Addition Of Γ-cyclodextrin Research Articles

Tuning composite nanofiltration membranes with γ-cyclodextrin for improved Mg2+/Li+ selectivity

As a new frontier method, nanofiltration (NF) membranes still face challenges in achieving a balance between selectivity and permeability, especially in the field of extracting lithium from brines. In the study, we addressed this issue by incorporating γ-cyclodextrins (CDs) with amphipathic cavities onto the polyamide chains using interfacial polymerization (IP) reaction, employing polyethyleneimine (PEI) and trimesoyl chloride (TMC). The addition of γ-cyclodextrin (γ-CD) enhances the hydrophilicity and water flux of NF membrane on account of its remarkable structural properties. The outer surface of γ-CD exhibits hydrophilic characteristics, while its inner cavity possesses hydrophobic properties. Benefiting from its water-attracting surface and water-repellent cavity, γ-CD could enhance the overall water affinity and water permeability of the NF membrane. Furthermore, the dimensions of the γ-CD cavity allowed for effective screening Mg2+ / Li+ to a certain extent. Notably, γ-CD exhibited a superior capability to accommodate and encapsulate Mg2+ ions, indicating a higher binding affinity compared to Li+. Thus, Li+ was easier to pass through the NF membrane grafted by γ-CDs than Mg2+. The optimized NF membrane demonstrated an enhanced magnesium-lithium separation coefficient of 23.61, 237 % better than that of the TFC-control membrane. This work introduces a novel approach for designing and constructing of high-permselectivity NF membranes for Mg2+ / Li+ separation utilization.

A Sensitive Fluorescent Assay for Tetracycline Detection Based on Triple-helix Aptamer Probe and Cyclodextrin Supramolecular Inclusion.

Herein, an effective pyrene excimer signaled fluorescent biosensor for the determination of tetracycline based on triple-helix aptamer probe (TAP) and supramolecular inclusion of cyclodextrin was reported. The TAP was devised containing an aptamer loop, two DNA segment stems and a triplex-forming oligonucleotide (signal probe) labeled with pyrenes at 5' and 3' ends. The presence of target could result in its binding towards aptamer with a mighty affinity, leading to a conformation change of the TAP and whereupon the release of the signal probe. This liberty of signal probe enabled the formation of pyrene excimer, generating fluorescence signals. Further, signal amplification was fulfilled through the addition of γ-cyclodextrin which could interact with pyrene dimer, thus leading to an enhanced "on-state" of the sensing ensemble. In contrast, when the target was absent, the sensing ensemble remained "off-state" because of the long distance between two pyrene molecules. When the conditions were properly optimized, the increasing signal kept a linear dependence on target concentrations ranging from 5.0nM to 100nM, and the detection limit reached as low as 1.6nM. In this way, a newly-constructed, simple, and economically affordable protocol enjoys desirable efficiency, sensitivity, specificity in biosensing. Also, its universality as another attractive behalf in assaying diverse targets was envisioned with only the need of matched aptamer replacement.

Investigation on the interaction between γ-cyclodextrin and α-amylase

A growing interest has been shown regarding the impact of α-amylase on the quality of fermented foods. Therefore, the interaction between γ-cyclodextrin and α-amylase was investigated in this article. The results showed that γ-cyclodextrin had an inhibitory effect on the activity of α-amylase under certain conditions, obtaining the strongest inhibitory effect when the concentration of γ-cyclodextrin was 10 mmol/L, the reaction temperature was 45 °C, pH = 5.9 and reaction time of 120 min. The results also showed important changes in the secondary structure of α-amylase induced by γ-cyclodextrin, including the transformation of α-helix, β-fold and random coil. Moreover, the addition of γ-cyclodextrin could induce the change of endogenous fluorescence intensity by changing the microenvironment of the α-amylase. According to the results of NMR, a part of the α-amylase molecule enters the cavity of the γ-cyclodextrin, and the other part forms a hydrogen bond with the outer cavity, forming a complex. The experimental results provide references for the application of γ-cyclodextrin and α-amylase.

Enantioseparation and impurity determination of ambrisentan using cyclodextrin-modified micellar electrokinetic chromatography: Visualizing the design space within quality by design framework

A capillary electrophoresis method for the simultaneous determination of the enantiomeric purity and of impurities of the chiral drug ambrisentan has been developed following the Quality by Design principles. The selected separation system consisted of a micellar pseudostationary phase made by sodium dodecyl sulphate with the addition of γ-cyclodextrin. The effects of critical process parameters (capillary length, temperature, voltage, borate concentration, pH, sodium dodecyl sulphate concentration, γ-cyclodextrin concentration) on enantioresolution of ambrisentan and analysis time were extensively investigated by multivariate strategies involving a screening phase and Response Surface Methodology. The Design Space was defined with a desired probability level π≥90%, and the working conditions, with the limits of the Design Space, corresponded to the following: capillary length, 64.5cm; temperature, 22°C; voltage, 30kV (26–30kV); background electrolyte, 100mM borate buffer pH 9.20 (8.80–9.60), 100mM sodium dodecyl sulphate, 50mM (43–50mM) γ-cyclodextrin. A Plackett-Burman design was applied for robustness testing, and a method control strategy was established. The method was fully validated according to the International Conference on Harmonisation guidelines and was applied to ambrisentan coated tablets.

Self-assembly behavior of amphiphilic C₆₀-end-capped poly(vinyl ether)s in water and dissociation of the aggregates by the complexing of the C₆₀ moieties with externally added γ-cyclodextrins.

C60-end-capped polymers consisting of an amphiphilic poly(2-methoxyethyl vinyl ether) (PMOVE) main chain were synthesized by living cationic polymerization using a C60-functionalized initiator (C60VE-TFA) in the presence of EtAlCl2 as an activator and dioxane as an added base. The obtained polymers (C60-PMOVE) dissolved in a wide range of solvents including water and exhibited solvatochromism depending on the polarity of the media employed. This phenomenon was attributed to self-assembly in polar media due to hydrophobicity of the C60 moieties at the terminus of the amphiphilic polymer chain. Furthermore, the addition of γ-cyclodextrin (γ-CD), a strong host molecule for fullerenes, to the self-assembled system brought about the dissociation of the aggregates into molecularly dispersed free polymer chains. Titration of the aqueous solution of the self-assembly of C60-PMOVE with γ-CD indicated the possible formation of inclusion complexes of C60-PMOVE and γ-CD, and this binding process occurs in a positive cooperative manner.

Aggregation property of glycyrrhizic acid and its interaction with cyclodextrins analyzed by dynamic light scattering, isothermal titration calorimetry, and NMR

The structural properties of glycyrrhizic acid, a sweet-tasting constituent of Glycyrrhiza glabra, and its interaction with cyclodextrins were analyzed using dynamic light scattering, isothermal titration calorimetry, and NMR. The dynamic light scattering and NMR studies showed that glycyrrhizic acid forms a water-soluble aggregate that disperses upon the addition of γ-cyclodextrin. The high sweetness of glycyrrhizic acid can be closely correlated with this aggregation, because the multimers of glycyrrhizic acid can simultaneously bind to the sweet taste receptors on the human tongue. The isothermal titration calorimetry experiments demonstrated that γ-cyclodextrin binds to glycyrrhizic acid more strongly than β-cyclodextrin, however, both reactions are accompanied by a favorable change in binding entropy. Considering the large negative change in heat capacity that is observed during the binding of γ-cyclodextrin, the main driving force for the binding is hydrophobic interactions with dehydration, which is typical for inclusion complex. NMR experiments showed that γ-cyclodextrin interacts with the central part of the aglycone moiety, not the glucuronic acid moieties, resulting in high binding affinity. It should also be noted that the two distinct complexes of glycyrrhizic acid with γ-cyclodextrin would exist in aqueous solution.

Self-assembly of zinc chlorophyll derivatives possessing a pyrenyl group at the 17-propionate residue and effects of additional γ-cyclodextrins on their optical properties

Two kinds of zinc 31-hydroxy-131-oxo-chlorins 1 and 2 possessing a pyrenyl group at the 17-propionate residue, of which the linker length between the chlorin and the pyrene moieties was varied, were synthesised from naturally occurring chlorophyll a, and were self-assembled in an aqueous solution. Both zinc chlorins 1 and 2 exhibited Qy absorption bands around 720 nm accompanying circular dichroism signals in the Qy region, indicating that these zinc chlorins could form self-aggregates like chlorosomes of green photosynthetic bacteria. Addition of γ-cyclodextrin into an aqueous solution containing the self-aggregates of zinc chlorin 1 esterified with 1-pyrenylmethanol induced the appearance of excimer emission of the pyrene moieties around 480 nm as well as increased the fluorescence intensities of the pyrene monomers at 378 and 396 nm, while only an increase in fluorescence from the monomeric pyrene moiety was observed in the case of 2 esterified with 4-(1-pyrenyl)butanol. Exogenous γ-cyclodextrin unchanged the spectral features derived from the chlorin moieties of 1 and 2 in the aqueous phase. These suggest that the encapsulation of the pyrenyl groups in the zinc chlorins unchanged their assembling states under the present conditions.

Chiral switch of enzymatic ketone reduction by addition of γ-cyclodextrin

We report a chiral switch in the configuration of 1-(p-methoxyphenyl)-propan-2-ol, synthesized in aqueous media by ketoreductase in the presence of high concentration of γ-CD. NMR, ECD and fluorescence spectrometry were used in the effort to explain this unexpected effect. A comparison has been made between the catalytic activity of the enzyme and α-helix content in the conformation and it has been observed that enzyme is most active at the maximum α-helix content. The β-sheet content and random coil conformation in the enzyme were found to be dependent on cyclodextrin concentration.

Pattern recognition based identification of nitrated explosives

We report an effective approach for the identification of nitro explosives by the reaction of an electron-acceptor with an electron-donor with and without the addition of γ-cyclodextrin (γ-CD). A charge-transfer complex was prepared in acetonitrile by the reaction of the nitro explosive TNT as an electron acceptor with the donor N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD). The complex TNT/TMPD converts gradually into TNT˙−/TMPD˙+ in water with 5% acetonitrile by volume. The inclusion behavior of TNT˙−/TMPD˙+ with γ-CD was studied by UV-visible spectroscopy. The effect of α- and β-CD with TNT˙−/TMPD˙+ was also studied. Similar experiments were also carried out for RDX˙−/TMPD˙+ with γ-CD. The binding of TNT˙−/TMPD˙+ and RDX˙−/TMPD˙+ with γ-CD were compared for the application of the complexes in a sensor array. Subsequently, the visible absorption spectra of nitro explosives as analytes, such as TNT, RDX, HMX and Tetryl with TMPD in the presence and absence of γ-CD, were measured with time. We worked with the same analytes with a second electron donor tetrakis(dimethylamino)ethylene (TDAE) using 96-well plate experiments. Pattern recognition analysis was applied to analyze the data collected and it showed successful discrimination of the nitro explosives. This work represents the simplest colorimetric chemical sensor technique to be used in monitoring the range of common nitro explosives.

Air Travel-Related Venous Thromboembolism

A capillary electrophoresis method for the simultaneous determination of the enantiomeric purity and of impurities of the chiral drug ambrisentan has been developed following the Quality by Design principles. The selected separation system consisted of a micellar pseudostationary phase made by sodium dodecyl sulphate with the addition of γ-cyclodextrin. The effects of critical process parameters (capillary length, temperature, voltage, borate concentration, pH, sodium dodecyl sulphate concentration, γ-cyclodextrin concentration) on enantioresolution of ambrisentan and analysis time were extensively investigated by multivariate strategies involving a screening phase and Response Surface Methodology. The Design Space was defined with a desired probability level π ≥ 90%, and the working conditions, with the limits of the Design Space, corresponded to the following: capillary length, 64.5 cm; temperature, 22 °C; voltage, 30 kV (26–30 kV); background electrolyte, 100 mM borate buffer pH 9.20 (8.80–9.60), 100 mM sodium dodecyl sulphate, 50 mM (43–50 mM) γ-cyclodextrin. A Plackett-Burman design was applied for robustness testing, and a method control strategy was established. The method was fully validated according to the International Conference on Harmonisation guidelines and was applied to ambrisentan coated tablets.

DEVELOPMENT OF A CYCLODEXTRIN MODIFIED MICELLAR ELECTROKINETIC CHROMATOGRAPHIC METHOD FOR THE SEPARATION OF β-METHYL ADC-13-ENOLPHOSPHATE DIPHENYL ESTER AND ITS α-METHYL DIASTEREOMER

ABSTRACT A cyclodextrin modified micellar electrokinetic chromatographic method for the separation of β-methyl ADC-13 enolphosphate diphenyl ester from its α-methyl diastereomer was developed. The influence of the organic modifier, sodium dodecyl sulfate (SDS), and γ-cyclodextrin concentration in the background electrolyte on the relative contributions of the efficiency, selectivity, and capacity function to the resolution between the diastereomers were studied. The results of these studies showed that, although, the resolution could be increased by varying the organic modifier and SDS concentrations, sufficient resolution for accurate determination of low levels of α-enol phosphate in the presence of higher levels of β-enol phosphate was not obtained. However, addition of γ-cyclodextrin to the background electrolyte (BGE) resulted in an almost two-fold increase in the resolution obtained. Optimized conditions allowed the detection of α-enol phosphate at levels as low as 0.1 area-% vs. β-enol phosphate. The method was validated in terms of sensitivity, linearity, and precision.

Photochromism of dithienylethene-bis(trimethylammonium) iodide in cyclodextrin cavities

On the addition of β-cyclodextrin, the proportion of the photoactive anti-parallel conformation of photochromic 2,2′-dimethyl-3,3′-(perfluorocyclopentene-1,2-diyl)bis(benzo[b]thiophen-6-yltrimethylammonium) iodide (1a) increased, and the cyclization quantum yield was found to increase. On the other hand, the proportion of the photoinactive conformation increased on the addition of γ-cyclodextrin and the quantum yield decreased. The structures of the complexes were estimated from NOESY spectra.

Capillary electrophoresis of tetrahydroberberine alkaloids: chiral separation by cyclodextrin-modified micellar electrokinetic chromatography

A micellar electrokinetic capillary chromatographic method for the separation of tetrahydroberberine alkaloids was established. An electrolyte solution of 0.02 M sodium dodecyl sulphate (SDS) in 0.03 M borate buffer (pH 9) containing 10% acetonitrile, and an applied voltage of 20 kV, were found to be the appropriate conditions for this separation. Enantiomers of the tetrahydroberberine alkaloids were separated by the addition of γ-cyclodextrin (γ-CD) to the SDS micelle solution with a maximum analysis time of 11 min. The resolution was optimized by changing the concentration of γ-CD. The method described is simple, rapid and reproducible. Copyright © 1999 John Wiley & Sons, Ltd.

Separation of selected PAHs by using high performance capillary electrophoresis with modifiers

The effect of varying SDS concentration in a micellar electrokinetic capillary chromatographic system (MECC) is investigated. In addition, the introduction of γ-cyclodextrin as modifier to the electrophoretic medium, containing SDS and a phosphate-borate buffer, is shown to give satisfactory separation of the seven selected PAHs. The separation efficiency is increased with the addition of γ-cyclodextrin.

Electrochromic properties of alkylviologen-cyclodextrin systems

Electrochromic properties of methyl, ethyl, n-hexyl and n-heptyl viologens, and α-, β-, γ-cyclodextrin systems were studied using cyclic voltammetry and absorption spectroscopy. Colourations of red-violet (λ max = 530 or 560 nm), blue (λ max = 600nm) and light purple (λ max = 560 and 600 nm) could be obtained by changing the length of the alkyl chain of viologens or the radius of cyclodextrin. The intermolecular interaction between viologen radicals is weakened when the radicals form inclusion complexes so the blue colour inherent in the monomer of viologen radical appears. The red-violet colour is ascribed to the dimer of the reduced viologen. With the addition of γ-cyclodextrin, viologens were found to be included as dimer. The light purple colour is ascribed to the mixed colour of the monomer and the dimer. Furthermore, since the ratio of monomer and dimer depends upon the concentration of cyclodextrin, any colour between the red-violet of the dimer and the blue of the monomer can be obtained by adjusting the concentration of cyclodextrin. The redox reaction of an inclusion complex was found to depend upon the length of the alkyl viologen and the size of the cavity in cyclodextrin.

γ-CYCLODEXTRIN-ENHANCED EXCIMER FLUORESCENCE OF PYRENE AND EFFECT OF n-BUTYL ALCOHOL

Abstract The fluorescence of pyrene has been measured in aqueous solutions in the presence of γ-cyclodextrin. The excimer emission of pyrene was enhanced upon addition of γ-cyclodextrin, indicating the formation of the 2:1 complex of pyrene with γ-cyclodextrin which degraded upon addition of n-butyl alcohol to yield the more stable three-component complex of pyrene, n-butyl alcohol, and γ-cyclodextrin.

Fluorescence enhancement of α-naphthyloxyacetic acid in the cavity of γ-cyclodextrin, assisted by a space-regulating molecule

The fluorescence intensity of α-naphthyloxy-acetic acid in aqueous solution is slightly enhanced by addition of γ-cyclodextrin (γ-CD), but markedly enhanced in the presence of both γ-CD and cyclohexanol, showing the role of cyclohexanol as a space-regulator which narrows the cavity of γ-CD to allow the inclusion of the fluorophore.