The synthesis of mono-6-thio-β-cyclodextrin capped CdTe QDs and its interaction with neutral red

This paper presents a novel method for the synthesis of CdTe quantum dots (QDs) capped with β-cyclodextrin in aqueous solution using both TGA and mono-6-thio-β-CD as stabilizers. The interaction between mono-6-thio-β-CD-CdTe QDs and neutral red (NR) was studied with fluorescence, UV-absorption and the resonance Rayleigh scattering spectrum. When its concentration was over 7.5 × 10^?6 mol/L, the neutral red began to aggregate on the surface of the mono-6-thio-β-CD-CdTe QDs, which resulted in the mono-6-thio-β-CD-CdTe QDs particle size increasing, the sharply quenched fluorescence, and the marked increase of RRS intensity.     

Electropolymerization of carboxymethyl-β-cyclodextrin based on co-electrodeposition gold nanoparticles electrode: electrocatalysis and nonenzymatic glucose sensing

A facile strategy is developed to fabricate an Au-CMCD/PCMCD electrode with high efficiency, universal, and selectivity electrocatalysis through electro-depositing carboxymethyl-β-cyclodextrins with gold nanoparticles (Au-CMCD) followed by employing electro-polymerization carboxymethyl-β-cyclodextrin (PCMCD). The chemical structure, microstructure, electrochemical activity, and electrocatalytic properties of Au-CMCD/PCMCD electrode are investigated. Due to the synergistic effect of the PCMCD and Au-CMCD layers, the as-prepared electrode exhibits an outstanding enhancement of universal electrocatalytic activity to eight kinds of crucial biomolecules and drugs, such as chloramphenicol, thymine, and glucose. Then, as a target analyte, glucose is used to investigate the sensing performances of Au-CMCD/PCMCD electrode. The amperometric detection of glucose shows a wide linear range expanding to 0.001～110 mM with a low detection limit of 0.99 μM. More importantly, the absorption effect of PCMCD is stronger to glucose than other interfering species, which is favorable to avoid the influence of possible interfering substances. Furthermore, the glucose sensors reveal good stability and repeatability.     

Biomimetic approach towards the preparation of hydroxyapatite and hydroxyapatite/chitosan/β-cyclodextrin nanoparticles: application to controlled drug release

Hydroxyapatite (HAp) and hydroxyapatite/chitosan/β-cyclodextrin (HAp/CS/β-CD) nanoparticles were successfully prepared in the modified simulated body fluid (SBF) solution at the physiological conditions (pH 7.4, temperature?=?37 °C). CS/β-CD nanoparticles acted as templates for the synthesis of HAp/CS/β-CD nanoparticles to improve the nanoarchitecture of HAp and its crystallinity.The nanoparticles were characterized by FT-IR spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD). Kneading and coprecipitation methods were applied to prepare the inclusion complex involving β-CD and p-THPP (5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin), a photosensitizer for anti-cancer drugs. The 1:1 stoichiometric ratio of the formed inclusion complex was characterized by a formation constant of 7.216?×?10² mol^?1 dm³ and analyzed by ¹H NMR, FTIR, and UV–Vis. The p-THPP delivery release in vitro was in this order: HAp/CS/β-CD?<?CS/β-CD?<?<?HAp/β-CD?<?β-CD, hinting at a better controlled release by HAp/CS/β-CD nanoparticles.     

Theoretical Studies on the Conformation of mono-6-O-p-nitrobenzoyl-β-cyclodextrin in Aqueous Solution

It is well known that a substituted cyclodextrin (CD) can often form a self-included complex, in which the substituent group is incarcerated into the CD cavity1. The phenomenon is interesting, as the self-inclusion is a nice model of protein folding2 and it has also been successfully used in the construction of various molecular devices3. Studies have showed that van der Waals force, hydrophobic effect, and electrostatic interaction are the major driving forces leading to the self-inclusion4…     

Electrochemical sensor for naphthols based on gold nanoparticles/hollow nitrogen-doped carbon microsphere hybrids functionalized with SH-β-cyclodextrin

Due to awfully harmful to the environment and human health, the qualitative and quantitative determinations of naphthols [1-naphthol (1-NAP) and 2-naphthol (2-NAP)] are of great significance and receive great attention. In this paper, gold nanoparticles (AuNPs)/hollow nitrogen-doped carbon microspheres (HNCMS) hybrids (AuNPs/HNCMS) were prepared and functionalized with thiolated-β-cyclodextrin (HS-β-CD) for the first time, and then applied successfully in sensitive and simultaneous electrochemical detection of naphthols. The results show that the oxidation peak currents of naphthols obtained on the HS-β-CD/AuNPs/HNCMS modified glassy carbon (GC) electrode are much higher than that on the AuNPs/HNCMS/GC, HNCMS/GC and bare GC electrodes. Additionally, compared with other electrochemical sensors developed previously, the proposed electrode results in improved detection limits of about four times for 1-NAP (1.0 nM) and two orders of magnitude for 2-NAP (1.2 nM). The linear response ranges of both 1-NAP and 2-NAP are 2–150 nM.     

Electrochemical biosensor for amplified detection of Pb2+ based on perfect match of reduced graphene oxide–gold nanoparticles and single-stranded DNAzyme

Analytical and Bioanalytical Chemistry - In this study, a sensitive amplification strategy for Pb2+ detection using reduced graphene oxide (RGO) and gold nanoparticles (AuNPs) was proposed....     

Effect of external factors on the curcumin/2-hydroxypropyl-β-cyclodextrin: in vitro and in vivo study

The effect of 2-hydroxypropyl-β-cyclodextrin (HPβCD) on solubility, stability and oral bioavailability of curcumin by external factors adjustment, was investigated with an aim of a simple, stable and effective formulation. The phase solubility studies showed the solubility of curcumin increased slightly with increasing pH. However, the apparent stability constant (K _S) were found to decrease with increasing pH from 1.29?×?10⁴?M^?1 at pH 3.0 to 5.22?×?10³?M^?1 at pH 7.0. The thermodynamic parameters were calculated for inclusion complex formation in aqueous solution. Interestingly, it could be concluded that the degrees of curcumin stability improved by HPβCD grew with increasing drug–cyclodextrin binding ability. Furthermore, in vivo study not only revealed that the bioavailability of curcumin after oral administration to rats was significantly improved by curcumin/HPβCD inclusion complex, but also showed more dramatic changes in the plasma concentration–time curve (1752.76–866.70?ng?mL^?1?h) and the peak plasma concentration (370.10–178.11?ng?mL^?1) of drug by formation of complexes in pH 3–7 solution.     

Electrochemical synthesis of copper nanoparticles on nafion–graphene nanoribbons and its application for the synthesis of diaryl ethers

Electrochemical synthesis of copper nanoparticles on nafion–graphene nanoribbons support for the synthesis of diaryl ethers via Ullmann type coupling is reported. The catalyst showed excellent performance for C–O cross coupling reactions under ligand free condition. The catalyst was characterized by various techniques such as SEM, TEM, XRD, EDX, BET, TGA, and UV spectrophotometry. It was recycled several times without significant loss in its catalytic activity.     

Electrochemical signal modulation in homogeneous solutions using the formation of an inclusion complex between ferrocene and β-cyclodextrin on a DNA scaffold

Two DNA conjugates modified with ferrocene and β-cyclodextrin were prepared as a pair of probes that work cooperatively for DNA sensing, in which the electrochemical signal of ferrocene on one probe was significantly "quenched" by the formation of an inclusion complex with β-cyclodextrin of the other probe on the DNA templates.     

Box�CBehnken design for studying inclusion complexes of triglycerides and ��-cyclodextrin: application to the heating protocol in molecular-dynamics simulations

In the present work, a Box?CBehnken 3⁴ design was applied to study inclusion complexes consisting of a saturated triglyceride with twelve carbons in each of the three side chains (TLG??trilaurylglyceride) and ??-cyclodextrin (??-CD) in different TLG:??-CD stoichiometries: 1:1 (TLG@1.??-CD), 1:2 (TLG@2.??-CD) and 1:3 (TLG@3.??-CD). Four intrinsic variables commonly used to set up the heating protocol in the classical molecular-dynamics (MD) simulation were monitored: the heating ramp (W), the equilibrium time (E), the time step (S) and the dielectric constant of the medium (C). Based on the obtained responses, the most appropriate heating protocol and general aspects concerning the MD simulation of the host?Cguest supramolecular systems are discussed.     

β-Tetra-brominated meso-tetraphenylporphyrin: A conformational study and application to the Mn-porphyrin catalyzed epoxidation of olefins with tetrabutylammonium oxone

X-ray crystallographic studies have shown that the free base β-tetra-brominated meso-tetraphenylporphyrin (H₂TPPBr₄) has a slightly ruffled structure with the dihedral angles of 70.1–79.2° between the phenyl groups and the porphyrin mean plane. The N(pyrrole)–N(pyrrolenine) distance is very similar to that of the standard planar porphyrins. The decreased N–H bond length of H₂TPPBr₄ with respect to that of meso-tetraphenylporphyrin (H₂TPP) seems to be due to the weaker intramolecular hydrogen bond of the former relative to the latter caused by the electron-withdrawing effects of the β-bromine substituents. The large red shifts of the Soret and Q(0,0) bands of H₂TPPBr₄ in comparison with those of H₂TPP, in spite of the nearly planar porphyrin core of the compound, also may be explained on the basis of the electron-withdrawing effects of the bromine atoms. Oxidation of styrene, the para-substituted derivatives and cyclooctene with tetrabutylammonium oxone in the presence of catalytic amounts of β-tetra-brominated meso-tetraphenylporphyrinatomanganese(III) acetate immediately gives the epoxide as the sole product. Terminal double bonds and unconjugated ones are less reactive than the conjugated double bonds and show lower selectivities. Catalytic activity of the electron-deficient Mn(H₂TPPBr₄)OAc dramatically depends on the Co-catalytic activity of the nitrogen donors as the axial base. The best axial bases are the nitrogenous donors with mixed σ- and π-donor ability to the metal centre.     

Correlation of polymer-like solution behaviors with electrospun fiber formation of hydroxypropyl-β-cyclodextrin and the adsorption study on the fiber

In this paper, the formation of hydroxypropyl-β-cyclodextrin (HPCD) nanofibers in electrospinning and the adsorption of organic molecules on the HPCD nanofiber were studied. The properties of a polymer-like solution from the highly concentrated HPCD/N,N-dimethylformamide (DMF) solution revealed HPCD supramolecular aggregates formation. The entanglements of HPCD self-organized aggregates were one of the most important factors that significantly influenced fiber formation during cyclodextrin electrospinning. The HPCD self-organized aggregates entanglement concentration (C(e)) was investigated. Analyzing the dependence of specific viscosity (η(sp)) on concentration enabled the determination of the aggregates unentangled and entangled regimes for HPCD polymer-like solutions. The dynamic light scattering (DLS) measurements and the (1)H NMR spectra of the HPCD solutions confirmed the presence of considerable HPCD self-organized aggregates in high concentrated HPCD/DMF solutions due to the intermolecular hydrogen bonding. The scanning electron microscopy (SEM) showed the electrospinning morphology transitioned from regular beads to uniform fibers with increasing the HPCD concentration. The dependence of the fiber diameter on the zero shear rate viscosity (η(0)) was determined. The static adsorption behavior of the HPCD fibers was studied. Neutral red (NR) was used as a model organic molecule. The adsorption of NR onto HPCD fibers fitted the pseudo-second-order kinetic model. The equilibrium adsorption amount of NR was 18.41 mg g(-1), and the apparent adsorption rate constant was 9.83 × 10(-4) g mg(-1) min(-1) at 25 °C.     

Electrochemical immunosensor for the carcinoembryonic antigen based on a nanocomposite consisting of reduced graphene oxide,gold nanoparticles and poly(indole-6-carboxylic acid)

We describe a label-free electrochemical immunosensor for the carcinoembryonic antigen (CEA). It is based on a nanocomposite consisting of electrochemically reduced graphene oxide, gold nanoparticles (AuNPs), and poly(indole-6-carboxylic acid). Coupled to nanoparticle-amplification techniques and modified with ionic liquid (IL), this immunoassay shows high sensitivity and good selectivity for CEA. At the best working voltage of 0.95 V (vs. Ag/AgCl), the lower detection limit is 0.02 ng·mL^?1, and the response to CEA is linear in the range from 0.02 to 90 ng·mL^?1. The method was applied to the determination of CEA in spiked serum samples and gave recoveries in the range from 98.5 % to 102 %.

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Graphical abstract A label-free electrochemical immunosensor was fabricated for the carcinoembryonic antigen (CEA) with a detection limit of 0.02 ng·mL^?1. It is based on a nanocomposite consisting of electrochemically reduced graphene oxide (erGO), gold nanoparticles (Au NP), and poly(indole-6-carboxylic acid) (PICA).

     

Synthesis and application of a novel single-isomer mono-6-deoxy-6-(3R,4R-dihydroxypyrrolidine)-β-cyclodextrin chloride as a chiral selector in capillary electrophoresis

A novel positively charged single-isomer of β-cyclodextrin, mono-6-deoxy-6-(3R,4R-dihydroxypyrrolidine)-β-CD chloride (dhypy-CDCl), was synthesized and employed as a chiral selector for the first time in capillary electrophoresis (CE) for the enantioseparation of anionic and ampholytic acids. The effects of the running buffer pH, chiral selector concentration, analyte structure and organic modifier on the enantioseparation were studied in detail. The chiral selectivity and resolution for most of the studied analytes decreased as the buffer pH increased in the range of 6.0–9.0. Increasing selector concentration led to decreased effective mobility, increased chiral selectivity and resolution for most of the studied analytes. Moreover, the hydroxyl groups located on the dihydroxypyrrolidine substituent of the dhypy-CDCl could have influence on the chiral separation.     

Theoretical study of the inclusion processes of octopamine with β-cyclodextrin: PM6, ONIOM,and NBO analysis

The inclusion process involving β-cyclodextrin with octopamine (OA) was investigated by using PM6, HF/3-21G*, B3LYP/6-31G (d), WB97XD/6-31G (d) methods and several combination of ONIOM2 hybrid calculations. The obtained results clearly indicate the orientation in which the guest molecule penetrates into the hydrophobic cavity of β-CD with the aromatic ring is energetically preferred. The structures show the presence of several intermolecular hydrogen bond interactions that were studied on the basis of natural bonding orbital (NBO) analysis, employed to quantify donor–acceptor interactions between host and guest molecules. A study of these complexes in solution was carried out using the CPCM model to examine the influence of solvation on the stability of the octopamine/β-CD complex.     

NMR and molecular fluorescence spectroscopic study of the structure and thermodynamic parameters of EGCG/β-cyclodextrin inclusion complexes with potential antioxidant activity

The present study is focused on the characterization of the interaction between (?)-epigallocatechingallate (EGCG) and cyclodextrins like β-cyclodextrin (βCD), heptakis(2,6 di-O-methyl)-β-cyclodextrin (DMβCD), and hydroxypropyl-β-cyclodextrin (HPβCD) in aqueous solution. These inclusion complexes previously demonstrated improvements in the antioxidant activity respect to free EGCG. The structural evidence obtained by 2D-ROESY and selective 1D-ROESY experiments was rationalized by autodock studies and indicates that all the complexes have similar inclusion geometries, but the difference resides on the exposition degree of the antioxidant rings of EGCG, such as pyrogallol and galloyl groups. The thermodynamic study allowed estimating that the inclusion process is entalpically driven for the derivatized cyclodextrins complexes and entropically driven for βCD complexes due to the predominance of hydrophobic interactions with EGCG.     

Effect of pH and α-, β- and γ-cyclodextrin on the spectral properties of etoricoxib: spectroscopic and molecular dynamics study

The spectral properties of etoricoxib (ETR) at pH 2.0, 6.0 and 10.0 in the presence of cyclodextrins (CDs) were investigated. The absorption spectrum of ETR in acidic medium exhibited two bands centered at 236 and 273 nm, while in basic medium it exhibited two bands centered at 236 and 285 nm. No change in the spectrum was observed in the presence of CDs. The fluorescence emission spectra of ETR in acidic and basic media exhibited one band at 380 nm and another one at 484 nm. The emission band at 484 nm was enhanced when ETR was complexed with β-CD and γ-CD at pH 2.0, 6.0 and 10.0, while the band at 380 nm was enhanced selectively when ETR was complexed with α-CD at pH 2.0. Molecular dynamics simulations computations revealed that at pH 2.0, the sulfonyl moiety of H₂ETR²⁺ is preferentially included within the α-CD cavity, which is believed to cause the enhancement of the band at 380 nm. Moreover, at pH 6.0 and 10.0, the enhancement of the band at 484 nm was related to the inclusion of the chloropyridinyl and methylpyridinyl groups of the bipyridine moiety of HETR⁺ and ETR within β-CD and γ-CD cavities. Benesi–Hildebrand analysis showed that the ETR/β-CD complex adopts a 1:1 stoichiometry with association constant of K ₁₁?=?64.8 at pH 2.0, K ₁₁?=?105.4 at pH 6.0 and K ₁₁?=?520.5 at pH 10.0.