESUMO

The aim of this study was to assess the enzymatic and non-enzymatic antioxidant status of kiwiberry (Actinidia arguta) leaf under different N regimes tested three times in field conditions during the 2015 growing season in two cultivars ('Weiki' and 'Geneva'). Leaf total antioxidant capacity using ABTS, DPPH and FRAP tests was evaluated in the years 2015 to 2017, which experienced different weather conditions. Both cultivars exhibited a significant fall in leaf L-ascorbic acid (L-AA) and reduced glutathione (GSH) as well as global content of these compounds during the growing season, while total phenolic contents slightly ('Weiki') or significantly ('Geneva') increased. There was a large fluctuation in antioxidative enzyme activity during the season. The correlation between individual antioxidants and trolox equivalent antioxidant capacity (TEAC) depended on the plant development phase. The study revealed two peaks of an increase in TEAC at the start and end of the growing season. Leaf L-AA, global phenolics, APX, CAT and TEAC depended on the N level, but thiol compounds were not affected. Over the three years, TEAC decreased as soil N fertility increased, and the strength of the N effect was year dependent. The relationship between leaf N content and ABTS and FRAP tests was highly negative. The antioxidant properties of kiwiberry leaves were found to be closely related to the plant development phase and affected by soil N fertility.


Assuntos
Actinidia/química , Nitrogênio/química , Compostos Fitoquímicos/química , Folhas de Planta/química , Solo/química , Actinidia/crescimento & desenvolvimento , Nitrogênio/metabolismo , Compostos Fitoquímicos/biossíntese , Folhas de Planta/crescimento & desenvolvimento , Especificidade da Espécie
3.
Int J Biol Macromol ; 185: 543-550, 2021 Aug 31.
Artigo em Inglês | MEDLINE | ID: mdl-34197857

RESUMO

Controlled or slow release fertilizers have been recommended to enhance crop yield, while minimizing environmental and economic issues related from current fertilizer applications. However, alternative biodegradable and non-toxic coating material should be suggested to produce biocoated fertilizers. Here we propose the use of lignin and poly(vinyl acetate) (PVAc) as biocoating materials for preparing slow release urea fertilizer. The blend of PVAc and lignin at a mass ratio of 75:25 improved the characteristics of the formed film and increased the nitrogen release time if compared to the pure polymers. The nitrogen release time from urea granules coated with a polymeric layer of 154.3 ±â€¯5.5 µm formed by lignin and PVAc was 36 times greater than from bare urea. The increase in the polymeric coating from 52.6 ±â€¯5.2 to 80.2 ±â€¯6.1 µm decreased the curvature of the nitrogen release data by a factor of at least 1.7, while the curvature was decreased in at least 1.3 with the increase in the polymeric coating from 80.2 ±â€¯6.1 to 158.9 ±â€¯10.6 µm. The adjustment of nitrogen release data to the Peppas-Sahlin model indicated the Fickian diffusion is more predominant than relaxation contributions, since the used polymers did not present considerable swelling. Thus, the blending of PVAc and lignin at 25 wt% of lignin and 75 wt% of PVAc is suggested as a biocoating material for producing slow release fertilizers.


Assuntos
Lignina/química , Nitrogênio/química , Polivinil/química , Composição de Medicamentos , Fertilizantes , Ureia/química
4.
Int J Mol Sci ; 22(14)2021 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-34298905

RESUMO

To evaluate the antioxidant activity of potential synthetic enzyme mimetics, we prepared new five copper(II) complexes via a self-assembly method and named them [Cu(2-(HOCH2)py)3](ClO4)2 (1), [Cu(2-(HOCH2)py)2(H2O)2]SiF6 (2), [Cu2(2-(HOCH2CH2)py)2(2-(OCH2CH2)py)2](ClO4)2 (3), [Cu(pyBIm)3](BF4)2·1.5H2O (4) and [Cu(py2C(OH)2)2](ClO4)2 (5). The synthetic protocol involved N,O- or N,N-donors: 2-(hydroxymethyl)pyridine (2-(HOCH2)py), 2-(hydroxyethyl)pyridine (2-(HOCH2CH2)py), 2-(2-pyridyl)benzimidazole (pyBIm), di(2-pyridyl)ketone (py2CO). The obtained Cu(II) complexes were fully characterised by elemental analysis, FTIR, EPR, UV-Vis, single-crystal X-ray diffraction and Hirshfeld surface analysis. Crystallographic and spectroscopic analyses confirmed chromophores of both monomeric ({CuN3O3} (1), {CuN2O4} (2), {CuN6} (4), {CuN4O2} (5)) and dimeric complex ({CuN2O3} (3)). Most of the obtained species possessed a distorted octahedral environment, except dimer 3, which consisted of two copper centres with square pyramidal geometries. The water-soluble compounds (1, 3 and 5) were selected for biological testing. The results of the study revealed that complex 1 in solutions displayed better radical scavenging activity than complexes 3, 5 and free ligands. Therefore, complex 1 has been selected for further studies to test its activity as an enzyme mimetic. The chosen compound was tested on the erythrocyte lysate of two groups of patients after undergoing chemotherapy and chemoradiotherapy. The effect of the tested compound (1) on enzyme activity levels (TAS, SOD and CAT) suggests that the selected complex can be treated as a functional mimetic of the enzymes.


Assuntos
Cobre/química , Sequestradores de Radicais Livres/química , Metaloproteínas/química , Nitrogênio/química , Oxigênio/química , Benzimidazóis/química , Domínio Catalítico/fisiologia , Complexos de Coordenação/química , Cristalografia por Raios X/métodos , Ligantes , Estrutura Molecular , Piridinas/química
5.
Int J Mol Sci ; 22(13)2021 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-34202099

RESUMO

We performed ab initio numerical simulations with the density functional theory to investigate the variations in the band structure, optical absorption, and the reflectivity of vacancy-graphene doped with nitrogen, oxygen, and fluorine for different densities. We considered the density values 0.78%, 1.02%, 1.39%, 2.00%, 3.12%, 5.55%, and 12.5% for the vacancies and doping. In the infrared and visible ranges for all cases, vacancies included, there is a substantial increment in the absorption and reflectivity concerning graphene. The most significant changes are for fluorine and oxygen at a concentration of 12.5%.


Assuntos
Flúor/química , Grafite/química , Nitrogênio/química , Oxigênio/química , Análise Espectral , Elétrons , Estrutura Molecular , Nanopartículas/química
6.
J Chem Ecol ; 47(7): 680-688, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-34101117

RESUMO

Past work shows a significant negative correlation between foliar oregonin concentration and western tent caterpillar (Malacosoma californicum Packard) feeding on red alder (Alnus rubra Bong.). Above an oregonin threshold of 20% leaf dry weight, little feeding by caterpillars is observed. Concentrations of defensive chemicals are influenced by plant genotype, environmental conditions, insect feeding, and the interactions of these factors. Our objective was to measure the effects of nitrogen (N) availability and wounding on foliar oregonin and condensed tannin concentrations in red alder genotypes. One-year-old seedlings from 100 half-sib red alder families were treated with two levels of ammonium nitrate (NH4NO3) for two growing seasons in a common garden. In the second year, leaves from 50 families from the fertilization experiment were used in a bioassay feeding experiment to determine the effects of N fertilization and genotype on WTC damage, and to identify a subset of 20 families with a range of damage to analyze for phytochemical composition. In separate experiments, wound-induction treatments were conducted outdoors and, in a greenhouse using the N treated trees in their third and fourth year, respectively. Foliar condensed tannin, oregonin and N concentrations were measured and ranked among the plant genotypes, and between the two N treatments and two wounding treatments. Results showed that oregonin and condensed tannin concentrations varied among the alder genotypes. Leaf N concentration was negatively correlated with concentration of oregonin. Neither of the measured phenolic compounds responded to wounding. The results suggest that red alder foliar oregonin and condensed tannin are likely constitutive defenses that are largely determined by genotype, and that the negative correlation of defense compounds with plant internal N status holds in this N-fixing tree.


Assuntos
Alnus/química , Diarileptanoides/química , Mariposas/efeitos dos fármacos , Compostos Fitoquímicos/farmacologia , Taninos/análise , Alnus/genética , Alnus/crescimento & desenvolvimento , Animais , Cromatografia Líquida de Alta Pressão , Diarileptanoides/farmacologia , Fertilizantes/análise , Genótipo , Herbivoria/efeitos dos fármacos , Larva/efeitos dos fármacos , Larva/fisiologia , Mariposas/crescimento & desenvolvimento , Mariposas/fisiologia , Nitrogênio/química , Nitrogênio/metabolismo , Compostos Fitoquímicos/química , Folhas de Planta/química , Folhas de Planta/metabolismo , Plântula , Espectrofotometria Ultravioleta , Taninos/farmacologia
7.
Nature ; 596(7871): 250-256, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-34182570

RESUMO

The substitution of an alkyl electrophile by a nucleophile is a foundational reaction in organic chemistry that enables the efficient and convergent synthesis of organic molecules. Although there has been substantial recent progress in exploiting transition-metal catalysis to expand the scope of nucleophilic substitution reactions to include carbon nucleophiles1-4, there has been limited progress in corresponding reactions with nitrogen nucleophiles5-8. For many substitution reactions, the bond construction itself is not the only challenge, as there is a need to control stereochemistry at the same time. Here we describe a method for the enantioconvergent substitution of unactivated racemic alkyl electrophiles by a ubiquitous nitrogen-containing functional group, an amide. Our method uses a photoinduced catalyst system based on copper, an Earth-abundant metal. This process for asymmetric N-alkylation relies on three distinct ligands-a bisphosphine, a phenoxide and a chiral diamine. The ligands assemble in situ to form two distinct catalysts that act cooperatively: a copper/bisphosphine/phenoxide complex that serves as a photocatalyst, and a chiral copper/diamine complex that catalyses enantioselective C-N bond formation. Our study thus expands enantioselective N-substitution by alkyl electrophiles beyond activated electrophiles (those bearing at least one sp- or sp2-hybridized substituent on the carbon undergoing substitution)8-13 to include unactivated electrophiles.


Assuntos
Amidas/química , Cobre/química , Fotoquímica , Brometos/química , Carbono/química , Catálise , Ciclização , Diaminas/química , Ligantes , Nitrogênio/química , Fosfinas/química
8.
J Chromatogr A ; 1651: 462260, 2021 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-34090059

RESUMO

Monolithic polymers are described as continuous and highly porous materials. They have been gaining popularity as an effective extracting phase for some sample preparation methods, due to their variety of functionalities, such as wide pH range tolerance, good permeability, and its ability to allow changes into their surface. Polypyrrole represents an interesting alternative for the modification in extraction phases due to its well related ability to perform multiple interactions, such as acid-base, π - π, ion exchange, interactions with hydrophobic affinities or polar functional groups. Among the different sample preparation techniques, solid-phase extraction (SPE) is one of the most popular and used; a miniaturized version of SPE is the disposable pipette extraction (DPX). DPX is a recent miniaturized extraction technique that usually employing silica-based sorbents inside a pipette tip (5 or 1 mL). The present study proposes the development of a monolithic extraction phase composed by styrene divinylbenzene (1:1) modified with polypyrrole for SPE and DPX techniques. The efficiency of the material was evaluated in face of the extraction of different samples and analytes, triazine herbicides in water and dexamethasone in synthetic synovial liquid by conventional and miniaturized solid-phase extraction techniques. The extractions performed by SPE and DPX presented absolute recovery values ranging from 74.8 to 105.0%, inter-day precision ranging from 0.6 to 14.0%, and limit of quantification of 0.5 and 5.0 ng.mL-1, respectively. The DPX miniaturized method exhibited results equivalent to the methods reported in the literature for extraction of dexamethasone in synovial fluid samples. Moreover, this technique proved to be quicker and cheaper than SPE, and produced fewer residual volumes, supporting the preference for green chemistry. Monolithic polymers modified with polypyrrole presented to be a feasible alternative extraction phase for miniaturized sample preparation techniques.


Assuntos
Métodos Analíticos de Preparação de Amostras , Miniaturização/métodos , Polímeros/isolamento & purificação , Pirróis/isolamento & purificação , Adsorção , Interações Hidrofóbicas e Hidrofílicas , Nitrogênio/química , Polimerização , Extração em Fase Sólida , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura , Água/química , Poluentes Químicos da Água/análise
9.
Ecotoxicol Environ Saf ; 221: 112451, 2021 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-34174737

RESUMO

Manganese oxides and iron oxides have been widely introduced in constructed wetlands (CWs) for sewage treatment due to their extensiveness in nature and their ability to participate in various reactions, but their effects on greenhouse gas (GHG) emissions remain unclear. Here, a set of vertical subsurface-flow CWs (Control, Fe-VSSCWs, and Mn-VSSCWs) was established to comprehensively evaluate which are the better metal substrate materials for CWs, iron oxides or manganese oxides, through water quality and the global warming potential (GWP) of nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2). The results revealed that the removal efficiencies of chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) in Mn-VSSCWs were all higher than that in Fe-VSSCWs, and manganese oxides could almost completely suppress the CH4 production and reduce GWP (from 8.15 CO2-eq/m2/h to 7.17 mg CO2-eq/m2/h), however, iron oxides promoted GWP (from 8.15 CO2-eq/m2/h to 10.84 mg CO2-eq/m2/h), so manganese oxides are the better CW substrate materials to achieve effective sewage treatment while reducing the greenhouse gas effect.


Assuntos
Poluentes Atmosféricos/química , Compostos Férricos/química , Efeito Estufa/prevenção & controle , Compostos de Manganês/química , Óxidos/química , Purificação da Água/métodos , Áreas Alagadas , Análise da Demanda Biológica de Oxigênio , Dióxido de Carbono/química , Metano/química , Nitrogênio/química , Óxido Nitroso/química , Fósforo/química , Poluentes da Água/química , Qualidade da Água
10.
Transfusion ; 61(8): 2234-2239, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-34145914

RESUMO

BACKGROUND: Our cell processing facility was planning to transfer more than 20 Liquid Nitrogen (LN2) freezers to a new location. Moving LN2 freezers is a complex task that can pose potential risk to the storage units' integrity as well as to the products that they hold. Careful planning is required, especially when moving multiple freezer units at once. METHODS: To achieve the task, we put together a detailed project plan, collaborated with all the involved partners, hired qualified professionals to perform the project-specific tasks, and put together a detailed risk assessment and risk mitigation plan. RESULTS: A facility was chosen and prepared according the project plan and safety department recommendations. Risk mitigation strategies were developed and implemented, and all freezers were transfered uneventfully to a new location. CONCLUSIONS: By performing detailed planning and engaging the appropriate partners, LN2 freezers can be successfully transferred to a new home.


Assuntos
Criopreservação/instrumentação , Congelamento , Humanos , Nitrogênio/química , Transportes
11.
Molecules ; 26(11)2021 May 27.
Artigo em Inglês | MEDLINE | ID: mdl-34071844

RESUMO

Due to their structural similarity with natural α-amino acids, α-aminophosphonic acid derivatives are known biologically active molecules. In view of the relevance of tetrasubstituted carbons in nature and medicine and the strong dependence of the biological activity of chiral molecules into their absolute configuration, the synthesis of α-aminophosphonates bearing tetrasubstituted carbons in an asymmetric fashion has grown in interest in the past few decades. In the following lines, the existing literatures for the synthesis of optically active tetrasubstituted α-aminophosphonates are summarized, comprising diastereoselective and enantioselective approaches.


Assuntos
Técnicas de Química Sintética , Química Farmacêutica/métodos , Ácidos Fosforosos/análise , Ácidos Fosforosos/síntese química , Aminoácidos/química , Carbono/química , Catálise , Desenho de Fármacos , Iminas/química , Estrutura Molecular , Nitrogênio/química , Organofosfonatos/síntese química , Paládio/química , Fósforo/química , Ródio/química , Estereoisomerismo
12.
Nat Commun ; 12(1): 3729, 2021 06 17.
Artigo em Inglês | MEDLINE | ID: mdl-34140496

RESUMO

Aldehydes and ketones are widely found in biomass resources and play important roles in organic synthesis. However, the direct deoxygenative coupling of aldehydes or ketones to construct C(sp3)-C(sp3) bond remains a scientific challenge. Here we report a nickel-catalyzed reductive homo-coupling of moisture- and air-stable hydrazones generated in-situ from naturally abundant aldehydes and ketones to construct challenging C(sp3)-C(sp3) bond. This transformation has great functional group compatibility and can suit a broad substrate scope with innocuous H2O, N2 and H2 as the by-products. Furthermore, the application in several biological molecules and the transformation of PEEK model demonstrate the generality, practicability, and applicability of this novel methodology.


Assuntos
Aldeídos/química , Hidrazinas/química , Hidrazonas/química , Cetonas/química , Níquel/química , Catálise , Hidrazonas/síntese química , Hidrogênio/química , Nitrogênio/química , Oxirredução , Água/química
13.
Molecules ; 26(9)2021 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-34067110

RESUMO

A new and simple method, based entirely on a physical approach, was proposed to produce activated carbon from longan fruit seed with controlled mesoporosity. This method, referred to as the OTA, consisted of three consecutive steps of (1) air oxidation of initial microporous activated carbon of about 30% char burn-off to introduce oxygen surface functional groups, (2) the thermal destruction of the functional groups by heating the oxidized carbon in a nitrogen atmosphere at a high temperature to increase the surface reactivity due to increased surface defects by bond disruption, and (3) the final reactivation of the resulting carbon in carbon dioxide. The formation of mesopores was achieved through the enlargement of the original micropores after heat treatment via the CO2 gasification, and at the same time new micropores were also produced, resulting in a larger increase in the percentage of mesopore volume and the total specific surface area, in comparison with the production of activated carbon by the conventional two-step activation method using the same activation time and temperature. For the activation temperatures of 850 and 900 °C and the activation time of up to 240 min, it was found that the porous properties of activated carbon increased with the increase in activation time and temperature for both preparation methods. A maximum volume of mesopores of 0.474 cm3/g, which accounts for 44.1% of the total pore volume, and a maximum BET surface area of 1773 m2/g was achieved using three cycles of the OTA method at the activation temperature of 850 °C and 60 min activation time for each preparation cycle. The two-step activation method yielded activated carbon with a maximum mesopore volume of 0.270 cm3/g (33.0% of total pore volume) and surface area of 1499 m2/g when the activation temperature of 900 °C and a comparable activation time of 240 min were employed. Production of activated carbon by the OTA method is superior to the two-step activation method for better and more precise control of mesopore development.


Assuntos
Ar , Carvão Vegetal/química , Temperatura , Biomassa , Carbono/química , Dióxido de Carbono/química , Modelos Moleculares , Nitrogênio/química , Oxirredução , Porosidade , Sementes/química , Espectroscopia de Infravermelho com Transformada de Fourier , Propriedades de Superfície , Termogravimetria
14.
J Mater Chem B ; 9(23): 4654-4662, 2021 06 16.
Artigo em Inglês | MEDLINE | ID: mdl-34018537

RESUMO

Due to the essential role of Fe3+ in physiological and pathological processes, the detection of Fe3+ has drawn increasing attention in the field of disease diagnosis and environmental protection. However, most existing methods require either cumbersome sample pretreatment or sophisticated and expensive test equipment. Recently, carbon quantum dots have found a wide range of applications such as nanoprobes for Fe3+ determination, albeit with limited sensitivity and selectivity. Herein, we report core-shell carbon quantum dots B1N2CQDs via a two-step hydrothermal approach using citric acid, boric acid and ethylenediamine as precursors. The obtained B1N2CQDs exhibit excellent water solubility and remarkable stability as well as a high fluorescence quantum yield of 15.4%. In addition, the fluorescence of B1N2CQDs is quenched exclusively by Fe3+ with minimal interference from other metal ions. A linear relationship with R2 = 0.998 was observed between the fluorescence quenching capacity and the Fe3+ concentration in the range of 2-160 µM, with the limit of detection calculated to be 80 nM. Finally, the as-prepared B1N2CQDs were successfully applied as a highly efficient fluorescent probe for Fe3+ detection in river water samples and intracellular Fe3+ imaging in biological systems.


Assuntos
Boro/química , Carbono/química , Compostos Férricos/análise , Nitrogênio/química , Pontos Quânticos/química , Células HeLa , Humanos , Limite de Detecção
15.
Int J Biol Macromol ; 182: 1484-1494, 2021 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-34019923

RESUMO

Development of lignin-derived carbon adsorbents with ultrahigh phosphate adsorption activity and rapid adsorption kinetics is of great importance, yet limited success has been achieved. Herein, we develop a CeO2 functionalized N-doped lignin-derived biochar (Ce@NLC) via a cooperative modification strategy for effective and fast phosphate capture. The novel modification strategy not only contributes greatly to the loading of well-dispersed CeO2 nanoparticles with a smaller size, but also significantly increases the relative concentration of Ce(III) species on Ce@NLC. Consequently, an enhanced capture capacity for phosphate (196.85 mg g-1) as well as extremely rapid adsorption kinetics were achieved in a wide operating pH range (2-10). Interestingly, Ce@NLC exhibited a strong phosphate adsorption activity at even low-concentration phosphorus-containing water. The removal efficiency and final P concentration reached 99.87% and 2.59 µg P L-1 within 1 min at the phosphate concentration of 2 mg P L-1. Experiments and characterization indicated that Ce(III) species plays a predominant role for the phosphate capture, and ligand exchange, together with electrostatic attraction, are the main adsorption mechanism. This work develops not only an efficient carbon-based adsorbent for phosphate capture, but also promotes the high-value application of industrial lignin.


Assuntos
Cério/química , Lignina/química , Nanopartículas Metálicas/química , Nitrogênio/química , Fosfatos/química
16.
Nature ; 593(7858): 223-227, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33981048

RESUMO

Synthetic chemistry aims to build up molecular complexity from simple feedstocks1. However, the ability to exert precise changes that manipulate the connectivity of the molecular skeleton itself remains limited, despite possessing substantial potential to expand the accessible chemical space2,3. Here we report a reaction that 'deletes' nitrogen from organic molecules. We show that N-pivaloyloxy-N-alkoxyamides, a subclass of anomeric amides, promote the intermolecular activation of secondary aliphatic amines to yield intramolecular carbon-carbon coupling products. Mechanistic experiments indicate that the reactions proceed via isodiazene intermediates that extrude the nitrogen atom as dinitrogen, producing short-lived diradicals that rapidly couple to form the new carbon-carbon bond. The reaction shows broad functional-group tolerance, which enables the translation of routine amine synthesis protocols into a strategy for carbon-carbon bond constructions and ring syntheses. This is highlighted by the use of this reaction in the syntheses and skeletal editing of bioactive compounds.


Assuntos
Aminas/química , Técnicas de Química Sintética , Nitrogênio/química , Amidas/química , Produtos Biológicos/síntese química , Produtos Biológicos/química , Carbono/química , Indicadores e Reagentes/química
17.
Int J Biol Macromol ; 183: 1450-1458, 2021 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-33974926

RESUMO

In this work, the coordination-based energy sacrificial bonds have been constructed in the interphase between lignin and polyolefin elastomer to prepare high performance lignin-based thermoplastic elastomers (TPEs). The strength and toughness of lignin-based TPEs can be adjusted by choosing different nitrogen heterocyclic compounds as reactive assistants and Fe3+ or Zn2+ as metal coordination centers. It was demonstrated that 3-Amino-1,2,4-triazole with three nitrogen atoms in the heterocyclic ring and one nitrogen branch chain could form the most efficient coordination bond system and generate the best mechanical performance. The system with ferric iron as coordination center exhibited better enhancement effect than divalent zinc. By adjusting the nitrogen-containing reactive additives or metal salts as coordination centers, the mechanical performance of the lignin-based TPE can be regulated, which provides a method for making green bio-composites with good strength and toughness, and also promotes the high value utilization of lignin in polymer materials.


Assuntos
Elastômeros/química , Lignina/química , Nitrogênio/química , Polienos/química
18.
Int J Nanomedicine ; 16: 3041-3057, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33948084

RESUMO

Background: The dentin exposure always leads to dentin hypersensitivity and/or caries. Given the dentin's tubular structure and low mineralization degree, reestablishing an effective biobarrier to stably protect dentin remains significantly challenging. This study reports a versatile dentin surface biobarrier consisting of a mesoporous silica-based epigallocatechin-3-gallate (EGCG)/nanohydroxyapatite delivery system and evaluates its stability on the dentinal tubule occlusion and the Streptococcus mutans (S. mutans) biofilm inhibition. Materials and Methods: The mesoporous delivery system was fabricated and characterized. Sensitive dentin discs were prepared and randomly allocated to three groups: 1, control group; 2, casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) group; and 3, the mesoporous delivery system group. The dentin permeability, dentinal tubule occlusion, acid and abrasion resistance, and S. mutans biofilm inhibition were determined for 1 week and 1 month. The in vitro release profiles of EGCG, Ca, and P were also monitored. Results: The mesoporous delivery system held the ability to sustainably release EGCG, Ca, and P and could persistently occlude dentinal tubules with acid and abrasion resistance, reduce the dentin permeability, and inhibit the S. mutans biofilm formation for up to 1 month compared with the two other groups. The system provided prolonged stability to combat oral adverse challenges and served as an effective surface biobarrier to protect the exposed dentin. Conclusion: The establishment of the dentin surface biobarrier consisting of a mesoporous delivery system indicates a promising strategy for the prevention and the management of dentin hypersensitivity and caries after enamel loss.


Assuntos
Biofilmes/crescimento & desenvolvimento , Dentina/química , Streptococcus mutans/fisiologia , Ácidos , Adsorção , Biofilmes/efeitos dos fármacos , Cálcio/análise , Caseínas/farmacologia , Catequina/análogos & derivados , Catequina/química , Catequina/farmacologia , Morte Celular/efeitos dos fármacos , Contagem de Colônia Microbiana , Polpa Dentária/citologia , Humanos , Nanopartículas/química , Nanopartículas/ultraestrutura , Nitrogênio/química , Permeabilidade , Fósforo/análise , Porosidade , Dióxido de Silício/química , Streptococcus mutans/ultraestrutura
19.
Molecules ; 26(5)2021 Mar 08.
Artigo em Inglês | MEDLINE | ID: mdl-33800455

RESUMO

The thin film of N-doped ZnO/CNT nanocomposite was successfully fabricated on soda lime glass substrate by a simple sol-gel drop-coating method. The structural, morphological, chemical, and optical properties of as prepared samples were characterized by a variety of tools such as X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Fourier Transform Infrared spectroscopy (FT-IR), and UV-visible spectroscopy. The hexagonal crystalline structure was confirmed from XRD measurement without any other impurity phase detection in samples. The N-doped ZnO/CNT composite showed excellent photo-catalytic activity towards cationic methylene blue (MB) dye degradation with 100% removal rate under UV light irradiation as compared to N-doped ZnO (65%) and pure ZnO (47.36%). The convincing performance has also been observed for the case of visible light irradiation. The enhancement of that photocatalytic activity might be due to narrowing the band gap as well as the reduction of electron-hole pair recombination in ZnO matrix with the incorporation of dopant nitrogen and CNT. It is assumed from the obtained results that N-doped ZnO/CNT nanocomposite thin film can be employed as an economically achievable and ecofriendly method to degrade dye with UV and visible light irradiation. Additionally, density functional theory (DFT) calculations were applied to explore the effect of N-doping on electronic structure of ZnO. The computational study has supported the experimental results of significant band gap contraction, which leads to the maximum absorption towards higher wavelength and no appreciable change of lattice parameters after doping. A conceivable photocatalytic mechanism of N-doped ZnO/CNT nanocomposite has been proposed as well.


Assuntos
Nanocompostos/química , Nitrogênio/química , Óxido de Zinco/química , Catálise , Contaminação de Medicamentos , Luz , Microscopia Eletrônica de Varredura/métodos , Processos Fotoquímicos , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Raios Ultravioleta , Difração de Raios X/métodos
20.
Bioelectrochemistry ; 140: 107815, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-33862546

RESUMO

Creatinine is an indicator of hindrance in urination and renal insufficiency. Creatinine levels are the marker of the late stages of prostate cancer. Early and sensitive detection of creatinine can reduce deaths associated with prostate cancer. In this work, nitrogen-doped porous carbon antimony (Sb/NPC) nanoparticles are fabricated to be employed as a non-enzymatic biosensor. Sb/NPC has promising redox activity and is synthesized by a two-step reaction using low-cost precursors. Electrochemical sensing by Sb/NPC is conducted for standard creatinine solutions on a three-electrodes system. Cyclic voltammetry, amperometry, and electrochemical impedance spectroscopy are used to sense creatinine. LOD and LOQ of the Sb/NPC modified electrode are 0.74 µM and 2.4 µM, respectively. This electrode system analyzes creatinine in the serum of prostate cancer patients who have elevated PSA levels. More than 90% creatinine is recovered from a spiked serum sample of a prostate cancer patient. A direct relation is observed between PSA levels and creatinine levels in prostate cancer. The developed cyclic voltammetric setup detects trace concentrations of creatinine in serum.


Assuntos
Antimônio/química , Análise Química do Sangue/métodos , Carbono/química , Creatinina/sangue , Nanopartículas/química , Neoplasias da Próstata/sangue , Biomarcadores Tumorais/sangue , Eletroquímica , Humanos , Limite de Detecção , Masculino , Nitrogênio/química , Porosidade
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