Effect of crosslinking in chitosan/aloe vera-based membranes for biomedical applications

The  positive  interaction  between  polysaccharides  with  active  phytochemicals found  in  medicinal  plants  may  represent  a  strategy  to  create  active  wound dressing  materials  useful  for  skin  repair.  In  the  present  work,  blended membranes  composed  of  chitosan  (Cht)  and  Aloe  vera  gel  were  prepared through the solvent casting, and were crosslinked with genipin to improve their properties. Topography, swelling, wettability, mechanical properties and in vitro cellular response of the membranes were investigated. With the incorporation of aloe  vera  gel  into  chitosan  solution,  the  developed  chitosan/aloe-based membranes  displayed  increased  roughness  and  wettability;  while  the  genipin crosslinking  promoted  the  formation  of  stiffer  membranes  in  comparison  to those  of  the  non-modified  membranes.  Moreover, in  vitro cell  culture  studies evidenced that the L929 cells have high cell viability, confirmed by MTS test and calcein-AM staining. The findings suggested that both blend compositions and crosslinking  affected  the  physico-chemical  properties  and  cellular  behavior  of the developed membranes.The authors acknowledge financial support from Portuguese Foundation for Science and Technology - FCT (Grant SFRH/BPD/45307/2008; SFRH/BD/64601/2009), "Fundo Social Europeu" - FSE, and "Programa Diferencial de Potencial Humano - POPH". This work was partially supported by the FEDER through POCTEP 0330_IBEROMARE_1_P

A combined approach for comparative exoproteome analysis of Corynebacterium pseudotuberculosis

Background: Bacterial exported proteins represent key components of the host-pathogen interplay. Hence, we sought to implement a combined approach for characterizing the entire exoproteome of the pathogenic bacterium Corynebacterium pseudotuberculosis, the etiological agent of caseous lymphadenitis (CLA) in sheep and goats. Results: An optimized protocol of three-phase partitioning (TPP) was used to obtain the C. pseudotuberculosis exoproteins, and a newly introduced method of data-independent MS acquisition (LC-MSE) was employed for protein identification and label-free quantification. Additionally, the recently developed tool SurfG+ was used for in silico prediction of sub-cellular localization of the identified proteins. In total, 93 different extracellular proteins of C. pseudotuberculosis were identified with high confidence by this strategy; 44 proteins were commonly identified in two different strains, isolated from distinct hosts, then composing a core C. pseudotuberculosis exoproteome. Analysis with the SurfG+ tool showed that more than 75% (70/93) of the identified proteins could be predicted as containing signals for active exportation. Moreover, evidence could be found for probable non-classical export of most of the remaining proteins. Conclusions: Comparative analyses of the exoproteomes of two C. pseudotuberculosis strains, in addition to comparison with other experimentally determined corynebacterial exoproteomes, were helpful to gain novel insights into the contribution of the exported proteins in the virulence of this bacterium. The results presented here compose the most comprehensive coverage of the exoproteome of a corynebacterial species so far

Kinematics of planet-host stars and their relation with dynamical streams in the solar neighbourhood

We present a detailed study on the kinematics of metal-rich stars with and without planets, and their relation with the Hyades, Sirius and Hercules dynamical streams in the solar neighbourhood. Accurate kinematics have been derived for all the stars belonging to the CORALIE planet search survey. We used precise radial velocity measurements and CCF parameters from the CORALIE database, and parallaxes, photometry and proper motions from the HIPPARCOS and Tycho-2 catalogues. The location of stars with planets in the thin or thick discs has been analysed using both kinematic and chemical constraints. We compare the kinematic behaviour of known planet-host stars to the remaining targets belonging to the volume-limited sample, in particular to its metal-rich population. The high average metallicity of the Hyades stream is confirmed. The planet-host targets show a kinematic behaviour similar to that of the metal-rich comparison subsample, rather than to that of the comparison sample as a whole, thus supporting a primordial origin for the metal excess observed in stars with known planetary companions. According to the scenarios proposed as an explanation for the dynamical streams, systems with giant planets could have formed more easily in metal-rich inner Galactic regions and then been brought into the solar neighbourhood by dynamical streams.Comment: 14 pages, 12 figures, accepted for publication in A&A (28 August 2006

In vitro evaluation of the behaviour of human polymorphonuclear neutrophils in direct contact with chitosan-based membranes

Several novel biodegradable materials have been proposed for wound healing applications in the past few years. Taking into consideration the biocompatibility of chitosan-based biomaterials, and that they promote adequate cell adhesion, this work aims at investigating the effect of chitosanbased membranes, over the activation of human polymorphonuclear neutrophils (PMNs). The recruitment and activation of polymorphonuclear neutrophils (PMNs) reflects a primary reaction to foreign bodies. Activation of neutrophils results in the production of reactive oxygen species (ROS) such as O2 − and HO− and the release of hydrolytic enzymes which are determinant factors in the inflammatory process, playing an essential role in the healing mechanisms. PMNs isolated from human peripheral blood of healthy volunteers were cultured in the presence of chitosan or chitosan/soy newly developed membranes. The effect of the biomaterials on the activation of PMNs was assessed by the quantification of lysozyme and ROS. The results showed that PMNs, in the presence of the chitosan-based membranes secrete similar lysozyme amounts, as compared to controls (PMNs without materials) and also showed that the materials do not stimulate the production of either O2 − or HO−. Moreover, PMNs incubated with the biomaterials when stimulated with phorbol 12-myristate 13-acetate (PMA) or formyl-methionyl-leucyl-phenylalanine (fMLP) showed a chemiluminescence profile with a slightly lower intensity, to that observed for positive controls (cells without materials and stimulated with PMA), which reflects the maintenance of their stimulation capacity. Our data suggests that the new biomaterials studied herein do not elicit activation of PMNs, as assessed by the low lysozyme activity and by the minor detection of ROS by chemiluminescence. These findings reinforce previous statements supporting the suitability of chitosan-based materials for wound healing applications

Hybrid biodegradable membranes of silane-treated chitosan/soy protein for biomedical applications

In recent years, progress in the field of hybrid materials has been accelerated through use of the sol–gel process for creating materials and devices, which benefit from the incorporation of both inorganic and organic components. In this work, organic–inorganic hybrid membranes were prepared from tetraethoxysilane and a blend system composed of chitosan and soy protein. By introducing a small amount of siloxane bond into the chitosan/soy protein system, the chitosan/soy protein hybrid membranes were improved in terms of structure, topography and mechanical properties. It appears that the chitosan/soy protein hybrid membranes were formed by discrete inorganic moieties entrapped in the chitosan/soy protein blend, which improved the stability and mechanical performance assessed by the dynamic mechanical analysis as compared to chitosan/soy protein membrane. Also, in vitro cell culture studies evidenced that the chitosan/soy protein hybrid membranes are non-cytotoxic over a mouse fibroblast-like cell line. The hybrid membranes of silane-treated chitosan/soy protein developed in this work have potential in biomedical applications, including tissue engineering.This work was financially supported by the Portuguese Foundation for Science and Technology - FCT (Grant SFRH/BPD/45307/2008, SFRH/BPD/21786/2009, SFRH/BPD/39331/2007 and SFRH/BD/64601/2009), 'Fundo Social Europeu' - FSE and 'Programa Diferencial de Potencial Humano - POPH' and was partially supported by the FEDER through POCTEP 0330_IBEROMARE_1_P

Chitosan improves the biological performance of soy-based biomaterials

Soybean protein has been proposed for distinct applications within nutritional, pharmaceutical, and cosmetic industries among others. More recently, soy-based biomaterials have also demonstrated promising properties for biomedical applications.However, althoughmany reports within other fields exist, the inflammatory/immunogenic potential of those materials is still poorly understood and therefore can hardly be controlled. On the contrary, chitosan (Cht) has been well explored in the biomedical field, either by itself or combined with synthetic or other natural-based polymers. Therefore, the combination of chitosan with soybean protein is foreseen as a suitable approach to control the biological behavior of soy-based biomaterials. Under this context this work was designed to try to understand the influence of chitosan in the host response elicited by soy-based biomaterials. Soybean protein isolate powder (SI-P) and Cht powder (Cht-P) were injected as suspension into the intraperitoneal cavity of rats. SI-P induced the recruitment of higher numbers of leukocytes compared to the Cht-P during the entire observation period. In this sense, SI-P elicited a considerable reaction from the host comparing to the Cht-P, which elicited leukocyte recruitment similar to the negative control.After subcutaneous implantation of the soybean and denatured membranes, (SI-M and dSI-M) a severe host inflammatory reaction was observed. Conversely, Cht/soy-based membranes (Cht/soy-based membranes) showed the induction of a normal host response after subcutaneous implantation in rats, which allowed concluding that the addition of chitosan to the soy-based membranes improved their in vivo performance. Thus, the presented results assert the improvement of the host response, considering inflammatory cells recruitment, and overall inflammatory reaction,when chitosan is combined to soybean. Together with previous results that reported their promising physicochemical characteristics and their inability to activate human polymorphonuclear neutrophils in vitro, the herein presented conclusions reinforce the usefulness of theCht/ soy-based membranes and justify the pursue for a specific application within the biomedical field.The author Tircia C. Santos acknowledges the Marie Curie European Program for a short-term scholarship in the Alea Jacta EST project (MEST-CT-2004-008104). This work was developed under the scope of the European Network of Excellence EXPERTISSUES (NMP3-CT-2004-5000283)

Life-Threatening Cardiac Manifestations of Pheochromocytoma

Pheochromocytoma is a catecholamine-secreting tumor of the adrenal glands, usually with benign manifestations, whose typical clinical presentation includes the triad of headache, palpitations and diaphoresis. However, a wide range of signs and symptoms may be present. In the cardiovascular system, the most common signs are labile hypertension and sinus tachycardia. Systolic heart failure and ST-segment deviations mimicking myocardial infarction have also been reported, as well as QT interval prolongation and, rarely, ventricular tachycardia. We describe a challenging diagnosis of pheochromocytoma with many cardiovascular manifestations, which could have been missed due to the absence of typical symptoms

Física téorica online: um desafio para o ensino superior

O objetivo deste trabalho é apresentar as etapas de construção da disciplina Fisica Teórica I na modalidade online. Esta disciplina apresenta um índice de reprovação de cerca de 40% na modalidade presencial, sendo um dos principais motivos de abandono nos cursos de Engenharia ainda no ciclo básico. Percebe-se que boa parte das reprovações ocorre devido às deficiências trazidas pelos alunos em matemática e física. No curso regular não há carga horária suficiente para sanar estas deficiências e cumprir o conteúdo integralmente. Este aspecto motivou a construção da disciplina na modalidade online para cursos presenciais. A disciplina foi construída permitindo-se flexibilidade de caminhos, incluindo revisão de conteúdos do ensino médio. Desta forma, pretende-se suprir as deficiências da formação com as quais os estudantes ingressam na universidade, reduzindo, assim a taxa de reprovação e consequente evasão. A disciplina foi implantada no primeiro periodo letivo de 2013 e a resposta por parte dos alunos foi positiva e encorajadora. Trabalhos adicionais estão sendo produzidos para análise do impacto da disciplina nas taxas de reprovação e evasão.The aim of this paper is to present the stages of development of the module Theoretical Physics I for online presentation. In previous face-to-face presentations, the module has had a failure rate of about 40%, constituting one of the main reasons for attrition in engineering courses during the first two study years. Our experience has been that failure occurs due to gaps in students’ previous knowledge of Mathematics and Physics. In face-to-face mode there is no sufficient time to both remedy these deficiencies and deliver the main module content. This has motivated development of the module in a Virtual Learning Environment including access for students enrolled in the traditional mode. The online module has been designed to allow for flexible pathways that include the option to learn or revise pre-requisite topics. Thus, it is intended to allow students to fill in knowledge gaps that exist as a consequence of deficient schooling. It is hoped that the module will give students the opportunity of restructuring their knowledge, reducing the failure rate and consequent attrition. The new scheme was implemented in the first academic semester of 2013, and, so far, student response has been positively and very encouraging. Further work is underway to examine the impact of the module on repetition and dropout rates.Universidade Aberta; Pavilhão do Conhecimento; LEA

‘Stay Home Without a Home’: Report from a webinar on the right to housing in Covid-19 lockdown times

This Update reports from a webinar on the impacts of lockdown measures put in place globally amid the Covid-19 pandemic on the right to housing and linked political struggles. Three main threads emerged from the conversation: the impacts of the pandemic are deepening pre-existing housing inequalities, while governments’ responses are largely insufficient; activists and contentious actors worldwide are changing their framings and repertoires to adapt to lockdown measures and attempt to radicalize their action; possibilities, albeit limited, are opening for the construction of global networks of struggle.info:eu-repo/semantics/publishedVersio

In vivo performance of chitosan/soy-based membranes as wound dressing devices for acute skin wounds

Wound management represents a major clinical challenge on what concerns healing enhancement and pain control. The selection of an appropriate dressing plays an important role in both recovery and esthetic ap- pearance of the regenerated tissue. Despite the wide range of available dressings, the progress in the wound care market relies on the increasing interest in using natural-based biomedical products. Herein, a rat wound- dressing model of partial-thickness skin wounds was used to study newly developed chitosan/soy (cht/soy)- based membranes as wound-dressing materials. Healing and repair of nondressed, cht/soy membrane-dressed, and Epigard -dressed wounds were followed macroscopically and histologically for 1 and 2 weeks. cht/soy membranes performed better than the controls, promoting a faster wound repair. Re-epithelialization, ob- served 1 week after wounding, was followed by cornification of the outermost epidermal layer at the second week of dressing, indicating repair of the wounded tissue. The use of this rodent model, although in impaired healing conditions, may enclose some drawbacks regarding the inevitable wound contraction. Moreover, being the main purpose the evaluation of cht/soy-based membranes’ performance in the absence of growth factors, the choice of a clinically relevant positive control was limited to a polymeric mesh, without any growth factor influencing skin healing/repair, Epigard. These new cht/soy membranes possess the desired features regarding healing/repair stimulation, ease of handling, and final esthetic appearance-thus, valuable prop- erties for wound dressings.The author Tircia C. Santos acknowledges the Portuguese Foundation for Science and Technology (FCT) for her PhD grant (SFRH/BD/40861/2007). This work was developed under the scope of the European Network of Excellence EXPERTISSUES (NMP3-CT-2004-5000283)