Controlled-release drug delivery system based on fluocinolone acetonide-cyclodextrin inclusion complex incorporated in multivesicular liposomes

Multivesicular liposomes (MVLs) have been widely studied for encapsulation of hydrophilic drugs due to their structural properties and large aqueous inner cavities. In this study, to investigate MVLs and their potential application for incorporation of hydrophobic drugs, new drug delivery system for fluocinolone acetonide (FA), as a lipophilic model drug, was developed combining the advantages of cyclodextrin inclusion complexes (CD-IC) and multivesicular liposomes. FA was complexed with several CDs to form inclusion complex (FA-CD-IC) and then FA-CD-IC was incorporated into MVLs by reverse-phase evaporation method. Physicochemical characterization of drug-CD-IC, at a molar ratio of 1:1 (drug to CD) was studied using ¹HNMR, FT-IR, DSC and UV spectroscopy. The influence of various types of CDs on the aqueous solubility of FA, encapsulation efficiency and release profile in MVLs was studied. The results revealed the formation of inclusion complexes between the drug and CDs. Both the CD's type and proportion played an important role in the physicochemical properties of the systems. The inclusion complex of the drug with hydroxypropyl-β-cyclodextrin exhibited the most appropriate loading and sustained-release profile over prolonged periods. The results reveal the promising potential of MVLs as a stable drug delivery system to release the drug in a sustained manner for the treatment of ocular inflammatory disease.

New ethanol and propylene glycol free gel formulations containing a minoxidil-methyl-β-cyclodextrin complex as promising tools for alopecia treatment

New topical totally aqueous formulations that improve the low water solubility of minoxidil and realize an adequate permeability of drug in the skin are proposed. These formulations are lacking in propylene glycol and alcohol that are the principal irritant ingredients present in minoxidil commercial solutions. In order to enhance poor water solubility of minoxidil randomly methyl-β-cyclodextrin was used, and four hydrogels such as, calcium alginate, sodium alginate, carbopol 934 and hydroxyethylcellulose were utilized to ensure a prolonged time of contact with the scalp. The inclusion complex minoxidil/methyl-β-cyclodextrin with a molar ratio 1:1 was obtained by freeze drying and evaluated by NMR, FT-IR and DSC analysis. An apparent stability constant of formed inclusion complex was calculated by phase solubility diagram and its value was 400 M(-1). The solid inclusion complex was used to prepare gel formulations with similar dose to minoxidil commercial solution. The gels were evaluated for various technological parameters including rheological behavior, in vitro drug release and ex vivo permeation through pig skin. The best performance was observed for the calcium alginate formulation.

Comparative assessment of effectiveness of ketoprofen and ketoprofen/beta-cyclodextrin complex in two experimental models of inflammation in rats

Oral administration of non-steroidal anti-inflammatory drugs (NSAIDs) can lead to adverse effects such as gastrointestinal distress. The complexation of different groups of active substances with β-cyclodextrin (β-CD) has drawn considerable interest over recent years. The purpose of this study was to analyze the ketoprofen/β-cyclodextrin (K/β-CD) conjugate complex as well as to assess its anti-inflammatory effect after oral administration (doses of 30 mg/m(2) and 15 mg/m(2) of body surface), compared with ketoprofen. The studies were done on two models of experimentally-induced acute inflammation in rats (n = 48, 6/group), by means of intraplantar administration of a 10% aqueous kaolin suspension and intraperitoneal administration of a 1% sodium thioglycolate solution. The dynamics of the acute inflammatory process and the anti-inflammatory effects were monitored using plethysmometric determinations after 3, 6, 9, 12, 24 and 48 h (plantar inflammation), and the absorbance of the exudates (spectrophotometrically read) and nucleated cell counts after 24 h (peritoneal inflammation). The coupling of ketoprofen with β-CD resulted in increased solubility (100% in 60 min) of the newly-formed product, which further resulted in a higher bioavailability compared with ketoprofen (<40% in 120 min). In both models of experimentally-induced inflammation, the K/β-CD complex had a higher anti-inflammatory activity than ketoprofen.

Structure elucidation of β-cyclodextrin-xylazine complex by a combination of quantitative (1)H-(1)H ROESY and molecular dynamics studies

The complexation of xylazine with β-cyclodextrin was studied in aqueous medium. ¹H NMR titrations confirmed the formation of a 1:1 inclusion complex. A ROESY spectrum was recorded with long mixing time which contained TOCSY artifacts. It only confirmed the presence of xylazine aromatic ring in the β-cyclodextrin cavity. No information regarding the mode of penetration, from the wide or narrow side, could be obtained. We calculated the peak intensity ratio from the inter-proton distances for the most stable conformations obtained by molecular dynamics studies in vacuum. The results show that highly accurate structural information can be deduced efficiently by the combined use of quantitative ROESY and molecular dynamics analysis. On the other hand, a ROESY spectrum with no spin diffusion can only compliment an averaged ensemble conformation obtained by molecular dynamics which is generally considered ambiguous.

Cyclodextrins as encapsulation agents for plant bioactive compounds

Plants possess a wide range of molecules capable of improve healing: fibre, vitamins, phytosterols, and further sulphur-containing compounds, carotenoids, organic acid anions and polyphenolics. However, they require an adequate level of protection from the environmental conditions to prevent losing their structural integrity and bioactivity. Cyclodextrins are cyclic oligosaccharides arising from the degradation of starch, which can be a viable option as encapsulation technique. Cyclodextrins are inexpensive, friendly to humans, and also capable of improving the biological, chemical and physical properties of bioactive molecules. Therefore, the aim of this review is to highlight the use of cyclodextrins as encapsulating agents for bioactive plant molecules in the pharmaceutical field.

Effect of β-cyclodextrin complexation on solubility and enzymatic hydrolysis rate of icariin

Objective:

The aim of this work was to investigate the effect of β-cyclodextrin complexation on the solubility and hydrolysis rate of icariin.

Material and Methods:

The inclusion complex of icariin at the molar ratio of 1:1 was obtained by the dropping method and was characterized by differential scanning calorimetry. The solubility of icariin complex in water at 37°C was 36 times greater than that of free icariin. Enzymatic hydrolysis conditions were tested for the bioconversion of icariin by mono-factor experimental design.

Methods:

The inclusion complex of icariin at the molar ratio of 1:1 was obtained by the dropping method and was characterized by differential scanning calorimetry. The solubility of icariin complex in water at 37°C was 36 times greater than that of free icariin. Enzymatic hydrolysis conditions were tested for the bioconversion of icariin by mono-factor experimental design.

Results:

The enzymatic hydrolysis experiment showed that icariin can be transformed into baohuoside I. The optimum conditions determined were as follows: pH 5.0, 50°C, the ratio of cellulase/substrate (0.6), the concentration of icariin 20 mg/ml, and reaction time 12 h. Under these enzymatic conditions, 98.2% transforming rate of baohuoside I from icariin in inclusion complexes was obtained.

Conclusion

The aqueous solubility and enzymatic hydrolysis rate of icariin were improved owing to the inclusion complexation.

The β-cyclodextrin/benzene complex and its hydrogen bonds - a theoretical study using molecular dynamics, quantum mechanics and COSMO-RS

Four highly ordered hydrogen-bonded models of β-cyclodextrin (β-CD) and its inclusion complex with benzene were investigated by three different theoretical methods: classical quantum mechanics (QM) on AM1 and on the BP/TZVP-DISP3 level of approximation, and thirdly by classical molecular dynamics simulations (MD) at different temperatures (120 K and 273 to 300 K). The hydrogen bonds at the larger O2/O3 rim of empty β-CDs prefer the right-hand orientation, e.g., O3-H^…O2-H in the same glucose unit and bifurcated towards ^…O4 and O3 of the next glucose unit on the right side. On AM1 level the complex energy was −2.75 kcal mol⁻¹ when the benzene molecule was located parallel inside the β-CD cavity and −2.46 kcal mol⁻¹ when it was positioned vertically. The AM1 HOMO/LUMO gap of the empty β-CD with about 12 eV is lowered to about 10 eV in the complex, in agreement with data from the literature. AM1 IR spectra displayed a splitting of the O–H frequencies of cyclodextrin upon complex formation. At the BP/TZVP-DISP3 level the parallel and vertical positions from the starting structures converged to a structure where benzene assumes a more oblique position (−20.16 kcal mol⁻¹ and −20.22 kcal mol⁻¹, resp.) as was reported in the literature. The character of the COSMO-RS σ-surface of β-CD was much more hydrophobic on its O6 rim than on its O2/O3 side when all hydrogen bonds were arranged in a concerted mode.

This static QM picture of the β-CD/benzene complex at 0 K was extended by MD simulations. At 120 K benzene was mobile but always stayed inside the cavity of β-CD. The trajectories at 273, 280, 290 and 300 K certainly no longer displayed the highly ordered hydrogen bonds of β-CD and benzene occupied many different positions inside the cavity, before it left the β-CD finally at its O2/O3 side.

Inclusion of the insecticide fenitrothion in dimethylated-β-cyclodextrin: unusual guest disorder in the solid state and efficient retardation of the hydrolysis rate of the complexed guest in alkaline solution

An anhydrous 1:1 crystalline inclusion complex between the organophosphorus insecticide fenitrothion [O,O-dimethyl O-(3-methyl-4-nitrophenyl)phosphorothioate] and the host compound heptakis(2,6-di-O-methyl)-β-cyclodextrin (DIMEB) was prepared and its structure elucidated by single-crystal X-ray diffraction. This revealed two independent host molecules in the asymmetric unit. In one of these, the cavity is occupied by two disordered guest components (distinguishable as rotamers with respect to the P–OAr bond) while in the other, three distinct guest components with site-occupancies 0.44, 0.29 and 0.27 appear, the last having a reversed orientation relative to all the other components. Kinetic studies of the alkaline hydrolysis of fenitrothion in the presence of DIMEB showed a remarkable reduction of 84% in the rate of this reaction relative to that for the free substrate, a value exceeding those previously attained with the native hosts, β- and γ-cyclodextrin, and fully methylated β-cyclodextrin.

Changes in the intestinal absorption mechanism of icariin in the nanocavities of cyclodextrins

Icariin is a bioactive herbal ingredient isolated from Herba epimedii, which has been widely used for the treatment of osteoporosis and male sexual dysfunction in traditional Chinese medicine. The major objective of this work is to investigate the different enhancing effects of β-cyclodextrin (β-CD) and hydroxypropyl-β-cyclodextrin (HP-β-CD) on the intestinal absorption of icariin, and to identify the molecular mechanisms of this action. Host-guest-type interactions of icariin with cyclodextrins nanocavities were unambiguously demonstrated by the phase-solubility diagram, ultraviolet spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, X-ray powder diffractometry, and two dimensional proton nuclear magnetic resonance rotating-frame Overhauser effect spectroscopy. These results were further supported using molecular modeling studies. The rat single-pass intestinal perfusion model showed that the absorption of icariin was affected by P-glycoprotein (Pgp). The icariin/HP-β-CD inclusion complex provided greater enhancement in the intestinal absorption than the icariin/β-CD inclusion complex. Therefore, the enhancing effect was involved in a solubilizing effect and/or Pgp inhibitory effect. Finally, fluorescence anisotropy measurements and Pgp adenosine triphosphatase (ATPase) assay demonstrated that β-CD exhibited no effect on Pgp, while HP-β-CD showed inhibition by restraining the Pgp ATPase activity rather than changing the fluidity of cell membrane.

Oxygen radical absorbance capacity (ORAC) of cyclodextrin-solubilized flavonoids, resveratrol and astaxanthin as measured with the ORAC-EPR method

Recently, we proposed an oxygen radical absorbance capacity method that directly quantifies the antioxidant's scavenging capacity against free radicals and evaluated the radical scavenging abilities for water soluble antioxidant compounds. In this study, we determined the radical scavenging abilities of lipophilic antioxidants which were solubilized by cyclodextrin in water. Commonly employed fluorescence-based method measures the antioxidant's protection capability for the fluorescent probe, while we directly quantify free-radical level using electron paramagnetic resonance spin trapping technique. In addition, the spin trapping-based method adopted controlled UV-photolysis of azo-initiator for free radical generation, but in fluorescence-based method, thermal decomposition of azo-initiator was utilized. We determined the radical scavenging abilities of seven well-known lipophilic antioxidants (five flavonoids, resveratrol and astaxanthin), using methylated β-cyclodextrin as a solubilizer. The results indicated that the agreement between spin trapping-based and fluorescence-based values was only fair partly because of a large variation in the previous fluorescence-based data. Typical radical scavenging abilities in trolox equivalent unit are: catechin 0.96; epicatechin 0.94; epigallocatechin gallate 1.3; kaempferol 0.37; myricetin 3.2; resveratrol 0.64; and astaxanthin 0.28, indicating that myricetin possesses the highest antioxidant capacity among the compounds tested. We sorted out the possible causes of the deviation between the two methods.

Conventional study on novel dicationic ionic liquid inclusion with β-cyclodextrin

This study focuses on the synthesis and characterization of the inclusion complex of β-Cyclodextrin (β-CD) with dicationic ionic liquid, 3,3′-(1,4-Phenylenebis [methylene]) bis(1-methyl-1H-imidazol-3-ium) di(bromide) (PhenmimBr). The inclusion complex was prepared at room temperature utilizing conventional kneading technique. Proton (¹H) NMR and 2D (¹H–¹H) COSY NMR were the primary characterization tools employed to verify the formation of the inclusion complex. COSY spectra showed strong correlations between protons of imidazolium and protons of β-CD which indicates that the imidazolium ring of PhenmimBr has entered the cavity of β-CD. UV absorption indicated that β-CD reacts with PhenmimBr to form a 2:1 β-CD-PhenmimBr complex with an apparent formation constant of 2.61 × 10⁵ mol&⁻² L². Other characterization studies such as UV, FT-IR, XRD, TGA, DSC and SEM studies were also used to further support the formation of the β-CD-PhenmimBr inclusion complex.

Solid State Characterization of Domperidone: Hydroxypropyl-β-Cyclodextrin Inclusion Complex

The purpose of the present study was to prepare inclusion complex of domperidone with hydroxylpropyl-β-cyclodextrin in order improved the solubility and hence to increase dissolution of domperidone. An effect of concentration of hydroxylpropyl-β-cyclodextrin on the aqueous solubility of domperidone was determined by phase-solubility method. The aqueous solubility of domperidone increased as a function of hydroxylpropyl-β-cyclodextrin concentration, showing AL type diagram. Solid domperidone/hydroxylpropyl-β-cyclodextrin complex was prepared in ratio 1:1 by ultrasonication and kneading method. Solid state inclusion complex was characterized by FTIR, powder X-ray diffraction and differential-scanning calorimetry techniques. FTIR studies showed intactness of drug in complex whereas powder diffraction studies showed that hydroxylpropyl-β-cyclodextrin complex was amorphous. Solubility studies showed that complexation increased domperidone solubility as compared to pure drug in 0.1M hydrochloric acid and distilled water. Drug content confirms that ultrasonication is one of the efficient methods to prepare inclusion complex. Dissolution data of inclusion complexes also indicated that there is 1.4 folds increase in dissolution as compared to pure drug and was observed in case of inclusion complexes prepared by ultrasonication.

Liposome-encapsulated EF24-HPβCD inclusion complex: a preformulation study and biodistribution in a rat model

3,5-Bis(2-fluorobenzylidene)-4-piperidone (EF24) is an anti-proliferative diphenyldifluoroketone analog of curcumin with more potent activity. The authors describe a liposome preparation of EF24 using a "drug-in-CD-in liposome" approach. An aqueous solution of EF24 and hydroxypropyl-β-cyclodextrin (HPβCD) inclusion complex (IC) was used to prepare EF24 liposomes. The liposome size was reduced by a combination of multiple freeze-thaw cycles. Co-encapsulation of glutathione inside the liposomes conferred them with the capability of labeling with imageable radionuclide Tc-99m. Phase solubility analysis of EF24-HPβCD mixture provided k(1:1) value of 9.9 M(-1). The enhanced aqueous solubility of EF24 (from 1.64 to 13.8 mg/mL) due to the presence of HPβCD helped in the liposome preparation. About 19% of the EF24 IC was encapsulated inside the liposomes (320.5 ± 2.6 nm) by dehydration-rehydration technique. With extrusion technique, the size of 177 ± 6.5 nm was obtained without any effect on encapsulation efficiency. The EF24-liposomes were evaluated for anti-proliferative activity in lung adenocarcinoma H441 and prostate cancer PC-3 cells. The EF24-liposomes demonstrated anti-proliferative activity superior to that of plain EF24 at 10 μM dose. When injected in rats, the Tc-99m-labeled EF24-liposomes cleared from blood with an α-t(1/2) of 21.4 min and β-t(1/2) of 397 min. Tissue radioactivity counting upon necropsy showed that the majority of clearance was due to the uptake in liver and spleen. The results suggest that using "drug-in-CD-in liposome" approach is a feasible strategy to formulate an effective parenteral preparation of EF24. In vitro studies show that the liposomal EF24 remains anti-proliferative, while presenting an opportunity to image its biodistribution.

Synthesis and characterization of the inclusion complex of dicationic ionic liquid and β-cyclodextrin

The supramolecular structure of the inclusion complex of β-cyclodextrin (β-CD) with 1,1',2,2'-tetramethyl-3,3'-(p-phenylenedimethylene) diimidazolium dibromide (TetraPhimBr), a dicationic ionic liquid, has been investigated. The inclusion complex with 1:1 molar ratio was prepared by a kneading method. Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (XRD) analysis, (1)H NMR and thermogravimetric analysis (TGA) confirmed the formation of the inclusion complex. The results showed that the host-guest system is a fine crystalline powder. The decomposition temperature of the inclusion complex is lower than that of its parent molecules, TetraPhimBr and β-CD individually.

Preformulation study of the inclusion complex irbesartan-beta-cyclodextrin

The aim of the present work was to improve the solubility and dissolution profile of irbesartan (IRB), a poorly water-soluble drug by formation of inclusion complex with beta-cyclodextrin (betaCD). Phase solubility studies revealed increase in solubility of the drug upon cyclodextrin addition, showing A(L)-type of graph with slope less than one indicating formation of 1:1 stoichiometry inclusion complex. The stability constant (K(s)) was found to be 104.39 M(-1). IRB-betaCD binary systems were prepared by cogrinding, kneading using alcohol, kneading using aqueous alcohol, and coevaporation methods. Characterization of the binary systems were carried out by differential scanning calorimetry, Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, and proton nuclear magnetic resonance. The dissolution profiles of inclusion complexes were determined and compared with those of IRB alone and physical mixture. Among the various methods, coevaporation was the best in which the solubility was increased and dissolution rate of the drug was the highest. The study indicated the usefulness of cyclodextrin technology to overcome the solubility problem of IRB.

Spectroscopic and Thermal Characterization of the Host-Guest Interactions between α-, β-, and γ-cyclodextrins and vanadocene dichloride

Host-guest interactions between α-, β-, and γ-cyclodextrins and vanadocene dichloride (Cp(2)VCl(2)) have been investigated by a combination of thermogravimetric analysis, differential scanning calorimeters, PXRD and solid state and solution EPR spectroscopy. The solid state results demonstrated that only β- and γ-cyclodextrins form 1:1 inclusion complexes, while α-cyclodextrin does not form an inclusion complex with Cp(2)VCl(2). The β- and γ-CD-Cp(2)VCl(2) inclusion complexes exhibited anisotropic electron-(51)V (I = 7/2) hyperfine coupling constants whereas the α-CD- Cp(2)VCl(2) system showed only an asymmetric peak with no anisotropic hyperfine constant. On the other hand, solution EPR spectroscopy showed that α-CD may be involved in weak host-guest interactions in equilibrium with free vanadocene species.

A novel solid dosage form of rifampicin and isoniazid with improved functionality

The aim of the present investigation was to develop a novel dosage form of rifampicin and isoniazid to minimize degradation of rifampicin in acidic medium and to modulate the release of rifampicin in the stomach and isoniazid in the intestine. Gastroretentive tablets of rifampicin (150 mg) were prepared by the wet granulation method using hydroxypropyl methylcellulose, calcium carbonate, and polyethylene glycol 4000. The granules and tablets of rifampicin were characterized. Hard gelatin capsules (size 4) containing a compacted mass of isoniazid (150 mg) and dicalcium phosphate (75 mg) were enteric coated. Two tablets of rifampicin and 1 capsule (size 4) of isoniazid were put into a hard gelatin capsule (size 00). The in vitro drug release and in vitro drug degradation studies were performed. Rifampicin was released over 4 hours by zero-order kinetics from the novel dosage form. More than 90% of isoniazid was released in alkaline medium in 30 minutes. The results of dissolution studies with the US Pharmacopeia XXIII method revealed that a substantial amount of rifampicin was degraded from the immediate release capsule containing rifampicin and isoniazid powder owing to drug accumulation in the dissolution vessel and also to the presence of isoniazid. The degradation of rifampicin to 3-formyl rifampicin SV (3FRSV) was arrested (3.6%-4.8% degradation of rifampicin at 4 hours) because of the minimization of physical contact between the 2 drugs and controlled release of rifampicin in acidic medium in the modified Rossett-Rice apparatus. This study concludes that the problem of rifampicin degradation can be alleviated to a certain extent by this novel dosage form.