A molecular template designed by the modification of a helix-forming β-1,3-glucan polysaccharide to fabricate one-dimensional nanostructures

We report the development of a new templating molecule designed by the modification of a helix-forming β-1,3-glucan polysaccharide to the cationic semiartificial one and its application to the fabrication of one-dimensional (1D) gold nanostructures by simple photoirradiation. Transmission electron microscopy observation showed that Au(III) ions are primarily reduced to gold nanoparticles self-assembling into the 1D array with the aid of the cationic β-1,3-glucan polysaccharide, which gradually fuse into the 1D gold nanostructure with the tapelike structure. The gold nanotape structure could not be created by neutral β-1,3-glucan polysaccharides or random coil synthetic cationic polymers. These findings consistently support the view that Au(III) ions are reduced by unmodified OH groups to gold nanoparticles under the photoirradiation, which are wrapped in the helical structure of the cationic β-1,3-glucan polysaccharide and eventually fuse into gold nanotapes. One may regard, therefore, that this cationic β-1,3-glucan polysaccharide can act as an "all-in-one" template playing three roles of reduction, 1D arrangement, and fusion of gold nanoparticles. In addition, we found an interesting phenomenon that the obtained gold nanotapes coated with cationic β-1,3-glucan polysaccharides show unique surface-enhanced Raman scattering for anionic porphyrines organized on the surface of gold nanotapes through the electrostatic interaction.     

A novel polycondensation method for the synthesis of a two-faced β-1,4-glucan

Abstract  

The stereospecific synthesis of a chitosan derivative repeating 2-azido-3,6-di-O-benzyl-2-deoxy-β-d-glucopyranosyl-(1 → 4)-3,6-di-O-benzyl-2-deoxy-2-phthalimido-d-glucopyranose, which has two distinguishing faces, was achieved by polycondensation of the sole starting disaccharide, trichloroacetimidoyl 2-azido-3,6-di-O-benzyl-2-deoxy-β-d-glucopyranosyl-(1 → 4)-3,6-di-O-benzyl-2-deoxy-2-phthalimido-d-glucopyranoside in a short and efficient way.     

Liposome solubilization induced by complexation with dimeric β-cyclodextrin

Dimeric β-cyclodextrins (β-CD) were prepared from the reaction of native β-CD with epichlorohydrin under basic conditions, and the effects on the diacetylene (DA) and polydiacetylene (PDA) liposomes have been investigated. Vesicular DA was solubilized in the presence of dimeric β-CD with the consequent inhibition of polymerization. The result is attributed to the formation of a complex between dimeric β-CD and DA liposomes, and it is clearly differentiated from that of monomeric β-CD. Furthermore, the ordered supramolecular structure of PDA was perturbed by the dimeric β-CD, which was detected from the visible color change. Finally, the morphological characteristics and size of PDA in the absence and presence of dimeric β-CD were examined using transmission electron microscopy and dynamic light scattering The results show fused structure of size more than 200 nm along with the deformation of the vesicles, and they represent a novel phenomenon of liposome structure induced by complexation with dimeric β-CD. The evaluated physicochemical characteristics can be applied to the development of carbohydrate-based detergents.     

Synthesis of a β-glucan polysaccharide analogue by an iterative copper-catalyzed azide-acetylene coupling reaction

A triazole-linked β-glucan analogue was prepared using a copper-catalyzed azide-acetylene coupling reaction. The alkynylsilyl moiety was inactive under the conditions of the copper-catalyzed azide-acetylene coupling reaction and was readily converted into a terminal acetylene group by treatment with tetrabutylammonium fluoride. Using the method, we successfully synthesized a β-glucan analogue containing three laminaripentaose units.     

Zaleplon co-ground complexes with natural and polymeric β-cyclodextrin

In this study, we compared the suitability of parent β-cyclodextrin (βCD) and its water soluble polymeric derivative (PβCD) as co-grinding additives aimed to enhance the solubility of zaleplon (ZAL), a hypnotic drug. Equimolar drug/carrier mixtures were co-ground in a high-energy micromill over different time intervals. Data obtained by differential scanning calorimetry, X-ray powder diffractometry and scanning electron microscopy showed a higher affinity of ZAL for the solid state interaction with PβCD, resulting in powders with lower relative drug crystallinity (RDC) compared to that obtained with natural βCD (RDC = 51.10 and 12.5 % for complexes with βCD and PβCD co-grounded for 90 min, respectively). On the other hand, grinding the drug alone did not result in a significant reduction of the drug crystallinity (RDC = 99.87 % for the sample ground for 90 min). Although ¹H-NMR spectroscopy confirmed that both co-ground products were readily converted into inclusion complexes upon dissolution in water, they presented different dissolution properties. The dissolution velocity of co-ground complex with PβCD was 25 % faster compared to that prepared with the parent βCD and almost double compared to that of the drug alone, irrespective of the pH value of the dissolution media. This clearly demonstrated the suitability of co-ground ZAL/PβCD complex in the development of an immediate release oral formulation of ZAL.     

A joint QM/MD study on α-, β- and γ-cyclodextrins in selective complexation with cathinone

In this article, density functional theory (DFT) calculations and 30 ns molecular dynamic (MD) simulations were performed to investigate the ability of α-, β- and γ-cyclodextrins (CDs) to form selective complexes with cathinone. DFT calculations in the gas phase, water, chloroform and methanol reveal that the solvents, reduce the stability of the complexes. Optimized structures confirm that α-CD cannot encapsulate cathinone, completely, while other CDs showed an opposite behavior. DFT calculations indicate that cathinone has the most stable complex with γ-CD in comparison to the α- and β-CDs. Natural bond orbital and quantum theory of atoms in molecules analyses reveal that the electrostatic interactions between cathinone and CDs are the driving force of the complex formation. MD simulations confirm that different solvents play an important role in the stability of the cathinone complexes and the obtained MD results are in good agreement with the DFT calculations.     

Improvement of opipramol base solubility by complexation with β-cyclodextrin

Opipramol (OPI), a tricyclic antidepressant and anxiolytic compound, is administered orally in the form of a dihydrochloride. Salt form of the drug has a higher solubility in water and hence bioavailability and stability. A similar effect can be achieved by closing the hydrophobic part of the drug molecule in the cyclodextrin cavity. The paper presents opipramol inclusion complexes with beta-cyclodextrin (β-CD) in 1:1 molar ratio. Studies on the formation of inclusion complexes were carried out both in solution and in the solid state. The formation and physicochemical characterisation of the complexes were determined by UV spectroscopic measurement (UV–vis), Fourier Transform Infrared (FTIR) Spectroscopy, ¹H Nuclear Magnetic Resonance (¹H NMR, 2D NOESY NMR), thermoanalytical methods (TGA – Termogravimetric analysis, DSC – differential scanning calorimetry), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The phase solubility profile with β-CD was classified as the A_N- type, indicating the formation of the inclusion complex with a drug.     

Inclusion complexation of 4,4′-dihydroxybenzophenone and 4-hydroxybenzophenone with α- and β-cyclodextrins

The inclusion complexation behaviours of 4,4′-dihydroxybenzophenone (DHBP) and 4-hydroxybenzophenone (HBP) with α-cyclodextrin (α-CD) and β-cyclodextrin (β-CD) were investigated using UV–visible fluorescence, time-resolved fluorescence, molecular modelling, scanning electron microscopy (SEM), FTIR, differential scanning calorimeter, X-ray diffraction, ¹H NMR and molecular modelling techniques. In both molecules, biexponential decay was observed in water, whereas triexponential decay was observed in the CD medium. The DSC thermogram of the DHBP/α-CD and DHBP/β-CD inclusion complex nanomaterials shows the endothermic peak at 60.8, 101.9, 119.6 and 112.8°C. The upfield chemical shift observed for HBP protons reveal that the phenyl ring (without hydroxyl substitution) entered the CD cavity and the hydroxyl group of HBP is exposed outside the CD cavity. The SEM image of DHBP appears as needle-shaped crystals on the micrometre scale, whereas the irregular bar shape was observed for HBP. Transmission electron microscopy images show that both guest molecules formed nano vesicles with α-CD and formed nano rods with β-CD.     

A study on the inclusion complexation of 3,4,5-trihydroxybenzoic acid with β-cyclodextrin at different pH

Effect of β-cyclodextrin (β-CD) on the absorption and fluorescence spectra of 3,4,5-trihydroxybenzoic acid (THB) have been studied buffer solutions of different pHs (pH ~1, pH ~7 and pH ~10). The study reveals that in all the above pHs THB forms 1:1 inclusion complex. The hydroxyl groups are present in the interior part of the β-CD cavity and carboxyl group is present in the hydrophilic part of the β-CD cavity. Dual luminescence is observed at pH ~1 and pH ~7 solutions which shows that intramolecular charge transfer present at these pH. The broad spectral maximum at pH ~10 indicates that intramolecular proton transfer is present in THB.     

Effect of preparation method on complexation of Cefdinir with β-cyclodextrin

The inclusion behaviour of β-cyclodextrin (βCD) was studied toward Cefdinir (CEF) in order to enhance the solubility and dissolution rate, following cyclodextrin complexation. Drug cyclodextrin solid systems were prepared by conventional methods of kneading (KN), co-evaporation (CE), spray drying (SD) and with a novel approach of microwave irradiation (MWI). The formation of inclusion complexes with βCD in the solid state, were confirmed by Differential scanning calorimetry (DSC), Fourier Transform Infrared spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) studies, and comparative studies on the in vitro dissolution of CEF were carried out. Characterization of binary system by DSC, FTIR and SEM indicated that SD and MWI method resulted in formation of true complexes. Binary systems showed significant increase in dissolution rate as compared to plain drug. Amongst the binary systems MWI products were prepared in least time with better yield and highest dissolution rate.     

Natural effectors of β-1,3-glucanases activator of the β-1,3-glucanases of marine mollusks

The capacity of certain extracts of marine invertebrates of the Indian and Pacific Oceans for activating -1,3-glucanases has been detected. It has been shown that an individual compound — swinholide A from the spongeTheonella swinhoei — specifically activates -1,3-glucanases of bivlve mollusks. In the presence of swinholide A both the hydrolysis of laminarin by -1,3-glucanase L-IV fromSpisula sachalinensis and the transglycosylation reaction are accelerated.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, Nos. 3,4, pp. 316–320, May–August, 1992.     

Release control of fragrances by complexation with β-cyclodextrin and its derivatives

The release control of fragrances, benzyl acetate (BA), citral (CR), linalool (LL), citronellol (CL) and linalyl acetate (LA), was conducted using β-cyclodextrin (β-CyD), 2-hydroxypropyl-β-CyD (HP-β-CyD) and 2,6-di-O-methyl β-CyD (DM-β-CyD). The release rate of the fragrances from 30% ethanol/water solution was significantly suppressed by the complexation with these CyDs, and the suppressing effect increased in the order of β-CyD?<?HP-β-CyD?<?DM-β-CyD. The concentration-dependent change of the release rate was quantitatively analyzed to obtain the stability constant (Kc) of the fragrance-CyD complexes. These Kc values were in good agreement with those determined by the solubility method. The results suggest that the release of fragrances can be prolonged by the complexation with β-CyDs and their effects can be controlled by choosing appropriate CyD derivatives with higher Kc values and by setting proper concentrations of the host molecules.     

A quartz crystal microbalance study of β-cyclodextrin self assembly on gold and complexation of immobilized β-cyclodextrin with adamantane derivatives

Quartz crystal microbalance (QCM) was used to study the self-assembly of per-6-thio-β-cyclodextrin (t₇-βCD) on gold surfaces, and the subsequent inclusion interactions of immobilized βCD with adamantane-poly(ethylene glycol) (5,000 MW, AD-PEG), 1-adamantanecarboxylic acid (AD-C) and 1-adamantylamine (AD-A). From a 50 μM solution of t₇-βCD in 60:40 DMSO:H₂O, a t₇-βCD layer was formed on gold with surface density of 71.7 ± 2.7 pmol/cm², corresponding to 80 ± 3% of close-packed monolayer coverage. Gold sensors with immobilized t₇-βCD were then exposed alternately to six different concentrations of AD-PEG, 500 μM AD-C or 500 μM AD-A aqueous solutions for association, and water for dissociation. Association of AD-PEG conformed to a Langmuir isotherm, with a best fit equilibrium constant K = 125,000 ± 18,000 M⁻¹. For AD-C and AD-A, association (k _a ) and dissociation (k _d ) rate constants were extracted from kinetic profiles by fitting to the Langmuir model, and equilibrium constants were calculated. The parameters for AD-C were found to be: k _a = 100 ± 5 M⁻¹ s⁻¹, k _d = 110 (±18) × 10⁻⁴ s⁻¹, and K = 9,400 ± 1,700 M⁻¹. For AD-A, k _a = 58 ± 6 M⁻¹ s⁻¹, k _d = 154 (±7) × 10⁻⁴ s⁻¹, and K = 3,800 ± 400 M⁻¹. The results demonstrate the utility of QCM as a tool for studying small molecule surface adsorption and guest–host interactions on surfaces. More specifically, the kinetic and thermodynamic data of AD-C, AD-A, and AD-PEG inclusion with immobilized t₇-βCD form a basis for further surface association studies of AD-X conjugates to advance surface sensory and coupling applications.     

Solubility enhancement and QSPR correlations for polycyclic aromatic hydrocarbons complexation with α, β, and γ cyclodextrins

Through batch equilibrium experiments, hydroxypropyl substituted α, β, and γ cyclodextrin (CDs) were shown to greatly increase the apparent solubility of eight common polycyclic aromatic hydrocarbons (PAHs) in aqueous solutions. Equations based on the volume fraction of solution composed of water and CDs have been developed to determine guest phase distribution. Based on these equations, the results of this and similar studies for CD showed that a log–log relationship exists between the fraction of CD occupied with a guest organic compound and the aqueous solubility of those guests (rsq 0.980). Analysis of potential quantitative structure property relationship (QSPR) found strong correlations between structural properties of the guests (e.g. aqueous solubility, octanol/water partitioning coefficient, molar volume, molecular surface area, and polarizability) and water/CD partitioning coefficients, phase distribution of the PAH between water and CD phases, and the fraction of CD molecules occupied with a guest PAH. Noteworthy among these, is the inverse relationship between the log of the fraction of CD molecules occupied under saturated conditions and the ratio of the molar volume of the PAH to the volume of the CD cavities (rsq for α, β, and γ: 0.887–0.892). Comparisons of the three CDs shows that while the size of the guest compound reduces its propensity to enter into the CD cavity, the effect of the guest size is lessened as the width of the CD ring increases. Development of these QSPR correlations provides a means to predict and evaluate guest/CD interactions for homologous series of compounds.     

The reaction of trifluoromethanesulfenyl chloride with enamines of β-keto carboxylic acid anilides

1-Morpholino-cyclopenten-2-carboxylic acid anilides react with CF₃SCl in molar ratio 1:2 to give products of the displacement of two hydrogen atoms at C-2 and C-5. The analogous reaction with enamines of cyclohexanono- and cycloheptanono- 2-carboxylic acid anilides and benzoylacetanilides proceeds in 1:1 molar ratios affording enamines and keto compounds.     

Study of complexation of gliclazide with β-cyclodextrin in solution by nmr techniques

The study of complexation between GL and -CD in liquid medium has been carried out by phase-solubility,¹H and¹³C NMR studies. A formation complex is observed from the phase solubility diagram, being the average association constant of 1094 M^–1, The NMR studies revealed the preferent complexation of the aliphatic moiety of GL. The aromatic moiety is also entrapped, but in minor extent, by the CD molecules.     

An investigation of the complexation of a TTF derivative with α-, β- and γ-cyclodextrins in aqueous media

This Letter, describes the complexation of α-, β- and γ-cyclodextrins (1-3) with TTF derivative 4 in water. In particular, we show using ¹H, ¹³C NMR, UV-vis spectroscopy and isothermal titration calorimetry that β-cyclodextrin 2 forms an effective complex with 4. Complex 2·4 can be conveniently disassembled upon the addition of 1-adamantanol.     

A comparative study of complexation methods for cefdinir-hydroxypropyl-��-cyclodextrin system

The aim of this study was to investigate the effect of hydroxypropyl-??-cyclodextrin (HP??CD) on the solubility and dissolution rate of Cefdinir (CEF). The methods that were employed to prepare CEF?CHP??CD complexes were Kneading (KN), Co-evaporation (CE), Spray drying (SD) and a novel approach of Microwave irradiation (MWI). The formation of inclusion complexes with HP??CD in the solid state, were characterized by Differential Scanning Calorimetry (DSC), Fourier Transformation Infrared spectroscopy (FTIR), Proton Nuclear Magnetic Resonance Spectroscopy (NMR), X Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) studies, and comparative studies on the in vitro dissolution of CEF were carried out. Phase solubility profile with HP??CD was classified as A_L type, indicating the formation of 1:1 stoichiometric inclusion complexes. Characterization of binary systems by DSC, FTIR, NMR, XRD and SEM indicated that SD and MWI method resulted in formation of true complexes. Binary systems showed significant increase in dissolution rate as compared to plain drug. Amongst the various binary systems, MWI products were prepared in least time with better yield and highest dissolution rate.     

Inclusion complexation of chloropropham with β-cyclodextrin: preparation, characterization and molecular modeling

An inclusion complex between the agrochemical chloropropham (CIPC) and β-cyclodextrin (β-CD) was prepared. A 2:1 host-guest stoichiometry was conformed by elemental analysis. From the phase solubility studies, the calculated stepwise stability constants were K(1)=224.6L/mol and K(2)=939.2L/mol, respectively. FT-IR, thermoanalysis and (1)H NMR spectra were applied to characterize the complex. It was speculated that the inclusion mode was two β-CD cavities included the chlorophenyl and the isopropyl moiety of one CIPC molecule, which was in agreement with the most predominant configuration optimized by molecular modeling. By complexation with β-CD, the water solubility and the thermal stability of CIPC were prominently improved.