A moderate interaction of maltosyl-alpha-cyclodextrin with Caco-2 cells in comparison with the parent cyclodextrin

New Antifungal Compound: Impact of Cosolvency, Micellization and Complexation on Solubility and Permeability Processes

Poor solubility of new antifungal of 1,2,4-triazole class (S-119)—a structural analogue of fluconazole in aqueous media was estimated. The solubility improvement using different excipients: biopolymers (PEGs, PVP), surfactants (Brij S20, pluronic F-127) and cyclodextrins (α-CD, β-CD, 2-HP-β-CD, 6-O-Maltosyl-β-CD) was assessed in buffer solutions pH 2.0 and pH 7.4. Additionally, 2-HP-β-CD and 6-O-Maltosyl-β-CD were proposed as promising solubilizers for S-119. According to the solubilization capacity and micelle/water partition coefficients in buffer pH 7.4 pluronic F-127 was shown to improve S-119 solubility better than Brij S20. Among biopolymers, the greatest increase in solubility was shown in PVP solutions (pH 7.4) at concentrations above 4 w/v%. Complex analysis of the driving forces of solubilization, micellization and complexation processes matched the solubility results and suggested pluronic F-127 and 6-O-Maltosyl-β-CD as the most effective solubilizing agents for S-119. The comparison of S-119 diffusion through the cellulose membrane and lipophilic PermeaPad barrier revealed a considerable effect of the lipid layer on the decrease in the permeability coefficient. According to the PermeaPad, S-119 was classified as a highly permeated substance. The addition of 1.5 w/v% CDs in donor solution moves it to low-medium permeability class.

Supramolecular Complex of Methyl-β-cyclodextrin with Adamantane-Grafted Hyaluronic Acid as a Novel Antitumor Agent

Methyl-β-cyclodextrin (M-β-CyD) exhibits cytotoxic activity, and has the potentials as an antitumor agent. However, a tumor-selectivity of M-β-CyD is low, leading to low antitumor activity and the adverse effects. Meanwhile, hyaluronic acid (HA) is known as a promising tumor targeting ligand, because various cancer cells overexpress CD44, a HA-binding glycoprotein. In the present study, to develop a tumor-selective delivery system for M-β-CyD, we designed a supramolecular complex of M-β-CyD with adamantane-grafted HA (Ad-HA/M-β-CyD) and evaluated it as a tumor-selective antitumor agent. M-β-CyD formed a stable complex with Ad-HA (K_c>10⁴ M^-1). In addition, Ad-HA/M-β-CyD formed slightly a negative-charged nanoparticle with ca. 140 nm of a particle size, indicating the favorable physicochemical properties for antitumor agents. Ad-HA/M-β-CyD showed the superior cytotoxic activity via CD44-mediated endosomal pathways in HCT116 cells (CD44(+)), a human colon cancer cell line. In addition, cytotoxic activity of Ad-HA/M-β-CyD was induced by apoptosis. These results suggest that Ad-HA/M-β-CyD has the potentials as a tumor-selective supramolecular antitumor agent.

Chlorophyll a in cyclodextrin supramolecular complexes as a natural photosensitizer for photodynamic therapy (PDT) applications

Chlorophyll a (Chl a), an amphipathic porphyrin, was employed as natural photosensitizer for photodynamic therapy applications. Due to its lacking solubility in water and high tendency to aggregate, Chl a was included into different modified cyclodextrins (CDs) to form stable water-soluble supramolecular complexes. To achieve this aim, 2-Hydroxypropyl-β-cyclodextrin (2-HP-β-CD), 2-Hydroxypropyl-γ-cyclodextrin (2-HP-γ-CD), Heptakis(2,6-di-o-methyl)-β-cyclodextrin (DIMEB) and Heptakis(2,3,6-tri-o-methyl)-β-cyclodextrin (TRIMEB) were used. The chemical physical properties of Chl a/CD complexes in cellular medium were studied by means of UV-Vis absorption spectroscopy. Results demonstrated the good aptitude of 2-HP-γ-CD, and more particularly of 2-HP-β-CD, to solubilize the Chl a in cell culture medium in monomeric and photoactive form. Then, Chl a/2-HP-β-CD and Chl a/2-HP-γ-CD complexes were evaluated in vitro on human colorectal adenocarcinoma HT-29 cell line, and cytotoxicity and intracellular localization were respectively assessed. Further tests, such as phototoxicity, ROS generation, intracellular localization and mechanism of cell death were then focused exclusively on Chl a/2-HP-β-CD system. This complex exhibited no dark toxicity and a high phototoxicity toward HT-29 cells inducing cell death via necrotic mechanism. Therefore, it is possible to affirm that Chl a/2-HP-β-CD supramolecular complex could be a promising and potential formulation for applications in photodynamic therapy.

Alpha- and Beta-Cyclodextrin Inclusion Complexes with 5-Fluorouracil: Characterization and Cytotoxic Activity Evaluation

Cyclodextrins are natural macrocyclic oligosaccharides able to form inclusion complexes with a wide variety of guests, affecting their physicochemical and pharmaceutical properties. In order to obtain an improvement of the bioavailability and solubility of 5-fluorouracil, a pyrimidine analogue used as chemotherapeutic agent in the treatment of the colon, liver, and stomac cancers, the drug was complexed with alpha- and beta-cyclodextrin. The inclusion complexes were prepared in the solid state by kneading method and characterized by Fourier transform-infrared (FT-IR) spectroscopy and X-ray powder diffractometry. In solution, the 1:1 stoichiometry for all the inclusion complexes was established by the Job plot method and the binding constants were determined at different pHs by UV-VIS titration. Furthermore, the cytotoxic activity of 5-fluorouracil and its complexation products were evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay on MCF-7 (breast cancer cell line), Hep G2 (hepatocyte carcinoma cell line), Caco-2 (colon adenocarcinoma cell line), and A-549 (alveolar basal epithelial carcinoma cell line). The results showed that both inclusion complexes increased the 5-fluorouracil capability of inhibiting cell growth. In particular, 5-fluorouracil complexed with beta-cyclodextrin had the highest cytotoxic activity on MCF-7; with alpha-cyclodextrin the highest cytotoxic activity was observed on A-549. The IC₅₀ values were equal to 31 and 73 µM at 72 h, respectively. Our results underline the possibility of using these inclusion complexes in pharmaceutical formulations for improving 5-fluorouracil therapeutic efficacy.

Evaluation of the Cytotoxicity of α-Cyclodextrin Derivatives on the Caco-2 Cell Line and Human Erythrocytes

Cyclodextrins, even the 6-membered α-cyclodextrin, are approved in the various pharmacopoeias as pharmaceutical excipients for solubilizing and stabilizing drugs as well as for controlling drug release. Recently α-cyclodextrin has also been marketed as health food with beneficial effects on blood lipid profiles. However, the concentration of α-cyclodextrin used may be very high in these cases, and its toxic attributes have to be seriously considered. The objective of this study was to investigate the cytotoxicity of various, differently substituted α-cyclodextrin derivatives and determine relationship between the structures and cytotoxicity. Three different methods were used, viability tests (MTT assay and Real Time Cell Electronic Sensing on Caco-2 cells) as well as hemolysis test on human red blood cells. The effect of α-cyclodextrin derivatives resulted in concentration-dependent cytotoxicity, so the IC50 values have been determined. Based on our evaluation, the Real Time Cell Electronic Sensing method is the most accurate for describing the time and concentration dependency of the observed toxic effects. Regarding the cytotoxicity on Caco-2 cells, phosphatidylcholine extraction may play a main role in the mechanism. Our results should provide help in selecting those α-cyclodextrin derivatives which have the potential of being used safely in medical formulations.

A Comprehensive Review on Cyclodextrin-Based Carriers for Delivery of Chemotherapeutic Cytotoxic Anticancer Drugs

Most of the cytotoxic chemotherapeutic agents have poor aqueous solubility. These molecules are associated with poor physicochemical and biopharmaceutical properties, which makes the formulation difficult. An important approach in this regard is the use of combination of cyclodextrin and nanotechnology in delivery system. This paper provides an overview of limitations associated with anticancer drugs, their complexation with cyclodextrins, loading/encapsulating the complexed drugs into carriers, and various approaches used for the delivery. The present review article aims to assess the utility of cyclodextrin-based carriers like liposomes, niosomes, nanoparticles, micelles, millirods, and siRNA for delivery of antineoplastic agents. These systems based on cyclodextrin complexation and nanotechnology will camouflage the undesirable properties of drug and lead to synergistic or additive effect. Cyclodextrin-based nanotechnology seems to provide better therapeutic effect and sustain long life of healthy and recovered cells. Still, considerable study on delivery system and administration routes of cyclodextrin-based carriers is necessary with respect to their pharmacokinetics and toxicology to substantiate their safety and efficiency. In future, it would be possible to resolve the conventional and current issues associated with the development and commercialization of antineoplastic agents.

Potential use of folate-appended methyl-β-cyclodextrin as an anticancer agent

To obtain a tumor cell-selectivity of methyl-β-cyclodextrin (M-β-CyD), we newly synthesized folate-appended M-β-CyD (FA-M-β-CyD), and evaluated the potential of FA-M-β-CyD as a novel anticancer agent in vitro and in vivo. Potent antitumor activity and cellular association of FA-M-β-CyD were higher than those of M-β-CyD in KB cells, folate receptor (FR)-positive cells. FA-M-β-CyD drastically inhibited the tumor growth after intratumoral or intravenous injection to FR-positive Colon-26 cells-bearing mice. The antitumor activity of FA-M-β-CyD was comparable and superior to that of doxorubicin after both intratumoral and intravenous administrations, respectively, at the same dose, in the tumor-bearing mice. All of the tumor-bearing mice after an intravenous injection of FA-M-β-CyD survived for at least more than 140 days. Importantly, an intravenous administration of FA-M-β-CyD to tumor-bearing mice did not show any significant change in blood chemistry values. These results strongly suggest that FA-M-β-CyD has the potential as a novel anticancer agent.

Studying on inclusion complexes of Wogonin with β-cyclodextrin and hydroxypropyl-cyclodextrin

The formation of the complexes of Wogonin with β-cyclodextrin (β-CD) and hydroxypropyl-cyclodextrin (HP-β-CD) was studied by fluorescence spectra and nuclear magnetic resonance spectroscopy (NMR). The formation constants (Ks) of complexes were determined by fluorescence method. The results suggested that HP-β-CD was easier to form inclusion with Wogonin than β-CD in solution. In different pH solutions, CDs have different inclusive capacity to Wo. β-CD was most suitable for inclusion of neutral form and HP-β-CD was suitable for acidic form. In addition, the experimental resulted confirmed the existence of 1:1 inclusion complex of Wogonin with CDs. Besides, kinetic studies of DPPH with Wogonin and CDs complexes were done. The results obtained indicated that the complex was the most reactive form. Special configuration of complex has been proposed on NMR technique.

Preparation and characterization of the inclusion complex of Baicalin (BG) with beta-CD and HP-beta-CD in solution: an antioxidant ability study

The formation of the complexes of BG with beta-CD and HP-beta-CD was studied by UV-vis absorption spectroscopy, fluorescence spectra, Phase-solubility measurements and nuclear magnetic resonance spectroscopy (NMR) in solution. The formation constants (K) of complexes were determined by fluorescence method and Phase-solubility measurements. The results showed that the inclusion ability of beta-CD and its derivatives was the order: HP-beta-CD>beta-CD. In addition, the experimental resulted confirmed the existence of 1:1 inclusion complex of BG with CDs. The antioxidant ability studies of BG and CDs complexes were done. The results obtained indicated that the BG/HP-beta-CD complex was the most reactive form, and then was the BG/beta-CD complex; the last was BG. Special configuration of complex has been proposed on NMR technique.

Involvement of PI3K-Akt-Bad pathway in apoptosis induced by 2,6-di-O-methyl-beta-cyclodextrin, not 2,6-di-O-methyl-alpha-cyclodextrin, through cholesterol depletion from lipid rafts on plasma membranes in cells

Cyclodextrins (CyDs), which are widely used to increase the solubility of drug in pharmaceutical fields, are known to induce hemolysis and cytotoxicity at high concentrations. However, it is still not unclear whether cell death induced by CyDs is apoptosis or not. Therefore, in the present study, we investigated the effects of various kinds of CyDs on apoptosis in the cells such as NR8383 cells, A549 cells and Jurkat cells. Of various CyDs, methylated CyDs inducted cell death under the present experimental conditions, but hydroxypropylated CyDs or sulfobutyl ether-beta-CyD (SBE7-beta-CyD) did not. Of methylated CyDs, 2,6-di-O-methyl-beta-cyclodextrin (DM-beta-CyD) and 2,3,6-tri-O-methyl-beta-cyclodextrin (TM-beta-CyD) markedly caused apoptosis in NR8383 cells, A549 cells and Jurkat cells, through cholesterol depletion in cell membranes. In sharp contrast, 2,6-di-O-methyl-alpha-cyclodextrin (DM-alpha-CyD) and methyl-beta-cyclodextrin (M-beta-CyD) induced cell death in an anti-apoptotic mechanism. DM-beta-CyD induced apoptosis through the inhibition of the activation of PI3K-Akt-Bad pathway. Neither p38 MAP kinase nor p53 was contributed to the induction of apoptosis by DM-beta-CyD. Additionally, DM-beta-CyD significantly decreased mitochondrial transmembrane potential, and then caused the release of cytochrome c from mitochondria to cytosol in NR8383 cells. Furthermore, we confirmed that down-regulation of pro-caspase-3 and activation of caspase-3 after incubation with DM-beta-CyD. These results suggest that of methylated CyDs, DM-beta-CyD, not DM-alpha-CyD, induces apoptosis through the PI3K-Akt-Bad pathway, resulting from cholesterol depletion in lipid rafts of cell membranes.

Inhibitory effects of 2,6-di-O-methyl-alpha-cyclodextrin on poly I:C signaling in macrophages

In the present study, we examined the effects of alpha-cyclodextrin (alpha-CyD), 2-hydroxypropyl-alpha-cyclodextrin (HP-alpha-CyD) and 2,6-di-O-methyl-alpha-cyclodextrin (DM-alpha-CyD) on the nitric oxide (NO) and interferon-beta (IFN-beta) production in murine and human macrophages stimulated with Poly I:C and CpG-DNA, toll-like receptor 3 (TLR3) and TLR9 ligands, respectively. DM-alpha-CyD significantly inhibited NO production in RAW264.7 cells and U937 cells differentiated by phorbol myristate acetate (PMA), murine and human macrophage-like cell lines, respectively, stimulated with Poly I:C without cytotoxicity, but neither alpha-CyD nor HP-alpha-CyD did. Meanwhile, the three alpha-CyDs did not inhibit NO production in RAW264.7 cells stimulated with CpG-DNA. DM-alpha-CyD inhibited inducible NO synthase (iNOS) and IFN-beta expression upon stimulation with Poly I:C. Furthermore, DM-alpha-CyD markedly decreased the cellular uptake of Poly I:C in RAW264.7 cells. Therefore, DM-alpha-CyD may be useful as a potent inhibitor for excess activation of macrophages stimulated with Poly I:C.

Decreased B16F10 melanoma growth and impaired tumour vascularization in BDF1 mice with quercetin-cyclodextrin binary system

The aim of this work was to study the inclusion behaviour of a poorly water-soluble bioflavonoid, quercetin, towards sulfobutyl ether-7beta-cyclodextrin. It also involves angiogenesis inhibition in-vivo in addition to in-vitro human cancer cell growth inhibition study of quercetin and its cyclodextrin complex. Drug-cyclodextrin solid inclusion complexes were prepared and characterized in solution and in the solid state. An in-vitro anti-proliferation study using plain drug and its solubilized form was carried out on human cancer cell lines of different origin. Further, an in-vivo tumour growth inhibition study was carried out using a mouse melanoma model. Histological sections of tumours were examined for the evaluation of tumour microvessel density. Significant enhancement of the solubility and dissolution rate of the quercetin, which occurred after complexation, might be attributed to the decrease in crystallinity of drug. SBE7betaCD complex of quercetin was more potent for inhibiting cell proliferation in human erythroleukaemia and cervix cancer cells. Decreased tumour microvessel density in mouse melanoma after oral quercetin administration led to diminished tumour cell proliferation. Quercetin-SBE7betaCD complex showed significantly improved anti-cancer activity at much lower concentration than the plain drug, providing evidence for dose reduction without affecting therapeutic efficacy when using cyclodextrin carriers.

Preparation, characterization and in vivo evaluation of formulation of baicalein with hydroxypropyl-beta-cyclodextrin

The interaction of 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CD) and a poorly water-soluble flavonoid, baicalein (Ba), chemically 5,6,7-trihydroxy flavone in solution and solid-state was studied. Ba/HP-beta-CD solid systems were prepared by freeze-drying method. The formation of Ba/HP-beta-CD complex in aqueous solution was demonstrated by UV spectroscopy, while Ba/HP-beta-CD co-lyophilized product was characterized by differential scanning calorimetry (DSC) and X-ray diffractometry (XRD). Through complexation with HP-beta-CD, the solubility of Ba in neutral aqueous solution was improved significantly. The phase-solubility profile was AP-type, indicating the formation of higher-order complexes or complex aggregates. Ba/HP-beta-CD solid powders were amorphous and show a significantly improved dissolution rate in comparison with free Ba. Comparison of the pharmacokinetics between Ba/HP-beta-CD co-lyophilized product and free Ba was also performed in rats. The concentration of Ba and its mainly conjugated metabolite, 7-O-glucuronide of baicalein (BG) in rat plasma was determined by HPLC method. The in vivo results show that Ba/HP-beta-CD co-lyophilized product exhibits the similar pharmacokinetics as that of free Ba after intravenous administration. Ba/HP-beta-CD co-lyophilized product displays earlier tmax and higher Cmax of BG than free Ba after oral dosing. By comparing the AUC0-infinity of BG between oral dosing, the relative bioavailability of Ba/HP-beta-CD co-lyophilized product to free Ba was 165.0%, which highlighted the evidence of significantly improved bioavailability of formulation of Ba with HP-beta-CD.

Lack of effect of β-cyclodextrin and its water-soluble derivatives on in vitro drug transport across rat intestinal epithelium

The present study aimed to investigate whether beta-cyclodetxrin (beta-CD) and its water-soluble derivatives, hydroxypropyl-beta-cyclodextrin (HP-beta-CD) and sulfobutyl ether beta-cyclodextrin (SBE-beta-CD), exert any effects on the permeation of two drug transport markers (propranolol and lucifer yellow) across rat intestinal epithelium. Rat ileum was stripped of its serosa and mounted inside an Ussing Chamber. Apparent permeability coefficients (P(app)) of the markers from the mucosal to serosal side of the tissue were determined at 37 degrees C in the presence and absence of the beta-cyclodextrins on the mucosal side. Potential difference (PD) was constantly monitored during each experiment to ensure maintenance of the viability and integrity of the tissue. Pre-incubation with 1% beta-CD, 1% HP-beta-CD or 1.48% SBE-beta-CD on the mucosal side for 30 min did not significantly alter the PD and the propranolol permeability (p>0.05). Co-incubation with 1% beta-CD or 1% HP-beta-CD exerted no significant effect on the P(app) of both propranolol and lucifer yellow (p>0.05), but co-incubation with 1.48% SBE-beta-CD lowered the P(app) of propranolol from (1.71+/-0.44)x10(-5) to (0.19+/-0.04)x10(-5)cm/s, which may be ascribed to the molecular complexation of propranolol with SBE-beta-CD. All three beta-cyclodextrins exert no apparent impact on both (passive) transcellar and paracellular drug transports.

Inhibitory effects of dimethylacetyl-beta-cyclodextrin on lipopolysaccharide-induced macrophage activation and endotoxin shock in mice

The potential use of hydrophilic cyclodextrins (CyDs) as an inhibitor for lipopolysaccharide (LPS) was examined. Of the five CyDs used in this study, dimethylacetyl-beta-cyclodextrin (DMA7-beta-CyD) had greater inhibitory activity than other CyDs against the production of nitric oxide (NO) and various proinflammatory cytokines including tumor necrosis factor-alpha (TNF-alpha) in murine macrophages stimulated with two serotypes of LPS and lipid A. The inhibitory effect of DMA7-beta-CyD on NO production was also observed in macrophages stimulated with lipoteichoic acid (LTA), but not peptidoglycan (PGN), polyinosinic-polycytidylic acid (poly I:C) or CpG oligonucleotide (CpG-ODN). Several studies have suggested that the inhibitory effects of DMA7-beta-CyD could be ascribed to the interaction with LPS. Simultaneous administration of DMA7-beta-CyD not only intraperitoneally but also intravenously and intraperitoneal injection of aqueous solution containing LPS and d-galactosamine in murine endotoxin shock model suppressed fatality. Also, DMA7-beta-CyD decreased blood level of TNF-alpha as well as serum levels of aspartate transaminase (AST) and alanine transaminase (ALT) in mice. In conclusion, DMA7-beta-CyD may have promise as a new therapeutic agent for endotoxin shock induced by LPS.

Improvement of gene delivery mediated by mannosylated dendrimer/alpha-cyclodextrin conjugates

The purpose of this study is to evaluate in vitro and in vivo gene delivery efficiency of polyamidoamine (PAMAM) starburst dendrimer (generation 2, G2) conjugate with alpha-cyclodextrin (alpha-CDE conjugate (G2)) bearing mannose (Man-alpha-CDE conjugates) with the various degrees of substitution of the mannose moiety (DSM) as a novel non-viral vector in a variety of cells. Man-alpha-CDE conjugates (DSM 3.3 and 4.9) were found to have much higher gene transfer activity than dendrimer, alpha-CDE conjugate and Man-alpha-CDE conjugates (DSM 1.1 and 8.3) in various cells, which are independent of the expression of cell surface mannose receptors. Cellular association of pDNA complexes with dendrimer, alpha-CDE conjugate and Man-alpha-CDE conjugate (DSM 3.3) and their cytotoxic effects differed only very slightly. Surface plasmon resonance study demonstrated that the specific binding activity of Man-alpha-CDE conjugates to concanavalin A was not very strong. Much more conjugation of the mannose moiety to alpha-CDE conjugates provided unfavorable physicochemical properties of pDNA complexes for gene transfer, e.g. the low interaction with pDNA, the low enzymatic stability of pDNA and the lack of pDNA compaction. Man-alpha-CDE conjugate (DSM 3.3) provided gene transfer activity higher than dendrimer and alpha-CDE conjugate in kidney 12 h after intravenous injection in mice. These results suggest the potential use of Man-alpha-CDE conjugate (DSM 3.3) as a non-viral vector.

Design and evaluation of cyclodextrin-based drug formulation

The pharmaceutically useful cyclodextrins (CyDs) are classified into hydrophilic, hydrophobic, and ionic derivatives. Because of the multi-functional characteristics and bioadaptability, these CyDs are capable of alleviating the undesirable properties of drug molecules through the formation of inclusion complexes or the form of CyD/drug conjugates. This review outlines the current application of CyDs in design and evaluation of CyD-based drug formulation, focusing on their ability to enhance the drug absorption across biological barriers, the ability to control the rate and time profiles of drug release, and the ability to deliver a drug to a targeted site.

Involvement of CD14 in the inhibitory effects of dimethyl-α-cyclodextrin on lipopolysaccharide signaling in macrophages

The potential use of alpha-cyclodextrin and its hydrophilic alpha-cyclodextrin derivatives (alpha-CyDs) as antagonists against lipopolysaccharide (LPS), which stimulates the nitric oxide (NO) and tumor necrosis factor-alpha (TNF-alpha) production as well as nuclear factor-kappaB (NF-kappaB) activation in macrophages was examined. Of three alpha-CyDs used in the present study, 2,6-di-O-methyl-alpha-CyD (DM-alpha-CyD) had greater inhibitory activity than did the other CyDs against NO and TNF-alpha production through an impairment of gene expression in macrophage cell lines and primary macrophages stimulated with LPS and lipid A in a concentration-dependent manner. Concomitantly, DM-alpha-CyD inhibited NF-kappaB translocation into nucleus. These inhibitory effects of DM-alpha-CyD could be attributed to the release of CD14 from lipid rafts caused by an efflux of phospholipids, but not cholesterol. These results suggest that DM-alpha-CyD may have promise as a potent and unique antagonist for excess activation of macrophages stimulated with LPS.

[Pharmaceutical application of cyclodextrins as multi-functional drug carriers]

Owing to the increasingly globalized nature of the cyclodextrin (CyD)-related science and technology, development of the CyD-based pharmaceutical formulation is rapidly progressing. The pharmaceutically useful CyDs are classified into hydrophilic, hydrophobic, and ionic derivatives. Because of the multi-functional characteristics and bioadaptability, these CyDs are capable of alleviating the undesirable properties of drug molecules through the formation of inclusion complexes or the form of CyD/drug conjugates. This review outlines the current application of CyDs in drug delivery and pharmaceutical formulation, focusing on the following evidences. 1) The hydrophilic CyDs enhance the rate and extent of bioavailability of poorly water-soluble drugs. 2) The amorphous CyDs such as 2-hydroxypropyl-beta-CyD are useful for inhibition of polymorphic transition and crystallization rates of drugs during storage. 3) The delayed release formulation can be obtained by the use of enteric type CyDs such as O-carboxymethyl-O-ethyl-beta-CyD. 4) The hydrophobic CyDs are useful for modification of the release site and/or time profile of water-soluble drugs with prolonged therapeutic effects. 5) The branched CyDs are particularly effective in inhibiting the adsorption to hydrophobic surface of containers and aggregation of polypeptide and protein drugs. 6) The combined use of different CyDs and/or pharmaceutical additives can serve as more functional drug carriers, improving efficacy and reducing side effects. 7) The CyD/drug conjugates may provide a versatile means for the constructions of not only colonic delivery system but also site-specific drug release system, including gene delivery. On the basis of the above-mentioned knowledge, the advantages and limitations of CyDs in the design of advanced dosage forms will be discussed.

Study of freeze-dried quercetin-cyclodextrin binary systems by DSC, FT-IR, X-ray diffraction and SEM analysis

The inclusion behavior of 2-hydroxypropyl beta-cyclodextrin (HPbetaCD) and beta-cyclodextrin (betaCD), in solution and solid-state was studied towards a poorly water-soluble bioflavonoid, quercetin (QURC), chemically 3,3',4',5',7-pentahydroxy flavone. Drug-cyclodextrin solid systems were prepared by freeze-drying. Phase solubility study was used to evaluate the complexation in solution, of two cyclodextrins, i.e., betaCD and HPbetaCD. The stoichiometry and stability constants of QURC-betaCD (1:1 and 402M(-1)) and QURC-HPbetaCD (1:1 and 532M(-1)) complexes were calculated by phase solubility method. The formation of inclusion complexes with betaCD and HPbetaCD in the solid-state were confirmed by infrared spectroscopy, differential scanning calorimetry, X-ray diffractometry, and scanning electron microscopy (SEM).

β-Cyclodextrin as a suitable solubilizing agent for in situ absorption study of poorly water-soluble drugs

To evaluate the intestinal permeability of poorly water-soluble compounds, it is of importance to completely dissolve them in a medium and to avoid precipitation during experiments. This study was undertaken to find an agent possessing a high-solubilizing capacity and exhibiting minimal modulating impact on membrane integrity and absorption systems such as passive diffusion and carrier-mediated permeation. Phenytoin dissolution was compared in the presence of seven solubilizing agents at concentrations of 1, 2, or 5% using a centrifugation method. The capacity to dissolve phenytoin was great in beta-cyclodextrin (beta-CD) and hydroxypropyl beta-cyclodextrin, followed by Tween 80. Those of methanol, dimethyl sulfoxide, dimethyl acetoamide, and polyethylene glycol 400 were much lower than expected. One percent beta-CD did not alter the absorption of fluorescein isothiocyanate-dextran 4,000 or the release of protein and lactate dehydrogenase into in situ loop contents, suggesting that 1% beta-CD had no significant impact on the integrity of the intestinal membrane. One percent beta-CD also did not alter the absorption of caffeine, ceftibuten, or rhodamine 123 from in situ jejunal loops, indicating no interference with passive diffusion and active transports mediated by a peptide transporter and P-glycoprotein. In conclusion, 1% beta-CD is a suitable solubilizing agent for evaluating in situ intestinal absorption of poorly water-soluble compounds.

Behavior of α-, β-, and γ-Cyclodextrins and Their Derivatives on an in Vitro Model of Blood-Brain Barrier

Cyclodextrins (CDs) can be envisaged to cure some diseases related to the brain, but the behavior of these compounds toward the blood-brain barrier (BBB) remains largely unexplored to envisage such clinical applications. To fulfill this gap, the toxicity and endothelial permeability for native, methylated, and hydroxypropylated alpha-, beta-, and gamma-CDs have been studied on an in vitro model of BBB. As shown by the endothelial permeability for sucrose and immunofluorescence stainings, the native CDs are the most toxic CDs (alpha- > beta- > gamma-CD). Whereas the chemical modification of beta-CD did not affect the toxicity of this CD, differences are observed for the alpha- and gamma-CD. To determine the origin of toxicity, lipid effluxes on the brain capillary endothelial cells were performed in the presence of native CDs. It was found that alpha-CD removed phospholipids and that beta-CD extracted phospholipids and cholesterol. gamma-CD was less lipid-selective than the other CDs. Finally, the endothelial permeability of each CD has been determined. Surprisingly, no structure/permeability relationship has been observed according to the nature and chemical modifications of CDs.

Inhibitory Effect of Sulfobutyl Ether β‐cyclodextrin on DY‐9760e‐Induced Cellular Damage: In vitro and in vivo Studies

The effects of water-soluble beta-cyclodextrin derivatives (beta-CyDs), such as 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CyD) and sulfobutyl ether beta-cyclodextrin (SBE7-beta-CyD) on cytotoxicity of DY-9760e (3-[2-[4-(3-chloro-2-methylphenyl)-1-piperazinyl]ethyl]-5,6-dimethoxy-1-(4-imidazolylmethyl)-1H-indazole dihydrochloride 3.5 hydrate) toward human umbilical vein endothelial cells (HUVECs) in vitro and vascular damage of the auricular vein of rabbits by DY-9760e in vivo were investigated. The spectroscopic study revealed that of the four beta-CyDs SBE7-beta-CyD forms the most stable inclusion complex in phosphate-buffered saline, probably because of a synergetic effect of hydrophobic and electrostatic interactions. beta-CyDs inhibited DY-9760e-induced cell death toward HUVECs in an order of G(2)-beta-CyD < beta-CyD < HP-beta-CyD < SBE7-beta-CyD, which was consistent with the order of the magnitude of stability constants. When the DY-9760e solution was infused into the auricular vein of rabbits for 24 h, SBE7-beta-CyD suppressed a DY-9760e-induced irritation such as thrombus, desquamation of the endothelium vasculitis, and perivasculitis. The present data indicated that SBE7-beta-CyD formed an inclusion complex with DY-9760e in a buffer solution and possessed the protective effect on DY-9760e-induced cytotoxicity toward HUVECs and vascular damage in rabbits. These results suggested potential use of SBE7-beta-CyD as a parenteral carrier for DY-9760e.

Involvement of cholesterol in the inhibitory effect of dimethyl-beta-cyclodextrin on P-glycoprotein and MRP2 function in Caco-2 cells

We compared the inhibitory effect of various cyclodextrins (CyDs) on P-glycoprotein (P-gp) and multidrug resistance-associated protein 2 (MRP2) function and examined the contribution of cholesterol to the inhibitory effect of 2,6-di-O-methyl-beta-cyclodextrin (DM-beta-CyD) on the efflux activity of the function in Caco-2 cell monolayers. Of various CyDs, DM-beta-CyD significantly impaired the efflux activity of P-gp and MRP2. DM-beta-CyD released P-gp and MRP2 from the monolayers in the apical side's transport buffer and decreased the extent of cholesterol as well as P-gp and MRP2 in caveolae of Caco-2 cell monolayers, but not caveolin and flotillin-1. On the other hand, DM-beta-CyD did not change MDR1 and MRP2 mRNA levels. Therefore, these results suggest that the inhibitory effect of DM-beta-CyD on P-gp and MRP2 function, at least in part, could be attributed to the release of these transporters from the apical membranes into the medium as secondary effects through cholesterol-depletion in caveolae after treatment of Caco-2 cell monolayers with DM-beta-CyD.