Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 6.750
Filtrar
1.
Food Chem ; 338: 127839, 2021 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-32822901

RESUMO

Cyclodextrin (CD)-metal-organic frameworks (MOFs) are developed as a new type of food-acceptable multi-porous material, which shows a great potential for controlled volatile compound release. This study aimed to synthesize CD-MOFs from potassium nitrate, crystallized with α-cyclodextrin (α-CD), ß-CD or γ-CD, and their complex capacities were further evaluated using menthol encapsulation. Compared with CD, all the CD-MOFs had highly ordered crystal structures and more regular shapes. ß-CD-MOF showed better thermal stability, with an initial thermal degradation temperature of 253 °C, higher than the other two CD-MOFs. The CD-MOFs were used for menthol encapsulation and the resulting menthol concentration within the inclusion complexes (ICs) was determined. The menthol concentration in ICs followed the order: ß-CD-MOF > ß-CD > Î³-CD-MOF > Î³-CD > α-CD ≥ α-CD-MOF. The menthol content and encapsulation efficiency of ß-CD-MOF were 21.76% (w/w) and 22.54% (w/w) respectively, significantly higher than those of other reported solid materials, such as amylose, CD and V-type starch.


Assuntos
Ciclodextrinas/química , Mentol/química , Estruturas Metalorgânicas/química , Cristalografia por Raios X , Porosidade , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura , Termogravimetria , alfa-Ciclodextrinas/química , beta-Ciclodextrinas/química , gama-Ciclodextrinas/química
2.
Environ Sci Pollut Res Int ; 28(2): 1317-1340, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33079345

RESUMO

Water is a vital substance that constitutes biological structures and sustains life. However, water pollution is currently among the major environmental challenges and has attracted increasing study attention. How to handle contaminated water now mainly focuses on removing or reducing the pollutants from the wastewater. Cyclodextrin derivatives, possessing external hydrophilic and internal hydrophobic properties, have been recognized as new-generation adsorbents to exert positive effects on water pollution treatment. This article outlines recent contributions of cyclodextrin-based adsorbents on wastewater treatment, highlighting different adsorption mechanisms of cyclodextrin-based adsorbents under different influencing factors. The crosslinked and immobilized cyclodextrin-based adsorbents all displayed outstanding adsorption capacities. Particularly, according to specific pollutants including metal ions, organic chemicals, pesticides, and drugs in wastewater, this article has classified and organized various cyclodextrin-based adsorbents into tables, which could pave an intuitive shortcut for designing and developing efficient cyclodextrin-based adsorbents for targeted wastewater pollutants. Besides, this article specially discusses cost-effectiveness and regeneration performance of current cyclodextrin-based adsorbents. Finally, the challenges and future directions of cyclodextrin-based adsorbents are prospected in this article, which may shed substantial light on practical industrial applications of cyclodextrin-based adsorbents.


Assuntos
Ciclodextrinas , Poluentes Ambientais , Preparações Farmacêuticas , Poluentes Químicos da Água , Purificação da Água , Adsorção , Águas Residuárias , Poluentes Químicos da Água/análise
3.
PLoS One ; 15(11): e0241912, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33211750

RESUMO

Cyclic α-maltosyl-(1→6)-maltose (CMM) is a cyclic glucotetrasaccharide with alternating α-1,4 and α-1,6 linkages. Here, we report functional and structural analyses on CMM-binding protein (CMMBP), which is a substrate-binding protein (SBP) of an ABC importer system of the bacteria Arthrobacter globiformis. Isothermal titration calorimetry analysis revealed that CMMBP specifically bound to CMM with a Kd value of 9.6 nM. The crystal structure of CMMBP was determined at a resolution of 1.47 Å, and a panose molecule was bound in a cleft between two domains. To delineate its structural features, the crystal structure of CMMBP was compared with other SBPs specific for carbohydrates, such as cyclic α-nigerosyl-(1→6)-nigerose and cyclodextrins. These results indicate that A. globiformis has a unique metabolic pathway specialized for CMM.


Assuntos
Arthrobacter/metabolismo , Proteínas Ligantes de Maltose/química , Proteínas Ligantes de Maltose/metabolismo , Calorimetria , Cristalografia por Raios X , Ciclodextrinas/metabolismo , Dissacarídeos/metabolismo , Redes e Vias Metabólicas , Modelos Moleculares , Conformação Proteica , Domínios Proteicos
4.
J Chromatogr A ; 1632: 461585, 2020 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-33039941

RESUMO

The separation of the ll- and dd-enantiomers of the dipeptides Ala-Phe, Ala-phenylglycine (Phg), Ala-homoPhe, Ala-ß-Phe, Gly-Phe and ß-Ala-Phe was studied by capillary electrophoresis in the presence of negatively charged α-, ß- and γ-cyclodextrin (CD) derivatives. Analysis was performed under standardized conditions in fused-silica capillaries at pH 2.5, 3.5 and 5.3. All analyte enantiomers could be separated at pH 2.5 under at least one of the experimental conditions. Especially ß-CD derivatives proved to be effective chiral selectors. The enantiomer migration order depended on CD cavity size and substituent type, while peptide structure had only a minor effect. Upon increasing the pH from 2.5 to 5.3, reversal of the enantiomer migration order was observed frequently. Investigation of the apparent and, in the case of randomly substituted CDs, averaged complexation constants and mobilities of the diastereomeric peptide enantiomer-CD complexes indicated that in most cases the migration order in the presence of sulfated α-, ß- and γ-CD and heptakis(6-O-sulfo)-ß-CD could be explained by the stronger binding of the second migrating analyte by the CD at pH 2.5. However, in few cases the weaker bound enantiomer migrated second, which could be attributed to the higher mobility of the respective CD complexes. At pH 5.3, similar data were obtained for sulfated ß-CD and heptakis(6-O-sulfo)-ß-CD, i.e. the strength of the complexes determined the migration order for some peptides, while the migration sequence was based on the apparent (and averaged) mobility of the diastereomeric analyte-CD complexes in other cases.


Assuntos
Ciclodextrinas/química , Dipeptídeos/isolamento & purificação , Eletroforese Capilar/métodos , Dipeptídeos/química , Eletrólitos/química , Concentração de Íons de Hidrogênio , Cinética , Peptídeos/química , Estereoisomerismo
5.
Braz Dent J ; 31(4): 423-430, 2020 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-32901720

RESUMO

The aim of this study was to assess the effect of a newly developed nanocomplex formed of hydroxypropyl-b-cyclodextrin and 1% titanium tetrafluoride (TiF4) after distinct complexation periods (12/72 h) on demineralization of bovine enamel in vitro. Enamel blocks (n=60) were allocated in different groups: Mili-Q water, hydroxypropyl-b-cyclodextrin, 1% TiF4, hydroxypropyl-b-cyclodextrin + 1% TiF4 after 12 h of complexation and hydroxypropyl-b-cyclodextrin + 1% TiF4 after 72 h of complexation. The samples were evaluated by surface microhardness, cross-sectional microhardness and micro-CT. Scanning electron microscopy and energy dispersive X-ray spectrometry (SEM/EDX) were also obtained. Hydroxypropyl-b-cyclodextrin + 1% TiF4 after 12 h complexation resulted in lower percentage of surface microhardness loss compared to Mili-Q water, hydroxypropyl-b-cyclodextrin, 1% TiF4 and hydroxypropyl-b-cyclodextrin + 1% TiF4 after 72 h of complexation group, with a large effect size (from 1.307 to 2.943) and high power (84.9 to 99%). All groups resulted in similar integrated mineral loss (ΔZ) obtained by both internal microhardness and micro-CT techniques. Enamel treated with TiF4 and TiF4 + hydroxypropyl-b-cyclodextrin groups showed a TiO2 glaze-layer, while EDX evaluation identified Ti. The solution containing the inclusion complex of hydroxypropyl-b-cyclodextrin + TiF4 with 12 h of complexation period demonstrated a significant ability to reduce surface demineralization of sound enamel under an artificial cariogenic challenge.


Assuntos
Ciclodextrinas , Fluoretos , Animais , Bovinos , Estudos Transversais , Esmalte Dentário , Titânio
6.
Sci Rep ; 10(1): 15111, 2020 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-32934292

RESUMO

The plasma membrane of eukaryotic cells is asymmetric with respect to its phospholipid composition. Analysis of the lipid composition of the outer leaflet is important for understanding cell membrane biology in health and disease. Here, a method based on cyclodextrin-mediated lipid exchange to characterize the phospholipids in the outer leaflet of red blood cells (RBCs) is reported. Methyl-α-cyclodextrin, loaded with exogenous lipids, was used to extract phospholipids from the membrane outer leaflet, while delivering lipids to the cell to maintain cell membrane integrity. Thin layer chromatography and lipidomics demonstrated that the extracted lipids were from the membrane outer leaflet. Phosphatidylcholines (PC) and sphingomyelins (SM) were the most abundant phospholipids in the RBCs outer leaflet with PC 34:1 and SM 34:1 being the most abundant species. Fluorescence quenching confirmed the delivery of exogenous lipids to the cell outer leaflet. The developed lipid exchange method was then used to remove phosphatidylserine, a phagocyte recognition marker, from the outer leaflet of senescent RBCs. Senescent RBCs with reconstituted membranes were phagocytosed in significantly lower amounts compared to control cells, demonstrating the efficiency of the lipid exchange process and its application in modifying cell-cell interactions.


Assuntos
Ciclodextrinas/metabolismo , Membrana Eritrocítica/metabolismo , Eritrócitos/metabolismo , Bicamadas Lipídicas/metabolismo , Macrófagos/metabolismo , Lipídeos de Membrana/metabolismo , Fosfolipídeos/análise , Comunicação Celular , Humanos
7.
J Chromatogr A ; 1626: 461383, 2020 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-32797856

RESUMO

The potential of Micellar Electrokinetic Chromatography to achieve enantiomeric separations is reviewed in this article. The separation principles and the most frequently employed separation strategies to achieve chiral separations by Micellar Electrokinetic Chromatography are described. The use of chiral micellar systems alone or combined with other micellar systems or chiral selectors, as well as of mixtures of achiral micellar systems with chiral selectors is discussed together with the effect of different additives present in the separation medium. Indirect methods based on the derivatization of analytes with chiral derivatizing reagents and the use of achiral micelles are also considered. Preconcentration techniques employed to improve sensitivity and the main approaches developed to facilitate the coupling with Mass Spectrometry are included. The most recent and relevant methodologies developed by chiral Micellar Electrokinetic Chromatography and their applications in different fields are presented.


Assuntos
Cromatografia Capilar Eletrocinética Micelar/métodos , Aminoácidos/química , Ciclodextrinas/química , Análise de Alimentos , Espectrometria de Massas , Oryza/química , Oryza/metabolismo , Estereoisomerismo , Vinho/análise
8.
Bioresour Technol ; 317: 124002, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32810732

RESUMO

Cyclodextrins (CDs) have been widely used due to the excellent solubilization of hydrophobic organics. However, their effect on the biotransformation process of hydrophilic pollutants is unclear. This study first evaluated the effect and mechanism of CDs on nitrate reduction by S.oneidensis.MR-1. The three CDs (α-CD, ß-CD and γ-CD) all accelerated nitrate reduction, among which ß-CD had the best effect. The nitrate reduction rate was increased by 21.8% with 0.5 mM ß-CD. As for the mechanism, ß-CD increased the biomass, membrane permeability and EPS of S.oneidensis.MR-1. The nitrate reductase activity was also increased by 1.34-fold with 0.5 mM ß-CD. The current exchange density and the electron transfer system activity were increased by 11.4% and 99.5% in the ß-CD-supply system, respectively. It confirmed that ß-CD enhanced the biological and electrochemical characteristics and then enhanced bio-activity. This study provides a new understanding of CDs in microbial remediation and broadens the practical application.


Assuntos
Ciclodextrinas , Interações Hidrofóbicas e Hidrofílicas , Nitratos , Óxidos de Nitrogênio , Oxirredução
9.
J Chromatogr A ; 1628: 461438, 2020 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-32822978

RESUMO

A fast, simple, environmentally friendly and sensitive on-line concentration method using microemulsion system as background solution (BGS) was developed for the trace detection of propazine, atrazine, simazine in food samples. The electrokinetic injection assisted micelle to cyclodextrin stacking (MCDS) was designed for the enrichment of target compounds. The factors affected enrichment performance, such as the kind of CDs, the amount of CDs, the concentration of methanol in BGS, the concentration of micelle in sample matrix, the concentration of phosphoric acid in BGS and the sample injection time were optimized. The optimized electrophoretic condition was obtained as following: 50 mM α-CD, 20 mM SDS in sample matrix., 80 mM PA and 20% MeOH (v/v) in BGS, sample solution by electrokinetic injection at -10 kV for 80 s. Under the optimized conditions described above, the linear range was 0.1-20 ug/mL with a good linear relationship with a correlation coefficient (r) ≥ 0.9985. The SEFs for the propazine, atrazine, simazine were found to be 123, 85 and 62 respectively. The proposed MCDS-MEEKC method provided an efficient method for trace analysis of triazine herbicides in honey and dendrobium officinale samples.


Assuntos
Técnicas de Química Analítica/métodos , Cromatografia Capilar Eletrocinética Micelar , Ciclodextrinas/química , Herbicidas/isolamento & purificação , Micelas , Triazinas/isolamento & purificação , Atrazina , Ácidos Fosfóricos , Simazina
10.
J Chromatogr A ; 1627: 461375, 2020 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-32823120

RESUMO

Since decades, cyclodextrins are one of the most powerful selectors in chiral capillary electrophoresis for the enantioseparation of diverse organic compounds. This review concerns papers published over the last decade (from 2009 until nowadays), dealing with the capillary electrophoretic application of single isomer cyclodextrin derivatives in chiral separations. Following a brief overview of their synthetic approaches, the inventory of the neutral, negatively and positively charged (including both permanently ionic and pH-tunable ionizable substituents) and zwitterionic CD derivatives is presented, with insights to underlying structural aspects by NMR spectroscopy and molecular modeling. CE represents an ideal tool to study the weak, non-covalent supramolecular interactions. The published methods are reviewed in the light of enantioselectivity, enantiomer migration order and the fine-tuning of enantiodiscrimination by the substitution pattern of the single entity selector molecules, which is hardly possible for their randomly substituted counterparts. All the reviewed publications herein support that cyclodextrin-based chiral capillary electrophoresis seems to remain a popular choice in pharmaceutical and biomedical analysis.


Assuntos
Ciclodextrinas/química , Eletroforese Capilar/métodos , Concentração de Íons de Hidrogênio , Espectroscopia de Ressonância Magnética , Modelos Moleculares , Estereoisomerismo
11.
Water Res ; 183: 116095, 2020 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-32645579

RESUMO

Photocatalytic water treatment has significant potential to disinfect and degrade recalcitrant organic pollutants while minimizing the need to add chemicals, but current approaches have poor energy efficiency due, in part, to inefficient utilization of photo-generated reactive oxygen species (ROS). Organic coatings such as cyclodextrin (CD) can adsorb target contaminants and bring them close to the photocatalyst surface to enhance ROS utilization efficiency, but the coatings themselves are susceptible to ROS attack. Here, we report an ROS-resistant fluorinated CD polymer (CDP) that can both adsorb contaminants and resist degradation by ROS, yielding a more efficient material for "trap and zap" water treatment. We produced the CDP through condensation polymerization of ß-cyclodextrin and tetrafluoroterephthalonitrile, resulting in a cross-linked, covalently bound CD film that is much more stable than prior approaches involving physi-sorption. We optimized the coating thickness on TiO2 microspheres to improve the efficiency of contaminant degradation, and found that increasing the CDP content enhanced BPA adsorption but also occluded photocatalytic sites and hindered photocatalytic degradation. The optimum content of CDP was 5% by weight, and this optimal CDP-TiO2 composition had a BPA adsorption capacity of 36.9 ± 1.0 mg g-1 compared with 24.1 ± 1.1 mg g-1 for CD-coated TiO2 (CD-TiO2) and 21.9 ± 1.5 mg g-1 for bare TiO2. CDP-TiO2 exhibited minimal photoactivity loss after 1000 h of repeated use in DI water under UVA irradiation (365 nm, 3.83 × 10-6 E L-1s-1), and no release of organic carbon from the coating was detected. Photocatalytic treatment using CDP-TiO2 only showed a small decrease in BPA removal efficiency in secondary effluent after four 3-h cycles, from 80.2% to 71.7%. In contrast, CD-TiO2 and P25 removed only 29.8% and 6.2% of BPA after 4 cycles, respectively. Altogether, the CDP-TiO2 microspheres represent promising materials for potential use in photocatalytic water treatment.


Assuntos
Ciclodextrinas , Titânio , Compostos Benzidrílicos , Catálise , Microesferas , Fenóis
12.
Food Chem ; 333: 127495, 2020 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-32663747

RESUMO

Various pesticides employed in modern agriculture result in large amounts of pesticide residues in agricultural production, greatly threatening human health. Herein, we report a facile approach to fabricate a reduced graphene oxide/cyclodextrin modified glassy carbon electrode (rGO/CD/GCE) for the sensitive electrochemical sensing of imidacloprid (IDP). Three different modified electrodes using CDs (α-, ß-, γ-CD) were fabricated, and their electrochemical performance was further studied. The results demonstrate that α-CD possesses the best signal amplification for IDP. Compared with wet-chemical synthesis of rGO/CDs (W-rGO/CDs), the electrochemical synthesis of rGO/CDs (E-rGO/CDs) produced sensors that showed better performance for IDP sensing. Taking advantage of prepared E-rGO/α-CD nanocomposite, the fabricated sensor offered a low detection limit (0.02 µM) with a wider linear range (0.5-40 µM) and long-term stability. The new sensor was successfully applied for the detection of IDP in brown rice, providing a new technique for efficient and convenient monitoring of pesticide residues in food.


Assuntos
Ciclodextrinas/química , Técnicas Eletroquímicas/métodos , Grafite/química , Inseticidas/análise , Neonicotinoides/análise , Nitrocompostos/análise , Oryza/química , Carbono/química , Técnicas Eletroquímicas/instrumentação , Eletrodos , Contaminação de Alimentos/análise , Nanocompostos/química , Oxirredução , Sementes/química , Sensibilidade e Especificidade
13.
AAPS PharmSciTech ; 21(5): 183, 2020 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-32632576

RESUMO

Pulmonary drug delivery is a noninvasive therapeutic approach that offers many advantages including localized drug delivery and higher patient compliance. As with all formulations, the low aqueous solubility of a drug often poses a challenge in the formulation development. Thus, strategies such as cyclodextrin (CD) complexation have been utilized to overcome this challenge. Resveratrol (RES), a natural stilbene, has shown abundant anti-cancer properties. Due to many drawbacks of conventional chemotherapeutics, RES has been proposed as an emerging alternative with promising pharmacological effects. However, RES has limited therapeutic applications due to low water solubility, chemical stability, and bioavailability. This study was aimed at developing an inhalable therapy that would increase the aqueous solubility and stability of RES by complexation with sulfobutylether-ß-cyclodextrin (SBECD). Phase solubility profiles indicated an optimal stoichiometric inclusion complex at 1:1 (SBECD:RES) ratio for formulation considerations. Physiochemical characterizations were performed to analyze CD-RES. Stability studies at pH 7.4 and in plasma indicated significant improvement in RES stability after complexation, with a much longer half-life. The mass median aerodynamic diameter (MMAD) of CD-RES was 2.6 ± 0.7 µm and fine particle fraction (FPF) of 83.4 ± 3.0% are suitable for pulmonary delivery and efficient deposition. Lung cancer was selected as the respiratory model disease, owing to its high relevance as the major cause of cancer deaths worldwide. Cell viability studies in 5 non-small-cell-lung-cancer (NSCLC) cell lines suggest CD-RES retained significant cytotoxic potential of RES. Taken together, CD-RES proves to be a promising inhalation treatment for NSCLC.


Assuntos
Carcinoma Pulmonar de Células não Pequenas/tratamento farmacológico , Ciclodextrinas/química , Neoplasias Pulmonares/tratamento farmacológico , Resveratrol/administração & dosagem , Administração por Inalação , Disponibilidade Biológica , Portadores de Fármacos/metabolismo , Estabilidade de Medicamentos , Humanos , Pulmão/metabolismo , Solubilidade
14.
Int J Pharm ; 588: 119689, 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-32717282

RESUMO

A handful of singular structures and laws can be observed in nature. They are not always evident but, once discovered, it seems obvious how to take advantage of them. In chemistry, the discovery of reproducible patterns stimulates the imagination to develop new functional materials and technological or medical applications. Two clear examples are helical structures at different levels in biological polymers as well as ring and spherical structures of different size and composition. Rings are intuitively observed as holes able to thread elongated structures. A large number of real and fictional stories have rings as inanimate protagonists. The design, development or just discovering of a special ring has often been taken as a symbol of power or success. Several examples are the Piscatory Ring wore by the Pope of the Catholic Church, the NBA Championship ring and the One Ring created by the Dark Lord Sauron in the epic story The Lord of the Rings. In this work, we reveal the power of another extremely powerful kind of rings to fight against the pandemic which is currently affecting the whole world. These rings are as small as ~1 nm of diameter and so versatile that they are able to participate in the attack of viruses, and specifically SARS-CoV-2, in a large range of different ways. This includes the encapsulation and transport of specific drugs, as adjuvants to stabilize proteins, vaccines or other molecules involved in the infection, as cholesterol trappers to destabilize the virus envelope, as carriers for RNA therapies, as direct antiviral drugs and even to rescue blood coagulation upon heparin treatment. "One ring to rule them all. One ring to find them. One ring to bring them all and in the darkness bind them." J. R. R. Tolkien.


Assuntos
Betacoronavirus/efeitos dos fármacos , Infecções por Coronavirus/tratamento farmacológico , Ciclodextrinas/química , Ciclodextrinas/farmacologia , Nanoestruturas , Pneumonia Viral/tratamento farmacológico , Betacoronavirus/metabolismo , Coagulação Sanguínea/efeitos dos fármacos , Infecções por Coronavirus/prevenção & controle , Portadores de Fármacos/química , Portadores de Fármacos/farmacologia , Estabilidade de Medicamentos , Excipientes/química , Excipientes/farmacologia , Pandemias/prevenção & controle , Pneumonia Viral/prevenção & controle , Vacinas Virais/química , Vacinas Virais/farmacologia
15.
Zhongguo Zhong Yao Za Zhi ; 45(7): 1611-1619, 2020 Apr.
Artigo em Chinês | MEDLINE | ID: mdl-32489040

RESUMO

Ingredients with the anti-tumor property from traditional Chinese medicine/natural products have effects in treating tumor by regulating immune function, inhibiting tumor cell growth, inducing apoptosis, and reversing multidrug resistance. However, the potential of clinical application was restricted by the low hydrophilicity, stability and bioavailability and the lack of targeting. The above problems can be solved through research and development of supramolecular chemistry based on the non-covalent interactions between molecules. The supramolecular macrocyclic host molecules are characterized by a special cavity structure, low toxicity, high stability and rich derivatives spot. The anti-tumor supramolecular drug delivery system loading traditional Chinese medicine/natural products were designed to solve the above problems. In this paper, different supramolecular macrocyclic molecules, including crown ethers, cyclodextrin, calixarene, cucurbituril and two new-type supramolecular macrocyclic hosts were introduced. Their inclusion in enhancing drug solubility and stability, targeting drug delivery, synergies, combinative administration and new-type therapies in different applications, as well as such drug load modes as supramolecular polymers, indirect combination drug mode and polyrotaxanes were also reviewed in this paper, in order to provide a new idea for effective drug utilization.


Assuntos
Antineoplásicos/uso terapêutico , Produtos Biológicos/uso terapêutico , Medicina Tradicional Chinesa , Neoplasias/tratamento farmacológico , Ciclodextrinas , Sistemas de Liberação de Medicamentos , Humanos
16.
J Chromatogr A ; 1623: 461209, 2020 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-32505293

RESUMO

In most cases, determination of binding constant for analyte-cyclodextrin complexes in capillary electrophoresis is investigated by affinity capillary electrophoresis using a UV detector (ACE-UV). The limitations induced by the UV-detector include : (i) the difficulty of dealing with poor chromogenic analytes and more generally with any analyte presenting strong affinity towards the cyclodextrin (CD), i.e. for which the prerequisite to work with analyte concentration much smaller than those of the CD is difficult to fulfill (ii) the impossibility of studying non-chromogenic analyte. In this paper, two simple methodologies were developed to overcome these limitations. Regarding the analytes which present poor UV-absorbance and/or very high CD-affinity, a methodology using an algorithmic data treatment and taking into account the real analyte concentration in the capillary at the determined migration times allows to correctly estimate the binding constants, even if the experimental prerequisite ([analyte]<<[CD]) is not complied. Moreover, it is proved that classical linearization treatment by picking the migration time of the infinite diluted analytes (at the start of the peak) also provide satisfactory results. Regarding UV-transparent analyte, a competitive methodology combined with algorithmic data treatment allows the determination of their affinity towards cyclodextrins. Last, the applicability of the described competitive method is extended to the study of interaction between two neutral partners, which is another well-known limitation of ACE.


Assuntos
Ciclodextrinas/química , Eletroforese Capilar/métodos , Raios Ultravioleta , Ibuprofeno/análise , Cinética , Modelos Lineares , Termodinâmica
17.
J Chromatogr A ; 1623: 461158, 2020 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-32505274

RESUMO

In the present study, the enantioseparation of the ll- and dd-enantiomers of the dipeptides Ala-Phe, Ala-phenylglycine (Phg), Ala-homoPhe, Ala-ß-Phe, Gly-Phe and ß-Ala-Phe was studied by capillary electrophoresis in the presence of native α-, ß- and γ-cyclodextrin (CD) as well as their methyl and hydroxypropyl derivatives. Separations were performed under standardized conditions in fused-silica capillaries at pH 2.5, 3.5 and 9.5. All analyte enantiomers could be separated at acidic pH under at least one of the experimental conditions. ß-CDs proved to be more universal chiral selectors than α- and γ-CDs. Only few alkaline conditions led to an enantioseparation. For a given dipeptide, the enantiomer migration order depended on the type of CD with regard to cavity size and degree of substitution. Little effect was found with regard to the structure of the dipeptides. pH-dependent reversal of the enantiomer migration order upon increasing the pH from 2.5 to 3.5 was observed for all dipeptides with at least one of the ß-CD derivatives. In the case of ß-CD, analysis of the complexation constants and the apparent limiting mobilities of the diastereomeric peptide enantiomer-CD complexes revealed, that the enantiomer migration order of Ala-Phe, Ala-homoPhe and Ala-ß-Phe was determined by the stereoselective complexation by ß-CD at pH 2.5. At pH 3.5 opposite chiral recognition of the enantiomers by ß-CD was found for Ala-Phe and Ala-ß-Phe resulting in the reversed migration order. In contrast, chiral recognition did not change in the case of Ala-homoPhe, but reversal of the enantiomer migration order was based on the apparent mobility of the diastereomeric analyte-CD complexes.


Assuntos
Ciclodextrinas/química , Dipeptídeos/química , Eletroforese Capilar/métodos , Dipeptídeos/isolamento & purificação , Concentração de Íons de Hidrogênio , Estereoisomerismo
18.
Chemosphere ; 259: 127439, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32593825

RESUMO

The presence of emerging micropollutants and dyes in water resource has raised global concern about their intense effects to aquatic environments, ecosystem and human health in general. So far, various adsorbents have been suggested for reducing the levels of bisphenol A, methylene blue and neutral red contamination in wastewaters. However, a number of these adsorbents seemed to have low adsorptive capacities and regeneration performances. In view of these, batch experiment was performed to decontaminate these pollutants from aqueous solutions using an optimized bagasse-ß-cyclodextrin polymer (SB-ß-CD). Characterization studies of SB-ß-CD were performed using FTIR, pH point of zero charge, XRD and BET methods. Adsorption of BPA, MB and NR was favored at lower temperature (298 K) and pH of 7.0, 9.0 and 6.0, respectively. The maximum adsorption capacity of BPA, MB and NR at 298 K was 121, 963 and 685 mg g-1, respectively. Hydrogen bonding through host-guest inclusion and electrostatic interactions could respectively attribute to uptake of BPA and MB/NR onto SB-ß-CD. Adsorption kinetics of three pollutants followed pseudo-second-order model. Langmuir and Freundlich models were fitted to describe the adsorption of BPA and MB/NR, respectively. Thermodynamic parameters confirmed the occurrence of physical adsorption which is spontaneous and exothermic in nature. SB-ß-CD loaded with BPA and MB/NR was certainly reused by 75% ethanol and 0.1 mol L-1 HCl solutions, respectively. Novel SB-ß-CD showed better adsorptive capacity and regeneration performances; consequently can offers practical application for removal of BPA, MB and NR from wastewaters.


Assuntos
Compostos Benzidrílicos/química , Celulose/química , Ciclodextrinas/química , Azul de Metileno/química , Vermelho Neutro/química , Fenóis/química , Adsorção , Ecossistema , Polímeros , Poluentes Químicos da Água/análise , Purificação da Água/métodos , beta-Ciclodextrinas
19.
J Ind Microbiol Biotechnol ; 47(6-7): 449-464, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32507955

RESUMO

Cytochrome P450 enzymes catalyse reactions of significant industrial interest but are underutilised in large-scale bioprocesses due to enzyme stability, cofactor requirements and the poor aqueous solubility and microbial toxicity of typical substrates and products. In this work, we investigate the potential for preparative-scale N-demethylation of the opium poppy alkaloid noscapine by a P450BM3 (CYP102A1) mutant enzyme in a whole-cell biotransformation system. We identify and address several common limitations of whole-cell P450 biotransformations using this model N-demethylation process. Mass transfer into Escherichia coli cells was found to be a major limitation of biotransformation rate and an alternative Gram-positive expression host Bacillus megaterium provided a 25-fold improvement in specific initial rate. Two methods were investigated to address poor substrate solubility. First, a biphasic biotransformation system was developed by systematic selection of potentially biocompatible solvents and in silico solubility modelling using Hansen solubility parameters. The best-performing biphasic system gave a 2.3-fold improvement in final product titre compared to a single-phase system but had slower initial rates of biotransformation due to low substrate concentration in the aqueous phase. The second strategy aimed to improve aqueous substrate solubility using cyclodextrin and hydrophilic polymers. This approach provided a fivefold improvement in initial biotransformation rate and allowed a sixfold increase in final product concentration. Enzyme stability and cell viability were identified as the next parameters requiring optimisation to improve productivity. The approaches used are also applicable to the development of other pharmaceutical P450-mediated biotransformations.


Assuntos
Biotransformação , Sistema Enzimático do Citocromo P-450/metabolismo , Microbiologia Industrial/métodos , Noscapina/química , Bacillus megaterium/metabolismo , Catálise , Simulação por Computador , Ciclodextrinas/química , Desmetilação , Escherichia coli/metabolismo , Mutação , Compostos Orgânicos/metabolismo , Oxirredução , Polímeros/química , Solubilidade , Solventes
20.
Photochem Photobiol Sci ; 19(7): 956-965, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32519735

RESUMO

Although cyclodextrins have been extensively utilized in various branches of supramolecular chemistry due to their numerous attractive attributes, however, to achieve even advanced applications, they often need structural modification through substitutions of suitable functional groups at their rims. A systematic investigation on how the degree of substitution on the cyclodextrin rims affects the binding affinity for a given guest molecule has however rarely been reported, especially from the perspective of photophysical studies. Herein, we report the non-covalent interaction of a styryl based dye, LDS-798, with three different sulfobutylether beta cyclodextrin (SBEnßCD) derivatives bearing varying degrees of substitution (n), using ground state absorption, steady-state emission, excited-state lifetime and time-resolved fluorescence anisotropy measurements. The dye-host binding constant values indicate that the strength of the interaction between LDS-798 and SBEnßCD derivatives follows an increasing trend with an increasing number of tethered sulfobutylether substituents on the cyclodextrin rims, which is attributed to the gradual increase of the electrostatic interaction between the negatively charged sulfobutylether groups and the positively charged LDS-798. Excited state lifetime measurements and ionic strength dependent studies on the dye-SBEnßCD complexes further support the increased affinity between the dye and the host in the supramolecular complexes, with an increasing number of sulfobutylether substituents on the ßCD rims. The obtained results suggest that the molecular recognition of LDS-798 with SBEnßCD derivatives can be tuned very effectively by varying the number of sulfobutylether substituents on the cyclodextrin rims. Considering that SBE7ßCD is one of the FDA approved agents for drug formulations, the obtained results with other SBEnßCD hosts may be useful in designing selective drug delivery applications, drug formulations, and effective fluorescence on-off switches.


Assuntos
Compostos de Anilina/química , Ciclodextrinas/química , Corantes Fluorescentes/química , Compostos de Quinolínio/química , Fluorescência , Estrutura Molecular
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA