Gel formation in systems composed of drug containing catanionic vesicles and oppositely charged hydrophobically modified polymer

The aim of this study was to explore if mixtures of drug containing catanionic vesicles and polymers give rise to gel formation, and if so, if drug release from these gels could be prolonged. Catanionic vesicles formed from the drug substances alprenolol or tetracaine, and the oppositely charged surfactant sodium dodecyl sulphate were mixed with polymers. Three polymers with different properties were employed: one bearing hydrophobic modifications, one positively charged and one positively charged polymer bearing hydrophobic modifications. The structure of the vesicles before and after addition of polymer was investigated by using cryo-TEM. Gel formation was confirmed by using rheological measurements. Drug release was studied using a modified USP paddle method. Gels were observed to form only in the case when catanionic vesicles, most likely with a net negative charge, were mixed with positively charged polymer bearing lipophilic modifications. The release of drug substance from these systems, where the vesicles are not trapped within the gel but constitute a founding part of it, could be significantly prolonged. The drug release rate was found to depend on vesicle concentration to a higher extent than on polymer concentration.     

Effect of lipid headgroup composition on the interaction between melittin and lipid bilayers

The effect of the lipid polar headgroup on melittin-phospholipid interaction was investigated by cryo-TEM, fluorescence spectroscopy, ellipsometry, circular dichroism, electrophoresis and photon correlation spectroscopy. In particular, focus was placed on the effect of the lipid polar headgroup on peptide adsorption to, and penetration into, the lipid bilayer, as well as on resulting colloidal stability effects for large unilamellar liposomes. The effect of phospholipid headgroup properties on melittin-bilayer interaction was addressed by comparing liposomes containing phosphatidylcholine, -acid, and -inositol at varying ionic strength. Increasing the bilayer negative charge leads to an increased liposome tolerance toward melittin which is due to an electrostatic arrest of melittin at the membrane interface. Balancing the electrostatic attraction between the melittin positive charges and the phospholipid negative charges through a hydration repulsion, caused by inositol, reduced this surface arrest and increased liposome susceptibility to the disruptive actions of melittin. Furthermore, melittin was demonstrated to induce liposome structural destabilization on a colloidal scale which coincided with leakage induction for both anionic and zwitterionic systems. The latter findings thus clearly show that coalescence, aggregation, and fragmentation contribute to melittin-induced liposome leakage, and that detailed molecular analyses of melittin pore formation are incomplete without considering also these colloidal aspects.     

Determination of organic acids in wine by zone electrophoresis on a chip with conductivity detection

An appropriate combination of separation mechanisms (simultaneous use of differences in pK values, host-guest complexations, and the ionic strength dependences of the actual ionic mobilities) provided zone electrophoresis (ZE) resolution of 22 organic and inorganic acids expected in wines on a polymethylmethacrylate (PMMA) chip with integrated conductivity detection. These separating conditions offered a framework for the ZE determination of organic acids responsible for some important organoleptic characteristics of wines (tartrate, malate, succinate, acetate, citrate, and lactate). The ZE procedure developed in this context is simple and rapid (ca. 10 minutes' analysis time), while affording reproducible migration and quantitation data for the acids. For example, 0.8-2.0% RSD values characterized the migration times of the acids for 25 repeated ZE runs with the same sample carried out in 5 days in the background electrolyte solution prepared freshly on a daily basis, while 3-5% RSD values were typical for the accompanying peak area data. The concentration ranges within which the acids of analytical interest could be determined in one ZE run covered all wine samples included in our study (100-400-fold sample dilutions were needed to work under the conditions corresponding to the validities of the calibration data). 90-110% recoveries of the acids as obtained repeatedly for one of the reference wine samples used in our experiments indicate a good predisposition of the present method to provide accurate analytical results. This statement also supports the results from the determination of the acids in reference wine samples with claimed concentrations of malic (five samples), tartaric (one sample), and lactic (one sample) acids.     

Complexes of iron(II), iron(III) and zinc(II) with condensation derivatives of 2-acetylpyridine and oxalic or malonic dihydrazide. Crystal structure of tris[(1-(2-pyridyl)ethylidene)hydrazine]iron(II) perchlorate

Complexes of zinc and iron with N, N²-bis[(1E)-1-(2-pyridyl)ethylidene]ethanedihydrazide (H₂L1) and N ,N²-bis[(1E)-1-(2-pyridyl)ethylidene]propanedihydrazide (H₂L2) were prepared. Zn^II complexes with both ligands have an octahedral geometry. In the complex of Zn^II with H₂L1, the ligand is coordinated as a tridentate species in the monoanionic form, building two five-membered rings around Zn^II. Three remaining coordination sites are occupied by water molecules, and in the outer sphere there is a ClO ₄^– ion. In the other Zn^II complex, the H₂L2 ligand is coordinated in the enol form as a tetradenate species, forming a five-memebered, a six-membered and a seven-membered ring, the remaining coordination sites being occupied by water molecules, while in the outer sphere there are two ClO ₄^– ions. The Fe^III complex with H₂L2 is a high-spin octahedral complex. The ligand is coordinated in the enol form, in a tetradentate fashion via pyridine and hydrazone nitrogens. The remaining two coordination sites in the complex are occupied by water molecules and a Cl^– ion, and in the outer sphere there are two Cl^– anions. The octahedral Fe^III complex obtained from the reaction of FeCl₃·6H₂O and H₂L1 in absolute ethanol has the formula [Fe(HL1)Cl₂(H₂O)]·1.5H₂O. However, during coordination of the H₂L1 ligand to Fe^III in water, oxidative degradation of the side chain (–CO–CO–) and reduction of Fe^III to Fe^II occurs, affording octahedral tris(1-(2-pyridyl)ethylidenehydrazine] iron^II perchlorate, as confirmed by X-ray structure analysis.     

Technical and radiological characterisation of fly ash and bottom ash from thermal power plant

Journal of Radioanalytical and Nuclear Chemistry - Huge quantities of fly ash and bottom ash are generated from thermal power plants and it presents great concern for country, mainly due...     

Interaction of heparin and tetraarginine in capillary electrophoresis: Implication for analytical applications

Interactions between heparin and tetraarginine in an acidic background electrolyte were investigated in capillary electrophoresis. The results showed that tetraarginine and heparin form a stable complex that migrates toward the anode immediately after coming into contact. When a zone of tetraarginine at a mg/mL concentration level passes through a zone of heparin at a μg/mL concentration level, tetraarginine is gradually removed by the formation of the complex that migrates in the opposite direction, thereby decreasing the tetraarginine peak area. The variation of the tetraarginine peak area as a function of the unfractionated heparin concentration was linear within the range 2–20 μg/mL, which enables us to detect and determine heparin concentrations undetectable with a UV detector. The same behavior was confirmed for low molecular weight heparin.     

A PAMPA assay as fast predictive model of passive human skin permeability of new synthesized corticosteroid C-21 esters

The permeation properties of twenty newly synthesized α-alkoxyalkanoyl and α-aryloxyalkanoyl C-21 esters of standard corticosteroids: Fluocinolone acetonide, dexamethasone, triamcinolone acetonide and hydrocortisone were established using a PAMPA assay (70% silicone oil and 30% isopropyl myristate). The data were compared with parent corticosteroids with addition of mometasone furoate and hydrocortisone acetate. All newly synthesized corticosteroid C-21 esters have effective permeability coefficients higher then -6, mostly followed with high values of retention factors and low permeation. The examined compounds were grouped through relationship between obtained retention factors and permeation parameters (groups I-III). The classification confirmed group I (membrane retentions as well as permeation lower then 30%) for all corticosteroid standards except mometasone furoate, a potent topical corticosteroid which, with high membrane retention (81%) and low permeation (7.7%) fits into group III. The largest number of new synthesized corticosteroids C-21 esters, among them all fluocinolone acetonide C-21 esters, have high membrane retentions (32.4%-86.5%) and low permeations (1.3%-27.1%), fitting in group III. The classification was related to previously obtained anti-inflammatory activity data for the fluocinolone acetonide C-21 esters series. According to the PAMPA results the new synthesized esters could be considered as potential new prodrugs with useful benefit/risk ratio.     

Existence and uniqueness analysis of a detached shock problem for the potential flow

We study a problem for two-dimensional steady potential and isentropic Euler equations in a bounded domain, where an artificial detached shock interacts with a wedge. Using the stream function, we obtain a free boundary problem for the subsonic state and the detached artificial shock curve and we prove that such configuration admits a unique solution in certain weighted Hölder spaces. The proof is based on various Hölder and Schauder estimates for second-order elliptic equations and fixed point theorems. Moreover, we pose an energy principle and remark that the physical attached shock is the minimizer of the energy functional.