1,720,961 research outputs found
Carbon nanotube-polymer scaffolds and biomimetic peptides as a system to promote human cell differentiation toward the neuronal phenotype: analysis of a model cell line and circulating multipotent cells
Full text linkCarbon nanotubes (CNTs) are attractive candidates for the development of scaffolds for neural regeneration thanks to their ability to conduct electrical stimuli, to interface with cells and to mimic the neural environment. This thesis work concerns the development of a freestanding nanocomposite scaffold composed of multi-walled CNTs in a poly-L-lactic (PLLA) matrix that combines the conductive, mechanical and topographical features of CNTs with the biocompatibility of PLLA. Such CNT-PLLA scaffold resulted to support growth and differentiation of neuronal SH-SY5Y cells better than PLLA alone. In order to mimic guidance cues from the neural environment, biomimetic peptides were designed to reproduce regulatory motifs from L1CAM and LINGO1 proteins, that are involved in neurite outgrowth control. Both peptides - which neither alter cell proliferation nor induce cell death - could specifically and positively modulate neuronal differentiation when either used to coat well bottoms or added to the culture medium (with highest efficiency at 1 uM concentration). Furthermore, cell differentiation resulted to be synergistically improved by the combination of the nanocomposite scaffold and the peptides, thus suggesting a prototype for the development of implants for long-term neuronal growth and differentiation.
Then, the CNT-PLLA matrix was electrospun into fibres of submicrometric size in order to better mimic the neural environment, i.e. neuronal processes and collagenous components of the extracellular matrix. These scaffolds were shown to be biocompatible and to promote the formation of new neurites that extend along the scaffold fibres. Since cells are influenced by the scaffold topography, the orientation of the scaffold fibres opens up the perspective to promote a polarized neurite outgrowth. Moreover, the neuritogenic properties of the scaffolds are further enhanced when LINGO1 derivative peptide is added to culture medium; this represents a good starting point for developing next generation scaffolds upon peptide functionalization. Moreover, human circulating multipotent cells (hCMCs) were grown onto the scaffolds and treated with peptides in order to asses if this autologous and accessible source of stem cells is capable of neuronal differentiation thanks to the scaffold and peptide characteristics. The CNT-PLLA scaffolds and its respective electrospun version resulted to be suitable for hCMCs adhesion and growth, showing a very good level of biocompatibility, and the hCMCs growing onto the scaffolds showed typical features of cells from the neuronal lineage, such as long neuritic protrusions that are tipped with fan-shaped structures resembling growth cones. Moreover, soon after cell seeding, the scaffolds were shown to promote the upregulation of markers typical of the neuronal lineage.The biomimetic peptides were also shown to influence cell morphology and to upregulate neuronal markers. These results suggest that hCMCs can acquire neuronal commitment thanks to scaffold/peptide properties per se, i.e. even in the absence of those typical growth factors that are normally used to promote the neuronal differentiation of stem cells. Further improvements in the scaffold geometry and composition, functionalization with peptides and culture conditions are necessary to achieve the complete neuronal differentiation of cells and to control the neuron subtype obtained, but our system resulted to be a good starting point for setting up implantable scaffolds for autologous neuronal differentiation. Future functional assessment of synaptic transmission and electrophysiological properties of cells onto the scaffolds will be of great interest. Moreover, coupling such scaffolds with electrical stimulation (which is readily achievable using CNT based materials) can boost further analyses aimed at studying neuronal differentiation and has great potential in nerve injury repair as well as neuron prosthesis
Covalent functionalization enables good dispersion and anisotropic orientation of multi-walled carbon nanotubes in a poly(l-lactic acid) electrospun nanofibrous matrix boosting neuronal differentiation
No full textA biocompatible porous scaffold obtained via electrospinning a nanocomposite solution of poly(l-lactic acid) and 4-methoxyphenyl functionalized multi-walled carbon nanotubes is presented here for the first time for the enhancement of neurite outgrowth. Optimization of blend preparation and deposition parameters paves the way to the obtainment of defect-free random networks of nanofibers with homogeneous diameters in the hundreds of nanometers length scale. The tailored covalent functionalization of nanotube surfaces allows a homogeneous dispersion of the nanofillers within the polymer matrix, diminishing their natural tendency to aggregate and form bundles. This results in a remarkable effect on the crystallization temperature, as evidenced through differential scanning calorimetry. Furthermore, transmission electron microscopy shows carbon nanotubes anisotropically aligned along the fiber axes, a feature believed to enhance neurite adhesion and growth. Indeed, microscopy images show neurites extension along the direction of nanofibers, highlighting the extreme relevance of scaffold morphology in engineering complex tissue environments. Furthermore, a remarkable effect on increasing the neurite outgrowth results when using the fibrous scaffold containing dispersed carbon nanotubes in comparison with an analogous one made of only polymer, providing further evidence of the key role played by carbon nanostructures in inducing neuronal differentiation
Carbon Nanotubes-Polymer Electrospun Nanofibers as Biocompatible Scaffold for Neuronal Cells Differentiation
No full textEnhanced neuronal cell differentiation combining biomimetic peptides and a carbon nanotube-polymer scaffold
No full textCarbon nanotubes are attractive candidates for the development of scaffolds able to support neuronal growth and differentiation thanks to their ability to conduct electrical stimuli, to interface with cells and to mimic the neural environment. We developed a biocompatible composite scaffold, consisting of multi-walled carbon nanotubes dispersed in a poly-L-lactic acid matrix able to support growth and differentiation of human neuronal cells. Moreover, to mimic guidance cues from the neural environment, we also designed synthetic peptides, derived from L1 and LINGO1 proteins. Such peptides could positively modulate neuronal differentiation, which is synergistically improved by the combination of the nanocomposite scaffold and the peptides, thus suggesting a prototype for the development of implants for long-term neuronal growth and differentiation.
The study describes the design and preparation of nanocomposite scaffolds with multi-walled carbon nanotubes in a poly-L-lactic acid matrix. This compound used in combination with peptides leads to synergistic effects in supporting neuronal cell growth and differentiation
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
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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