1,721,002 research outputs found
Comparison of classical, stealth and super-stealth liposomes for intravenous delivery of lumefantrine: Formulation, characterization and pharmacodynamic study
Full text linkPurpose: To develop and compare classical liposomes (CL), stealth liposomes (SL) and super-stealth liposomes (SSL) encapsulating lumefantrine for intravenous administration. Method: CL, SL or SSL were prepared by thin-layer evaporation method and evaluated for particle size, polydispersity index (PdI), encapsulation efficiency and short-term stability. Pharmacodynamic study using mice infected with Plasmodium berghei was also carried out. Results: The particle sizes (nm) and PDI of the liposomes were: CL (248 ± 44.89; 0.78 ± 0.02), SL (235.8 ± 45.18; 0.39 ± 0.06) and SSL (238.2 ± 23.0; 0.24 ± 0.04). Encapsulation efficiency was highest in SSL (66 %), followed by SL (44.4 %) and then by CL (42.5 %). SSL was the most stable after 72 h of storage. In vivo, lumefantrine produced significant reduction in parasitaemia after 7 days (p < 0.05) by SSL (68.3 ± 8.9 %) followed by CL (55.8 ± 15.2 %) and then SL (53.4 ± 14.9 %). Conclusion: SSL formulation of lumefantrine exhibits good physicochemical and pharmacodynamic potentials and should be further investigated in future studies for the treatment of malaria
The evolution of polymer conjugation and drug targeting for the delivery of proteins and bioactive molecules
No full textPolymer conjugation can be considered one of the leading approaches within the vast field of nanotechnology-based drug delivery systems. In fact, such technology can be exploited for delivering an active molecule, such as a small drug, a protein, or genetic material, or it can be applied to other drug delivery systems as a strategy to improve their in vivo behavior or pharmacokinetic activities such as prolonging the half-life of a drug, conferring stealth properties, providing external stimuli responsiveness, and so on. If on the one hand, polymer conjugation with biotech drug is considered the linchpin of the protein delivery field boasting several products in clinical use, on the other, despite dedicated research, conjugation with low molecular weight drugs has not yet achieved the milestone of the first clinical approval. Some of the primary reasons for this debacle are the difficulties connected to achieving selective targeting to diseased tissue, organs, or cells, which is the main goal not only of polymer conjugation but of all delivery systems of small drugs. In light of the need to achieve better drug targeting, researchers are striving to identify more sophisticated, biocompatible delivery approaches and to open new horizons for drug targeting methodologies leading to successful clinical applications. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Toxicology and Regulatory Issues in Nanomedicine > Regulatory and Policy Issues in Nanomedicine
The influence of initiator concentration on selected properties of thermosensitive poly(Acrylamide-co-2-acrylamido-2-methyl-1-propanesulfonic acid) microparticles
Full text linkThermosensitive polymers PS1–PS5 were synthesized via the surfactant free precipitation polymerization (SFPP) using 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPSA), and potassium persulfate (KPS) at 70◦C in aqueous environment. The effect of KPS concentrations on particle size and lower critical temperature solution (LCST) was examined by dynamic light scattering (DLS). The conductivity in the course of the synthesis and during cooling were investigated. The structural studies were performed by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), H nuclear magnetic resonance (1H NMR), thermogravimetric analysis (TGA/DTA) and powder X-ray diffraction (PXRD). ATR-FTIR,1H NMR and PXRD data confirmed the polymeric nature of the material. TGA/DTA curves demonstrated thermal stability up to approx. 160◦C. The effect of temperature on the hydrodynamic diameter (HD) and zeta potential (ZP) were evaluated by dynamic light scattering (DLS) and electrophoretic mobility (EM) in 18–45◦C range. The LCST values were between 30 and 34◦C. HD and polydispersity index (PDI) of aqueous dispersions of the synthesized polymers PS1–PS5 at 18◦C were found to be 226 ± 35 nm (PDI = 0.42 ± 0.04), 299 ± 145 nm (PDI = 0.49 ± 0.29), 389 ± 39 nm (PDI = 0.28 ± 0.07), 584 ± 75 nm (PDI = 0.44 ± 0.06), and 271 ± 50.00 nm (PDI = 0.26 ± 0.14), respectively. At 18◦C the ZPs of synthesized polymers suspensions were −13.14 ± 2.85 mV, −19.52 ± 2.86 mV, −7.73 ± 2.76 mV, −7.99 ± 1.70 mV, and −9.05 ± 2.60 mV for PS1–PS5, respectively. We found that the initiator concentration influences the physicochemical properties of products including the size of polymeric particles and the LCST
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Transglutaminase and Sialyltransferase Enzymatic Approaches for Polymer Conjugation to Proteins
No full textProteins hold a central role in medicine and biology, also confirmed by the several therapeutic applications based on biologic drugs. Such therapies are of great relevance thanks to high potency and safety of proteins. Nevertheless, many proteins as therapeutics might present issues like fast kidney clearance, rapid enzymatic degradation, or immunogenicity. Such defects implicate frequent administrations or administrations at high doses of the therapeutics, thus yielding or exacerbating potential side effects. A successful technology for improving the clinical profiles of proteins is the conjugation of polymers to the protein surface. The design of a protein-polymer conjugate presents critical aspects that determine the efficacy and safety of the final product. The control over stoichiometry and conjugation site is a strict criterion on which researchers have been intensively focused during the years, in order to obtain homogeneous and batch-to-batch reproducible products. An innovative site-specific conjugation strategy relies on the use of enzymes as tools to mediate polymer conjugation. Enzymatic approaches are attractive because they allow site-selective polymer conjugation at specific protein amino acids. In these reactions, the polymer is a substrate analog that replaces the native substrate. Furthermore, enzymes can count other advantages such as high yields of conversion and physiological conditions of reaction. This chapter provides a meaningful description of protein-polymer conjugation through transglutaminase-mediated and sialyltransferase-mediated enzymatic strategies, reporting the mechanism of action and some relevant examples
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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