Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 1.803
Filtrar
1.
J Chromatogr A ; 1650: 462247, 2021 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-34087520

RESUMO

The adsorptive loss of acidic analytes in liquid chromatography was investigated using metal frits. Repetitive injections of acidic small molecules or an oligonucleotide were made on individual 2.1 or 4.6 mm i.d. column frits. Losses were observed for adenosine 5'-(α,ß-methylene) diphosphate, 2-pyridinol 1-oxide and the 25-mer phosphorothioate oligonucleotide Trecovirsen (GEM91) on stainless steel and titanium frits. Analyte adsorption was greatest at acidic pH due to the positive charge on the metal oxide surface. Analyte recovery increased when a series of injections was performed; this effect is known as sample conditioning. Nearly complete recovery was achieved when the metal adsorptive sites were saturated with the analyte. A similar effect was achieved by conditioning the frits with phosphoric, citric or etidronic acids, or their buffered solutions. These procedures can be utilized to mitigate analyte loss. However, the effect is temporary, as the conditioning agent is gradually removed by the running mobile phase. Metal frits modified with hybrid organic/inorganic surface technology were shown to mitigate analyte-to-metal surface interactions and improve recovery of acidic analytes. Quantitative recovery of a 15-35 mer oligodeoxythymidine mixture was achieved using column hardware modified with hybrid surface technology, without a need for column conditioning prior to analysis.


Assuntos
Cromatografia Líquida , Metais , Adsorção , Tampões (Química) , Cromatografia Líquida/métodos , Cromatografia Líquida/normas , Ácido Cítrico/química , Ácido Etidrônico/química , Indicadores e Reagentes , Metais/química , Ácidos Fosfóricos/química , Aço Inoxidável/química , Propriedades de Superfície , Titânio/química
2.
Int J Nanomedicine ; 16: 3021-3040, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33935497

RESUMO

Purpose: Silver nanoparticles (AgNPs) are one of the most commonly investigated nanomaterials, especially due to their biomedical applications. However, their excellent cytotoxic and antimicrobial activity is often compromised in biological media due to nanoparticle aggregation. In this work, the aggregation behavior and the related biological activity of three different samples of citrate capped silver nanoparticles, with mean diameters of 10, 20, and 50 nm, respectively, were examined. Methods: Following nanoparticle synthesis and characterization with transmission electron microscopy, their aggregation behavior under various pH values, NaCl, glucose, and glutamine concentrations, furthermore in cell culture medium components such as Dulbecco's Modified Eagle's Medium and fetal bovine serum, was assessed through dynamic light scattering and ultraviolet-visible spectroscopy. Results: The results indicated that acidic pH and physiological electrolyte content universally induce micron-scale aggregation, which can be mediated by biomolecular corona formation. Remarkably, larger particles demonstrated higher resistance against external influences than smaller counterparts. In vitro cytotoxicity and antimicrobial assays were performed by treating cells with nanoparticulate aggregates in differing stages of aggregation. Conclusion: Our results revealed a profound association between colloidal stability and toxicity of AgNPs, as extreme aggregation led to the complete loss of biological activity. The higher degree of aggregation resistance observed for larger particles had a significant impact on the in vitro toxicity, since such samples retained more of their activity against microbes and mammalian cells. These findings lead to the conclusion that aiming for the smallest possible nanoparticles might not be the best course of action, despite the general standpoint of the relevant literature.


Assuntos
Nanopartículas Metálicas/química , Tamanho da Partícula , Prata/química , Anti-Infecciosos/farmacologia , Bactérias/efeitos dos fármacos , Morte Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Ácido Cítrico/química , Meios de Cultura/química , Difusão Dinâmica da Luz , Fungos/efeitos dos fármacos , Glucose/farmacologia , Glutamina/farmacologia , Humanos , Concentração de Íons de Hidrogênio , Nanopartículas Metálicas/ultraestrutura , Testes de Sensibilidade Microbiana , Cloreto de Sódio/química
3.
Food Chem ; 358: 129819, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-33933974

RESUMO

The formation mechanism of furan has been studied extensively in model systems, however, furan formation in real foods are complex and far from being fully understood. In this study, the effects of acid-regulating agent (citric acid), sugar addition (glucose, fructose and sucrose) and thickening agents (xanthan gum, κ-carrageenan and pectin) on furan levels in strawberry jams were studied; meanwhile the formation pathway of furan in canned strawberry jam was proposed by carbon module labeling (CAMOLA) technique. Our results suggested low pH promoted furan formation in strawberry jam. Besides, fructose produces more furans than sucrose and glucose, and the addition of xanthan gum reduced furan levels significantly. The kinetic data showed that ascorbic and dehydroascorbic acid degradation followed first-order kinetics while rate of furan formation followed zero-order kinetics. This study presented the possibility of mitigating furan formation in canned strawberry jams by optimization of processing parameters and addition of xanthan gum.


Assuntos
Indústria de Processamento de Alimentos/métodos , Fragaria/química , Furanos/química , Carragenina/química , Ácido Cítrico/química , Ácido Desidroascórbico/química , Frutose/química , Frutas/química , Glucose/química , Cinética , Pectinas/química , Polissacarídeos Bacterianos/química , Sacarose/química
4.
Int J Mol Sci ; 22(7)2021 Mar 31.
Artigo em Inglês | MEDLINE | ID: mdl-33807473

RESUMO

The vision impairments suffered by millions of people worldwide and the shortage of corneal donors show the need of substitutes that mimic native tissue to promote cell growth and subsequent tissue regeneration. The current study focused on the in vitro assessment of protein-based biomaterials that could be a potential source for corneal scaffolds. Collagen, soy protein isolate (SPI), and gelatin films cross-linked with lactose or citric acid were prepared and physicochemical, transmittance, and degradation measurements were carried out. In vitro cytotoxicity, cell adhesion, and migration studies were performed with human corneal epithelial (HCE) cells and 3T3 fibroblasts for the films' cytocompatibility assessment. Transmittance values met the cornea's needs, and the degradation profile revealed a progressive biomaterials' decomposition in enzymatic and hydrolytic assays. Cell viability at 72 h was above 70% when exposed to SPI and gelatin films. Live/dead assays and scanning electron microscopy (SEM) analysis demonstrated the adhesion of both cell types to the films, with a similar arrangement to that observed in controls. Besides, both cell lines were able to proliferate and migrate over the films. Without ruling out any material, the appropriate optical and biological properties shown by lactose-crosslinked gelatin film highlight its potential for corneal bioengineering.


Assuntos
Materiais Biocompatíveis/química , Córnea/metabolismo , Engenharia Tecidual/métodos , Células 3T3 , Animais , Linhagem Celular , Ácido Cítrico/química , Colágeno/química , Colágeno/metabolismo , Reagentes para Ligações Cruzadas/química , Epitélio Anterior/efeitos dos fármacos , Gelatina/química , Humanos , Lactose/química , Camundongos , Proteínas de Soja/química , Proteínas de Soja/metabolismo , Suínos , Tecidos Suporte/química
5.
Nature ; 591(7848): 157-161, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33597751

RESUMO

Citrate is best known as an intermediate in the tricarboxylic acid cycle of the cell. In addition to this essential role in energy metabolism, the tricarboxylate anion also acts as both a precursor and a regulator of fatty acid synthesis1-3. Thus, the rate of fatty acid synthesis correlates directly with the cytosolic concentration of citrate4,5. Liver cells import citrate through the sodium-dependent citrate transporter NaCT (encoded by SLC13A5) and, as a consequence, this protein is a potential target for anti-obesity drugs. Here, to understand the structural basis of its inhibition mechanism, we determined cryo-electron microscopy structures of human NaCT in complexes with citrate or a small-molecule inhibitor. These structures reveal how the inhibitor-which binds to the same site as citrate-arrests the transport cycle of NaCT. The NaCT-inhibitor structure also explains why the compound selectively inhibits NaCT over two homologous human dicarboxylate transporters, and suggests ways to further improve the affinity and selectivity. Finally, the NaCT structures provide a framework for understanding how various mutations abolish the transport activity of NaCT in the brain and thereby cause epilepsy associated with mutations in SLC13A5 in newborns (which is known as SLC13A5-epilepsy)6-8.


Assuntos
Proteínas de Transporte/antagonistas & inibidores , Proteínas de Transporte/química , Ácido Cítrico/metabolismo , Microscopia Crioeletrônica , Malatos/farmacologia , Fenilbutiratos/farmacologia , Simportadores/antagonistas & inibidores , Simportadores/química , Sítios de Ligação , Encéfalo/metabolismo , Proteínas de Transporte/genética , Proteínas de Transporte/ultraestrutura , Ácido Cítrico/química , Transportadores de Ácidos Dicarboxílicos/química , Transportadores de Ácidos Dicarboxílicos/metabolismo , Epilepsia/genética , Epilepsia/metabolismo , Humanos , Malatos/química , Modelos Moleculares , Mutação , Fenilbutiratos/química , Multimerização Proteica , Sódio/metabolismo , Especificidade por Substrato/efeitos dos fármacos , Especificidade por Substrato/genética , Simportadores/genética , Simportadores/ultraestrutura
6.
Biochem Biophys Res Commun ; 546: 145-149, 2021 03 26.
Artigo em Inglês | MEDLINE | ID: mdl-33582557

RESUMO

In times of widespread multiple antibiotic resistance, the bacterial colonization of crucial medical surfaces should be detected as fast as possible. In this work, we present the non-destructive SERS method for the detection of bacterial colonization. SERS is an excellent tool for the monitoring of suitable substances in low concentrations. The SERS substrate was prepared by the aggregation of citrate-stabilized gold nanoparticles and the adsorption of the reporters (crystal violet, thiamine, and adenine). We have tested the substrate for the detection of clinically relevant S. aureus and P. aeruginosa bacteria. The SERS spectra before and after the substrate incubation revealed the degradation of the reporter by the growing bacteria. The growth of P. aeruginosa was detected using the substrates with preadsorbed crystal violet or adenine. The suitable reporter for the detection of S. aureus remains to be discovered. The selection of the reporters resistant to exposure but easily degraded by bacteria will open the way for the in situ monitoring of bacterial colonization, thus complementing the arsenal of methods in the battle against hospital infections.


Assuntos
Adenina/química , Violeta Genciana/química , Pseudomonas aeruginosa/crescimento & desenvolvimento , Pseudomonas aeruginosa/isolamento & purificação , Análise Espectral Raman/métodos , Ácido Cítrico/química , Ouro/química , Nanopartículas Metálicas/análise , Nanopartículas Metálicas/química , Sondas Moleculares/análise , Sondas Moleculares/química , Staphylococcus aureus , Tiamina/química
7.
Molecules ; 26(3)2021 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-33513731

RESUMO

Lignin isolated from black liquor waste was studied in this research to be utilized as binderless, all-lignin briquette, with a calorific value in the range of 5670-5876 kcal/kg. Isolation of lignin from black liquor was conducted using the acid precipitation method. Sulfuric acid, citric acid, and acetic acid were used to maintain the pH level, which varied from 5 to 2 for the precipitation process. The influence of these isolation conditions on the characteristic of lignin and the properties of the resulted briquette was evaluated through the Klasson method, proximate analysis, ultimate analysis, Fourier Transform Infrared (FTIR), adiabatic bomb calorimeter, density measurement, and Drop Shatter Index (DSI) testing. The finding showed that the lignin isolated using citric acid maintained to pH 3 resulted in briquette with 72% fixed carbon content, excellent 99.7% DSI, and a calorific value equivalent to coal-based briquette.


Assuntos
Bebidas Alcoólicas/análise , Etanol/química , Lignina/química , Ácido Acético/química , Precipitação Química , Ácido Cítrico/química , Carvão Mineral/análise , Concentração de Íons de Hidrogênio , Resíduos Industriais , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Ácidos Sulfúricos/química
8.
Carbohydr Polym ; 256: 117549, 2021 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-33483056

RESUMO

Citrate-based thermoset bioelastomer has numerous tissue engineering applications. However, its insoluble and unmeltable features restricted processing techniques for fabricating complex scaffolds. Herein, direct ink writing (DIW) was explored for 3D printing of poly(1, 8-octanediol-co-Pluronic F127 citrate) (POFC) bioelastomer scaffolds considering that POFC prepolymer (pre-POFC) was waterborne and could form a stable emulsion. The pre-POFC emulsion couldn't be printed, however, chitin nanocrystal (ChiNC) could be as a rheological modifier to tune the flow behavior of pre-POFC emulsion, and thus DIW printing of POFC scaffolds was successfully realized; moreover, ChiNC was also as a supporting agent to prevent collapse of filaments during thermocuring, and simultaneously as a biobased nanofiller to reinforce scaffolds. The rheological analyses showed the pre-POFC/ChiNC inks fulfilled the requirements for DIW printing. The printed scaffolds exhibited low swelling, and good performances in strength and resilence. Furthermore, the entire process was easily performed and eco-friendly.


Assuntos
Quitina/química , Nanopartículas/química , Polímeros/química , Impressão Tridimensional , Ácido Cítrico/química , Força Compressiva , Elastômeros , Emulsões , Hidrogéis/química , Tinta , Teste de Materiais , Oscilometria , Poloxâmero/química , Reologia , Engenharia Tecidual , Viscosidade
9.
Carbohydr Polym ; 256: 117577, 2021 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-33483072

RESUMO

In the field of neurosurgery, timely and effective repair of dura mater plays an important role in stabilizing the physiological functions of the human body. Therefore, the aim of this study is to develop a new type of bilayer membrane as a dural substitute candidate. It consists of a dense layer that prevents cerebrospinal fluid leakage and a porous layer that promotes tissue regeneration. The dense layer, a composite polysaccharid film, was composed of high molecular weight chitosan (CS) and bacterial cellulose (BC). The porous layer, a composite polysaccharid scaffold cross-linked by glutaraldehyde (GA) or citric acid (CA) respectively, was composed of O-carboxymethyl chitin (O-CMCH) and BC. The bilayer dural substitutes were characterized in terms of SEM, mechanical behavior, swelling rate, anti-leakage test, in vitro cytotoxicity, proliferation, and animal experiment. Results indicated that all prepared dural substitutes were tightly bound between layers without excessively large cavities. The porous layer showed appropriate pore size (90~200 µm) with high porous connectivity. The optimized bilayer dural substitutes showed suitable swelling rate and mechanical behavior. Furthermore, no leakage was observed during testing, no cytotoxicity effect on NIH/3T3 cells, and exhibited excellent cell proliferation promoting properties. Also, it was observed that it did not deform in the peritoneal environment of mice, and tissue inflammation was mild.


Assuntos
Celulose/química , Quitina/química , Dura-Máter/patologia , Glutaral/química , Animais , Materiais Biocompatíveis , Proliferação de Células , Quitina/análogos & derivados , Quitosana/química , Ácido Cítrico/química , Humanos , Interações Hidrofóbicas e Hidrofílicas , Inflamação , Camundongos , Microscopia Eletrônica de Varredura , Células NIH 3T3 , Polissacarídeos , Porosidade , Espectroscopia de Infravermelho com Transformada de Fourier , Estresse Mecânico , Tecidos Suporte/química , Difração de Raios X
10.
Int J Biol Macromol ; 171: 17-27, 2021 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-33412196

RESUMO

Herein, an effective adsorbent, 3D porous tubular network-structured citric acid-chitosan/Fe/polyethyleneimine beads (CCFPB) with multifunctional active groups and strong selectivity, was prepared for the selective removal of Cu2+ from simulated wastewater. Compared with pure chitosan beads (CB), the adsorption capacity of CCFPB for Cu2+ was increased by 127 mg g-1 (238%), and the adsorption equilibrium time was shortened by 480 min. The CCFPB showed porous surface and a novel 3D porous tubular network structure in interior, which were benefit to the diffusion of Cu2+ from surface to interior of the CCFPB and the shortening of adsorption equilibrium time. The common coexisting ions in the simulated wastewater had almost no effect on the adsorption of Cu2+ by CCFPB, and the adsorption was fast and reached equilibrium within 10 h. The adsorption process followed pseudo-second-order kinetics and the Langmuir isotherm model (qm = 240.9 mg g-1 for Cu2+). The adsorption mechanism of CCFPB for Cu2+ was mainly the synergistic interaction with amino, carboxyl, and hydroxyl groups. This strategy shows great potential for developing a variety of novel, highly active, and reusable immobilized functional beads materials for effective separation of Cu2+ from multi-ion wastewater.


Assuntos
Quitosana/química , Ácido Cítrico/química , Cobre/isolamento & purificação , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Adsorção , Cátions Bivalentes , Humanos , Concentração de Íons de Hidrogênio , Ferro/química , Cinética , Polietilenoimina/química , Porosidade , Termodinâmica , Águas Residuárias/química
11.
Int J Biol Macromol ; 171: 123-129, 2021 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-33418038

RESUMO

Native corn starch was modified by enzymatic debranching (ED), microwave assisted citric acid esterification (MCAE), and by dual ED/MCAE. The structure and properties of native starch (NS), and the resulting debranched starch (DS), microwave assisted citric acid esterified starch (MCS), and microwave assisted citric acid debranched starch (MCDS) were determined and compared. Both the morphology and crystalline regions of the modified starches were changed by ED and MCAE. ED increased significantly the amylose content and transparency, but decreased the in vitro enzymatic digestibility, freeze thaw stability and relative crystallinity of DS compared to those of NS. MCAE produced a decrease in amylose content, transparency, in vitro enzymatic digestibility, and relative crystallinity, but increased the freeze-thaw stability of MCS compared to NS, and of MCDS compared to DS. The A-type crystalline structure of NS and DS was changed to B-type crystalline structure after MCAE treatment, and a new FTIR characteristic band at 1735 cm-1 was observed for MCS and MCDS. This work provides insights for producing esterified corn starches by a combined enzyme, microwave and organic acid novel technology.


Assuntos
Amilose/química , Ácido Cítrico/química , Amido/química , Zea mays/química , Amilose/ultraestrutura , Cristalização , Esterificação , Tecnologia de Alimentos/métodos , Humanos , Hidrólise , Micro-Ondas , Amido/ultraestrutura
12.
AAPS PharmSciTech ; 22(1): 31, 2021 Jan 06.
Artigo em Inglês | MEDLINE | ID: mdl-33405012

RESUMO

Aripiprazole (APZ) has poor physicochemical properties and bitter taste. The current study aimed to prepare salts of APZ with polycarboxylic acids (citric, malic, and tartaric acids) to improve physicochemical properties and impart sour taste to the drug. The salts were prepared by solubilization-crystallization method, and characterized by electron microscopic, spectroscopic, diffractometry, and thermal methods. The salts were assessed for pH solubility, pH-stability, dissolution, and solid-state stability. Fourier transformed infrared, X-ray powder diffraction, and differential scanning calorimetry data indicated formation of new solid phases. APZ and the salts exhibited pH-dependent solubility. The pH solubility curve shape was inverted "V," inverted "W," and inverted "U" for APZ, APZ-Citrate, and APZ-Malate and APZ-Tartrate, respectively. Compared to APZ, the solubility of salts at pH 4, 5, and 6 was 3.6-7.1, 23.9-31.5, and 143.4-373.3 folds of APZ. Increase in solubility in water by citrate, malate, and tartrate salts was 5562.8, 21,284.7, and 22,846.7 folds of APZ. The salt formation also leads to an increase in rate and extent of dissolution. The dissolution extent was 3.5 ± 0.5, 71.3 ± 1.2, 80.1 ± 6.2, and 86.1 ± 1.1% for APZ, APZ-Citrate, APZ-Malate, and APZ-Tartrate, respectively. Liquid and solid-state stabilities of the salts were comparable to APZ. In conclusion, salts of APZ with polycarboxylic acids improved solubility, and dissolution, and impart sour taste, which may improve palatability of the drug.


Assuntos
Antipsicóticos/química , Aripiprazol/química , Varredura Diferencial de Calorimetria , Ácido Cítrico/química , Cristalização , Estabilidade de Medicamentos , Malatos/química , Microscopia Eletrônica de Varredura , Difração de Pó , Solubilidade , Espectroscopia de Infravermelho com Transformada de Fourier , Tartaratos/química
13.
ACS Appl Mater Interfaces ; 13(4): 5877-5886, 2021 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-33482691

RESUMO

Chiral carbon dots (CDs) integrated the advantages of achiral CDs and the unique chiral property, which expand the prospect of the biological applications of CDs. However, the structure control and the origin of chirality for chiral CDs remain unclear. Herein, chiral CDs were obtained by thermal polymerization of chiral amino acids and citric acid, and their handedness of chirality could be controlled by adjusting the reaction temperature, which leads to different kinds of surface modifications. With aliphatic amino acids as a chiral source, all of the CDs that reacted at different temperatures (90-200 °C) have the same handedness of the chiral source. But with aromatic amino acids as a chiral source, CDs with maintained or inversed handedness compared with the chiral source could be obtained by adjusting the reaction temperature. Below a temperature of 120 °C, the chiral source was modified with CDs by esterification and transferred the handedness of chirality; at high temperatures (above 150 °C), which mainly connected by amidation accompanying with the formation of rigid structure generated by the π conjugation between the aromatic nucleus of chiral source and the carbon core of CDs, caused the inversing of the chiral signal. Further, we investigated the chiral effects of CDs on the glucose oxidase activity for a highly sensitive electrochemical biosensor.


Assuntos
Aminoácidos/química , Técnicas Biossensoriais/métodos , Glucose Oxidase/química , Glucose/análise , Pontos Quânticos/química , Carbono/química , Ácido Cítrico/química , Estabilidade Enzimática , Esterificação , Modelos Moleculares , Polimerização , Pontos Quânticos/ultraestrutura , Estereoisomerismo , Propriedades de Superfície
14.
Ecotoxicol Environ Saf ; 211: 111942, 2021 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-33476850

RESUMO

In this work, the internalization and distribution of citric acid-coated magnetite nanoparticles (here, Fe3O4-NPs) in soybean and alfalfa tissues and their effects on plant growth were studied. Both legumes were germinated in pots containing an inert growing matrix (vermiculite) to which Hoagland solution without (control, C), with Fe3O4-NPs (50 and 100 mgironL-1, NP50 and NP100), or with the same amount of soluble iron supplied as Fe-EDTA (Fe50, Fe100) was added once before sowing. Then, plants were watered with the standard nutrient solution. The observation of superparamagnetic signals in root tissues at harvest (26 days after emergence) indicated Fe3O4-NPs uptake by both legumes. A weak superparamagnetic signal was also present in the stems and leaves of alfalfa plants. These findings suggest that Fe3O4-NPs are readily absorbed but not translocated (soybean) or scarcely translocated (alfalfa) from the roots to the shoots. The addition of both iron sources resulted in increased root weight; however, only the addition of Fe3O4-NPs resulted in significantly higher root surface; shoot weight also increased significantly. As a general trend, chlorophyll content enhanced in plants grown in vermiculite supplemented with extra iron at pre-sowing; the greatest increase was observed with NP50. The only antioxidant enzyme significantly affected by our treatments was catalase, whose activity increased in the roots and shoots of both species exposed to Fe3O4-NPs. However, no symptoms of oxidative stress, such as increased lipid peroxidation or reactive oxygen species accumulation, were evidenced in any of these legumes. Besides, no evidence of cell membrane damage or cell death was found. Our results suggest that citric acid-coated Fe3O4-NPs are not toxic to soybean and alfalfa; instead, they behave as plant growth stimulators.


Assuntos
Ácido Cítrico/química , Nanopartículas de Magnetita/química , Medicago sativa/crescimento & desenvolvimento , Soja/crescimento & desenvolvimento , Clorofila/metabolismo , Ácido Cítrico/metabolismo , Germinação , Ferro/metabolismo , Nanopartículas de Magnetita/toxicidade , Medicago sativa/metabolismo , Nanopartículas/metabolismo , Desenvolvimento Vegetal , Folhas de Planta/metabolismo , Raízes de Plantas/metabolismo , Soja/metabolismo
15.
Phys Chem Chem Phys ; 23(2): 1706-1717, 2021 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-33427255

RESUMO

The use of water as a component of deep eutectic systems (DES) has raised some questions regarding its influence on the nature of the mixture. Does it form a DES or an aqueous solution and what is the role of water? In this work, the nature of citric acid:l-arginine:water mixtures was explored through phase equilibria studies and spectroscopic analysis. In a first step, PC-SAFT was validated as a predictive tool to model the water influence on the solid liquid equilibria (SLE) of the DES reline using the individual-component approach. Hence, activity coefficients in the ternary systems citric acid:l-arginine:water and respective binary combinations were studied and compared using ePC-SAFT. It was observed that the water-free mixtures citric acid:l-arginine showed positive deviation from Raoult's law, while upon addition of water strong negative deviation from Raoult's law was found, yielding melting depressions around 100 K. Besides these strong interactions, pH was found to become acidic (pH = 3.5) upon water addition, which yields the formation of charged species ([H2Cit]- and [l-arg]+). Thus, the increased interactions between the molecules upon water addition might be caused by several mechanisms such as hydrogen bonding or ionic forces, both being induced by water. For further investigation, the liquid mixtures citric acid:l-arginine:water were studied by FTIR and NMR spectroscopy. FTIR spectra disproved a possible solubility enhancement caused by salt formation between citric acid and l-arginine, while NMR spectra supported the formation of a hydrogen bonding network different from the binary systems citric acid:water and l-arginine:water. Either being a DES or other type of non-ideal solution, the liquefaction of the studied systems is certainly caused by a water-mediator effect based on the formation of charged species and cross interactions between the mixture constituents.


Assuntos
Arginina/química , Ácido Cítrico/química , Água/química , Cloreto de Cálcio/química , Congelamento , Modelos Químicos , Termodinâmica , Temperatura de Transição , Ureia/química
16.
Carbohydr Polym ; 252: 117208, 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-33183641

RESUMO

Silver nanoparticles (AgNP L) synthesis using the active compounds of lemon juice was optimized. The obtained nanoparticles were included in starch-based film formulations, studying the relevant properties that condition their application in the packaging area. The optimized conditions for AgNP L' synthesis were 30 min at 90 °C, which led to the lowest nanoparticle size (5.5 nm) with the highest associated stability (ζ= -29.5 mV) up to 90 days. Nanocomposite films resulted with an orange tone that increased with AgNP L concentration (14.3-143 ppm). Water vapor permeability decreased while tensile mechanical resistance increased up to an aggregate of 71.5 ppm of AgNP L, indicating the nanoparticles' reinforcement of the polymer matrix. Besides, the citric acid content provided by lemon juice also affected the starch-based relevant film properties. Regarding antimicrobial capacity, a synergic effect between active compounds of lemon juice and silver nanoparticles was evidenced, being Salmonella spp. the most sensitive bacteria.


Assuntos
Antibacterianos , Ácido Cítrico/química , Embalagem de Alimentos , Nanopartículas Metálicas/química , Amido/química , Antibacterianos/química , Antibacterianos/farmacologia , Bactérias/efeitos dos fármacos , Citrus , Excipientes , Sucos de Frutas e Vegetais , Química Verde/métodos , Nanocompostos/química , Permeabilidade , Prata/química , Vapor , Resistência à Tração , Água/química
17.
Carbohydr Polym ; 253: 117247, 2021 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-33279002

RESUMO

In this work, we present a novel ex situ modification of bacterial cellulose (BC) polymer, that significantly improves its ability to absorb water after drying. The method involves a single inexpensive and easy-to-perform process of BC crosslinking, using citric acid along with catalysts, such as disodium phosphate, sodium bicarbonate, ammonium bicarbonate or their mixtures. In particular, the mixture of disodium phosphate and sodium bicarbonate was the most promising, yielding significantly greater water capacity (over 5 times higher as compared to the unmodified BC) and slower water release (over 6 times as compared to the unmodified BC). Further, our optimized crosslinked BC had over 1.5x higher water capacity than modern commercial dressings dedicated to highly exuding wounds, while exhibiting no cytotoxic effects against fibroblast cell line L929 in vitro. Therefore, our novel BC biomaterial may find application in super-absorbent dressings, designed for chronic wounds with imbalanced moisture level.


Assuntos
Absorção Fisico-Química , Bandagens , Materiais Biocompatíveis/química , Celulose/química , Reagentes para Ligações Cruzadas/química , Gluconacetobacter xylinus/metabolismo , Polissacarídeos Bacterianos/química , Cicatrização , Animais , Materiais Biocompatíveis/farmacologia , Catálise , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Celulose/farmacologia , Ácido Cítrico/química , Reagentes para Ligações Cruzadas/farmacologia , Fibroblastos/efeitos dos fármacos , Camundongos , Fosfatos/química , Polissacarídeos Bacterianos/farmacologia , Bicarbonato de Sódio/química , Água/química
18.
Food Chem ; 336: 127717, 2021 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-32763740

RESUMO

Continued industrialization and increasing environmental problems have highlighted the need to research new eco-friendly solvents, also known as deep eutectic solvents (DESs). To implement these solvents in industrial processes, the knowledge of their molecular organization and thermophysical properties must be enhanced. In this work, two DESs have been characterized: d-glucose:choline chloride:water (GCH) and d-glucose:citric acid:water (GCiH). NMR techniques were used to analyse both the supramolecular structure and the role of water and to calculate the diffusion coefficients. Moreover, seven thermophysical properties at several temperatures were evaluated. As a second aim, the solubility of quercetin was determined. NMR studies showed a stronger supramolecular structure of GCH and a high ratio of ß-glucose in both DESs. Based on the thermophysical results, the solvent with choline chloride had the most compact fluid structure. Finally, the solubility of quercetin in the DESs was higher than in water, especially for GCH.


Assuntos
Glucose/química , Solventes/química , Colina/química , Ácido Cítrico/química , Espectroscopia de Ressonância Magnética , Quercetina/química , Solubilidade , Temperatura , Termodinâmica , Água/química
19.
Food Chem ; 338: 127819, 2021 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-32810812

RESUMO

Impacts of citric acid (CA) treatment under non-acidic conditions (pH 7.0, 8.0 and 9.0) on whey protein isolate (WPI) were examined in this study. Size exclusion chromatography and SDS-PAGE indicated that molecular size and weight of WPI-CA became larger at pH 7.0, 8.0 and 9.0 with CA ranged from 0 to 15 mg/mL, but the protein aggregates disappeared after ß-mercaptoethanol was added. The free SH groups of WPI-CA gradually decreased. This could be deduced that CA could promote disulfide bond formation of WPI at the non-acidic pH values. Furthermore, fourier transform infra-red (FTIR) spectroscopy and fluorescence spectroscopy data confirmed the conformational changes of secondary and tertiary structures of CA-modified WPI, respectively. Therefore, these results suggested that disulfide bond formation of WPI occurred at citric acid treatment under non-acidic conditions, being contributed to production of its larger molecular size substances and alteration of its structural characteristics.


Assuntos
Ácido Cítrico/química , Dissulfetos/química , Proteínas do Soro do Leite/química , Cromatografia em Gel , Reagentes para Ligações Cruzadas/química , Eletroforese em Gel de Poliacrilamida , Concentração de Íons de Hidrogênio , Mercaptoetanol/química , Conformação Proteica , Espectrometria de Fluorescência , Espectroscopia de Infravermelho com Transformada de Fourier , Água/química
20.
Food Chem ; 338: 127842, 2021 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-32822902

RESUMO

Cadmium, inorganic arsenic and, potentially, dimethyl arsenic acid are carcinogens widely elevated in rice. Here it was identified that the food-safe and common cadmium chelator citric acid efficiently removed cadmium from intact grain via pre-soaking procedure, while also reducing arsenic species. A twostep pre-soaking stage was developed whereby rice was first incubated, at ambient temperature, in 1 M citric acid for 12 h, and then in 1 M calcium carbonate for another 12 h, the latter step to neutralize pH, followed by cooking. When 10 different individual types of rice were processed in such a way this resulted in removal rates of 79% for cadmium, 81% for inorganic arsenic and a 66% for DMA. The technology is particularly suitable for bulk food processing and could be deployed in the most cadmium and arsenic impacted regions where rice is a staple.


Assuntos
Arsenicais/química , Ácido Cacodílico/química , Cádmio/química , Contaminação de Alimentos/análise , Oryza/química , Arsenicais/análise , Ácido Cacodílico/análise , Cádmio/análise , Carbonato de Cálcio/química , Ácido Cítrico/química , Culinária/métodos , Concentração de Íons de Hidrogênio , Espectrometria de Massas/métodos , Oryza/metabolismo
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...