1,720,962 research outputs found
CPA-loaded polymeric nanoparticles prepared via a non-aqueous nanoprecipitation method
No full textPurpose: A novel non-aqueous nanoprecipitation method was used to achieve the encapsulation of a small weight hydrophilic drug (N6-cyclopentyladenosine, CPA) in PLA or PLGA nanoparticles. The drug release properties and the size characteristics of nanoparticles were investigated.
Methods: Nanoparticles were prepared by a nanoprecipitation method using an organic solvent in the presence of Tween 80. The obtained nanoparticles were purified by ultrafiltration, suspended in water by sonication and freeze-dried. The release studies were performed in water and drug stability was evaluated in physiologic fluids.
Results: The freeze-dryed nanoparticles re-dispersed by sonication produced a monodispersed colloidal system. The drug loading capability obtained by this technique appeared considerably higher than that found by the conventional encapsulation methods. Using either PLA or PLGA polymer, a biphasic drug release profile was observed. The extent of the first burst release was dependent on the initial amount of drug in the preparation. The second release phase was slow and characterized by a probable diffusion mechanism. The rate of the second drug release phase can be accelerated or retarded by the presence of a filler (such as lauric acid) or a pore former agent (such as Tween 20), respectively.
Conclusions: The novel method used allows an efficient drug loading to be obtained along with a prolonged drug release, despite the small size of the nanoparticles and the hydrophilic nature of the drug. The most interesting feature of this novel method is not only the possibility to produce high loaded nanoparticles but also modulate their drug release rate
New formulation strategies of nanoparticles for the controlled relase of drugs with small or large molecuar weight
No full textWe report a study of encapsulation and release from polymeric micro- and nano-particles of the antiischemic drug N6-cyclopentyladenosine (CPA) and bovine serum albumin (BSA). Classical preparation methods of the particles (nanoprecipitation, single or double emulsion/solvent evaporation) are compared with those obtained by their formulation with a novel method, employing a thermosensible gel of Pluronic F-127, whose aqueous solutions can be liquid when refrigerated, but gel upon warming. CPA-loaded nanoparticles obtained by classical methods drastically reduce their drug content and the ability to control its release. The novel method allows us to obtain, instead, CPA encapsulation values in nanoparticles similar to those obtained for microparticles, achieving also a control of the drug release. Any drastic reduction of BSA particle content is observed by decreasing their size from micro- to nano-scales, independently on the employment of classical or novel preparation methods. Moreover, the size reduction induces only a weak increase of the BSA release rate. The patterns of protein released from micro- and nano-particles obtained by the same formulation method are similar: the micro- and nano-spheres prepared by double emulsion technique show an incomplete BSA release, characterized by an elevated burst effect followed by a very slow phase; the release from micro- and nano-particles obtained by the novel method is complete and quite regular, being characterized by a little burst release followed by a fast phase. The results can be related to the strong BSA distribution in the surface or in the core of microparticles (observed by confocal laser scanning microscope) obtained by the classical or novel methods, respectively
Polymeric nanoparticles as drug controlled release systems: a new formulation strategy for drugs with small or large molecular weight
No full textWe report a study evaluating the encapsulation and release modalities from poly(D,L lactic acid) (PLA) or poly(D,L-lactide-co-glicolide) (PLGA) micro- and nano-particles of the antiischemic drug N6-cyclopentyladenosine (CPA) and bovine serum albumin (BSA), chosen as protein model. The results obtained by classical preparation methods (nanoprecipitation, single or double emulsion/solvent evaporation) of the particles were compared with those obtained by their formulation with a novel
method, employing a thermosensible gel of Pluronic F-127, whose aqueous solutions can be liquid when refrigerated, but gel upon warming. Our results indicate that CPA-loaded nanoparticles, obtained by classical methods, drastically reduce their drug content showing, moreover, any control
of the drug release with respect to CPA-loaded microparticles. The novel preparation method allowed us to obtain, instead, CPA encapsulation values in nanoparticles similar to those obtained
for microparticles, achieving also a weak control of the drug release. Any drastic reduction of BSA particle content was obtained by decreasing their size from micro- to nano-scales, independently on the employment of classical or novel preparation methods. Moreover, the size reduction induced
only a weak increase of the BSA release rate. The patterns of protein released from micro- and nano-particles obtained by the same formulation method were similar. In particular, the micro- and nano-spheres prepared by double emulsion technique showed an incomplete BSA release, characterized by an elevated burst effect followed by a very slow phase. On the other hand, the release from micro- and nano-particles obtained by the novel method was complete and quite regular, being characterized by a little burst release followed by a fast phase. These results have been related to the strong BSA distribution (observed by confocal laser scanning microscope) in the surface or in the core of microparticles obtained by the classical or novel methods, respectively
Polymeric nanoparticles as drug controlled release systems: A new formulation strategy for drugs with small or large molecular weight
No full textWe report a study evaluating the encapsulation and release modalities from poly(D,L lactic acid) (PLA) or poly(D,L-lactide-co-glicolide) (PLGA) micro- and nano-particles of the antiischemic drug N-6-cyclopentyladenosine (CPA) and bovine serum albumin (BSA), chosen as protein model. The results obtained by classical preparation methods (nanoprecipitation, single or double emulsion/solvent evaporation) of the particles were compared with those obtained by their formulation with a novel method, employing a thermosensible gel of Pluronic F-127, whose aqueous solutions can be liquid when refrigerated, but gel upon warming. Our results indicate that CPA-loaded nanoparticles, obtained by classical methods, drastically reduce their drug content showing, moreover, any control of the drug release with respect to CPA-loaded microparticles. The novel preparation method allowed us to obtain, instead, CPA encapsulation values in nanoparticles similar to those obtained for microparticles, achieving also a weak control of the drug release. Any drastic reduction of BSA particle content was obtained by decreasing their size from micro- to nano-scales, independently on the employment of classical or novel preparation methods. Moreover, the size reduction induced only a weak increase of the BSA release rate. The patterns of protein released from micro- and nano-particles obtained by the same formulation method were similar. In particular, the micro- and nano-spheres prepared by double emulsion technique showed an incomplete BSA release, characterized by an elevated burst effect followed by a very slow phase. On the other hand, the release from micro- and nano-particles obtained by the novel method was complete and quite regular, being characterized by a little-burst release followed by a fast phase. These results have been related to the strong BSA distribution (observed by confocal laser scanning microscope) in the surface or in the core of microparticles obtained by the classical or novel methods, respectively
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
Preparation and characterization of particulate drug delivery systems for the brain targeting
No full textThis chapter will describe how the employment of polymeric
particulate systems can be of great utility in trying to
transport drugs into the CNS. We will describe nanoparticles
as the best systems able to induce drug delivery from
the bloodstream to the brain. In particular, the preparation,
drug loading, and characterization methods of nanoparticles
will be illustrated, taking into account the surface
modifications necessary to obtain both long-circulating and
brain-targeting properties.
Another aspect that we will cover is based on the following
considerations: recently, the nasal route has been proposed
as a promising way to target drugs into the brain that
were unable to overcome the physiologic barriers between
the blood and CNS. Currently, there is great interest in
exploiting the potential for direct transport into the brain
via the olfactory region. We will analyze the potential role
of polymeric micro- and nanoparticulate systems that can
be employed for nasal administration of drugs
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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