Achieving extremely concentrated aqueous dispersions of graphene flakes and catalytically efficient graphene-metal nanoparticle hybrids with flavin mononucleotide as a high-performance stabilizer.

The stable dispersion of graphene flakes in an aqueous medium is highly desirable for the development of materials based on this two-dimensional carbon structure, but current production protocols that make use of a number of surfactants typically suffer from limitations regarding graphene concentration or the amount of surfactant required to colloidally stabilize the sheets. Here, we demonstrate that an innocuous and readily available derivative of vitamin B2, namely the sodium salt of flavin mononucleotide (FMNS), is a highly efficient dispersant in the preparation of aqueous dispersions of defect-free, few-layer graphene flakes. Most notably, graphene concentrations in water as high as ∼50 mg mL(-1) using low amounts of FMNS (FMNS/graphene mass ratios of about 0.04) could be attained, which facilitated the formation of free-standing graphene films displaying high electrical conductivity (∼52000 S m(-1)) without the need of carrying out thermal annealing or other types of post-treatment. The excellent performance of FMNS as a graphene dispersant could be attributed to the combined effect of strong adsorption on the sheets through the isoalloxazine moiety of the molecule and efficient colloidal stabilization provided by its negatively charged phosphate group. The FMNS-stabilized graphene sheets could be decorated with nanoparticles of several noble metals (Ag, Pd, and Pt), and the resulting hybrids exhibited a high catalytic activity in the reduction of nitroarenes and electroreduction of oxygen. Overall, the present results should expedite the processing and implementation of graphene in, e.g., conductive inks, composites, and hybrid materials with practical utility in a wide range of applications.

Molecular imprinted ormosils for nafcillin recognition by room temperature phosphorescence optosensing.

Nafcillin imprinted sol-gels were used as specific binding materials for the room temperature phosphorescence (RTP) recognition of nafcillin using a flow injection system. Selective and reversible binding of the template to imprinted sol-gels could be observed by tailoring the hydrophobic/hydrophilic balance of the materials. Also, the possibility of minimizing non-specific interactions was evaluated by end-capping with trimethyl silyl groups. Control experiments were performed with non imprinted reference sol-gels. The recognition mechanism and the analytical potential of these materials for developing stable, selective and sensitive approaches for nafcillin recognition in real samples are outlined.

Assessment of molecularly imprinted sol-gel materials for selective room temperature phosphorescence recognition of nafcillin.

Sol-gel imprinted materials were prepared against nafcillin, a semisynthetic beta-lactamic antibiotic employed in the treatment of serious infections caused by penicillinase-producing staphylococci. Two approaches were addressed for preparation of the imprinted materials and the controls: as conventional monoliths, which were ground and sieved to a desired particle size for rebinding analysis, and as films on supporting glass slides. The specific binding sites that are created during the imprinting process are analyzed via selective room temperature phosphorescence (RTP) (sol-gel films) measurements as well as via competitive room temperature phosphorescence ligand assay. Results demonstrated the importance of the physical configuration of the imprinted material for minimizing non-specific binding. The close similarities between the structures of different beta-lactamic antibiotics made it possible to interpret the roles of the template structure on specific molecular recognition. In this article, we introduce the use of room temperature phosphorescence as selective transduction method for the template. The imprinted sol-gel films displayed enhanced specific binding characteristics respect to the monolithic sol-gel and can be envisaged for the use as recognition matrices for the screening and rapid selection of antibiotics from a combinatorial library or for the rapid control of nafcillin in biological samples (e.g. milk, serum, urine).

Treatment with interferon gamma versus interferons alfa and gamma in children with chronic hepatitis B.

Thirty-five children with chronic hepatitis B were randomly assigned to three groups: group 1 (n = 12), untreated; group 2 (n = 11), treated with 1 million units of interferon gamma per square meter of body surface (MU/m2), three times a week for 24 weeks; and group 3 (n = 12), treated with interferon alfa at a dose of 5 MU/m2, three times a week for 12 weeks followed by 1 MU/m2 of interferon gamma with the same schedule. At the end of the treatment (6th month), hepatitis B virus DNA was negative in 16.5% of the control group, in 9% of the children treated with interferon gamma, and in 16.5% of those treated with interferons alfa and gamma. No child had lost the hepatitis B e antigen by this time. No basal differences in the serum hepatitis B virus DNA concentration among the groups were observed. At follow-up (15th month), viral genome was negative in 25% of the untreated children, in 36% of the group treated with interferon gamma, and in 41.5% of the children who had received interferons alfa and gamma. Hepatitis B e antigen was negative in 25% of the children who belonged to groups 1 and 3 and in 27% of the children treated with interferon gamma only. These data suggest that interferon gamma does not have a powerful antiviral effect on chronic hepatitis B in children. However, it is well tolerated.

Salivary levels of thallium in acute human poisoning.

Thallium intoxication in a 28-year-old woman was characterized by neurological and gastrointestinal symptoms and alopecia. Treatment was started 4 days after poisoning and consisted of forced diuresis and administration of Prussian Blue at four daily doses of 5 g by duodenal tube for 20 days. Thallium was measured by atomic absorption spectrophotometry in urine, faeces and saliva. Considerable amounts of thallium were detected in saliva, salivary concentrations being up to 15 times higher than urinary ones. Evidence was also obtained that only a little fraction of the ingested dose was excreted by the intestine during the hospital course in spite of Prussian Blue administration.