Liquid crystals complexed to copper (II) : an X-ray diffractometric study on monodomains of (DCBBA) 2 -Cu and (HOBBA)2-Cu

We present the first experimental results of X-ray diffraction on monodomains of two Schiff bases complexed with copper : the (DOBBA)2 —Cu : Bis-[N-(phényl-4n-butyl)(4n-dodecyloxy)-2-salicylideneamino]-Copper(II) and the (HOBBA)2 —Cu : Bis-[N-(phényl-4n-butyl)(4n-heptyloxy)-2-salicylideneamino]-Copper(II), both in the smectic A phase and in a solid-like lower temperature phase. The results give new insights into the structures of these peculiar liquid crystals : the proposed model of interdigitated layers or of partially melted chains is confirmed ; moreover, a copper-copper correlation is found so that the molecules are coupled at least in pairs (or even possibly in larger ribbons) inside the smectic layers.Une étude par diffraction des rayons X a été menée sur des monodomaines de la phase smectique A de deux bases de Schiff complexées par du cuivre : les dérivés dodécyloxy - et heptyloxy - de la série des Bis-[N-(phényl-butyl)(4n-alkyloxy)-2-salicylidèneamino]-cuivre II respectivement (DOBBA)2 Cu et (HOBBA)2 Cu. Par refroidissement de ces monodomaines nous obtenons une phase solide orientée sous forme de fibre qui a également été étudiée. Ces études mettent en évidence une organisation des molécules de la mésophase, liée au caractère spécifique des complexes ; nous confirmons le modèle proposé lors d'études préliminaires, où les chaînes paraffiniques sont, soit imbriquées de couche à couche, soit partiellement fondues. En outre, l'existence de corrélations cuivre-cuivre montre que les molécules sont associées au moins par paire sinon en rubans de taille plus importante

SANS experiments on micellar nematic mesophases

Lyotropic Nematics are liquid crystalline mixtures characterized by anisotropic aggregates of amphiphilic molecules with finite shape and long range orientational but no positional order. They are distinguished according to their macroscopic properties in positive and negative uniaxial nematics and in biaxial nematics. Very few notices are available on the structure and on the evolution of the micelles through the different nematic mesophases. We have studied by Small Angle Neutrons Scattering the potassium laurate, decylammonium hydrochloride, water system which was found to exhibit the three nematic phases as a function of temperature and concentration. SANS preliminary experiments were performed at PAXY spectrometer of Orphée reactor at Saclay on adequate combinations of fully deuterated components

Dry emulsions based on alpha cyclodextrin and vegetable oils for buccal delivery of lipophilic drugs

Background: Buccal delivery of drugs can be used as an alternative administration route to conventional oral route avoiding the liver first-pass effect and improving patient compliance. Objective: The goal of this work was to develop dry emulsions for buccal delivery of ketoprofen, used as a lipophilic model drug. The influence of two vegetable oils, olive oil or wheat germ oil, in the pres-ence of \u3b1-cyclodextrin and different drying techniques on the dry emulsion properties was evaluated. Methods: Emulsions were prepared by adding olive oil or wheat germ oil to an aqueous solution of \u3b1-cyclodextrin and subsequently dried through an oven, freeze-dryer or spray-dryer. Dry emulsions were characterized in terms of yield, encapsulation efficiency, morphology and drug solid-state. In vitro drug release and permeation studies were carried out to evaluate dry emulsion ability to release the drug and to allow its permeation through the esophageal porcine epithelium. Results: The formation of stable and milky emulsion was assured by cyclodextrin ability to interact with oil components obtaining an inclusion complex with amphiphilic property able to act as a surface-active agent. The drying process influenced the yield and the encapsulation efficiency, while no signifi-cant differences were observed between olive oil and wheat germ oil. Freeze-dried emulsions, selected as the best formulations, resulted in fast release of drug thereby ensuring its permeation across the epi-thelium. Conclusion: Dry emulsions prepared with a simple and easy method, using natural ingredients and avoiding synthetic surfactants and organic solvents, could be used for buccal delivery of lipophilic drugs

Microparticles based on chitosan/carboxymethylcellulose polyelectrolyte complexes for colon delivery of vancomycin

The aim of this work was to prepare polyelectrolyte complexes based on chitosan (CH) and carboxymethylcellulose (CMC) for colon delivery of vancomycin (VM). Various batches of polyelectrolyte complexes, using three different CH/CMC weight ratios (3:1, 1:1 and 1:3), were prepared and collected as microparticles by spray-drying process. Microparticles were characterized in terms of yield, encapsulation efficiency, drug loading, morphology and mucoadhesion properties. Microparticles water-uptake and VM release as well as its protection against gastric pepsin degradation were also investigated. Finally, the antibacterial activity against Staphylococcus aureus, a Gram-positive model strain, was evaluated. The best formulation CH/CMC 1:3 was selected based on the encapsulation efficiency, water-uptake and drug release rate. Moreover, microparticles were able to prevent VM degradation and showed a good antibacterial activity against S. aureus. Finally, to improve the release of VM in the colon the selected formulation was coated with lauric acid

X-ray investigations on a homologous series of mesogenic azo compounds complexed with Palladium (II)

The X-ray diffraction experimental data concerning a homologous series of p-alkyl-p’-alkoxy-azobenzene cyclopalladated chloro-bridged dimers, both as powder and monodomain samples, are reported. These results, compared with those obtained for the parent non-metallated materials, suggest a model for the molecular arrangement wherein the alkoxy and alkyl chains are roughly coplanar with the palladium-containing rigid core and, depending on the chain length, bent towards each other

Freeze-Dried Matrices Based on Polyanion Polymers for Chlorhexidine Local Release in the Buccal and Vaginal Cavities

Chlorhexidine (CLX) is a wide spectrum cationic antimicrobial used for prevention and treatment of infections of buccal and vaginal cavities. To increase the residence time of CLX-based formulations at the application site and consequently reduce the daily dose frequency, new formulations composed of mucoadhesive polymers should be designed. The objective of this work was the development of matrices based on polyanionic polymers, such as sodium alginate, carboxymethylcellulose, xanthan gum and sodium hyaluronate, aimed to prolong the local release of CLX into the buccal or vaginal cavity. Matrices were prepared by freeze-drying and comply with 2 different preparative methods and characterized in terms of resistance to compression, water uptake ability, mucoadhesion, in vitro drug release behavior and antimicrobial activity toward representative pathogens of buccal and vaginal cavities. Results showed that the selection of suitable polymers associated to the adequate preparative method allowed to modulate matrix ability to hydrate, adhere to the mucosa and release the drug as well as to exert antimicrobial activity. In particular, matrix based on sodium hyaluronate was found to be the best performing formulation and could represent a versatile system for local release of CLX with potential application in both buccal and vaginal cavities