Visualizing the Flexibility of RHO Nanozeolite: Experiment and Modeling.

Structural flexibility is an intrinsic feature of zeolites, and the characterization of such dynamic behavior is key to maximizing their performance and realizing their potential in both existing and emerging applications. Here, the flexibility of a high-aluminum nano-sized RHO zeolite is directly visualized with in situ TEM for the first time. Variable temperature experiments directly observe the physical expansion of the discrete nanocrystals in response to changes in both guest-molecule chemistry (Ar vs CO2) and temperature. The observations are complemented by operando FTIR spectroscopy verifying the nature of the adsorbed CO2 within the pore network, the desorption kinetics of carbonate species, and changes to the structural bands at high temperatures. Quantum chemical modeling of the RHO zeolite structure substantiates the effect of cation (Na+ and Cs+) mobility in the absence and presence of CO2 on the flexibility behavior of the structure. The results demonstrate the combined influences of temperature and CO2 on the structural flexibility consistent with the experimental microscopy observations.

Freeze-Dried Matrices for Buccal Administration of Propranolol in Children: Physico-Chemical and Functional Characterization.

Buccal matrices represent a widely accepted dosage form permitting a convenient, easy, reliable drug administration and reducing administration errors. The aim of this study was the development of mucoadhesive buccal matrices for propranolol administration in children. Matrices were obtained by freeze-drying of drug loaded polymeric solutions based on gum tragacanth (GT), pectin (PEC), hydroxypropylmethylcellulose (HPMC), sodium hyaluronate (HA), gelatin (GEL), chitosan (CH) or a mixture of CH and HPMC (CH/HPMC). Matrices were characterized for drug solid state, morphology, water-uptake, mucoadhesion ability, in vitro drug release and permeation through porcine epithelium. The most promising formulations were tested for in vitro biocompatibility in human dental pulp fibroblasts. The preparative method and the polymeric composition influenced the drug solid state, as a complete amorphization as well as different polymorphic forms were observed. GEL and PEC guaranteed a fast and complete drug release due to their rapid dissolution, while for the other matrices the release was influenced by drug diffusion through the viscous gelled matrix. Moreover, matrices based on CH and CH/HPMC showed the best mucoadhesive properties, favoured the drug permeation, in virtue of CH ability to interfere with the lipid organization of biological membrane, and were characterized by a good biocompatibility profile.

Ondansetron buccal administration for paediatric use: A comparison between films and wafers.

The objective of this study was the development of different solid formulations, such as wafers and films, for buccal administration of ondansetron, a selective and potent antagonist of 5-hydroxytryptamine 3 receptors used in children for the treatment of nausea and vomiting. Wafers and films have been prepared drying an aqueous solution of pectin, hydroxypropyl methylcellulose, sodium hyaluronate, sodium carboxymethylcellulose, chitosan or gelatin, through lyophilization or oven. Formulations were characterized in terms of morphology, drug solid state and ability to hydrate, adhere to mucosa, release and favour the permeation of the drug through porcine esophageal epithelium, used as model of human buccal epithelium. The most promising formulations were tested for in vitro biocompatibility in human pulp fibroblasts. Films showed greater hydration and mucoadhesion abilities and allowed the release and the permeation of a greater amount of ondansetron with respect to wafers. Chitosan or hyaluronate provided films with the best mucoadhesion properties and good biocompatibility profile. Moreover, chitosan based film allowed to obtain the highest amount of permeated drug and could represent a novel child-appropriate dosage form able to combine the advantages of solid dosage form with the possibility to avoid the swallowing.

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.

Advances in Methanol Production and Utilization, with Particular Emphasis toward Hydrogen Generation via Membrane Reactor Technology.

Methanol is currently considered one of the most useful chemical products and is a promising building block for obtaining more complex chemical compounds, such as acetic acid, methyl tertiary butyl ether, dimethyl ether, methylamine, etc. Methanol is the simplest alcohol, appearing as a colorless liquid and with a distinctive smell, and can be produced by converting CO2 and H2, with the further benefit of significantly reducing CO2 emissions in the atmosphere. Indeed, methanol synthesis currently represents the second largest source of hydrogen consumption after ammonia production. Furthermore, a wide range of literature is focused on methanol utilization as a convenient energy carrier for hydrogen production via steam and autothermal reforming, partial oxidation, methanol decomposition, or methanol⁻water electrolysis reactions. Last but not least, methanol supply for direct methanol fuel cells is a well-established technology for power production. The aim of this work is to propose an overview on the commonly used feedstocks (natural gas, CO2, or char/biomass) and methanol production processes (from BASF-Badische Anilin und Soda Fabrik, to ICI-Imperial Chemical Industries process), as well as on membrane reactor technology utilization for generating high grade hydrogen from the catalytic conversion of methanol, reviewing the most updated state of the art in this field.

Vaginal Bifidobacterium breve for preventing urogenital infections: Development of delayed release mucoadhesive oral tablets.

Bifidobacteria are predominant microorganisms in the intestinal flora, but at the same time represent a subdominant group of the vaginal microbiota. For this reason, oral administration of these probiotic bacteria can provide beneficial effect for both intestinal and urogenital ecosystems. The first aim of this study was to test the strain Bifidobacterium breve BC204, isolated from a vaginal swab of a healthy woman, for its capability to adhere to human cells, to survive to gastric acids and bile salts and to exert antimicrobial activities. The second aim of the work was to develop an oral formulation able to guarantee bacterial survival during storage and administration, thus favouring intestinal and vaginal colonization. B. breve BC204 was encapsulated by spray-drying and subsequently formulated in time-dependent erodible tablets. B. breve BC204 showed good ability to adhere to Caco-2 cells and moderate ability to resist to gastrointestinal stress. Moreover, it exerted a strong antimicrobial activity against urogenital and enteric pathogens. Microencapsulation followed by tablet production allowed high loading and survival of B. breve BC204, associated to a delayed release and mucoadhesive ability. These characteristics are required to achieve appropriate amount and persistence of viable microbial cells in the treatment site.

Bilayered buccal films as child-appropriate dosage form for systemic administration of propranolol.

Buccal mucosa has emerged as an attractive site for systemic administration of drug in paediatric patients. This route is simple and non-invasive, even if the saliva wash-out effect and the relative permeability of the mucosa can reduce drug absorption. Mucoadhesive polymers represent a common employed strategy to increase the contact time of the formulation at the application site and to improve drug absorption. Among the different mucoadhesive dosage forms, buccal films are particularly addressed for paediatric population since they are thin, adaptable to the mucosal surface and able to offer an exact and flexible dose. The objective of the present study was to develop bilayered buccal films for the release of propranolol hydrochloride. A primary polymeric layer was prepared by casting and drying of solutions of film-forming polymers, such as polyvinylpyrrolidone (PVP) or polyvinylalcohol (PVA), added with different weight ratios of gelatin (GEL) or chitosan (CH). In order to achieve unidirectional drug delivery towards buccal mucosa, a secondary ethylcellulose layer was applied onto the primary layer. Bilayered films were characterized for their physico-chemical (morphology, thickness, drug content and solid state) and functional (water uptake, mucoadhesion, drug release and permeation) properties. The inclusion of CH into PVP and PVA primary layer provided the best mucoadhesion ability. Films containing CH provided a lower drug release with respect to films containing GEL and increased the amount of permeated drug through buccal mucosa, thanks to its ability of interfering with the lipid organization. The secondary ethylcellulose layer did not interfere with drug permeation, but it could limit drug release in the buccal cavity.

Spanish Broom (Spartium junceum L.) fibers impregnated with vancomycin-loaded chitosan nanoparticles as new antibacterial wound dressing: Preparation, characterization and antibacterial activity.

In this work, we propose as new wound dressing, the Spanish Broom fibers impregnated with vancomycin (VM) loaded chitosan nanoparticles. Spanish Broom fibers were extracted by patented method DiCoDe and the morphological, physical and mechanical properties were investigated. Chitosan nanoparticles were prepared by ionic gelation using different weight ratios between chitosan (CH) and tripolyphosphate (TPP). Nanoparticles were characterized in terms of size, zeta potential, yield, encapsulation efficiency, stability and drug release. Finally, the antibacterial activity against Staphylococcus aureus as well as in vitro cytotoxicity on HaCaT cells were evaluated. The best formulation CH/TPP 4:1 was selected based on the encapsulation efficiency and yield. Spanish Broom fibers impregnated with loaded nanoparticles showed an increased antibacterial activity against S. aureus compared to the same fibers containing VM without nanoparticles. Moreover, these fibers were not toxic to HaCaT keratinocytes cells. In conclusion, Spanish Broom fibers impregnated with VM loaded CH/TPP nanoparticles would appear to be a promising candidate for wound dressing application.

Association of Lactobacillus crispatus with fructo-oligosaccharides and ascorbic acid in hydroxypropyl methylcellulose vaginal insert.

The aim of this work was to develop a synbiotic vaginal insert containing the probiotic strain Lactobacillus crispatus BC5, the prebiotic substrate fructo-oligosaccharide and the antioxidant agent ascorbic acid, for the prophylaxis and therapy of vaginal infections. Mucoadhesive in situ gelling vaginal inserts based on hydroxypropyl methylcellulose were prepared by freeze-drying, stored at +2-8 °C for 90 days and characterized in terms of technological and functional properties. Complete survival of L. crispatus BC5 was found immediately after insert preparation (96.08%) as well as after 90 days of storage (95.82%) in the vaginal inserts containing fructo-oligosaccharide, ascorbic acid and skimmed milk. Synbiotic inserts showed improved mucoadhesion ability (from three- to five-fold) with respect to a standard formulation based on hydroxypropyl methylcellulose alone. Moreover, inserts allowed to modulate lactobacilli release in virtue of the different amounts of fructo-oligosaccharide. Finally, antimicrobial activity was exerted by L. crispatus BC5 released from the vaginal formulation.

Performance and Long-Term Stability of Pd/PSS and Pd/Al2O3 Membranes for Hydrogen Separation.

The present work is focused on the investigation of the performance and long-term stability of two composite palladium membranes under different operating conditions. One membrane (Pd/porous stainless steel (PSS)) is characterized by a ~10 µm-thick palladium layer on a porous stainless steel substrate, which is pretreated by means of surface modification and oxidation; the other membrane (Pd/Al2O3) is constituted by a ~7 µm-thick palladium layer on an asymmetric microporous Al2O3 substrate. The operating temperature and pressure ranges, used for studying the performance of these two kinds of membranes, are 350-450 °C and 200-800 kPa, respectively. The H2 permeances and the H2/N2 selectivities of both membranes were investigated and compared with literature data. At 400 °C and 200 kPa as pressure difference, Pd/PSS and Pd/Al2O3 membranes exhibited an H2/N2 ideal selectivity equal to 11700 and 6200, respectively, showing stability for 600 h. Thereafter, H2/N2 selectivity of both membranes progressively decreased and after around 2000 h, dropped dramatically to 55 and 310 for the Pd/PSS and Pd/Al2O3 membranes, respectively. As evidenced by Scanning Electron Microscope (SEM) analyses, the pinholes appear on the whole surface of the Pd/PSS membrane and this is probably due to release of sulphur from the graphite seal rings.