Influence of Surfactants over the Dissolution of Mequitazine

Influence of surfactants over the dissolution of mequitazine was investigated by studying the dissolution of mequitazine (a poorly water-soluble drug) in different binary media prepared by adding different amounts of surfactants (Brij 35, Tween 20 or sodium lauryl sulfate (SLS)) into 1 liter of water. An improvement in drug dissolution rate was observed from all of the binary dissolution media, except those containing lower amounts of sodium lauryl sulfate. At lower concentrations, SLS acts as a true salt, and a competition is produced between drug and SLS for water molecules. Due to this saline effect, a decline in drug dissolution was observed from binary media with lower concentration of SLS     

Inclusion Complexes of Tolnaftate with β-Cyclodextrin and Hydroxypropyl β-Cyclodextrin

Tolnaftate, an antifungal agent, was found to form inclusion complexes with both β-cyclodextrin (β-CD) and hydroxypropyl β-cyclodextrins (HPBCDs) with two different degrees of substitution [HPBCD(A)-8% and HPBCD(B)-3%]. Complex formation in the solution state was studied using phase solubility and spectral shift methods. Solid complexes were prepared by the coprecipitation method. Solubilities and dissolution rates were determined for each solid complex, its corresponding physical mixture, and free drug. The increase in solubility of tolnaftate with added HPBCD was found to be significantly greater than with added β-CD. For both HPBCD(A) and HPBCD(B), over the concentration range 0-0.05 M. 1:1 complexes with stability constants of 1460 ± 139 M^-1 and 1860 ± 165 M^-1 were observed, respectively. Over the β-CD concentration range 0-0.02 M, a 1:1 complex with a stability constant of 1190 ± 105 M^-1 was observed. At higher HPBCD concentrations, the increase in solubility was observed to show a positive deviation from linearity (type A_p phase diagram). Using the spectral method, in a 2 5% v/v methanol in water system, the stability constants were determined to be 1020 ± 150 M^-1 1110 ± 120 M^-1 and 1100 ± 260 M^-1 for HPBCD(A), HPBCD(B) and β-CD, respectively. The solid complexes prepared showed improved dissolution over physical mixtures and free drug.     

Solubilization of Glibenclamide with β-Cyclodextrin & its Derivatives

Gilbenclamide, a widely used potent hypoglycaemic agent was solubllized using β -Cyclodextrin and β -Cyclodextrin derivatives. Complexes were prepared by kneading method in a molar ratio of 1:1 of the drug and the cyclodextrlns respectively. The Glibenclamide β -Cyelocextrin complex was characterized and evaluated by I.R. studies, Differential Scanning Calorimotry 6 X-ray diffractometry. The in-vitro dissolution rates of drug from inclusion complexes of β Cyclodextrins and its derivatives were compared. A significant Improvement In dissolution lor, rates of Gllbenclamide was observed with Inclusion complexes of all the Cyclodextrins. However, the solubilizing effect was more in case of β-Cyclodextrin derivatives.     

Influence of Hydroxypropyl β-Cyclodextrin on Solubility and Dissolution Profile of Ketoprofen in Its Solid Dispersions

Solid dispersions of hydroxypropyl β-cyclodextrins (HPB), a highly water soluble derivative of β-cyclodextrin and ketoprofen (KPF), were prepared by kneading, coevaporation, and freeze-drying. X-ray diffraction, differential scanning calorimetry, and scanning electron microscopy were used to investigate characteristics of the solid dispersions and to study the possibility of complexation of the drug with HPB. A marked difference in characteristics of dispersions was observed due to their methods of preparation. The solubility of KPF in the solid dispersions was studied by the dispersed powder technique and was found to have improved considerably over that of the drug pure alone. The dispersions had good compressibiliry. Tablets so compressed displayed good dissolution profiles.     

Inclusion Complexation of 4-Biphenylacetic Acid with β-Cyclodextrin

The preparation of an inclusion complex of 4-biphenylacetic acid (BPAA), a non-steroidal antiinflammatory drug, with β-cyclo-dextrin is described. The presumible structure of the inclusion system, the molar ratio, which was found 1:1, and the formation constant were calculated by the analysis of IR, UV, DSC, X-ray diffraction, and ¹H-NMR. Dissolution rate and solubility were also studied. BPAA solubility in water resulted significantly (4,2-fold) increased by complexation, such as its dissolution rate which appears, in the first 12 min, 18 times greater for the complex than the drug alone.     

Simple Prediction of Stability Constants for Inclusion Complexes of β-Cyclodextrin with various Drug Molecules Using β-Cyclodextrin Bonded Phases(Cyclobond® I Column)

The stability constants(K_c) for inclusion complexes of cyclodextrin with sulfonamides, sulfonylureas and p-aminobenzoic acid esters were investigated by high performance liquid chromatography (HPLC) using the cyclodextrin bonded phase. The retention time(R_t) of these drugs on a Cyclobond® I column showed a good relationship to K, values obtained by the solubility method and/or conventional HPLC method. The advantages of this method were that the K, values could be rapidly predicted by a simple procedure using a minimum quantity of the drugs.     

Comparative study on Inclusion compounds of 4-Biphenylacetic acid with β-Cyclodextrin, Hydroxypropylated-β-Cyclodextrins, and methylated-β-Cyclodextrins

The inclusion behavior of Hydroxypropyl-β-Cyclodextrin (HP-β-Cyd) and of methylated-β-Cyclodextrins, heptakis-(2,6-di-O-methyl)-β-Cyclodextrin (DM-β-Cyd) and heptakis-(2,3,6-tri-O-methyl)-β-Cyclodextrin (TM-β-Cyd), in solution and solid state was compared with that of natural β-Cyclodextrin (β-Cyd) using an anti-inflammatory drug, 4-biphenylacetic acid (BPAA), as a guest molecule. The solubility of BPAA with β-Cyd and β-Cyd derivatives in aqueous solution were determined. Stability constants were calculated by phase solubility method at various pH values and temperatures. The formation of inclusion complexes with β-Cyd and β-Cyd derivatives in the solid slate were confirmed by infrared spectroscopy, differential scanning calorimetry and X-Ray diffractometry, and in the liquid phase by ultraviolet spectroscopy, circular dichroism and NMR studies. Dissolution rate and “in vitro” release of BPAA from complexes were examined. The results obtained suggest that DM-β-Cyd is more effective than other β-Cyclodextrins in improving the pharmaceutical properties of BPAA.     

Effect of Hydrotropic Substances on the Complexation of Clotrimazole with β-Cyclodextrin

The phase diagrams of clotrimazole/β-cyclodextrin (β-CD) in phosphate buffer, pH = 7.1, containing 0.5 M of various hydrotropic agents were constructed. The water structure disruptors, urea and nicotinamide, increased the intrinsic solubility of the antimycotic drug clotrimazole while the water structure forming agents, sorbitol and fructose, decreased the solubility. Concerning the complex constant between clotrimazole and β-CD, it was the other way around. The connection between the slopes of the phase diagrams, the intrinsic solubility of clotrimazole and the complex constant was discussed. Nicothamide decreased the solubility of β-CD in the buffer solution. The results reported in this study are in disagreement with the claim that addition of water structure forming agents to cyclodextrin solutions can be used to increase the total solubility of drugs     

Physico-chemical study of inclusion compound Phenothiazine-β-Cyclodextrin

In this work, the authors have made many assays to prove the inclusion of phenothiazine in β-cyclodextrin.

The inclusion compound was prepared in two various ways and we have checked the inclusion using NMR and Differential Thermal Analysis tests.

This experimentation leads to other assays making inclusion compounds with molecules using the phenothiazine core and used in humans medicines.     

Inclusion of Vitamin D2 in β-Cyclodextrin. Evaluation of Different Complexation Methods

Evaluation of inclusion complexation of vitamin D2 with β-cyclodextrin in aqueous solution and solid state was performed by Phase Solubility Diagramm, HPLC, DSC, X-RAY Diffractometry, NMR. Solid inclusion complexes were prepared by spray-drying, kneading and solid dispersion. The dissolution profiles of the complex either in powder or in tablets were studied in order to select the best inclusion process.     

Study of autoabsorption for total α and β counting

The RaMsEs Group (Radioprotection et Mesures Environnementales) of the IPHC performs research and offers services mainly in the field of radioactivity measurements and sample analysis. This report will describe some of our recent experience using a semiautomatic evaporation system to prepare large area thin deposits for total α and β counting and gives experimental and simulated results for the autoabsorption coefficients.     

The Influence of β-Cyclodextrin on the Solubility of Chlorthalidone and Its Enantiomers

The solubility of chlorthalidone in 16 solvent systems was determined in the absence and presence of different amounts of β-cyclodextrin (β-CD). Chlorthalidone (CT) was shown to be more soluble in hydrophilic organic solvents, with the highest solubility in ethylacetate (EtOAc) saturated with water. The solubility of CT in water, butanol, octanol, and dichloromethane (DCM) was enhanced by the addition of β-cyclodextrin. The enantioselective partitioning of CT between water and EtOAc, DCM, butan-1-ol, butan-2-ol, and octan-1-ol was determined in the presence of β-CD at pH 5, 7, and 9. According to the results, both the solubility and partition- ing properties of CT are affected by β-CD in aqueous solution. It was also shown that the solubility of the individual enantiomers differs in the presence of β-CD.     

Terfenadine-β-Cyclodextrin Inclusion Complex with Antihistaminic Activity Enhancement

Terfenadine, an antihistaminic drug, has relatively low bioavailability after oral administration due to its limited solubility in water. To enhance the antihistaminic activity of terfenadine, the terfenadine-β-cyclodextrin (1 : 2) inclusion complex was prepared by the neutralization method. The solubility and dissolution of the inclusion complex were carried out, and its antihistaminic activity was then evaluated and compared with terfenadine powder by the passive subcutaneous anaphylaxis method in rats. The formation constant of the inclusion complex was higher at lower pH, while its formation ratio was 1 : 2 irrespective of pH. For terfenadine, it improved the solubility 200 times and the dissolution rate 5 times. It gave a low histamine level at 30 min, followed by a sustained low level until 60 min, while terfenadine powder gave a low histamine level at 60 min, suggesting that it had faster and more effective antihistaminic activity than terfenadine powder in rats due to fast dissolution and absorption of terfenadine. It is concluded that this inclusion complex enhanced the antihistaminic activity of terfenadine following the enhanced solubility and dissolution of terfenadine.     

In Situ Study of γ‐TiAl Lamellae Formation in Supersaturated α2‐Ti3Al Grains

In situ heating transmission electron microscopy (TEM) was used to investigate the initial stage of γ‐TiAl lamellae formation in an intermetallic Ti–45Al–7.5Nb alloy (in at.%). The material was heat treated and quenched in a non‐equilibrium state to consist mainly of supersaturated, ordered α₂‐Ti₃Al grains. Subsequently, specimens were annealed inside a TEM up to 750 °C. The in situ TEM study revealed that ultra‐fine γ‐TiAl laths precipitate in the α₂‐matrix at ≈730 °C which exhibit the classical Blackburn orientation relationship, i.e. (0001)α₂//(111)γ and [$11{\bar {2}}0$ ]α₂//<110]γ. The microstructural development observed in the in situ TEM experiment is compared to results from conventional ex situ TEM studies. In order to investigate the precipitation behavior of the γ‐phase with a complementary method, in situ high energy X‐ray diffraction experiments were performed which confirmed the finding that γ‐laths start to precipitate at ≈730 °C from the supersaturated α₂‐matrix.     

Interactions between preservatives and 2-hydroxypropyl-β-cyclodextrin

The interactions between several commonly used preservatives, i.e. benzalkonium chloride, chlorhexidine gluconate, chlorobutanol, methylparaben and propylparaben, and 2-hydroxypropyl-β-cyclodextrin were investigated. The interactions were shown to be twofold. Firstly, the preservative molecules can displace the drug molecules from the cyclodextrin cavity, thus, reducing the solubilizing effects of the cyclodextrin. Secondly, the antimicrobial activity of the preservatives were reduced by formation of preservative-cyclodextrin inclusion complexes. The magnitude of the interactions were dependent on the degree of complexation.     

Multilayer Amorphous‐Si‐B‐C‐N/γ‐Al2O3/α‐Al2O3 Membranes for Hydrogen Purification

The hydrogen and carbon monoxide separation is an important step in the hydrogen production process. If H₂ can be selectively removed from the product side during hydrogen production in membrane reactors, then it would be possible to achieve complete CO conversion in a single‐step under high temperature conditions. In the present work, the multilayer amorphous‐Si‐B‐C‐N/γ‐Al₂O₃/α‐Al₂O₃ membranes with gradient porosity have been realized and assessed with respect to the thermal stability, geometry of pore space and H₂/CO permeance. The α‐Al₂O₃ support has a bimodal pore‐size distribution of about 0.64 and 0.045 µm being macroporous and the intermediate γ‐Al₂O₃ layer—deposited from boehmite colloidal dispersion—has an average pore‐size of 8 nm being mesoporous. The results obtained by the N₂‐adsorption method indicate a decrease in the volume of micropores—0.35 vs. 0.75 cm³ g^?1—and a smaller pore size ?6.8 vs. 7.4 Å—in membranes with the intermediate mesoporous γ‐Al₂O₃ layer if compared to those without. The three times Si‐B‐C‐N coated multilayer membranes show higher H₂/CO permselectivities of about 10.5 and the H₂ permeance of about 1.05 × 10^?8 mol m^?2 s^?1 Pa^?1. If compared to the state of the art of microporous membranes, the multilayer Si‐B‐C‐N/γ‐Al₂O₃/α‐Al₂O₃ membranes are appeared to be interesting candidates for hydrogen separation because of their tunable nature and high‐temperature and high‐pressure stability.     

Facile Synthesis of γ‐In2Se3 Nanoflowers toward High Performance Self‐Powered Broadband γ‐In2Se3/Si Heterojunction Photodiode

An effective colloidal process involving the hot‐injection method is developed to synthesize uniform nanoflowers consisting of 2D γ‐In₂Se₃ nanosheets. By exploiting the narrow direct bandgap and high absorption coefficient in the visible light range of In₂Se₃, a high‐quality γ‐In₂Se₃/Si heterojunction photodiode is fabricated. This photodiode shows a high photoresponse under light illumination, short response/recovery times, and long‐term durability. In addition, the γ‐In₂Se₃/Si heterojunction photodiode is self‐powered and displays a broadband spectral response ranging from UV to IR with a high responsivity and detectivity. These excellent performances make the γ‐In₂Se₃/Si heterojunction very interesting as highly efficient photodetectors.