Modification of Drug Crystallization by Cyclodextrins in Pre-formulation Study

Controlling drug crystallization is one of the important issues in pre-formulation study. In recent years, advanced approaches including the use of tailor-made additives have gathered considerable attention to control crystallization behavior of drugs. This review focuses on the use of hydrophilic cyclodextrins (CDs) as additives for controlling drug crystallization. CDs affect the crystallization of drugs in solution and in solid state based on a host-guest interaction. For example, 2,6-di-O-methyl-β-CD and 2-hydroxybutyl-β-CD suppressed solution-mediated transition of drugs during crystallization by the host-guest interaction; as a result, metastable forms selectively precipitated in solution. The use of CDs in crystal engineering provided an opportunity for the detection of a new polymorph by changing the crystallization pathway. It was also possible to modify crystal morphology (i.e., crystal habit) by selective suppression of crystal growth on a certain direction based on the host-gust interaction. For solid formulation, stable amorphous drug/CDs complex under humid conditions was prepared using two different CDs. An overview of some recent progress in the use of CDs in crystal engineering and in amorphous formulation is described in this review.

The Use of Enteric Capsules for Releasing a Fragrance over an Extended Period of Time

A system for releasing a fragrance, citral (CR) over an extended period of time using three types of enteric capsules is reported. The L- and M-type capsules released CR into media with a pH above 6, while the H-type capsule released CR at a pH above 7. The pH of the releasing medium was controlled by sodium borate (SB), i.e., by adding SB-methylcellulose (MC) prepared in different weight ratios (SB-MC 1 : 2, 1 : 1 and 2 : 1) to tablets and by compressing them at different pressures. The tablet containing a large amount of SB and that was pressed at higher pressures permitted the pH of the releasing medium to be changed from 5 to 9, at 4-5 h after the addition of SB to the tablets, while negligible changes were observed for tablets containing low amounts of SB and which were compressed at lower pressures. Reflecting these pH changes, CR was released after different periods of time when SB-MC tablets and capsules containing CR were simultaneously added to the releasing medium. When enteric capsules containing CR and the pH adjusting tablets were simultaneously added to a benzyl acetate (BA) solution, BA was released at a constant rate, while CR was released for different periods of time depending on the type of capsule used. The results suggest that fragrances could be released over different time frames by using enteric capsules and pH adjusting agents, for example, the release of fragrances with sedative effects at night time and with stimulating effects in the morning.

An oral absorbent, surface-deacetylated chitin nano-fiber ameliorates renal injury and oxidative stress in 5/6 nephrectomized rats

In this study, we report that surface-deacetylated chitin nano-fibers (SDACNFs) are more effective in decreasing renal injury and oxidative stress than deacetylated chitin powder (DAC) in 5/6 nephrectomized rats. An oral administration of low doses of SDACNFs (40mg/kg/day) over a 4 week period resulted in a significant decrease in serum indoxyl sulfate, creatinine and urea nitrogen levels, compared with a similar treatment with DAC or AST-120. The SDACNFs treatment also resulted in an increase in antioxidant potential, compared with that for DAC or AST-120. Immunohistochemical analyses also demonstrated that SDACNFs treated CRF rats showed a decrease in the amount of accumulated 8-OHdG compared with the CRF group. These results suggest that the ingestion of SDCH-NF results in a significant reduction in the levels of pro-oxidants, such as uremic toxins, in the gastrointestinal tract, thereby inhibiting the subsequent development of oxidative stress in the systemic circulation.

Biomaterials based on freeze dried surface-deacetylated chitin nanofibers reinforced with sulfobutyl ether β-cyclodextrin gel in wound dressing applications

A freeze-dried gel composed of surface-deacetylated chitin nanofibers (SDACNFs), reinforced with an anionic cyclodextrin, sulfobutyl ether β-cyclodextrin (SBE-β-CD) was evaluated for treating wounds in a rat model, and the results were compared with a SDACNFs gel without SBE-β-CD. The incorporation of prednisolone (PD), a poorly water-soluble drug, in both types of gels and its release from the gels were also compared. In both cases, wound areas were decreased and their effect was higher than that of commercially available wound dressings. The rate of release of PD from the freeze-dried SDACNFs/SBE-β-CD was much faster than that form SDACNFs alone without SBE-β-CD, due to fact that the PD is more soluble in the amorphous SBE-β-CD complex compared to the other preparations. The findings indicate that the freeze-dried SDACNFs/SBE-β-CD gel would be beneficial as a new biomaterial for the treatment of wounds and for preparing homogeneous high-content gels that contain poorly water-soluble drugs.

In Vitro and In Vivo Evaluation of Hydrophilic C60(OH)10/2-Hydroxypropyl-β-cyclodextrin Nanoparticles as an Antioxidant

The objective of this study was to assess the antioxidant ability of C60(OH)10/2-hydroxypropyl-β-cyclodextrin (HP-β-CD) nanoparticles, by comparing their scavenging ability for reactive nitrogen species, their cytoprotective effects under conditions of oxidative stress, and their therapeutic effects against diseases that are induced by oxidative stress. The C60(OH)10/HP-β-CD nanoparticles had a higher scavenging activity against nitric acid and peroxynitrite (ONOO(-)) than the other antioxidants such as ascorbic acid, trolox, and edaravone. The cytoprotective effect of C60(OH)10/HP-β-CD nanoparticles was examined on HeLa and HepG2 cells by monitoring the percentage of cell death induced by H2O2. Treatment with C60(OH)10/HP-β-CD nanoparticles resulted in an increase in cell viability, due to the suppression of the oxidative stress. Furthermore, the nanoparticles had a high cytoprotective effect, compared with other polyhydroxylated C60 (C60(OH)24 and C60(OH)40). The C60(OH)10/HP-β-CD nanoparticles were intravenously administered to mice with a liver injury induced by an over dose of acetaminophen. Levels of alanine transaminase and aspartate transaminase were essentially the same as those of normal mice and the survival rate was also prolonged by the intravenous administration of the C60(OH)10/HP-β-CD nanoparticles. The results indicate that C60(OH)10/HP-β-CD nanoparticles are a promising antioxidant for use in the treatment of diseases caused by oxidative stresses.

Ternary inclusion complex formation and stabilization of limaprost, a prostaglandin E1 derivative, in the presence of α- and β-cyclodextrins in the solid state

Limaprost/α-cyclodextrin (CD)/β-CD ternary inclusion complex was prepared by freeze-drying a solution containing all three components. Under humid conditions, limaprost was more stable in the ternary α-/β-CD inclusion complex than in the binary α- or β-CD complex. Specifically, during storage at 30°C/75% relative humidity (R.H.) for 4 weeks, about 19% of limaprost degraded into 17S,20-dimethyl-trans-Δ(2)-prostaglandin A1 (referred as 11-deoxy-Δ(10)) in the β-CD complex, 8.1% degraded in the α-CD complex, and only 2.2% degraded in the α-/β-CD complex. The mechanism of limaprost stabilization in the presence of both CDs was investigated by Raman and solid-state NMR spectroscopy and powder X-ray diffractometry. The fast degradation of limaprost to 11-deoxy-Δ(10) in the β-CD complex was due to the rapid crystallization of β-CD from the complex, liberating the free amorphous drug, which is susceptible to degradation. The dissociation and crystallization of β-CD from the inclusion complex were suppressed by freeze-drying limaprost in the presence of both α- and β-CDs. In addition, the interaction between limaprost and the two CDs was reinforced by inclusion of different moieties of limaprost: α-CD predominantly included the alkyl ω-chain, whereas β-CD included the five-membered ring. Thus, a stable ternary inclusion complex was formed that included limaprost, maintaining the amorphous state of the complex and dramatically stabilizing the drug under humid conditions.

The formation of an inclusion complex between a metabolite of ginsenoside, compound K and γ-cyclodextrin and its dissolution characteristics

OBJECTIVES

20S-protopanaxadiol 20-O-β-D-glucopyranoside (compound K), a metabolite of ginsenoside, is only sparingly soluble in water. The aim of this study was to improve the low solubility, slow dissolution rate and low oral bioavailability of compound K by forming an inclusion complex with γ-cyclodextrin (γ-CyD), and to compare the results with those of β-CyD complex.

METHODS

The interactions of compound K with β and γ-CyDs were studied by the solubility method and proton nuclear magnetic resonance spectroscopy. Solid forms of compound K/CyD complexes with different molar ratios were prepared by the kneading method, and the resulting complex was characterized by powder X-ray diffractometry. The dissolution rate of the complexes was measured by the rotary disk method. In-vivo absorption studies in rats were carried out, and the serum level of compound K, after its oral administration, was measured by a liquid chromatography-tandem mass spectrometry system.

KEY FINDINGS

γ-CyD markedly improved the low solubility of compound K at lower CyD concentrations (<0.03 M), whereas the solubility was decreased at higher concentrations (>0.06 m). The enhancement in solubility by γ-CyD at a lower concentration was much higher than the corresponding values for β-CyD. The apparent 1:1 stability constant (1.5 × 10(5)  m(-1) ) for the γ-CyD complex was 18-fold larger than that (8.2 × 10(3)  m(-1) ) of the β-CyD complex. The dissolution rate of the 1:1 compound K/γ-CyD complex was faster than that for the 1:3 (guest : host) complex. These results suggest that the dissolution rate of the 1:1 complex, in which the drug is partially included, was faster than that of the 1:3 complex, in which the drug was completely included, due to the higher solubility and amorphous property of the former complex compared with the properties of the latter complex. The fast dissolution of the γ-CyD complex was reflected in the maximum plasma level (Cmax ) of the drug and the time (Tmax ) to reach the maximum plasma level after its oral administration to rats.

CONCLUSIONS

The effect of γ-CyD on enhancing the solubility of compound K is much higher than that for the β-CyD complex, and the dissolution rate of the guest when it is partially included in the γ-CyD is faster the corresponding value when it is completely included in the cavity.

Antioxidant and renoprotective activity of 2-hydroxypropyl-β-cyclodextrin in nephrectomized rats

OBJECTIVES

Oxidative stress is known to be involved in the pathogenesis of chronic renal failure (CRF). In this study, the effect of cyclodextrins (CDs) on oxidative stress and CRF was investigated using 5/6 nephrectomized rats as model animals.

METHODS

CRF model rats were divided into five groups and treated for 8 weeks as follows: control, α-CD, β-CD, γ-CD and 2-hydroxypropyl-β-CD (HP-β-CD). Blood was collected from the rats after 4 and 8 weeks for an analysis of renal function and oxidative stress tests were carried out.

KEY FINDINGS

An oral administration of HP-β-CD over an 8-week period resulted in a significant decrease in serum indoxyl sulphate, creatinine and urea nitrogen levels, compared with the other CDs. The ingestion of HP-β-CD also resulted in an increase in antioxidant potential, compared with the other CDs. In in vitro studies, the interaction of HP-β-CD with a uremic toxin, indole molecule, was much higher than that for the other CDs, as evidenced by Proton nuclear magnetic resonance ((1) H NMR) measurements.

CONCLUSIONS

These results suggest that the ingestion of HP-β-CD might result in a significant reduction in the levels of pro-oxidants in the gastrointestinal tract, such as uremic toxins, thereby inhibiting the subsequent development of oxidative stress in the systemic circulation.

Slow-release of famotidine from tablets consisting of chitosan/sulfobutyl ether β-cyclodextrin composites

An intermolecular complex formed from a 1:1 weight ratio of chitosan (CS, molecular weight 30 kDa) and sulfobutyl ether β-cyclodextrin (SBE-β-CyD, degree of substitution 7) was less soluble than either of the original components. The release of famotidine from tablets composed of a simple mixture of CS and SBE-β-CyD is slower in media at pH 1.2 than at 6.8. Macroscopic observation of tablets and a kinetic analysis of release profiles suggested that, at pH 1.2, the drug was slowly released from the less-soluble CS/SBE-β-CyD complex formed on the surface of the tablet immediately after exposure to water, accompanied by the dissolution of the interpolymer complex and, ultimately, the erosion and disintegration of the tablet. In the case of the medium at pH 6.8, the formation of a gel by CS was the cause of the slow release, especially for CS/SBE-β-CyD tablets which were significantly gelated and both the diameter and thickness of the tablet had expanded. The in vitro slow releasing characteristic of the CS/SBE-β-CyD tablet was reflected in the in vivo absorption of the drug after oral administration to rats. These results suggest that a simple mixing of CS and SBE-β-CyD is potentially useful for the controlled release of a drug.

Preparation and antioxidant activity of PEGylated chitosans with different particle sizes

The preparation of water-soluble chitosans such as polyethylene glycol (PEG)-grafted derivatives is essential for improving the biocompatibility and water solubility of these types of polysaccharides. In this study, chitosans (CS1; 22 kDa, CS2; 38 kDa, CS3; 52 kDa) with different molecular weights were modified with a succinyl ester derivative of monomethoxypolyethylene glycol (mPEG-COONSu; 2 kDa), and the properties of the resulting conjugates (mPEG-CS1, mPEG-CS2, mPEG-CS3) were investigated. The antioxidant properties of these mPEG-CSs were examined using (1) N-centered radicals derived from 1,1'-diphenyl-2-picrylhydrazyl (DPPH), (2) reducing power, based on their ability to reduce Cu2+ and (3) hydroxyl radicals via the use of ESR spectrometry. The order of their effectiveness was mPEG-CS1>mPEG-CS2>mPEG-CS3, i.e. mPEG-CS1 with a low particle size had the highest scavenging activity of the mPEG-CSs tested. In an in vivo study, we examined the effect of mPEG-CS1 on liver injury, caused by injecting mice with Concanavalin A (Con A). The livers of mice that were treated with mPEG-CS1 were protected from Con A-induced injury. Further, pre-treatment with mPEG-CS1 dramatically reduced the mortality associated with Con A-induced mortality. These findings suggest that mPEG-CS1 could be potentially useful in the treatment of immune-mediated liver injury.

Effects of chitosan on oxidative stress and related factors in hemodialysis patients

In recent world-wide studies, chitosans were tested as a dietary supplement for inhibiting the absorption of certain lipids and bile acids. We previously demonstrated the antioxidative and renoprotective potential of chitosan supplementation in chronic renal failure using 5/6 nephrectomized rats. In this study, we report the effects of chitosan on oxidative stress and related factors in hemodialysis patients. The ingestion of chitosan over a 12-week period resulted in a significant decrease in serum indoxyl sulfate and phosphate levels, compared with the levels prior to the start of the study. The ingestion of chitosan also resulted in a lowered ratio of oxidized to reduced albumin and a decrease in the level of advanced oxidized protein products. In in vitro studies, chitosan solutions were found to bind 38.5% of the indoxyl sulfate and 17.8% of the phosphate, respectively. Further, the oxidized albumin ratio was correlated with serum indoxyl sulfate levels in vivo. These results suggest that the ingestion of chitosan results in a significant reduction in the levels of pro-oxidants, which include uremic toxins, in the gastrointestinal tract, thereby inhibiting the subsequent development of oxidative stress in the systemic circulation. In addition, the long-term ingestion of chitosan has the potential for use in treating hyperphosphatemia in hemodialysis patients.

Cyclodextrins improve oral absorption of a novel factor Xa inhibitor by interfering with interaction between the drug and bile acids in rats

Objectives

Poor oral absorption of a factor Xa inhibitor, DX-9065, is partly due to the interaction with bile acids in the gastrointestinal tract. The aim of this study is to improve the oral bioavailability of DX-9065 by cyclodextrins (CyDs) capable of interfering with such interaction.

Methods

The abilities of the CyDs to interfere with the interaction between DX-9065 and sodium chenodeoxycholate were evaluated using equilibrium dialysis. The interaction between DX-9065 and the CyDs was studied spectroscopically. Effects of the CyDs on the oral absorption of DX-9065 were examined in rats.

Key findings

Hydroxypropyl-β-CyD and γ-CyD were effective in interfering with the interaction between DX-9065 and sodium chenodeoxycholate as a representative bile acid. Spectroscopic studies revealed that DX-9065 was included into the CyD cavity to form inclusion complexes in an acidic medium. With dissociation of the carboxyl group of DX-9065 in a neutral medium, the stability of the complexes was decreased to such an extent that DX-9065 in the cavity is replaced with co-existing bile acids. The average area under the plasma concentration-time curve value after oral administration of DX-9065 with hydroxypropyl-β-CyD was 2.5 times higher than that of DX-9065 alone with a statistical difference in rats.

Conclusions

We suggest that the CyDs are useful in designing oral formulations of DX-9065 with an improved bioavailability.

Antioxidant and renoprotective activity of chitosan in nephrectomized rats

The effect of chitosan on oxidative stress and chronic renal failure was investigated using 5/6 nephrectomized rats. The ingestion of chitosan over a 4-week period resulted in a significant decrease in total body weight, glucose, serum creatinine and indoxyl sulfate levels (P=0.0011, P=0.0006, P=0.0012, and P=0.0005, respectively), compared with the non-treated nephrectomized group. The ingestion of chitosan also resulted in a lowered ratio of oxidized to reduced albumin (P=0.003) and an increase in biological antioxidant potential (P=0.023). Interestingly, the oxidized albumin ratio was correlated with serum indoxyl sulfate levels in vivo. These results suggest that the ingestion of chitosan results in a significant reduction in the levels of pro-oxidants, such as uremic toxins, in the gastrointestinal tract, thereby inhibiting the subsequent development of oxidative stress in the systemic circulation.

Evaluation of photodynamic activity of C60/2-hydroxypropyl-β-cyclodextrin nanoparticles

The objective of this study is to evaluate the ability of C(60)/2-hydroxypropyl-β-cyclodextrin (HP-β-CyD) naonparticles to generate reactive oxygen species (ROS) and to induce cell toxicity by the photoirradiation. C(60) nanoparticles were prepared by cogrinding with HP-β-CyD for 3 h at 4°C under reduced pressure. The photodynamic activity of C(60)/HP-β-CyD nanoparticles was evaluated by spectroscopic methods, including the electron spin resonance spin-trapping method, and by the cell viability test using Hela cells. C(60)/HP-β-CyD nanoparticles efficiently generated not only superoxide anion radical (O(2)(·-)) and hydroxyl radical (·OH), but also singlet oxygen ((1)O(2)) through photoirradiation. The ROS generation was enhanced by decreasing the mean particle diameter of C(60) nanoparticles, and the particle size smaller than 90 nm showed a high generation of ·OH and (1)O(2). In addition, HP-β-CyD enhanced the generation of (1)O(2), compared with polyvinylpyrrolidone (an effective solubillizer for C(60)), due to partial disposition of C(60) in the hydrophobic CyD cavity. Furthermore, C(60) /HP-β-CyD nanoparticles showed cell toxicity after the light irradiation, but no toxicity was observed without the light irradiation. Therefore, HP-β-CyD is useful for the preparation of stable C(60) nanoparticles with high ROS generation ability, and C(60)/HP-β-CyD nanoparticles are a promising photosensitizer for photodynamic therapy.

Peak-less hypoglycemic effect of insulin glargine by complexation with maltosyl-β-cyclodextrin

Long-acting insulin products are desired that provide sustained blood glucose lowering without blood glucose level peaks. In the present study, to obtain the more desirable blood glucose lowering effect of long-acting insulin products, we investigated the effect of maltosyl-β-cyclodextrin (G(2)-β-CyD) on physicochemical properties and pharmacokinetics/pharmacodynamics of insulin glargine, which is the one of the most widely used insulin analog. G(2)-β-CyD increased the solubility and suppressed the aggregation of insulin glargine in phosphate buffer at 9.5, probably due to the interaction of G(2)-β-CyD with aromatic residues of the insulin glargine such as tyrosine. In addition, the dissolution rates of insulin glargine from its precipitates were increased by a complexation with G(2)-β-CyD. Subcutaneous administration of an insulin glargine solution with G(2)-β-CyD to rats gradually decreased blood glucose levels and provided a sustained blood glucose lowering effect without showing the glucose level peaks. These results suggest that G(2)-β-CyD can be a useful excipient for sustained release and a truly peak-less formulation of insulin glargine.

Some pharmaceutical and inclusion properties of 2-hydroxybutyl-β-cyclodextrin derivative

2-Hydroxybutyl-β-cyclodextrins (HB-β-CyDs) with different degrees of substitution (D.S.) were prepared and their physicochemical and biological properties and solubilizing abilities were studied and compared with those of 2-hydroxypropyl-β-cyclodextrin (HP-β-CyD). The surface activity of HB-β-CyD was higher than that of HP-β-CyD (D.S. 5.6) and increased with its concentration and D.S. The moisture sorption of HB-β-CyD (D.S. 5.5) was less than that of HP-β-CyD (D.S. 5.6), because of the introduction of hydrophobic hydroxybutyl groups in a molecule. The hemolytic activity (rabbit erythrocytes) decreased in the order of 2,6-di-O-methyl-β-cyclodextrin (DM-β-CyD)>methyl-β-cyclodextrin (M-β-CyD)>HB-β-CyD (D.S. 5.5)>β-CyD>HP-β-CyD (D.S. 5.6). The hemolytic activity of HB-β-CyD increased with D.S. and HB-β-CyD induced echinocyte (or crenation), as well as DM-β-CyD does. It was suggested from the solubility study of membrane components that HB-β-CyD interacted predominantly with cholesterol in erythrocytes, resulting in the hemolysis. The inclusion ability of HB-β-CyD was higher than that of HP-β-CyD (D.S. 5.6), especially for poorly water-soluble drugs with long linear structures such as biphenylylacetic acid and flurbiprofen (FP). For example, HB-β-CyD formed the inclusion complex with FP in a molar ratio of 1:1, by including the biphenyl moiety in the host cavity. The dissolution rate of FP/HB-β-CyD (D.S. 5.5) complex was faster than that of HP-β-CyD (D.S. 5.6) complex. The results suggested that HB-β-CyDs have considerable pharmaceutical potential and can work as a fast-dissolving carrier for poorly water-soluble drugs.

Improved transdermal delivery of prostaglandin E1 through hairless mouse skin: combined use of carboxymethyl-ethyl-β-cyclodextrin and penetration enhancers

The optimal prescription of transdermal preparations of prostaglandin E1 (PGE1) for treatment of peripheral vascular diseases has been investigated. The chemical stability of PGE1 in fatty alcohol/propylene glycol (FAPG) ointment was markedly improved by carboxymethyl-ethyl-β-cyclodextrin (CME-β-CyD). Application of a PGE1 ointment containing the penetration enhancer, 1-dodecylazacycloheptane-2-one (Azone) or 1-[2-(decylthio)ethyl]azacyclopentane-2-one (HPE-101), onto the skin of hairless mice showed the increase of blood flow in the skin due to the vasodilating action of PGE1. In particular, the ointment containing a PGE1-CME-β-CyD complex supplemented with HPE-101 showed the most prominent increase of the blood flow. Compared with other ointments, this ointment was found to show significantly greater transfer of HPE-101 into in-vitro preparations of the skin of hairless mice. Transfer of PGE1 into the skin was thought to be facilitated by this increased transfer of HPE-101. These results suggest that a combination of CME-β-CyD and HPE-101 is useful for designing PGE1 ointments for topical application with good chemical stability and percutaneous permeability.

Inhibitory Effect of 2-Hydroxypropyl-β-cyclodextrin on Crystal-growth of Nifedipine During Storage: Superior Dissolution and Oral Bioavailability Compared with Polyvinylpyrrolidone K-30

To prevent the crystal-growth of nifedipine during storage, 2-hydroxypropyl-β-cyclodextrin (HP-β-CyD) was employed as a hydrophilic drug carrier and compared with polyvinylpyrrolidone K-30 (PVP). Amorphous nifedipine powders were prepared by spray-drying with HP-β-CyD or PVP, and their crystal-growing behaviour at accelerated storage conditions were examined by X-ray diffraction analysis and microscopy. Although PVP initially retarded the crystallization of nifedipine, it failed to control the increase of crystal size after prolonged storage at 60°C., 75% r.h., resulting in a remarkable decrease in dissolution rate in water. In sharp contrast, a relatively fine and uniform size of nifedipine crystals was maintained in the HP-β-CyD system even after accelerated storage conditions. The enhanced dissolution observed for all the HP-β-CyD systems in a dissolution medium containing 0·1% non-ionic surfactant HCO-60 were clearly reflected in the in-vivo absorption of nifedipine following oral administration to dogs. These results suggest that HP-β-CyD is particularly useful in solving problems encountered on storage of amorphous nifedipine in solid dosage forms.

Enhancement of the aqueous solubility and masking the bitter taste of famotidine using drug/SBE-beta-CyD/povidone K30 complexation approach

The objective of the present study was to evaluate the potential of ternary system (comprised of famotidine, beta-cyclodextrin (beta-CyD) or its derivatives and a hydrophilic polymer) as an approach for enhancing the aqueous solubility and masking the bitter taste of famotidine. The aqueous solubility of famotidine increased in the presence of beta-CyDs, particularly sulfobutyl ether beta-CyD (SBE-beta-CyD), and it was further enhanced by the combination of SBE-beta-CyD and polyvinyl pyrrolidone (Povidone) K30. The solid binary (drug-beta-CyDs) and ternary (drug-beta-CyDs-Povidone K30) systems were prepared by the kneading and freeze-drying methods. The dissolution rates of these solid systems were much faster than that of the drug alone. A taste perception study was carried out, initially using a taste sensory machine and subsequently on human volunteers to evaluate the taste masking ability of the ternary complexation. Our results indicated that the combination of SBE-beta-CyD and Povidone K30 is effective not only in the enhancement of the solubility and dissolution rate of famotidine, but also in masking of the bitter taste of the drug. This technique may be of value for the pharmaceutical industries, especially in preparation of rapidly disintegrating tablets dealing with bitter drugs to improve patient compliance and thus effective pharmacotherapy.

Evaluation of carboxymethyl-beta-cyclodextrin with acid function: improvement of chemical stability, oral bioavailability and bitter taste of famotidine

The objective of the present study was to evaluate the potential influence of carboxymethyl-beta-cyclodextrin (CM-beta-CyD) on the aqueous solubility, chemical stability and oral bioavailability of famotidine (FMT) as well as on its bitter taste. We examined the effect of the CM-beta-CyD on the acidic degradation of FMT compared with that for sulfobutyl-ether-beta-cyclodextrin (SBE-beta-CyD). The potential use of CM-beta-CyD for orally disintegrating tablets (ODTs) was evaluated in vitro and in vivo. A taste perception study was also carried out. A strong stabilizing influence of CM-beta-CyD was observed against the acidic degradation, in sharp contrast to SBE-beta-CyD which induced a weird destabilizing effect on FMT. (13)C NMR was used to investigate the interaction mode between FMT and the 2 CyDs. In vivo study of ODTs indicated a significant increase in C(max), AUC and oral bioavailability in the case of FMT-CM-beta-CyD tablets, compared with plain drug tablets. However, no significant difference in T(max) and t(1/2) was observed. CM-beta-CyD complexation appears to be an acceptable strategy for enhancing the oral bioavailability of FMT owing to its dramatic effect on the aqueous solubility and chemical stability of the drug. In addition, it has a pronounced effect on masking the bitter taste of FMT.

Potential use of 2-hydroxypropyl-beta-cyclodextrin for preparation of orally disintegrating tablets containing dl-alpha-tocopheryl acetate, an oily drug

To expand the application of a drug in orally disintegrating tablets, the potential use of beta-cyclodextrin (beta-CyD) and 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CyD) as excipients for the tablets containing dl-alpha-tocopheryl acetate (VE), an oily drug, was evaluated. HP-beta-CyD, not beta-CyD, solubilized VE in water through the formation of higher order of complexes at the molar ratio of 1 : 2 (VE : HP-beta-CyD). When prepared under the optimal preparation conditions, the VE tablets containing lactose and 5% (w/w) of HP-beta-CyD, not beta-CyD, had high hardness more than 4 kg and rapid disintegration within 100 s both in vitro and in vivo. In addition, VE tablets containing lactose and 5% (w/w) of HP-beta-CyD, not beta-CyD, maintained the high hardness and rapid disintegration under the accelerated stability test using different conditions for 4 weeks. Therefore, these results suggest the potential use of HP-beta-CyD, not beta-CyD, as an excipient for orally disintegrating tablets containing VE, an oily drug, in the molding method.

5-Fluorouracil acetic acid/beta-cyclodextrin conjugates: drug release behavior in enzymatic and rat cecal media

5-Fluorouracil-1-acetic acid (5-FUA) was prepared and covalently conjugated to beta-cyclodextrin (beta-CyD) through ester or amide linkage, and the drug release behavior of the conjugates in enzymatic solutions and rat cecal contents were investigated. The 5-FUA/beta-CyD ester conjugate was slowly hydrolyzed to 5-FUA in aqueous solutions (half lives (t(1/2))=38 and 17h at pH 6.8 and 7.4, respectively, at 37 degrees C), whereas the amide conjugate was hardly hydrolyzed at these physiological conditions, but hydrolyzed only in strong alkaline solutions (>0.1M NaOH) at 60 degrees C. Both ester and amide conjugates were degraded in solutions of a sugar-degrading enzyme, alpha-amylase, to 5-FUA/maltose and triose conjugates, but the release of 5-FUA was only slight in alpha-amylase solutions. In solutions of an ester-hydrolyzing enzyme, carboxylic esterase, the ester conjugate was hydrolyzed to 5-FUA at the same rate as that in the absence of the enzyme, whereas the amide conjugate was not hydrolyzed by the enzyme. On the other hand, 5-FUA was rapidly released when the ester conjugate was firstly hydrolyzed by alpha-amylase, followed secondly by carboxylic esterase. The results indicated that the ester conjugate was hydrolyzed to 5-FUA in a consecutive manner, i.e. it was firstly hydrolyzed to the small saccharide conjugates, such as the maltose conjugate, by alpha-amylase, and the resulting small saccharide conjugates having less steric hindrance was susceptible to the action of carboxylic esterase, giving 5-FUA. The in vitro release behavior of the ester conjugate was clearly reflected in the hydrolysis in rat cecal contents and in the in vivo release after oral administration to rats.

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.

Involvement of lipid rafts of rabbit red blood cells in morphological changes induced by methylated beta-cyclodextrins

Lipid rafts on cell membranes have heterogeneity such as cholesterol-rich microdomains and sphingolipids-rich microdomains. We previously reported that beta-cyclodextrin (beta-CyD) induced morphological changes of red blood cells (RBC) from discocyte to stomatocyte, possibly due to extraction of cholesterol from cholesterol-rich lipid rafts of RBC membranes. In this study, the effects of methyl-beta-cyclodextrin (M-beta-CyD) and 2,6-di-O-methyl-beta-cyclodextrin (DM-beta-CyD) on lipid rafts and morphological changes in rabbit RBC (RRBC) were examined, compared to those of beta-CyD. In sharp contrast to beta-CyD, M-beta-CyD and DM-beta-CyD induced morphological changes of RRBC from discocyte to echinocyte. At pre-hemolytic concentrations of beta-CyDs, M-beta-CyD and DM-beta-CyD strongly released cholesterol from cholesterol-rich lipid rafts, compared to beta-CyD. Meanwhile, the lowering effects of DM-beta-CyD on fluorescent sphingomyelin analogue in sphingolipids-rich lipid rafts were more potent than those of beta-CyD and M-beta-CyD. The magnitude of the abilities of M-beta-CyD and DM-beta-CyD to extract membrane constituents was higher than that of beta-CyD, consistent with that of hemolytic activity. Furthermore, DM-beta-CyD and M-beta-CyD, not beta-CyD, lowered the amount of proteins in cholesterol-rich lipid rafts of RRBC. These results suggest that higher hemolytic activity and morphological changes from discocyte to echinocyte in RRBC induced by M-beta-CyD and DM-beta-CyD may be due to the extraction of both cholesterol and proteins from cholesterol-rich lipid rafts of RRBC, although DM-beta-CyD may interact with sphingolipids-rich lipid rafts on RRBC membranes only slightly.

Slow-release system of pegylated lysozyme utilizing formation of polypseudorotaxanes with cyclodextrins

Poly(ethylene glycol) (PEG, MW 2200) chains were introduced into lysozyme molecule. The resulting pegylated lysozyme formed polypseudorotaxanes with alpha- and gamma-cyclodextrins (alpha- and gamma-CyDs, respectively), by inserting one PEG chain in the alpha-CyD cavity and two PEG chains in the gamma-CyD cavity. The pegylated lysozyme/CyD polypseudorotaxanes were less soluble in water and the release rate of the pegylated protein decreased in the order of the pegylated lysozyme>the gamma-CyD polypseudorotaxane>the alpha-CyD polypseudorotaxane. The enzymatic activity of the pegylated lysozyme released from the polypseudorotaxanes was the same as that of the pegylated protein alone, indicating no decrease in the activity through the polypseudorotaxane formation. The results indicate that the pegylated lysozyme/CyD polypseudorotaxanes can work as a slow-release system, and the polypseudorotaxane formation with CyDs may serve as a new strategy for the preparation of slow-release system of pegylated proteins and peptides.

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.