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PubMed2005

Simultaneous removal of organic compounds and heavy metals from soils by electrokinetic remediation with a modified cyclodextrin.

Thousands of sites are contaminated with both heavy metals and organic compounds and these sites pose a major threat to public health and the environment. Previous studies have shown that electrokinetic remediation has potential to remove heavy metals and organic compounds when they exist individually in low permeability soils. This paper presents the feasibility of using cyclodextrins in electrokinetic remediation for the simultaneous removal of heavy metals and polycyclic aromatic hydrocarbons (PAHs) from low permeability soils. Kaolin was selected as a model low permeability soil and it was spiked with phenanthrene as well as nickel at concentrations of 500 mg kg-1 each to simulate typical mixed field contamination. Bench-scale electrokinetic experiments were conducted using hydroxypropyl beta-cyclodextrin (HPCD) at low (1%) and high (10%) concentrations and using deionized water in control test. A periodic voltage gradient of 2VDC cm-1 (with 5 d on and 2 d off) was applied to all the tests, and 0.01 M NaOH was added during the experiments to maintain neutral pH conditions at anode. In all tests, nickel migrated as Ni2+ ions towards the cathode and most of it was precipitated as Ni(OH)2 within the soil close to the cathode due to high pH condition generated by electrolysis reaction. The solubility of phenanthrene in the flushing solution and the amount of electroosmotic flow controlled the migration and removal of phenanthrene in all the tests. Even though high flow was generated in tests using deionized water and 1% HPCD, migration and removal of phenanthrene was low due to low solubility of phenanthrene in these solutions. The test with 10% HPCD solution showed higher solubility of phenanthrene which caused it migrate towards the cathode, but further migration and removal was retarded due to reduced electric current and electroosmotic flow. Approximately one pore volume of flushing resulted in approximately 50% removal of phenanthrene from the soil near the anode. Sustained higher electroosmotic flow with higher concentration cyclodextrin and maintaining low soil pH near cathode should be investigated to increase removal efficiency of both phenanthrene and nickel.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed2004

Influence of hydroxypropyl-beta-cyclodextrin complexation on piroxicam release from buccoadhesive tablets.

Interaction of piroxicam (PX) and hydroxypropyl-beta-cyclodextrin (HPbetaCD) was investigated in solution and in the solid state. Solubility studies demonstrated the formation of the PX-HPbetaCD inclusion complex with 1:1 stoichiometry. Equimolecular PX-HPbetaCD solid systems were prepared and characterized by differential scanning calorimetry, Fourier transform infrared spectroscopy, and X-ray diffractometry. Modification of the release of a sparingly water-soluble drug, PX, from hydrophilic matrices using cyclodextrin complexation was evaluated. The buccoadhesive controlled release tablets for the delivery of PX were prepared by direct compression of hydroxypropylmethyl cellulose (HPMC) and Carbopol 940 (C940), which showed superior bioadhesion properties compared to HPMC. The tablets were evaluated for their dissolution, swelling and mucoadhesive properties. The in vitro release results demonstrated that matrix tablets containing the PX-HPbetaCD solid complex displayed faster PX release compared to those containing a physical mixture or "free" drug. Differences in release rates of PX from the tablets could be attributed to the presence of the polymers and to cyclodextrin complexation. The effect of the polymers on PX release can affect the drug solubility (complexation) and polymer water uptake (swelling). Higher polymer water uptake may result in higher drug solubility and diffusivity in a hydrated polymeric environment. Drug complexation affected also its diffusivity through the semipermeable membrane.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed2006

Influence of modified cyclodextrins on solubility and percutaneous absorption of celecoxib through human skin.

We evaluated the ability of two modified cyclodextrins, hydroxypropyl-beta-cyclodextrin (HP-beta-Cyd) and 2,6-di-O-methyl-beta-cyclodextrin (DM-beta-Cyd), to influence the percutaneous absorption through isolated human stratum corneum and epidermis (SCE) of celecoxib (CCB). Previous studies demonstrated that DM-beta-Cyd includes the drug, producing a significant increase of water solubility (0.5 mg/ml at 25 degrees C) and dissolution rate of CCB. In this work chemical-physical characterization studies were performed to evaluate the ability of HP-beta-Cyd to include CCB. We showed that only an external interaction could exist between CCB and HP-beta-Cyd that positively influences the water solubility of the drug (0.12 mg/ml at 25 degrees C for CCB-HP-beta-CyD system and 4.12 x 10(-3) mg/ml at 25 degrees C for free CCB). In vitro percutaneous experiments were performed using samples in solution and in suspension containing different Cyd concentrations. Both HP-beta-Cyd and DM-beta-Cyd enhanced drug flux through SCE by means of an increase of dissolution rate of the drug as well as a direct action on the stratum corneum (SC). Histological analysis of treated SCE showed a protective effect of the two Cyds towards an invasive action shown by CCB on SC.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed2004

Cyclodextrin enhanced transdermal delivery of piroxicam and carboxyfluorescein by electroporation.

The transdermal transport of cyclodextrins (CD) across porcine epidermis by electroporation was studied. Electroporation increased the permeation of beta-cyclodextrin (BCD) and hydroxy propyl beta-cyclodextrin (HPCD) by several orders of magnitude, relative to passive transport. The presence of BCD and HPCD enhanced the total transport of the test permeants piroxicam and carboxyfluorescein (CF), respectively, from both permeant solutions and suspensions. BCD enhanced the fraction of piroxicam transported across the epidermis into the receiver compartment medium. This was most likely due to the prolonged post-pulse permeability state of the epidermis. The fraction of CF retained in the epidermis was increased by HPCD. The rate of diffusion of CF from epidermis into the receiver compartment was decreased by the presence of HPCD, apparently due to the aggregate forming tendency of HPCD. The in vivo delivery of CF by electroporation in mice demonstrated the potential of HPCD for sustaining the transdermal absorption rate of hydrophilic molecules.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed2006

Investigation of the electron transfer site of p-benzoquinone in isolated photosystem II particles and thylakoid membranes using alpha- and beta-cyclodextrins.

The electron transfer sites of p-benzoquinone (pBQ) and 2,6-dichloro-p-benzoquinone (DCBQ) were investigated in thylakoid membranes and isolated photosystem II (PSII) particles from barley (Hordeum vulgare) using alpha- and beta-cyclodextrins (CD) at concentrations up to 16 mM. In CD-treated thylakoid membranes incubated with DCBQ the electron transport through PSII, estimated as oxygen evolution (OE), is largely enhanced according to a S-shaped (sigmoidal) dose-response curve displaying a sharp inflection point, or transition. The maxima percent OE enhancement at cyclodextrin concentrations above 14 mM are about 100% (alpha-CD) and 190% (beta-CD). On the contrary, in thylakoid membrane preparations incubated with pBQ as electron acceptor one observes an OE inhibition of about 30% which might result from the depletion of the thylakoid membrane of its plastoquinone content. It was also found that in isolated PSII particles incubated with either pBQ or DCBQ the cyclodextrins induce only a small OE enhancement. Moreover, the observation in CD-treated thylakoid membranes incubated with pBQ of a residual, non-inhibited oxygen-evolving activity of about 70% puts a twofold question. That is, either the plastoquinone depletion was not complete, or, pBQ binds to electron acceptor sites of different nature. From this and data published in the literature, it is concluded that in the thylakoid membrane (i) DCBQ binds to Q(B), as is generally accepted, and (ii) pBQ binds to the plastoquinol molecules in the PQ pool and most likely also to Q(B), thereby in accord with Satoh et al.'s model [K. Satoh, M. Ohhashi, Y. Kashino, H. Koike, Plant Cell Physiol. 36 (1995) 597-605]. An attractive alternative hypothesis is the direct interaction of pBQ with the non-haem Fe(2+) between Q(A) and Q(B).

Benzoquinones↗
PubMed2004

Degradation of pentachlorophenol in cyclodextrin extraction effluent using a photocatalytic process.

This work evaluates a process for the elimination of pentachlorophenol (PCP) from effluents provided by a cyclodextrin-assisted flushing of contaminated soils. The effectiveness of photocatalytic degradation of PCP in several cyclodextrin (CD) solutions was evaluated using TiO2 as a photocatalyst. Effects of CD type on PCP degradation rate were studied at two pH values. A similar effect was observed for all CDs used on degradation rate of PCP and the decay of PCP was found to be less extensive at pH 11 than at pH 7. The kinetic orders of the photocatalytic reactions of PCP for all of the solutions have been determined. The first-order rate constants were found to be 0.0884, 0.0362, 0.0197 and 0.0053 min(-1) in CD solutions, respectively, at 0, 1, 2 and 5 mmol l(-1) of CD. Batch experiments were performed in order to study the CD extraction enhancement of PCP previously adsorbed on soil. The results show that the removal capacity of PCP from soil increases with CD concentration (from 0 to 5 mmol l(-1)). When the CD concentration was 5 mmol l(-1), an extraction of about 70% of PCP adsorbed on soil was observed, whereas only 37% was removed when water was used as the flushing solution. The optimal conditions for such a coupled method depend on the nature and concentration of the extracting agent and also on the photocatalytic experimental conditions. This work revealed that the coupling of cyclodextrin-enhanced solubilization and photocatalytic treatment is a promising method for contaminated soil remediation.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed2004

Efficacy of alpha-cyclodextrin against experimental cryptosporidiosis in neonatal goats.

The efficacy of orally administered tablets containing alpha-cyclodextrin, an excipient used in the pharmaceutical industry with demonstrated anticryptosporidial activity in vitro and in neonatal mice, was evaluated in neonatal goat kids. The formulation was evaluated for hardness and was subjected to in vitro drug release studies. Twenty goat kids were orally inoculated with 10(6) oocysts of C. parvum within the first 6 days of age. Half of the animals were treated by oral administration of four tablets of alpha-cyclodextrin/day (500 mg/kg of body weight) for six consecutive days, the treatment beginning on the day of inoculation. Infection was monitored by daily examination of faecal samples from the first day to 25 days post-inoculation. The criteria studied in evaluating efficacy were: oocyst shedding, presence of diarrhoea and weight gain at 15 and 25 days post-inoculation. alpha-cyclodextrin was effective when given at the beginning of infection: there was a longer pre-patent period, a reduction in the patent period and a decrease in the intensity of infection, these differences being statistically significant (P < 0.05) compared with untreated neonatal kids. Moreover, except in one animal, the diarrhoea was prevented in infected neonatal kids. Animals from both groups increased the body weight and no significant differences were seen between the two groups.

Animals↗
PubMed2006

Solubilization and desorption of methyl-parathion from porous media: a comparison of hydroxypropyl-beta-cyclodextrin and two nonionic surfactants.

The removal of hydrophobic organic compounds (HOCs) from soils and sediments by water flushing is often constrained by sorption interactions. The development of improved methods for remediation of contaminated soils has emerged as a significant environmental priority. Increasing HOCs desorption and mobility in soil using surfactants is considered to be one of the most suitable on-site techniques for soil remediation. A major concern regarding the use of surfactants for environmental restoration is the potential loss to the environment of large amounts of surfactant through sorption of nonionic types. A study was conducted to investigate whether surfactants and cyclodextrins can be used to enhance the transport of methyl-parathion in a contaminated soil. At aqueous concentrations of surfactants tested, the proportion of each surfactant sorbed to the soil increased with increasing surfactant concentrations. The maximal adsorbed mass is about 5,130 and 14,200 microg/g for Brij 35 and Tween 80, respectively. In the case of nonionic surfactants, sorption attenuates surfactant effectiveness by increasing the organic carbon content of the soil matrix and retarding transport of methyl-parathion through batch and soil column experiments. However, in contrast with the surfactants, hydroxypropyl-beta-cyclodextrin (HPCD) does not interact with the soil tested. The nonreactive nature of cyclodextrins, combined with its large affinity for HOCs suggests that it should have an advantage versus adsorbing surfactants for decreasing HOC distribution coefficients in subsurface systems.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed2004

Safety assessment of gamma-cyclodextrin.

Gamma-cyclodextrin (gamma-CD) is a cyclic alpha-(1,4)-linked oligosaccharide consisting of eight glucose molecules. Like other cyclodextrins, gamma-CD can form inclusion complexes with a variety of organic molecules because the inner side of the torus-like molecule is less polar than the outer side. In foods, gamma-CD may be used as a carrier for flavors, vitamins, polyunsaturated fatty acids, and other ingredients. It also has useful properties as a stabilizer in different food systems. The daily intake from all its intended uses in food at highest feasible concentrations has been estimated at 4.1g/person/day for consumers of gamma-CD containing foods. The present review summarizes the safety data of gamma-CD. The toxicity studies consist of standard genotoxicity tests, subchronic rat studies with oral and intravenous administration of gamma-CD for up to 3 months, a subchronic (3-month) toxicity study in dogs, a (1-year) oral toxicity study in rats, and embryotoxicity/teratogenicity studies in rats and rabbits. In the studies with oral administration, gamma-CD was given at dietary concentrations of up to 20%. All these studies demonstrated that gamma-CD is well tolerated and elicits no toxicological effects. Metabolic studies in rats showed that gamma-CD is rapidly and essentially completely digested by salivary and pancreatic amylase. Therefore, the metabolism of gamma-CD closely resembles that of starch and linear dextrins. A human study with ingestion of single doses of 8 g gamma-CD or 8 g maltodextrin did not reveal a difference in gastrointestinal tolerance of these two products. An interaction of ingested gamma-CD with the absorption of fat-soluble vitamins or other lipophilic nutrients is not to be expected because the formation of inclusion complexes is a reversible process, gamma-CD is readily digested in the small intestine, and studies with beta-CD, a non-digestible cyclodextrin, have shown that the bioavailability of vitamins (A, D, and E) is not impaired. On basis of these studies it is concluded that gamma-CD is generally recognized as safe (GRAS) for its intended uses in food.

Animals↗
PubMed2000

Interaction of the noncovalent molecular adapter, beta-cyclodextrin, with the staphylococcal alpha-hemolysin pore.

Cyclodextrins act as noncovalent molecular adapters when lodged in the lumen of the alpha-hemolysin (alphaHL) pore. The adapters act as binding sites for channel blockers, thereby offering a basis for the detection of a variety of organic molecules with alphaHL as a biosensor element. To further such studies, it is important to find conditions under which the dwell time of cyclodextrins in the lumen of the pore is extended. Here, we use single-channel recording to explore the pH- and voltage-dependence of the interaction of beta-cyclodextrin (betaCD) with alphaHL. betaCD can access its binding site only from the trans entrance of pores inserted from the cis side of a bilayer. Analysis of the binding kinetics shows that there is a single binding site for betaCD, with an apparent equilibrium dissociation constant that varies by >100-fold under the conditions explored. The dissociation rate constant for the neutral betaCD molecule varies with pH and voltage, a result that is incompatible with two states of the alphaHL pore, one of high and the other of low affinity. Rather, the data suggest that the actual equilibrium dissociation constant for the alphaHL. betaCD complex varies continuously with the transmembrane potential.

Bacterial Toxins↗
PubMed2000

Selective oxidation of primary alcohol groups of beta-cyclodextrin mediated by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO).

Beta-cyclodextrin (beta-CD) was reacted with catalytic amounts of 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO), sodium hypochlorite and sodium bromide at 2 degrees C and a pH value of 10 in water. The primary alcohol groups were selectively oxidized into carboxylate groups within a few minutes, and mono- and dicarboxy-beta-cyclodextrin sodium salts were isolated and characterized by 1H, 13C NMR and mass spectroscopy. With this reaction system, the degradation of the cyclodextrin was limited, provided the oxidation was performed at 2 degrees C, at constant pH value of 10, with catalytic amounts of TEMPO and controlled quantities of sodium hypochlorite and sodium bromide for the continuous regeneration of the oxoammonium salt.

Alcohols↗
PubMed2000

Insoluble beta-cyclodextrin polymer for capillary gas chromatographic separation of enantiomers and isomers.

An insoluble beta-cyclodextrin polymer cross-linked with identified epichiorohydrin has been prepared; its structure was identified by means of infrared and 13C NMR spectra. Three capillary columns have been coated with the polymer treated by ultrasonication by three coating methods. Chromatographic characteristics such as column efficiency, thermal stability and polarity, have been studied, and two kinds of disubstituted benzene isomers and eight pairs of enantiomers have been separated on the three capillary columns. The results show that the beta-cyclodextrin polymer is suitable for use as a capillary gas chromatographic stationary phase, and that the column, prepared by loading beta-cyclodextrin polymer stationary phase with 50% methyl-50% phenylsilicone (OV-17), shows good chromatographic properties in separating enantiomers and positional isomers.

Chromatography, Gas↗
PubMed2000

Allylamine-beta-cyclodextrin copolymer. A novel chiral selector for capillary electrophoresis.

A novel, positively charged, copolymer of allylamine and 2-hydroxy-3-methacryloyl-beta-cyclodextrin was synthesized to be used as a chiral selector in capillary electrophoresis. In the copolymer, cyclodextrin molecules are spaced from the backbone though a spacer arm which prevents sterical hindrance of the CD cavity. The self-mobility of the CD polymer in its charged form, opposite to the analytes, is the cause for the enhanced separation factor provided by this selector. Moreover, the positive charged polymer induces a reversal of electroosmotic flow which is beneficial in enantioseparations of acidic compounds as it reduces analysis time and increases peak efficiency. The ability of this copolymer to act as a CE chiral selector in the separation of 2,4-dinitrophenylamino acid enantiomers was investigated in coated and uncoated capillaries and its performance was much better then that of native beta-cyclodextrin.

Allylamine↗
PubMed2001

Study on the chiral recognition of the enantiomers of ephedrine derivatives with neutral and sulfated heptakis(2,3-O-diacetyl)-beta-cyclodextrins using capillary electrophoresis, UV, nuclear magnetic resonance spectroscopy and mass spectrometry.

The enantiomers of methylephedrine, pseudoephedrine and ephedrine showed a different migration behavior in capillary electrophoresis in the presence of beta-cyclodextrin (beta-CD), heptakis(2,3-O-diacetyl)-beta-cyclodextrin and heptakis(2,3-O-diacetyl-6-sulfato)-beta-cyclodextrin (HDAS). Utilizing UV, MS and NMR spectroscopy, in particular rotating frame Overhauser experiments, an attempt was made to elucidate the chiral recognition mechanism. In the case of the neutral CDs 1:1 complexes were formed with ephedrine and methylephedrine characterized by the inclusion of the phenyl ring in the cavity and the side chain pointing out of the wider rim. In contrast, manifold complexes were formed with HDAS, which on average are characterized by an upside down inclusion of the phenyl ring in the cavity and the side chain pointing out of the narrow rim. This complex geometry is likely be stabilized by an ion-ion interaction between the positively charged nitrogens of the ephedrine derivatives and the negative charges of HDAS. In addition, an attachment of the ligand to the outside of HDAS and other complex stoichiometries are also possible.

Cyclodextrins↗
PubMed2002

Chromatographic behaviour of selected steroids and their inclusion complexes with beta-cyclodextrin on octadecylsilica stationary phases with different carbon loads.

Retention and separation studies of selected estrogens, progestogens and their inclusion complexes with beta-cyclodextrin were conducted using two C18 HPLC columns with different carbon loads. The difference in carbon load between investigated octadecylsilica packing materials was about 50%. The mobile phases were composed of a 30% v/v acetonitrile-water mixture without and with addition of beta-cyclodextrin at a concentration of 12 mM. The experimental data revealed that retention of the steroids was significantly reduced on the column with the lower carbon load. Moreover, it was found that this column offers better separation power and shorter analysis time at the temperatures studied. However, the calculated values of the retention factor ratios (k0(mMCD))/k(12mMCD)) of the steroids were similar for both columns investigated. This observation suggests that the stationary phase structure appears to have little effect on the formation of host-guest complexes if the complexation process is localised to the chromatographic mobile phase. From a practical point of view, when the mobile phase is modified with beta-cyclodextrin, the separation of the steroids is strongly influenced by temperature. The best chromatographic conditions were determined for the separation of multicomponent samples on the column with lower carbon load. A possible retention mechanism for components of interest in the presence of macrocyclic additives is discussed.

Carbon↗
PubMed2003

Extraordinary chiral discrimination in inclusion gas chromatography. thermodynamics of enantioselectivity between a racemic perfluorodiether and a modified gamma-cyclodextrin.

The enantiomers of the perfluorodiether "compound B" [2-(fluoromethoxy)-3-methoxy-1,1,1,3,3-pentafluoropropane], a decomposition product of the inhalational anesthetic sevoflurane [2-(fluoromethoxy)-1,1,1,3,3,3-hexafluoropropane], were separated by gas chromatography on octakis(3-O-butanoyl-2,6-di-O-n-pentyl)-gamma-cyclodextrin (Lipodex E), dissolved in polysiloxane PS 255 (30% w/w), with an unexpectedly high separation factor of alpha = 10.6 at 26 degrees C. Using the concept of the retention increment R', non-enantioselective and enantioselective contributions to retention were separated and thus reliable thermodynamic parameters of enantioselectivity, i.e. - deltaS,R(deltaG) = 5.7 (0.05) kJ/mol at 303 K, - deltaS,R(deltaH) = 20.1 (0.64) kJ/mol, deltaS,R(deltaS) = -47.4 (2.0) J/K mol and T(isoenant) = 424 (30) K or approximately 150 degrees C, were determined by temperature-dependent measurements. The enantiomeric bias represents the largest values ever measured in enantioselective gas chromatography. An equation is presented which allows calculation of the non-enantioselective contributions to retention from measurements at two arbitrary concentrations of Lipodex E in polysiloxane. Surprisingly, the enantioselectivity is greatly reduced when employing the beta-cyclodextrin analogue and breaks down completely with the alpha-cyclodextrin analogue of Lipodex E.

Chromatography, Gas↗
PubMed2003

Application of diaza-18-crown-6-capped beta-cyclodextrin bonded silica particles as chiral stationary phases for ultrahigh pressure capillary liquid chromatography.

Two bonded chiral stationary phases (CSPs), 8-aminoquinoline-2-ylmethyl- and 8-aminoquinoline-7-ylmethyl-diaza-18-crown-6-capped [3-(2-O-beta-cyclodextrin)-2-hydroxypropoxy]propylsilyl silica particles (non-porous, 1.5 microm), have been prepared and evaluated using capillary liquid chromatography at high pressures (> or = 8000 p.s.i.). High column efficiency (up to 400 000 plates m(-1)) was achieved for chiral separations. These CSPs with two recognition sites, i.e. substituted-diaza-18-crown-6 and beta-cyclodextrin combined with high chromatographic efficiency provide good resolution of a variety of enantiomers and positional isomers in relatively short times under reversed-phase conditions. After inclusion of a Ni (II) ion from the mobile phase, the positively charged crown ether-capped beta-cyclodextrin facilitates specific static, dipolar, and host-guest complexation interactions with solutes.

Aza Compounds↗
PubMed1997

Improved chiral separation using achiral modifiers in cyclodextrin modified capillary zone electrophoresis.

The influence of achiral modifiers on the chiral separation of propranolol is examined by cyclodextrin modified capillary zone electrophoresis. The improved chiral separation of propranolol is by molecules previously identified in our group as forming ternary complexes with cyclodextrin and pyrene. The polarity, chain size and heteroatom composition of the functional groups on the comodifiers was systematically varied in order to study the influence of these variables on the separation of propranolol. The improved chiral separation is accompanied by a decrease in retention time. The decrease in retention time is suggestive of a decrease in the association of beta-cyclodextrin (beta-CD) with propranolol which was verified by calculation of apparent association constants using fluorometric methods.

Cyclodextrins↗