First steps in the formulation of praziquantel nanosuspensions for pharmaceutical applications

Praziquantel (PZQ), a broad spectrum anthelmintic drug, cannot be found in acceptable dosage forms for elderly patients, paediatric patients, and for veterinary use. In fact, very little has been done up to now in the formulation of liquid dosage forms, being they always formulated for parenteral administration. To beat this important challenge, it was accomplished a comprehensive analysis of the influence of two elementary physicochemical aspects, i.e. surface thermodynamic and electrokinetic properties, on the colloidal stability of PZQ nanosuspensions. The hydrophobic character of the drug, intensely determining the flocculation curves, was confirmed by the thermodynamic characterization. The electrophoretic characterization, in combination with the sedimentation and relative absorbance versus time curves, highlighted that the electrical double layer thickness and the surface charge can play an essential role in the stability of the pharmaceutical colloid. Finally, it was demonstrated that controlling the pH values and the incorporation of electrolytes can help in formulating PZQ aqueous nanosuspensions with appropriate stability and redispersibility behaviours for pharmaceutical use.Fil: Martinez, Noelia Anabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Química de San Luis. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Instituto de Química de San Luis; ArgentinaFil: Fernández Álvarez, Fátima. Universidad de Granada; EspañaFil: Delgado, Ángel V.. Universidad de Granada; EspañaFil: Badillo García, María Luisa. Universidad de Granada; EspañaFil: Raba, Julio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Química de San Luis. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Instituto de Química de San Luis; ArgentinaFil: Cerutti, Estela Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Química de San Luis. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Instituto de Química de San Luis; ArgentinaFil: Arias, José L.. Universidad de Granada; Españ

Design of sustainable ionic liquids based on l-phenylalanine and l-alanine dipeptides: Synthesis, toxicity and biodegradation studies

A series of dipeptide ionic liquids (ILs) with l-phenylalanine and l-alanine fragments in structure were synthesized and their possible degradation pathways were analyzed. Based on this analysis, potential transformation products (PTPs) were proposed and synthesized. All of these compounds (25 in total) went through microbial toxicity screening and aerobic biodegradation testing. Obtained results demonstrated that by investigating ILs and PTPs with a dipeptide fragment (in tandem with single amino acid analogues), the design of ILs with high biodegradation values in closed bottle test can be accomplished. One finding was that within the scope of the compounds studied, l-phenylalanine containing compounds were more biodegradable than l-alanine derivatives. In addition to the choice of amino acid residue, its position in the dipeptide IL structure also had a significant effect on biodegradability. PyCH2CO-Phe-Ala-OEt IL, where l-phenylalanine was in close proximity to the positively charged pyridinium sub-unit, gave higher biodegradation percentages compared to PyCH2CO-Ala-Phe-OEt IL, where alanine was closer to pyridinium than the phenylalanine residue. Analysis of PTPs data showed that the presence of an alanine residue resulted in undesirable (less green) PTPs more often compared to PTPs containing phenylalanine, especially when alanine was in close proximity to the pyridinium headgroup. Based on both toxicity and biodegradation testing results preferable and less preferable subunits can be chosen for the design of new sustainable chemicals based on amino acids. Results from this study demonstrate a potential of designing new sustainable chemicals using amino acid moieties as part of their structure

What are communities of practice? A comparative review of four seminal works

This paper is a comparative review of four seminal works on communities of practice. It is argued that the ambiguities of the terms community and practice are a source of the concept's reusability allowing it to be reappropriated for different purposes, academic and practical. However, it is potentially confusing that the works differ so markedly in their conceptualizations of community, learning, power and change, diversity and informality. The three earlier works are underpinned by a common epistemological view, but Lave and Wenger's 1991 short monograph is often read as primarily about the socialization of newcomers into knowledge by a form of apprenticeship, while the focus in Brown and Duguid's article of the same year is, in contrast, on improvising new knowledge in an interstitial group that forms in resistance to management. Wenger's 1998 book treats communities of practice as the informal relations and understandings that develop in mutual engagement on an appropriated joint enterprise, but his focus is the impact on individual identity. The applicability of the concept to the heavily individualized and tightly managed work of the twenty-first century is questionable. The most recent work by Wenger – this time with McDermott and Snyder as coauthors – marks a distinct shift towards a managerialist stance. The proposition that managers should foster informal horizontal groups across organizational boundaries is in fact a fundamental redefinition of the concept. However it does identify a plausible, if limited, knowledge management (KM) tool. This paper discusses different interpretations of the idea of 'co-ordinating' communities of practice as a management ideology of empowerment

Complex biphase nature of the superconducting dome of the FeSe phase diagram

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Complex biphase nature of the superconducting dome of the FeSe phase diagram

Single crystal synchrotron X-ray diffraction as a function of temperature and pressure has revealed a complex biphase mixture in superconducting FeSe. Based on our experimental results we construct a phase diagram where structural behavior and superconducting properties of FeSe are found to be correlated. We show that below 6 GPa, where pressure promotes the superconducting critical temperature, the FeSe structure is composed of 2D layers of edge-shared FeSe4 tetrahedra, while above 6 GPa the superconductivity is strongly suppressed on formation of a new orthorhombic polymorph characterized by a 3D network of face sharing FeSe6 octahedra. Therefore changes in topology and connectivity of the FeSe structure are found to be detrimental for superconductivity to exist. This previously controversial crystal structure of the high pressure polymorph of FeSe was also unambiguously determined. High pressure FeSe adopts an orthorhombic MnP-type structure (Pnma) which corresponds to a slightly distorted hexagonal NiAs-type arrangement (P63/mmc). The structural transformation from the low- to high-pressure FeSe polymorph is first order in nature and is manifested as antiparallel displacements within the Fe and Se sublattices