1,720,975 research outputs found
Correlation between rheological propertiesm and limonene release in pectin gels using an electronic nose
No full textPectin gels at different polymer concentrations were used as matrices for the encapsulation of a volatile flavour (limonene). This provides a useful model system for studying the influence of the matrix viscoelastic properties on the flavour release towards the gel headspace. The electronic nose technique and principal component analysis (PCA), a multivariate data analysis, were used for detecting changes in the fingerprint of the released vapour as a function of pectin concentration. Samples with different composition were also studied by rheological measurements in order to discriminate the effects of polymer concentration on the gelation kinetics from those due to the addition of limonene and the detergent used to dissolve it.The combined approach, rheometry-electronic nose, allows obtaining a direct semi-quantitative correlation between the expected decrease of flavour release intensity and the increasing solid like character of the matrix due to trapping effect. In fact, the comparison of the viscoelastic properties for matrixes with and without the flavour, together with direct observation by optical microscopy, suggests that the release modulation is mainly due to interaction of the gelling pectin with the microemulsion of detergent and flavour.Fil: Monge, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Negri, Ricardo Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Giacomazza, Daniela. Consiglio Nazionale delle Ricerche; ItaliaFil: Bulone, Donatella. Consiglio Nazionale delle Ricerche; Itali
Physico-chemical and mechanical characterization of in-situ forming xyloglucan gels incorporating a growth factor to promote cartilage reconstruction
No full textThe development of growth factors is very promising in the field of tissue regeneration but specifically designed formulations have to be developed in order to enable such new biological entities (NBEs). In particular, the range of therapeutic concentrations is usually very low compared to other active proteins and the confinement in the target site can be of crucial importance. In-situ forming scaffolds are very promising solutions for minimally invasive intervention in cartilage reconstruction and targeting of NBEs. In this work injectable, in-situ forming gels of a temperature responsive partially degalactosylated xyloglucan (Deg-XG) incorporating the growth factor FGF-18 are formulated and characterized. In particular, injectability and shear viscosity at room temperature, time-to-gel at body temperature, morphology and mechanical properties of gels are investigated. The highly hydrophobic growth factor is favorably incorporated and retained by the gel. Gels undergo a slow erosion process when immersed in PBS at 37 °C that opens up their porous structure. The prolonged hydrothermal treatment leads to structural rearrangements towards tougher networks with increased dynamic shear modulus. Preliminary biological evaluations confirm absence of cytotoxicity and the ability of these scaffolds to host cells and promote their proliferation
Amyloid β-peptide insertion in liposomes containing GM1-cholesterol domains
Full text linkNeuronal membrane damage is related to the early impairments appearing in Alzheimer's disease due to the interaction of the amyloid β-peptide (Aβ) with the phospholipid bilayer. In particular, the ganglioside GM1, present with cholesterol in lipid rafts, seems to be able to initiate Aβ aggregation on membrane. We studied the thermodynamic and structural effects of the presence of GM1 on the interaction between Aβ and liposomes, a good membrane model system. Isothermal Titration Calorimetry highlighted the importance of the presence of GM1 in recruiting monomeric Aβ toward the lipid bilayer. Light and Small Angle X-ray Scattering revealed a different pattern for GM1 containing liposomes, both before and after interaction with Aβ. The results suggest that the interaction with GM1 brings to insertion of Aβ in the bilayer, producing a structural perturbation down to the internal layers of the liposome, as demonstrated by the obtained electron density profiles
Poly(vinyl alcohol)/κ-Carrageenan-based hydrogels enriched with the adhesive mussel protein Pvfp5β as 3D cell culture scaffold for tissue engineering applications
No full textMany marine organisms such as sandcastle worms, barnacles and mussels, produce natural adhesives to attach to wet surfaces in aqueous tidal environments. In mussels, the adhesion is possible through the secretion of a protein-based water-resistant glue, composed of a mixture of proteins called mussel adhesive proteins (MAPs) or mussel foot proteins (mfps), that allow anchoring to almost any kind of surface in wet conditions [1]. The proteins confined to adhesive plaques are mfp-2, -3, -4, -5, and -6. All these proteins contain an atypically high concentration of the catecholic amino acid 3,4- dihydroxy-l-phenylalanine (DOPA), obtained by the post-translational enzymatic hydroxylation of tyrosine (Tyr) [2]. DOPA is the key molecule allowing the underwater mussel adhesion to different surfaces through the formation of irreversible covalent and reversible noncovalent bonds [3]. However, growing evidences show that the presence of DOPA is not a sufficient condition to generate strong underwater adhesion. A synergistic effect of catechols and adjacent lysine in bioadhesion of mussels has been suggested. The pair structure of Tyr/DOPA with basic residues of lysine, rather than the post-translational modification of Tyr to DOPA, should be responsible for the strong binding ability of mussel adhesive proteins [4].
We have recently fine-tuned the expression of the recombinant Pvfp5β protein in Escherichia coli [5]. Furthermore, the structural characterization showed that the produced protein was correctly folded as a β-rich protein with precise pairing of the sulfur bridges. We have also demonstrated that surfaces coated with recombinant Pvfp5β are not toxic, and improve cell adhesion, proliferation and spreading of NIH-3T3 and HeLa cell lines [5]. Thus, adhesive protein/peptide coatings and efficient exposure of bioactive domains might improve the biological properties of scaffold materials.
Hydrogels, a unique class of polymeric materials, are three-dimensional porous networks constituted by polymeric chains crosslinked by chemical and/or physical bonds. They exhibit remarkable structure-derived properties, including high surface area, stimuli-responsiveness, inherent flexibility, controllable mechanical strength, and excellent biocompatibility. They are capable of absorbing and retaining large amounts of water in their networks and can extensively swell without dissolution due to the presence of crosslinks, that are at the basis of the network structure, and maintain macroscopic integrity [6].
k-carrageenan (kCar) is a naturally occurring polysaccharide extracted from marine red algae (Rhodophyceae). Chemically it consists of an alternating linear chain of (1->3)-β-D-galactose-4SO3- - (1->4)-3,6, anhydro-α-D-galactose. Due to its half-ester sulphate moieties, it is a strong anionic polymer and resembles the natural glycosaminoglycans (GAGs), which are an important component of the connective tissue. kCar is biocompatible, biodegradable, non-toxic, and gel-forming. Thus, kCar has been investigated for a wide range of biomedical puropses, such as wound dressing [7] and tissue engineering [8] applications. The generally accepted model of the gelling process of carrageenan solutions involves a coil-to-helix transition, followed, in the presence of certain cations, by aggregation of double helices to form a stiff, extended network [9]. Blending kCar with polyvinyl alcohol (PVA) allows obtaining composite scaffolds with higher, interconnected porosity, high swelling degree, improved toughness and degradability. PVA can be chemically crosslinked, with glutaraldehyde, or physically crosslinked by inducing the formation of crystalline domains via freeze-thawing [10].
In the present study, we used the crosslinking-agent free, freeze–thaw approach for the fabrication of PVA/kCar composite hydrogels as 3D scaffolds for cell culture, whose adhesion was enhanced by simple adsorption of cationic recombinant Pvfp5β protein. The physico-chemical properties of the PVA/kCar hydrogel (morphology, swelling and degradation, water absorption, mechanical strength) were evaluated. Furthermore, biocompatibility, adhesion, proliferation and morphology of the cells grown in presence of PVA/kCar-Pvfp5β hydrogel were investigated. All gathered information demonstrates the great potential of PVA/kCar-Pvfp5β scaffolds for tissue engineering applications.
Prospects for the future
PVA/kCar formulations are also being evaluated as bioinks for 3D bioprinting, a key enabling technology for the manufacture of complex tissue structures to mimic native organs and tissues. The bioprinting involves layer by layer deposition of cells-laden biomaterials in a predetermined structural architecture to generate functional tissues or organs. They provide structure for the bioprinted tissue and support and nutrients for the cells, creating an environment in which the cells can survive, grow, and proliferate.
The research will then explore the influence of Pvfp5β on 3D inkjet bioprinted PVA/kCar scaffolds integrated with human adipose stem-cell spheroids (SASCs) in terms of cell survival and differentiation and scaffold colonization.
References (max. 10 references)
[1] Y. He, C. Sun, F. Jiang, B. Yang, J. Li, C. Zhong, L. Zheng, H. Ding. Lipids as integral components in mussel adhesion. Soft Matter, 14:7145–7154, 2018
[2] W. Zhang, H. Yang, F. Liu, T. Chen, G. Hu, D. Guo, Q. Hou, X. Wu, Y. Su, J. Wang. Molecular interactions between DOPA and sur- faces with different functional groups: a chemical force microscopy study. RSC Adv., 7:32518 –32527, 2017
[3] S.M. Kelly, T.J. Jess, Price N.C. How to study proteins by circular dichroism. Biochim. Biophys. Acta, 1751: 119–139
[4] X Ou, B Xue, Y Lao, Y Wutthinitikornkit, R Tian, A Zou, L Yang, W Wang, Y Cao, Jingyuan Li. Structure and sequence features of mussel adhesive protein lead to its salt-tolerant adhesion ability. Sci. Adv. 6: eabb7620, 2020
[5] R. Santonocito, F. Venturella, F. Dal Piaz, M.A. Morando, A. Provenzano, E. Rao, M.A. Costa, D. Bulone, P.L. San Biagio, D. Giacomazza, A. Sicorello, C. Alfano, R. Passantino, A. Pastore. Recombinant mussel protein Pvfp-5β: A potential tissue biohadesive. J. Biol. Chem., 294:12826:12835, 2019
[6] G.M. Kavanagh, S.B. Ross-Murphy. Rheological characterization of polymer gels. Prog. Polym. Sci., 23:533-562, 1998
[7] L.A. Ditta, E. rao, F. Provenzano, J. Lozano Sanchez, R. Santonocito, R. Passantino, M.A. Costa, M.A. Sabatino, C. Dispenza, D. Giacomazza, P.L. San Biagio, R. Lapasin. Agarose/kCarrageenan-based hydrogel film enriched with natural plant extracts for the treatment of cutaneous wounds. Int. J. Biol. Macromol., 164:2818-2830
[8] S.M. Mihaila, A.K. Gaharwar, R.L. Reis, A.P. Marques, M.E. Gomes, A. Kademhosseini. Photocrosslinkable kappa-carrageenan hydrogels for tissue engineering applications. Advanced Healthcare Materials, 2:895-907, 2013
[9] L. Du, T. Brenner, J. Xie, S. Matsukawa. A study on phase separation behavior in kappa/iota carrageenan mixtures by micro DSC, rheological measurements and simulating water and cations migration between phases. Food Hydrocolloids, 55:8188, 2016
[10] S.R. Stauffer, N.A: Peppast. Poly(vinyl ancohol) hydrogels prepared by freezing-thawing cyclic processing. Polymer, 33:3932-3936, 199
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
The interplay between PolyQ and protein context delays aggregation by forming a reservoir of protofibrils.
Full text linkPolyglutamine (polyQ) diseases are inherited neurodegenerative disorders caused by the expansion of CAG codon repeats, which code for polyQ in the corresponding gene products. These diseases are associated with the presence of amyloid-like protein aggregates, induced by polyQ expansion. It has been suggested that the soluble aggregates rather than the mature fibrillar aggregates are the toxic species, and that the aggregation properties of polyQ can be strongly modulated by the surrounding protein context. To assess the importance of the protein carrier in polyQ aggregation, we have studied the misfolding pathway and the kinetics of aggregation of polyQ of lengths above (Q41) and below (Q22) the pathological threshold fused to the well-characterized protein carrier glutathione S-transferase (GST). This protein, chosen as a model system, is per se able to misfold and aggregate irreversibly, thus mimicking the behaviour of domains of naturally occurring polyQ proteins. We prove that, while it is generally accepted that the aggregation kinetics of polyQ depend on its length and are faster for longer polyQ tracts, the presence of GST alters the polyQ aggregation pathway and reverses this trend. Aggregation occurs through formation of a reservoir of soluble intermediates whose populations and kinetic stabilities increase with polyQ length. Our results provide a new model that explains the toxicity of expanded polyQ proteins, in which the interplay between polyQ regions and other aggregation-prone domains plays a key role in determining the aggregation pathway
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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