Polyacrylic acid polymers hydrogels intended to topical drug delivery: preparation and characterization

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Combining xanthan and chitosan membranes to multipotent mesenchymal stromal cells as bioactive dressings for dermo-epidermal wounds

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Chitosan/Carbomer-based tablets containing Metronidazole for potential treatment of periodontal diseases

Mucoadhesive tablets with different mixtures of chitosan and carbomer homopolymer type B were prepared in order to obtain new formulations containing metronidazole for periodontal disease treatment. All tablets were characterized by swelling and erosion studies, ex vivo mucoadhesion force and in vitro drug release. The drug released mechanism was described by Korsmeyer-Peppas and Weibull models. Tablets containing increased amounts of chitosan presented higher swelling ability and the drug release was prolonged in the simulated saliva fluid. The mechanisms for the drug release from tablets were complex, including diffusion, swelling and erosion simultaneously. This kind of delivery system is suitable for formulating metronidazole mucoadhesive systems, representing a good alternative for the local treatment of periodontal diseases.

Combining xanthan and chitosan membranes to multipotent mesenchymal stromal cells as bioactive dressings for dermo-epidermal wounds

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Enhancement of Electrical Conductivity in Plasticized Chitosan Based Membranes

Plasticized natural macromolecules-based polymer electrolyte samples were prepared and characterized. The plasticization of chitosonium acetate with glycerol increased the ionic conductivity value from 3.0 x 10(-7) S/cm to 1.1 x 10(-5) S/cm. The conductivity temperature relationship of the samples exhibits either VTF or Arrhenius type depending on the glycerol concentration in the sample. The dielectric studies evidencing the relaxation process in the plasticized sample at low frequency region are due to the electric polarization effect. Moreover, the samples were transparent in the Vis region, showed thermal stability up to 160 degrees C and good surface uniformity.

A biomimetic model membrane system on oxidic surfaces designed for the investigation of cytochrome c oxidase and other membrane proteins by fluorescence and waveguide spectroscopy

Die transmembrane Potenzialdifferenz Δφm ist direkt mit der katalytischen Aktivität der Cytochrom c Oxidase (CcO) verknüpft. Die CcO ist das terminale Enzym (Komplex IV) in der Atmungskette der Mitochondrien. Das Enzym katalysiert die Reduktion von O2 zu 2 H2O. Dabei werden Elektronen vom natürlichen Substrat Cytochrom c zur CcO übertragen. Der Eleltronentransfer innerhalb der CcO ist an die Protonentranslokation über die Membran gekoppelt. Folglich bildet sich über der inneren Membrane der Mitochondrien eine Differenz in der Protonenkonzentration. Zusätzlich wird eine Potenzialdifferenz Δφm generiert.rnrnDas Transmembranpotenzial Δφm kann mit Hilfe der Fluoreszenzspektroskopie unter Einsatz eines potenzialemfindlichen Farbstoffs gemessen werden. Um quantitative Aussagen aus solchen Untersuchungen ableiten zu können, müssen zuvor Kalibrierungsmessungen am Membransystem durchgeführt werden.rnrnIn dieser Arbeit werden Kalibrierungsmessungen von Δφm in einer Modellmembrane mit inkorporiertem CcO vorgestellt. Dazu wurde ein biomimetisches Membransystem, die Proteinverankerte Doppelschicht (protein-tethered Bilayer Lipid Membrane, ptBLM), auf einem transparenten, leitfähigem Substrat (Indiumzinnoxid, ITO) entwickelt. ITO ermöglicht den simultanen Einsatz von elektrochemischen und Fluoreszenz- oder optischen wellenleiterspektroskopischen Methoden. Das Δφm in der ptBLM wurde durch extern angelegte, definierte elektrische Spannungen induziert. rnrnEine dünne Hydrogelschicht wurde als "soft cushion" für die ptBLM auf ITO eingesetzt. Das Polymernetzwerk enthält die NTA Funktionsgruppen zur orientierten Immobilisierung der CcO auf der Oberfläche der Hydrogels mit Hilfe der Ni-NTA Technik. Die ptBLM wurde nach der Immobilisierung der CcO mittels in-situ Dialyse gebildet. Elektrochemische Impedanzmessungen zeigten einen hohen elektrischen Widerstand (≈ 1 MΩ) der ptBLM. Optische Wellenleiterspektren (SPR / OWS) zeigten eine erhöhte Anisotropie des Systems nach der Bildung der Doppellipidschicht. Cyklovoltammetriemessungen von reduziertem Cytochrom c bestätigten die Aktivität der CcO in der Hydrogel-gestützten ptBLM. Das Membranpotenzial in der Hydrogel-gestützten ptBLM, induziert durch definierte elektrische Spannungen, wurde mit Hilfe der ratiometrischen Fluoreszenzspektroskopie gemessen. Referenzmessungen mit einer einfach verankerten Dopplellipidschicht (tBLM) lieferten einen Umrechnungsfaktor zwischen dem ratiometrischen Parameter Rn und dem Membranpotenzial (0,05 / 100 mV). Die Nachweisgrenze für das Membranpotenzial in einer Hydrogel-gestützten ptBLM lag bei ≈ 80 mV. Diese Daten dienen als gute Grundlage für künftige Untersuchungen des selbstgenerierten Δφm der CcO in einer ptBLM.

New analytical LC-mass spectrometry methodologies for the quali-quantitative determination of natural substances and drugs in complex matrices

This thesis reports an integrated analytical and physicochemical approach for the study of natural substances and new drugs based on mass spectrometry techniques combined with liquid chromatography. In particular, Chapter 1 concerns the study of Berberine a natural substance with pharmacological activity for the treatment of hepatobiliary and intestinal diseases. The first part focused on the relationships between physicochemical properties, pharmacokinetics and metabolism of Berberine and its metabolites. For this purpose a sensitive HPLC-ES-MS/MS method have been developed, validated and used to determine these compounds during their physicochemical properties studies and plasma levels of berberine and its metabolites including berberrubine(M1), demethylenberberine(M3), and jatrorrhizine(M4) in humans. Data show that M1, could have an efficient intestinal absorption by passive diffusion due to a keto-enol tautomerism confirmed by NMR studies and its higher plasma concentration. In the second part of Chapter 1, a comparison between M1 and BBR in vivo biodistribution in rat has been studied. In Chapter 2 a new HPLC-ES-MS/MS method for the simultaneous determination and quantification of glucosinolates, as glucoraphanin, glucoerucin and sinigrin, and isothiocyanates, as sulforaphane and erucin, has developed and validated. This method has been used for the analysis of functional foods enriched with vegetable extracts. Chapter 3 focused on a physicochemical study of the interaction between the bile acid sequestrants used in the treatment of hypercholesterolemia including colesevelam and cholestyramine with obeticolic acid (OCA), potent agonist of nuclear receptor farnesoid X (FXR). In particular, a new experimental model for the determination of equilibrium binding isotherm was developed. Chapter 4 focused on methodological aspects of new hard ionization coupled with liquid chromatography (Direct-EI-UHPLC-MS) not yet commercially available and potentially useful for qualitative analysis and for “transparent” molecules to soft ionization techniques. This method was applied to the analysis of several steroid derivatives.

Complex tracer mobilities in polymer networks revealed by fluorescence correlation spectroscopy

Gels are elastic porous polymer networks that are accompanied by pronounced mechanical properties. Due to their biocompatibility, ‘responsive hydrogels’ (HG) have many biomedical applications ranging from biosensors and drug delivery to tissue engineering. They respond to external stimuli such as temperature and salt by changing their dimensions. Of paramount importance is the ability to engineer penetrability and diffusion of interacting molecules in the crowded HG environment, as this would enable one to optimize a specific functionality. Even though the conditions under which biomedical devices operate are rather complex, a bottom-up approach could reduce the complexity of mutually coupled parameters influencing tracer mobility. The present thesis focuses on the interaction-induced tracer diffusion in polymer solutions and their homologous gels, probed by means of Fluorescence Correlation Spectroscopy (FCS). This is a single-molecule-sensitive technique having the advantage of optimal performance under ultralow tracer concentrations, typically employed in biosensors. Two different types of hydrogels have been investigated, a conventional one with broad polydispersity in the distance between crosslink points and a so-called ‘ideal’, with uniform mesh size distribution. The former is based on a thermoresponsive polymer, exhibiting phase separation in water at temperatures close to the human body temperature. The latter represents an optimal platform to study tracer diffusion. Mobilities of different tracers have been investigated in each network, varying in size, geometry and in terms of tracer-polymer attractive strength, as perturbed by different stimuli. The thesis constitutes a systematic effort towards elucidating the role of the strength and nature of different tracer-polymer interactions, on tracer mobilities; it outlines that interactions can still be very important even in the simplified case of dilute polymer solutions; it also demonstrates that the presence of permanent crosslinks exerts distinct tracer slowdown, depending on the tracer type and the nature of the tracer-polymer interactions, expressed differently by each tracer with regard to the selected stimulus. In aqueous polymer solutions, the tracer slowdown is found to be system-dependent and no universal trend seems to hold, in contrast to predictions from scaling theory for non-interacting nanoparticle mobility and empirical relations concerning the mesh size in polymer solutions. Complex tracer dynamics in polymer networks may be distinctly expressed by FCS, depending on the specific synergy among-at least some of - the following parameters: nature of interactions, external stimuli employed, tracer size and type, crosslink density and swelling ratio.

Using the contribution matrix to evaluate complex study limitations in a network meta-analysis: a case study of bipolar maintenance pharmacotherapy review.

BACKGROUND Limitations in the primary studies constitute one important factor to be considered in the grading of recommendations assessment, development, and evaluation (GRADE) system of rating quality of evidence. However, in the network meta-analysis (NMA), such evaluation poses a special challenge because each network estimate receives different amounts of contributions from various studies via direct as well as indirect routes and because some biases have directions whose repercussion in the network can be complicated. FINDINGS In this report we use the NMA of maintenance pharmacotherapy of bipolar disorder (17 interventions, 33 studies) and demonstrate how to quantitatively evaluate the impact of study limitations using netweight, a STATA command for NMA. For each network estimate, the percentage of contributions from direct comparisons at high, moderate or low risk of bias were quantified, respectively. This method has proven flexible enough to accommodate complex biases with direction, such as the one due to the enrichment design seen in some trials of bipolar maintenance pharmacotherapy. CONCLUSIONS Using netweight, therefore, we can evaluate in a transparent and quantitative manner how study limitations of individual studies in the NMA impact on the quality of evidence of each network estimate, even when such limitations have clear directions.

Decision evaluation in complex risk network systems (DecernsSDSS) demo and Black River case study

The selection of metrics for ecosystem restoration programs is critical for improving the quality of monitoring programs and characterizing project success. Moreover it is oftentimes very difficult to balance the importance of multiple ecological, social, and economical metrics. Metric selection process is a complex and must simultaneously take into account monitoring data, environmental models, socio-economic considerations, and stakeholder interests. We propose multicriteria decision analysis (MCDA) methods, broadly defined, for the selection of optimal sets of metrics to enhance evaluation of ecosystem restoration alternatives. Two MCDA methods, a multiattribute utility analysis (MAUT), and a probabilistic multicriteria acceptability analysis (ProMAA), are applied and compared for a hypothetical case study of a river restoration involving multiple stakeholders. Overall, the MCDA results in a systematic, unbiased, and transparent solution, informing restoration alternatives evaluation. The two methods provide comparable results in terms of selected metrics. However, because ProMAA can consider probability distributions for weights and utility values of metrics for each criteria, it is suggested as the best option if data uncertainty is high. Despite the increase in complexity in the metric selection process, MCDA improves upon the current ad-hoc decision practice based on the consultations with stakeholders and experts, and encourages transparent and quantitative aggregation of data and judgement, increasing the transparency of decision making in restoration projects. We believe that MCDA can enhance the overall sustainability of ecosystem by enhancing both ecological and societal needs.

A formal framework for modelling complex network management systems

Society today is completely dependent on computer networks, the Internet and distributed systems, which place at our disposal the necessary services to perform our daily tasks. Subconsciously, we rely increasingly on network management systems. These systems allow us to, in general, maintain, manage, configure, scale, adapt, modify, edit, protect, and enhance the main distributed systems. Their role is secondary and is unknown and transparent to the users. They provide the necessary support to maintain the distributed systems whose services we use every day. If we do not consider network management systems during the development stage of distributed systems, then there could be serious consequences or even total failures in the development of the distributed system. It is necessary, therefore, to consider the management of the systems within the design of the distributed systems and to systematise their design to minimise the impact of network management in distributed systems projects. In this paper, we present a framework that allows the design of network management systems systematically. To accomplish this goal, formal modelling tools are used for modelling different views sequentially proposed of the same problem. These views cover all the aspects that are involved in the system; based on process definitions for identifying responsible and defining the involved agents to propose the deployment in a distributed architecture that is both feasible and appropriate.

Conceptual Modelling of Complex Network Management Systems

Society, as we know it today, is completely dependent on computer networks, Internet and distributed systems, which place at our disposal the necessary services to perform our daily tasks. Moreover, and unconsciously, all services and distributed systems require network management systems. These systems allow us to, in general, maintain, manage, configure, scale, adapt, modify, edit, protect or improve the main distributed systems. Their role is secondary and is unknown and transparent to the users. They provide the necessary support to maintain the distributed systems whose services we use every day. If we don’t consider network management systems during the development stage of main distributed systems, then there could be serious consequences or even total failures in the development of the distributed systems. It is necessary, therefore, to consider the management of the systems within the design of distributed systems and systematize their conception to minimize the impact of the management of networks within the project of distributed systems. In this paper, we present a formalization method of the conceptual modelling for design of a network management system through the use of formal modelling tools, thus allowing from the definition of processes to identify those responsible for these. Finally we will propose a use case to design a conceptual model intrusion detection system in network.

The effect of complexation on characteristics and drug release from PLGA microspheres loaded by cyclosporine-cyclodextrin complex

The purpose of this study was to evaluate the effect of cyclosporine (CyA)-cyclodextrin (CD) complex incorporated within PLGA inicrospheres on microsphere characteristics, with particular emphasis on drug release kinetics. For this purpose, microspheres encapsulated with CyA and those loaded by CyA-CD complex were prepared by solvent evaporation and multiple emulsification solvent evaporation methods, respectively. Morphology, size, encapsulation efficiency and drug release pattern from microspheres were evaluated. Also, physicochemical properties of drug inside microspheres were characterized by differential scanning calorimetry (DSC) and infrared spectroscopy (IR) studies. Scanning electron microscopy (SEM) studies showed that microspheres encapsulated with CyA had islands on the microsphere surface but the islands were not seen on the surface of microspheres loaded by complex. Size range varied from 1 to 25 mu m for CyA encapsulated microspheres and 1 to 50 mu m for complex loaded microspheres. The release of CyA was biphasic with an initial more rapid release phase followed by a slower phase but drug release was twice as fast for complex loaded microspheres. IR studies did not indicate any chemical interaction between the components of microspheres and DSC thermograms revealed that CyA was present either in its amorphous state in microspheres or the presence of CyA as an inclusion complex within microspheres loaded by complex. In conclusion, using CyA as an inclusion complex with CD within microspheres can affect microsphere characteristics and drug release and it is possible to modify microsphere properties like drug release by incorporating CDs as complexing agents.

3D Reconstruction of the complex dielectric function of glass during femtosecond laser micro-fabrication

We report on a new technique to reconstruct the 3D dielectric function change in transparent dielectric materials and the application of the technique for on-line monitoring of refractive index modification in BK7 glass during direct femtosecond laser microfabrication. The complex optical field scattered from the modified region is measured using two-beam, single-shot interferogram and the distribution of the modified refractive index is reconstructed by numerically solving the inverse scattering problem in Born approximation. The optical configuration suggested is further development of digital holographic microscopy (DHM). It takes advantage of high spatial resolution and almost the same optical paths for both interfering beams, and allows ultrafast time resolution.

Building cliques and alliances as practices to 'make things happen' in complex networks

The Roma population has become a policy issue highly debated in the European Union (EU). The EU acknowledges that this ethnic minority faces extreme poverty and complex social and economic problems. 52% of the Roma population live in extreme poverty, 75% in poverty (Soros Foundation, 2007, p. 8), with a life expectancy at birth of about ten years less than the majority population. As a result, Romania has received a great deal of policy attention and EU funding, being eligible for 19.7 billion Euros from the EU for 2007-2013. Yet progress is slow; it is debated whether Romania's government and companies were capable to use these funds (EurActiv.ro, 2012). Analysing three case studies, this research looks at policy implementation in relation to the role of Roma networks in different geographical regions of Romania. It gives insights about how to get things done in complex settings and it explains responses to the Roma problem as a „wicked‟ policy issue. This longitudinal research was conducted between 2008 and 2011, comprising 86 semi-structured interviews, 15 observations, and documentary sources and using a purposive sample focused on institutions responsible for implementing social policies for Roma: Public Health Departments, School Inspectorates, City Halls, Prefectures, and NGOs. Respondents included: governmental workers, academics, Roma school mediators, Roma health mediators, Roma experts, Roma Councillors, NGOs workers, and Roma service users. By triangulating the data collected with various methods and applied to various categories of respondents, a comprehensive and precise representation of Roma network practices was created. The provisions of the 2001 „Governmental Strategy to Improve the Situation of the Roma Population‟ facilitated forming a Roma network by introducing special jobs in local and central administration. In different counties, resources, people, their skills, and practices varied. As opposed to the communist period, a new Roma elite emerged: social entrepreneurs set the pace of change by creating either closed cliques or open alliances and by using more or less transparent practices. This research deploys the concept of social/institutional entrepreneurs to analyse how key actors influence clique and alliance formation and functioning. Significantly, by contrasting three case studies, it shows that both closed cliques and open alliances help to achieve public policy network objectives, but that closed cliques can also lead to failure to improve the health and education of Roma people in a certain region.