Effect of cyclodextrins on physico-chemical and release properties of Eudragit RS 100 microparticles containing glutathione

The objective of this work was to develop a novel microparticulate system based on the mucoadhesive polymer Eudragit-RS 100 and cyclodextrins (CDs), potentially useful for the oral administration of Glutathione (γ–glutamylcysteinylglycine, GSH). For this purpose, an oil-in-oil (O/O) emulsion-solvent evaporation method was used for the preparation of microparticles (MPs) containing GSH alone or together with one of the following CDs: α-, β-, γ-, methyl-β-(Me-β-), hydroxypropyl-β-(HP-β-) or sulfobutylether-β-cyclodextrin (SBE_7m-β-CD). MPs were obtained by emulsifying a mixture of Eudragit RS 100, GSH, CD and magnesium stearate in acetone or acetonitrile with a mixture of liquid paraffin and Span 80. Size, encapsulation efficiency, and drug release of the prepared MPs were evaluated. The results clearly indicated that all the examined properties were dependent on the water-miscible solvents and CD used. In particular, MPs prepared by using acetone or acetonitrile showed different size distributions with mean diameters in the ranges 82–350 and 15–22 μm, respectively. Moreover, encapsulation efficiency values were found to be high in all cases (71–99%) and was significantly affected by the CD type. The GSH release rates were evaluated employing dissolution media with different pH values (1.2, 6.8 and 7.4) and the following rank order was obtained for MPs prepared using acetone: MPs incorporating Me-β-CD > MPs without CD > MPs incorporating the remaining CDs. On the other hand, MPs prepared using acetonitrile gave the highest GSH release rate. Finally, stability of GSH encapsulated in MPs containing HP-β-CD to enzymatic attack by pepsin A, α-chymotrypsin, and γ-glutamyltranspeptidase was also investigated.     

Hydrogel matrices containing single and mixed natural cyclodextrins. Mechanisms of drug release

Hydrogel networks of α, β or γ-cyclodextrin (CD) and mixtures of α/β or β/γ CDs have been obtained using epichlorohydrin (EP) as a crosslinking agent. Discs of the resulting polymers were evaluated as drug carriers for controlled release using the antiinflammatory naproxen (NAP) as a model drug. βCD polymer (βCDP) has shown the highest amount of drug loaded and the lowest one corresponds to the polymer containing αCD, in agreement with the affinities of NAP for the corresponding cyclodextrins.     

Electrokinetic properties of bare and particles containing textile

Functional, reactive and smart textiles are nowadays of great interest in the fields of both cosmetic and pharmaceutical industries. Textile functionalization according to demands of the consumers can only be achieved with better understanding of the properties of the textile surface as well as sound knowledge about the technique to be used to functionalize the textiles. The aim of this work was to investigate the zeta potential of polyamide textile and prepared sponge like particles as a function of pH and salinity of the electrolyte. Special attention has been dedicated to the electrokinetic properties of textile as a function of sponge like particles amount present during adsorption process. As a general tendency, streaming potential measurement showed the changes in surface charge density of textile because of the changes in pH, salinity and adsorbed particles amount. All presented results were discussed in terms of zeta potential. Copyright © 2016 John Wiley & Sons, Ltd.     

Magnetorheological properties of ferrofluids containing clustered particles

A theoretical model is proposed to describe experimental data on the magnetorheological properties of magnetic fluids containing clustered particles consisting of single-domain ferromagnetic nanoparticles distributed in a polymeric shell 80–100 nm in diameter. These fluids combine the sedimentation stability typical of nanodisperse ferrofluids with the high sensitivity of rheological parameters to magnetic fields. The developed model explains the experimentally found long-term rheological relaxation and residual stress that is retained after the medium ceases to flow.     

Retention properties of cyclodextrins and modified cyclodextrins in reversed phase HPLC

Summary In the course of systematic studies on the solubility, hydrophobicity and complexation properties of cyclodextrins and modified cyclodextrins, the retention behavior of , , and of some glycosylated cyclodextrins has been examined by means of reverse phase HPLC. Mobile phase mixtures containing large amounts of water have been used because of the possible application of such systems to biological studies. Mobile phase mixtures with both methanol and acetonitrile show a linear relationship between the volume fraction of the organic part of the mobile phase and the logarithm of the capacity factor. The extrapolation of capacity factors to a total aquous system are used and compared to other techniques (including solubility) in order to evaluate the hydrophobic properties of the cyclodextrins. In particular, the solubility of cyclodextrins has been explored for a wide range of organic solvent/water mixtures. Whilst cyclodextrins are definitely the most hydrophobic, followed by glycosylated cyclodextrins, the others behave differently in the two mobile phase systems. The differences observed in the results are related to the chemical nature of the organic phase. Comparisons between chromatographic and solubility methods are given and interpretations are proposed. Some cyclodextrins have been modified to increase or modify not only the hydrophobicity but also the solubility, the complexation and the molecular recognition of drugs. The most important aim of this study was to define conditions and rules for further drug vectorization by cyclodextrin-drug complexation.     

Supramolecular assembly-enhanced chiroptical properties of pyrene-modified cyclodextrins

Di-pyrene-substituted γ-cyclodextrins (γ-CD) self-assembled into nanostrips in aqueous solution, which exhibited significant chiroptical properties with ultrahigh g_abs and g_lum values up to 4.3 × 10^?2 and 5.3 × 10^?2, respectively. Simultaneously, it also had excellent chiral emission performance with the highest Bⁱ_CPL value of 169.3 (mol/L)^?1cm^?1 so far for excimer fluorescence.

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Simulation of the rheological properties of liquid media containing solid anisometric particles

Theoretical simulation of the rheological properties of liquid media containing solid anisometric particles is performed. Procedures for the calculation of the degree of ordering in the nematic systems under equilibrium conditions and their rheological characteristics are proposed. Earlier developed notions of the calculation procedures for the properties of systems considered are analyzed and corrections to the theory are substantiated. Based on developed model notions, equilibrium and transport equations are derived and a program for their numerical solution is proposed. Model calculations of the lines of phase transition and the ordering of systems containing isotropic and nematic phases, as well as anisotropic (in orienting field) and effective dynamic viscosities under the conditions of free flow of such systems, are carried out at various concentrations and geometry of anisometric particles. A comparison of calculated and experimental data for the solutions of polymer-salt compositions with induced chain rigidity demonstrates the adequacy of the model proposed.     

Study on the aggregation and electrochemical properties of Rose Bengal in aqueous solution of cyclodextrins

The interactions of Rose Bengal (RB) with alpha-cyclodextrin (alpha-CD), hydroxypropyl-beta-cyclodextrin (HP-beta-CD), hydroxypropyl-gamma-cyclodextrin (HP-gamma-CD), heptakis(2,3,6-tri-O-methyll)-beta-cyclodextrin (TM-beta-CD) were studied in aqueous solutions of 0.1 M KClO(4) and 0.1 M LiClO(4) by vis absorption, fluorescence spectroscopy as well as electrochemical measurements at 298 K. The spectrophometric results indicate that RB is included in all beta- and gamma-CDs forming complexes with a stoichiometry 1:1 whose stability is slightly higher in KClO(4) than in LiClO(4) solutions. The complex stability constants determined for salt-containing CD solutions are lower than those for water solutions. The complexation of RB with beta- and gamma-CD and the differences between the complexes obtained in the presence of the two salts were confirmed by an electrochemical study.     

Control of optical properties of gel-derived oxide coating films containing fine metal particles

Control of the optical properties of gel-derived oxide films containing fine metal particles is described. The duration of the aging of Si(OC₂H₅)₄-derived sols and the amount of water for hydrolyzing Si(OC₂H₅)₄ were found to greatly affect the size and the shape of Au particles formed in the silica matrix, and accordingly the optical absorption of the Au/SiO₂ composite films. Employing dielectric media with high refractive indices like TiO₂ was shown to shift the absorption peak of Au particles to longer wavelengths. Pd/TiO₂ and Pt/TiO₂ composite films showed absorption in the visible region.     

Physicochemical characterization and stability of microbeads containing cod-liver oil encircled with natural cyclodextrins

The ability of cyclodextrins (CDs) to solubilize cod-liver oil in aqueous solutions was evaluated. Only the natural α-cyclodextrin (αCD) and γ-cyclodextrin (γCD) were able to fully disperse 10 % (v/v) cod-liver oil in aqueous solutions. Confocal imaging revealed that the oil was located in the center of the CD enveloped microbeads (<20 μm in diameter) where it was enclosed within nanocompartments (<1 μm in diameter). The aqueous microbead suspensions were lyophilized to produce dry powder microbeads with rough surfaces. To assess the stability of the cod-liver oil/γCD (3:1 molar ratio) microbead powder, three groups of samples were incubated over a period of 1, 2, 4, 12 and 84 weeks. Group 1 (G1) and group 2 (G2) were incubated at 25 °C and 60 % humidity. G1 was exposed to O₂ for 10 min before sealing off the glass containers while G2 was kept under nitrogen. Group 3 was stored under accelerated conditions at 40 °C and 75 % humidity under nitrogen. The reference was pure cod-liver oil. Results indicated that encapsulating cod-liver oil with γCD delays oxidative degradation when oxygen is present, but does not significantly decrease or increase the long term stability of cod-liver oil under anaerobic conditions. Cod-liver oil/γCD microbeads could be compressed into tablets without decreasing the integrity of encapsulation. The cod-liver oil/γCD microbead powder might be of interest to the pharmaceutical industry as a carrier for lipophilic drugs.     

Effect of filler shape on mechanical properties of rigid polyurethane composites containing plant particles

The effect of types of fillers on mechanical properties of rigid polyurethane composite samples was investigated. Polyurethane (PU) composites were prepared using a molasses polyol (MP, a mixture of molasses and polyethylene glycol, Mw=200) diphenylmethane diisocyanate (MDI) and fillers. The following plant particles, bamboo powder, roast bamboo powder, wood meal, coffee grounds, ground coffee bean parchment and cellulose powder, were used as fillers. The mixture of MP and fillers was reacted with MDI by adding an adequate amount of acetone as a solvent. The content of fillers was defined as the ratio of filler weight to total weight of polyol and fillers. The filler content was varied from 10 to 90 wt%. Polyurethane (PU) composites were prepared using fillers with MP. Lengths of major axis and minor axis for each particle regarded as an ellipse were measured using an optical microscope. Averages of diameter and aspect ratio were derived for each plant particle. The relationships between these average values and the mechanical properties, such as strength and elastic modulus, determined by the compression tests were investigated. The effect of filler content was estimated using the apparent volume ratio which is determined as the ratio of the apparent volume of fillers to the reciprocal values of the apparent density of samples. The master curves of the relationships between the specific values of mechanical properties and the apparent volume ratio were obtained. It was found that the compression strength and the elastic modulus for composite samples with different fillers showed maximum values at average aspect ratio around 3. It was also found that the apparent volume ratio, where the mechanical properties showed maximums, decreases with increasing aspect ratio. Using master curves, it is possible to evaluate the mechanical properties of plant particle filled polyurethane composites are described.     

Photophysical properties of glucoconjugated chlorins and porphyrins and their associations with cyclodextrins

Glucoconjugated analogues of the meta-hydroxyphenyl porphyrin (m-THPP) and meta-hydroxyphenyl chlorin (m-THPC) has been recently synthesized. The characteristics of their triplet states have been determined with regard to their involvement in the photodynamic (PDT) efficiency. In the case of porphyrin derivatives, triplet quantum yields (Phi(T)) were ranging from 0.42 to 0.55 and triplet life times (tau(T)) from 1 to 5 micros. High reaction rate constants (k(q)) with molecular oxygen (k(q): 1.2-1.6 x 10(9)s(-1)) have been found. The triplet lifetimes of chlorin derivatives were about four times higher than those of porphyrins whereas the Phi(T) and k(q) values remained quite similar. Singlet oxygen yields of glucosylated and non-glucosylated porphyrins and chlorins were not significantly different within experimental errors (Phi(Delta)((1)O(2)): 0.41-0.58). Furthermore, it has been shown that glucoconjugated photosensitizers could undergo associations with the methyl-beta-cyclodextrin (Me-beta-CD) which exhibit high triplet lifetimes and singlet oxygen yields ranging from 0.27 to 0.48.     

Preparation and characterization of inclusion complexes containing fixolide, a synthetic musk fragrance and cyclodextrins

AHTN (7-Acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphthalene), commercially known as fixolide or tonalide, is a synthetic fragrance widely used in replace of natural musk odor which is more expensive. It is a popular fragrance material added in the manufacturing of personal care and household products, such as perfumes, soaps, shampoos, detergents, and fabric softeners. AHTN is semivolatile and is degraded under light exposure and high temperature. This work focuses on the complexation of AHTN with cyclodextrins in the effort to stabilize the fragrance material. AHTN was complexed with β-cyclodextrin, methyl (MβCD), and hydroxypropyl (HPβCD) derivatives in the mole ratio 1:1, 1:2, and 1:3 guest:host, and the complexes formed by physical mixing, co-precipitation, kneading, and freeze-drying were analyzed by DSC and FTIR. Percent AHTN included in the complex was also determined by hexane extraction and GC analysis. It was found that no inclusion complex was formed in the physical mixture. When co-precipitation method was performed, only βCD could form inclusion complex with AHTN, while the other two derivatives could not. Using 1:2 AHTN:βCD, no free AHTN was left in the complex as evidenced by DSC and FTIR spectrum. In kneading and freeze-drying methods, complexes could be formed with all CDs tested. However, co-precipitation method with 1:2 AHTN:βCD and kneading method with 1:2 AHTN:MβCD provided the highest complex yield with highest amount of AHTN included in the complex. AHTN in the complex form was more stable against high temperature and UV exposure than its free form.     

Chromatographic study of the inclusion properties of cyclodextrins: Study of inclusion from the gaseous phase

The ability of cyclodextrins to form inclusion compounds with substances in the gaseous phase was studied chromatographically. Chromatographic measurements enabled the mechanism of the inclusion process to be clarified and have shown that other forces, mainly hydrogen bonding, play a role in the process in addition to the geometric properties of the interacting substances. These facts are expressed in terms of the changes in the chromatographic quantities and of the changes in the thermodynamic characteristics that are derived from the former quantities. The selective properties of cyclodextrins have been utilized in separations of substances that are otherwise separated with difficulty (xylenes, diethylbenzenes, trimethylbenzenes, etc.).     

Preparation,characterization and catalytic properties of perfluorosulfonated ion-exchange membranes containing surface-concentrated,hydrated ruthenium oxide particles

Microparticulate hydrated ruthenium oxide precipitates have been prepared in Nafion ion-exchange membranes by treatment of the Ru-exchanged membranes with KOH or NaOH solutions. These precipitates are concentrated near both membrane surfaces giving a concentration profile which depends on the conditions of preparation. The particle size, nature and distribution across the membrane thickness of the precipitates were characterized by scanning electron microprobe analysis, transmission electron microscopy, electron microdiffraction and X-ray diffraction. The oxide is present as very fine crystalline spherical particles whose size ranges from 200 to 1000 Å. Precipitation was also achieved at one side only in free-standing membranes with ruthenium oxide at one side and uranium oxide at the other. Nafion-coated modified electrodes containing precipitated ruthenium oxide particles catalyse the oxidation of water to oxygen and the reduction of oxygen to hydrogen peroxide and water in the presence of mediators. The relevance of these results to the construction of solid polymer electrolyte devices containing active electrocatalysts is discussed.     

Production of micron-sized polystyrene particles containing PEG near the particles surface

Polystyrene (PS) particles in the size range of 1-7 µm, containing poly(ethylene glycol) or PEG on the particles surface, were prepared by multi-step seeded polymerizations. Micron-sized PS particles were first prepared by dispersion polymerization using 2,2'-azobisisobutyronitrile as initiator and polyvinyl pyrrolidone as stabilizer. Conventional swelling method was then used to increase the size of the PS particles with a large amount of styrene in presence of oil soluble initiator, benzoyl peroxide. In the final step, the PS particles have been used to carry out seeded polymerization with small amount of styrene in presence of poly(ethylene glycol)-azo or PEGA initiator with average molecular weights of the PEG chains of 200 and 3000 g mol^-1 , respectively. The average size, size distribution, and surface morphology indicate that seeded polymerization in the final step with small amount of styrene in presence of PEGA is the best way to produce monodisperse polystyrene particles containing PEG near the particles surface.     

Absorption enhancement of polypeptide drugs by cyclodextrins. I. Enhanced rectal absorption of insulin from hollow-type suppositories containing insulin and cyclodextrins in rabbits.

The absorption of insulin (from porcine pancreas) from the rectum of rabbits after the administration of hollow-type suppositories containing insulin and five kinds of cyclodextrins (CyDs) was investigated. Three types of suppositories were employed: suppository I containing insulin (approximately 26 IU/mg) and various amounts of each CyD in citric buffer solution at pH 3.0 or powder in its cavity, suppository II containing CyD without insulin, and suppository III containing insulin without CyD. Without CyD, the insulin and glucose levels in plasma were unchanged, whereas a significant increase in the plasma insulin concentration and a marked decrease in the glucose levels were found following simultaneous administration of insulin and CyDs by suppository I. The enhancing effect of CyD on rectal insulin absorption (absorption-enhancing effect) by chemically modified CyDs (heptakis(2,6-di-O-methyl)-beta-CyD (DM-beta-CyD) and 2-hydroxypropyl-beta-CyD (HP-beta-CyD)) was higher than those by natural CyDs (alpha-, beta-, and gamma-CyD). The area under the plasma concentration-time curve (AUC) and Cmax of insulin significantly decreased with the preadministration (administration of CyD 6, 24 and 48 h before rectal insulin administration) of DM-beta-CyD. The absorption-enhancing effect disappeared 24 h after preadministration. These results suggest that CyDs enhance insulin absorption from the rectum, and that attenuation of the membrane transport barrier function in the rectum recovers at a maximum of 24 h after administration of CyDs.