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PubMed2000

Synthesis, characterization, and supramolecular properties of a hydrophilic porphyrin--beta-cyclodextrin conjugate.

Reductive amination of 6-deoxy-6-formyl-beta-cyclodextrin with 5-(p-aminophenyl)-10,15,20-tris(p-sulfonatophenyl)porphyrin in the presence of an excess of sodium cyanoborohydride affords the hydrophilic cyclodextrin-porphyrin conjugate 3 in 23% yield. The structure of 3 was confirmed by NMR spectroscopy and mass spectrometry techniques. Compound 3 showed a marked tendency to dimerize in aqueous conditions via the formation of intermolecular porphyrin-cyclodextrin inclusion complexes and/or through electrostatic interactions. Information on the structure of these aggregates has been obtained by the use of circular dichroism and UV-vis spectroscopy. Aggregation can be avoided by the use of heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin (TM beta CD) that forms a 1:1 inclusion complex with compound 3.

Circular Dichroism↗
PubMed2001

Synthesis of cyclodextrin-based carbohydrate clusters by photoaddition reactions.

The syntheses of homogeneous cyclodextrin-based carbohydrate clusters, persubstituted with beta-D-thioglucosyl or D-thiolactosyl residues on either (a) the primary face, (b) the secondary face, or (c) both the primary and the secondary faces of their cyclodextrin tori, are described. The key step in the synthetic methodology, namely the attachment of the carbohydrate residues to the cyclodextrin torus, proceeds in moderate-good yields (42-70%) by the photoaddition of thiol groups, positioned at the anomeric centers of the carbohydrate residues, to allyl ether functions on the cyclodextrins. Facile removal of protecting groups then affords the free cluster compounds. Extensive 1-D and 2-D NMR spectroscopic investigations were performed on these compounds to determine their structures and establish their homogeneities, and a brief computer molecular modeling study allowed estimates of the dimensions of the clusters to be determined.

Carbohydrate Sequence↗
PubMed2005

Complexation of adamantyl compounds by beta-cyclodextrin and monoaminoderivatives.

Since the beta-cyclodextrin cavity is not a smooth cone but has constrictions in the neighborhoods of the H3 and H5 atoms, the hypothesis that bulky hydrophobic guests can form two isomeric inclusion complexes (one of them, c(p), is formed by the entrance of the guest by the primary side of the cavity, and the other one, c(s), results from the entrance by the secondary side) is checked. Thus, the inclusion processes of two 1-substituted adamantyl derivatives (rimantidine and adamantylmethanol) with beta-cyclodextrin and its two monoamino derivatives at positions 6 (6-NH2beta-CD) and 3 (3-NH2beta-CD) were studied. From rotating-frame Overhauser enhancement spectroscopy experiments, it was deduced that both guests form c(s) complexes with beta-CD and 6-NH2beta-CD but c(p) complexes with 3-NH2beta-CD. In all cases, the hydrophilic group attached to the adamantyl residue protrudes toward the bulk solvent outside the cyclodextrin cavity. The thermodynamic parameters (free energy, equilibrium constant, enthalpy, and entropy) associated with the inclusion phenomena were measured by isothermal titration calorimetry experiments. From these results, the difference in the free energy for the formation of the two complexes, c(s) and c(p), for the same host/guest system has been estimated as being 11.5 +/- 0.8 kJ mol(-1). This large difference explains why under normal experimental conditions only one of the two complexes (c(s)) is detected. It is also concluded that a hyperboloid of revolution can be a better schematic picture to represent the actual geometry of the cyclodextrin cavities than the usual smooth cone or trapezium.

Adamantane↗
PubMed2005

Spectrophotometric study of fluorescence sensing and selective binding of biochemical substrates by 2,2'-bridged bis(beta-cyclodextrin) and its water-soluble fullerene conjugate.

A bis(beta-cyclodextrin)-fullerene conjugate (3) linked at the secondary hydroxyl side was prepared in a good yield from its precursor N,N'-bis(2-(2-aminoethylamino)ethyl)malonamide-bridged bis(beta-cyclodextrin) (2). Spectrophotomeric studies on the conformation and the inclusion complexation behavior of 3 with a variety of organic and biochemical substrates by means of UV-vis, FT-IR, NMR, fluorescence, and circular dichroism spectroscopy showed that the bis(beta-cyclodextrin)-fullerene conjugate displayed an intramolecular capsule-type conformation in aqueous solution. Because of the multiple binding of bis(beta-cyclodextrin) with substrates, 2 can act as an efficient fluorescence sensor for biochemical substrates, while its fullerene conjugate 3 displays a capability of cleaving DNA under visible-light irradiation.

Benzyl Compounds↗
PubMed2004

Formation of Langmuir layers and surface modification using new upper-rim fully tethered bipyridinyl or bithiazolyl cyclodextrins and their fluorescent metal complexes.

Seven new amphiphilic cyclodextrins bearing bipyridyl or bithiazolyl moieties at the narrow rim and free hydroxyl or methoxyl groups at the wide rim of the cyclooctaamylose crown were synthesized using a one step "phosphine imide" approach. These ligands form metal complexes that have fluorescence properties with potentials for optical applications. Here, the cyclodextrin derivatives were used as probes for evaluating the role of different moieties in the self-assembly process, providing crucial information in creating functional devices. The behavior of these molecules and of complexes with EuIII in some cases was studied in Langmuir films using surface pressure (pi) and surface potential (deltaV) measurements performed as a function of film compression (compression isotherms). For chosen cyclodextrins, Brewster angle microscopy (BAM) in monolayers was performed. Films formed with derivatives 1, 3, 7, and 2compl were transferred on mica using the Langmuir-Blodgett technique. The properties of the films deposited on mica were analyzed with fluorimetry and, in the case of derivative 7, using fringe of equal chromatic order technique (FECO). The monolayer structure and the fluorescence properties of the Langmuir-Blodgett films indicate that the derivatives studied can be used for preparing cyclodextrin-based optical devices.

Cyclodextrins↗
PubMed2006

Supramolecular assembly of cyclodextrin-based nanoparticles on solid surfaces for gene delivery.

In this work, a new approach for surface-mediated gene delivery based on inclusion complex formation between the solid surface and delivery vehicles is presented. beta-Cyclodextrin (CD) molecules form high-affinity inclusion complexes with adamantane. This complexation ability was used to specifically immobilize beta-CD-modified poly(ethylenimine) (CD-PEI) nanoparticles on adamantane- (AD-) modified self-assembled monolayers. To investigate the nanoparticle/surface interaction, CD-PEI-based and PEI-based nanoparticles were passed through a surface plasmon resonance flow cell containing the monolayers. CD-PEI nanoparticles are specifically immobilized on the chip surface by cyclodextrin-adamantane inclusion complex formation. Minimal nanoparticle adsorption was detected with PEI-based nanoparticles or on control surfaces. Competition studies with free cyclodextrins reveal that the multivalent interactions between CD-PEI nanoparticles and the adamantane-modified surface results in significantly higher binding affinity than single cyclodextrin-adamantane complexes. Immobilized nanoparticles were characterized by atomic force microscopy and quantified by fluorescence assay. Thus, the ability of CD-PEI nanoparticles to form inclusion complexes can be exploited to attain specific, high-affinity loading of delivery vehicles onto solid surfaces.

Adamantane↗
PubMed1998

Evaluation of cytotoxicity of various ophthalmic drugs, eye drop excipients and cyclodextrins in an immortalized human corneal epithelial cell line.

PURPOSE: An immortalized human corneal epithelial cell line (HCE) was tested as a screening tool for prediction of topical ocular irritation/toxicity by pharmaceuticals METHODS: Effects of various drugs, excipients and cyclodextrins (CDs) on viability of HCE cells were evaluated using two in vitro cytotoxicity tests, 3-(4,5-dimethlthiazol-2-yl)-205-diphenyl tetrazolium bromide (MTT) dye reduction assay and propidium iodide assay. RESULTS: Mitochondrion-based MTT test was a more sensitive indicator of cytotoxicity than the plasma membrane-based propidium iodide test. The tests revealed following cytotoxic rankings for ophthalmic drugs: dipivefrin > timolol > pilocarpine approximately equal to dexamethasone; for excipients: benzalkonium chloride (BAC) > sodium edetate (NA2 EDTA)>polyvinyl alcohol (PVA) > methylparaben; and for CDs :alpha- CD > dimethyl beta-cyclodextrin (DM-beta-CD) > sulfobutyl ether beta-cyclodextrin ((SBE)7m-beta-CD approximately equal to hydroxypropyl-beta-cyclodextrin (HP-beta-CD) > lambda CD. In consideration of the in vivo clinical situation, the short exposure time (5 min) is more relevant even though toxic effects of some test substances were seen only after longer exposure time (30 and 60 min). CONCLUSIONS: Immortalized HCE cells are a promising tool for rapid cytotoxicity assays of ocular medications. The cell line is potentially useful in predicting the in vivo coreal toxicity of ocularly applied compounds.

Cell Line, Transformed↗
PubMed1998

Beta cyclodextrins enhance adenoviral-mediated gene delivery to the intestine.

PURPOSE: In general, the intestinal epithelium is quite refractory to viral and non-viral methods of gene transfer. In this report, various cyclodextrin formulations were tested for their ability to enhance adenoviral transduction efficiency in two models of the intestinal epithelium: differentiated Caco-2 cells and rat jejunum. METHODS: Transduction efficiency of replication-deficient adenovirus type 5 vectors encoded with either the E. coli beta-galactosidase or the jellyfish green fluorescent protein gene was assessed by X-gal staining or visualization of fluorescence 48 hours after infection. In vivo experiments were performed using an intestinal loop ligation technique. RESULTS: Several formulations of neutral and positively charged beta cyclodextrins significantly enhanced adenoviral-mediated gene transfer in the selected models. The cyclodextrin formulations studied increased adenoviral transduction in the intestine by enhancing both viral binding and internalization. Viral binding was significantly increased on cell membranes treated with positively charged cyclodextrins, as seen with confocal microscopy and rhodamine-labeled virus. Permeability studies and TEER readings revealed that the most successful formulations gently disrupt cell membranes. This enhances internalization of viral particles and results in increased levels of gene expression. CONCLUSIONS: These formulations can be of value in gene transfer to cells and tissues in which adenoviral infection is limited due to a lack of fiber and alpha(v) integrin receptors. They are simple to prepare and do not affect the ability of the virus to transduce target cells.

Adenoviridae↗
PubMed1994

The effect of cyclodextrins on the stability of peptides in nasal enzymic systems.

Leucine enkephalin (YGGFL) undergoes rapid degradation in sheep nasal mucosa to yield GGFL which is further degraded to FL. The activity of the nasal mucosal homogenate against YGGFL and GGFL (t1/2 12 and 7 min) was significantly greater than that observed with a nasal wash fluid (t1/2 40 and 13 min). The effect of cyclodextrins on the rate of degradation of FGG and YGGFL by leucine aminopeptidase (LAP) and of GGF by carboxypeptidase A (CPA) was monitored. Little effect was observed with FGG (with LAP) but the half-life of YGGFL (with LAP) was extended from approximately 44 min to approximately 75 min in the presence of a 25-fold excess of beta-cyclodextrin. The stability of GGF (with CPA) was also enhanced; an effect was observable with a 5-fold excess of cyclodextrin and the half-life could be extended by 40-75%. An equation is presented which allows the estimation of the concentration of free peptide in the peptide-cyclodextrin solutions.

Animals↗
PubMed2004

Effects of fungal bioaugmentation and cyclodextrin amendment on fluorene degradation in soil slurry.

This study assesses the potential of fungal bioaugmentation and the effect of maltosyl-cyclodextrin amendment, as an approach to accelerate fluorene biodegradation in soil slurries. 47 fungal strains isolated from a contaminated site were tested in the biodegradation of fluorene. Results showed the greater efficiency of "adaptated" fungi isolated from contaminated soil vs. reference strains belonging to the collection of the laboratory. These assays allowed us to select the most efficient strain, Absidia cylindrospora, which was used in a bioaugmentation process. In the presence of Absidia cylindrospora, more than 90% of the fluorene was removed in 288 h while 576 h were necessary in the absence of fungal bioaugmentation. Maltosyl-cyclodextrin, a branched-cyclodextrin was chosen in order to optimize fluorene bioavailability and biodegradation in soil slurries. The results of this study indicate that Absidia cylindrospora and maltosyl-cyclodextrin could be used successfully in bioremediation systems.

Absidia↗
PubMed1999

Enhanced microdialysis recovery of some tricyclic antidepressants and structurally related drugs by cyclodextrin-mediated transport.

The enhanced microdialysis relative recovery (RR) of some hydrophobic tricyclic drugs (imipramine, desipramine, amitriptyline, carbamazepine and promethazine) is discussed. Enhanced RR was achieved by including a binding agent [beta-cyclodextrin (beta-CD) or 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CD)] in the microdialysis perfusion fluid to form inclusion complexes with the drugs, which increases the analyte flux through the membrane material. The maximum effect of the RR increase for all the drugs studied was observed using a commercially available polycarbonate-polyether (PC) membrane. With a 4 mm PC membrane and 4.41 mmol l-1 (0.5% w/v) beta-CD included in the microdialysis perfusion fluid (0.9% saline, pH 7.4) at a flow rate of 0.5 microliter min-1, RR enhancements over controls were as follows: carbamazepine 136, imipramine 268, desipramine 298, amitriptyline 634, and promethazine 987%. Increasing beta-CD [up to 17.63 mmol l-1 (2% w/v)] or HP-beta-CD [up to 32.5 mmol l-1 (5% w/v)] concentration in the microdialysis perfusion fluid enhanced carbamazepine RR three (beta-CD) to four (HP-beta-CD) times compared to controls through PC microdialysis membranes. The PC membrane gave enhanced RR values that were twice those for cuprophan or AN-69 membranes. Enhanced RR with cyclodextrins was successfully applied to sampling from a protein solution containing desipramine in a 4% w/v bovine serum albumin solution. These results suggest that addition of cyclodextrins to microdialysis perfusion fluids may be used to increase microdialysis RR during blood sampling.

Antidepressive Agents, Tricyclic↗
PubMed2003

Thermoanaerobacterium thermosulfurigenes cyclodextrin glycosyltransferase.

Cyclodextrin glycosyltransferase (CGTase) uses an alpha-retaining double displacement mechanism to catalyze three distinct transglycosylation reactions. To investigate these reactions as catalyzed by the CGTase from Thermoanaerobacterium thermosulfurigenes the enzyme was overproduced (8 mg.L(-1) culture) using Bacillus subtilis as a host. Detailed analysis revealed that the three reactions proceed via different kinetic mechanisms. The cyclization reaction (cyclodextrin formation from starch) is a one-substrate reaction, whereas the other two transglycosylation reactions are two-substrate reactions, which obey substituted enzyme mechanism kinetics (disproportionation reaction) or ternary complex mechanism kinetics (coupling reaction). Analysis of the effects of acarbose and cyclodextrins on the disproportionation reaction revealed that cyclodextrins are competitive inhibitors, whereas acarbose is a mixed type of inhibitor. Our results show that one molecule of acarbose binds either in the active site of the free enzyme, or at a secondary site of the enzyme-substrate complex. The mixed inhibition thus indicates the existence of a secondary sugar binding site near the active site of T. thermosulfurigenes CGTase.

Acarbose↗
PubMed2001

Cyclodextrin as a potential drug carrier in salbutamol dry powder aerosols: the in-vitro deposition and toxicity studies of the complexes.

This research was carried out to develop a new carrier in dry powder aerosols. Two types of cyclodextrin were chosen; gamma cyclodextrin (GCD) and dimethyl-beta-cyclodextrin (DMCD) as carriers in dry powder formulations. Salbutamol was used as a model drug and a control formulation containing lactose and the drug was included. A twin-stage impinger (TSI) was used to evaluate in delivery efficiency of those dry powder formulations. The toxicity of cyclodextrin complexes was investigated in the rat by monitoring blood urea nitrogen (BUN) and urinary creatinine, as well as determining haemolysis of human red blood cells. The release of salbutamol from dry powder formulations was also studied over a period of time. From the results obtained, it was found that the formulation containing GCD-enhanced drug delivery to the lower stage of the TSI (deposition = 65%) much greater than that of both formulations containing DMCD (50%) and the control formulation (40%) (P<0.05). After injecting the GCD complex BUN and creatinine levels in rats were similar to those obtained in the control while those receiving DMCD complex had higher BUN and creatinine. The haemolysis of red blood cells incubated with the DMCD complex was higher than that obtained in the GCD complex. The drug release in both formulations containing GCD and DMCD was fast (over 70% was released in 5 min) and nearly all the drug was released within 30 min. It can be concluded that GCD and DMCD are able to promote salbutamol delivery in dry powder inhaler compared to a formulation containing lactose. In addition, GCD is relatively safe in the rat if the amount of GCD in the formulation is similar to this experiment.

Aerosols↗
PubMed2007

Influence of cyclodextrin complexation on the Vibrio fischeri toxicity of phenylsulfonyl carboxylates.

This paper describes the research about the beta -cyclodextrin influence on Vibrio fischeri toxicity of 10 phenylsulfonyl carboxylates. It is illustrated that the formation of 1:1 cyclodextrin-solute inclusion complexes dominates the toxicity influence of phenylsulfonyl carboxylates to Vibrio fischeri and greatly weakens the toxicity level. Using the octanol-water partition coefficients lg KOW, the grouped electrotopological state (E-state) index S(> SO2) and the stability constants of inclusion complexes lg KS, three models with high squared correlation coefficients r2adj at 0.908, 0.951 and 0.917, respectively were constructed to evaluate the beta-cyclodextrin influence on Vibrio fischeri toxicity. For the type of phenylsulfonyl carboxylates, the inclusion stability constants lg KS can reliably model and predict the beta-cyclodextrin influence on Vibrio fischeri toxicity (TI).

Aliivibrio fischeri↗
PubMed1999

Preparation and characterization of albendazole beta-cyclodextrin complexes.

Albendazole (ABZ), mebendazole (MBZ), and ricobendazole (RBZ) are low-soluble anthelmintic benzimidazole carbamate drugs. To increase their aqueous solubility, three different types of beta-cyclodextrins (CyDs): beta-cyclodextrin (CD), hydroxypropyl-beta-cyclodextrin (HPCD), and methyl-beta-cyclodextrin (MCD) were used. Solubility depended on the type of CyDs. Increased solubility was obtained when the more substituted CyDs (HPCD or MCD) were used instead of nonsubstituted CD. Stability constants were calculated assuming a 1:1 stoichiometry. Calculated stability constant values depended on initial solubility of drug and pH of the medium. Solid ABZ complexes were prepared by coprecipitation and freeze-drying methods. These products were compared with physical mixtures of ABZ and CyDs. The characterization of these products was made by differential scanning calorimetry (DSC) and drug release studies. True inclusion complexes were obtained only by the freeze-drying method. Drug release studies showed that the freeze-dried inclusion complexes increased the solubility rate of ABZ, although a supersaturation effect was observed when drug release studies were performed in nonsink conditions. A bioavailability study on mice was done with a formulation of ABZ:HPCD complex and was compared to a conventional ABZ suspension. A significantly (p < .05) shorter Tmax of absorption was obtained by using the complex formulation. Greater and significant (p < .05) differences for AUC and Cmax were observed.

Albendazole↗
PubMed2001

Embryotoxicity of magainin-2-amide and its enhancement by cyclodextrin, albumin, hydrogen peroxide and acidification.

BACKGROUND: The channel-forming antimicrobial peptide, magainin-2-amide, interacts preferentially with negatively charged, non cholesterol-containing membranes, including those of sperm, oocytes and cells of pre-implantation embryos. Cyclodextrin and albumin remove membrane cholesterol and together with hydrogen peroxide (H2O2) are potential enhancers of embryotoxicity. METHODS: Two-cell murine embryos were cultured in vitro with magainin-2-amide at a high effective concentration (250 microg/ml) and at subthreshold concentrations (166 and 200 microg/ml). Embryos treated with sub-threshold concentrations of magainin were additionally treated with cyclodextrin, bovine serum albumin or H2O2 or were cultured under acidified conditions. Cell viability was verified with propidium iodide and fluorescein diacetate. RESULTS: The embryotoxic effect of magainin and H2O2 was dose- and time-dependent. Cyclodextrin, H2O2, acidification of the medium, and to a lesser extent albumin, enhanced the embryotoxicity of magainin at sub-threshold concentrations. CONCLUSION: Magainin on its own is highly embryotoxic. Its embryotoxicity is enhanced by cyclodextrin, albumin, H2O2 and acidification. Thus, magainin which has antibacterial, antifungal and antiprotozoal activity may also have a potential role as a contraceptive agent. The harmful effects of various concentrations of the exogenous H2O2 on 2-cell stage mouse embryos are reported here, to the best of our knowledge, for the first time.

Animals↗
PubMed2005

Pullulans and gamma-cyclodextrin affect apparent digestibility and metabolism in healthy adult ileal cannulated dogs.

Pullulan and gamma-cyclodextrin are incompletely digestible, glucose-based, nonstructural carbohydrates synthesized by microorganisms. To determine their effect when incorporated into a complete liquid diet on ileal and total tract nutrient digestibility, ileal cannulated dogs (n = 8) were used in a repeated 4 x 4 Latin-square design. Twice daily, diets were offered containing 30% (DMB) maltodextrin, high-molecular-weight (MW) pullulan (MW 100,000), low-MW pullulan (MW 6300), or gamma-cyclodextrin. Fecal and ileal samples were collected for the last 4 d of each 10-d period. Dogs consuming high-MW pullulan had lower (P < 0.05) dry matter, organic matter, crude protein, fat, carbohydrate ileal and total tract digestibilities, and fecal DM, and higher (P < 0.05) fecal output and fecal scores (indicating looser stools). To evaluate glycemic and insulinemic responses to pullulans, food-deprived dogs consumed 25 g maltodextrin, high-MW pullulan, or low-MW pullulan in a repeated 3 x 3 Latin-square design. Glucose and insulin responses were determined for 180 min. Consumption of 25 g alpha-, beta-, and gamma-cyclodextrin resulted in regurgitation within 60 min. High-MW pullulan reduced (P < 0.05) blood glucose concentration at 15, 30, 45, and 60 min. Compared with maltodextrin, low-MW pullulan and gamma-cyclodextrin did not alter nutrient digestibilities or fecal characteristics to any extent, and low MW pullulan did not affect glycemic response. Although high MW pullulan decreased glycemic response, consumption of large amounts negatively affected nutrient digestibility and fecal characteristics.

Animals↗
PubMed1996

Selective cyclodextrin inhibition of alfaxolone-induced ataxia.

The effect of the use of a number of popular solubility treatments was examined on alfaxolone- and diazepam-induced ataxia. The effects of diazepam were not significantly altered by solution in cyclodextrin, Alkamuls EL-620 or a mixture of propylene glycol and ethanol. The effects of alfaxolone were not altered by solution in Alkamuls EL-620, but were significantly lessened by solution in cyclodextrin. In a dose-response experiment, the ED50 of alfaxolone increased from 15.3 mg kg-1 (in Alkamuls EL-620) to 25.6 mg kg-1 (in hydroxypropyl-beta-cyclodextrin). The results suggest that although cyclodextrins are popular and effective solubilizers, their use must be considered carefully in the context of the experiments in which they are to be used.

Animals↗