Avaliação de progênies de Eucalyptus crebra no norte do Estado de Goiás.

Disponível em:

Morphology, mechanical characterization and in vivo neo-vascularization of chitosan particle aggregated scaffolds architectures

The present study intended to evaluate the performance of chitosan-based scaffolds produced by a particle aggregation method aimed to be used in tissue engineering applications addressing key issues such as morphological characteristics, mechanical performance and in vivo behaviour. It is claimed that the particle aggregation methodology may present several advantages, such as combine simultaneously a high interconnectivity with high mechanical properties that are both critical for an in vivo successful application. In order to evaluate these properties, micro-Computed Tomography (micro-CT) and Dynamical Mechanical Analysis (DMA) were applied. The herein proposed scaffolds present an interesting morphology as assessed by micro-CT that generally seems to be adequate for the proposed applications. At a mechanical level, DMA has shown that chitosan scaffolds have an elastic behaviour under dynamic compression solicitation, being simultaneously mechanically stable in the wet state and exhibiting a storage modulus of 4.21 ! 1.04 MPa at 1 Hz frequency. Furthermore, chitosan scaffolds were evaluated in vivo using a rat muscle-pockets model for different implantation periods (1, 2 and 12 weeks). The histological and immunohistochemistry results have demonstrated that chitosan scaffolds can provide the required in vivo functionality. In addition, the scaffolds interconnectivity has been shown to be favourable to the connective tissues ingrowth into the scaffolds and to promote the neo-vascularization even in early stages of implantation. It is concluded that the proposed chitosan scaffolds produced by particle aggregation method are suitable alternatives, being simultaneously mechanical stable and in vivo biofunctional that might be used in load-bearing tissue engineering applications, including bone and cartilage regeneration.The authors would like to acknowledge the Portuguese Foundation for Science and Technology for the PhD Grant to Patricia B Malafaya (SFRH/BD/11155/2002). This work was partially supported and carried out under the scope of the European STREP Project HIPPOCRATES (NMP3-CT-2003-505758) and European NoE EXPERTISSUES (NMP3-CT-2004-500283). The authors also thank Prof. Heinz Redl for the collaboration in the in VIVO Studies, as well as Bernhard Horing for the surgical procedures both from LBI, Austria and Joao Oliveira from 3B's Research Group, Portugal for the initial assistance with the DMA equipment

Evidence for entanglement at high temperatures in an engineered molecular magnet

The molecular compound [Fe$_{2}$($\mu_{2}$-oxo)(C$_{3}$H$_{4}$N$_{2}$)$_{6}$(C$_{2}$O$_{4}$)$_{2}$] was designed and synthesized for the first time and its structure was determined using single-crystal X-ray diffraction. The magnetic susceptibility of this compound was measured from 2 to 300 K. The analysis of the susceptibility data using protocols developed for other spin singlet ground-state systems indicates that the quantum entanglement would remain at temperatures up to 732 K, significantly above the highest entanglement temperature reported to date. The large gap between the ground state and the first-excited state (282 K) suggests that the spin system may be somewhat immune to decohering mechanisms. Our measurements strongly suggest that molecular magnets are promising candidate platforms for quantum information processing

Sistemas de rotação de culturas com trigo para a região sul do Brasil.

bitstream/item/84156/1/CNPT-COM.-TEC.-2-97.pd

Natural origin scaffolds with in situ pore forming capability for bone tissue engineering applications

This work describes the development of a biodegradable matrix, based on chitosan and starch, with the ability to form a porous structure in situ due to the attack by specific enzymes present in the human body (a-amylase and lysozyme). Scaffolds with three different compositions were developed: chitosan (C100) and chitosan/starch (CS80-20, CS60-40). Compressive test results showed that these materials exhibit very promising mechanical properties, namely a high modulus in both the dry and wet states. The compressive modulus in the dry state for C100 was 580 ± 33 MPa, CS80-20 (402 ± 62 MPa) and CS60-40 (337 ± 78 MPa). Degradation studies were performed using a-amylase and/or lysozyme at concentrations similar to those found in human serum, at 37 C for up to 90 days. Scanning electron micrographs showed that enzymatic degradation caused a porous structure to be formed, indicating the potential of this methodology to obtain in situ forming scaffolds. In order to evaluate the biocompatibility of the scaffolds, extracts and direct contact tests were performed. Results with the MTT test showed that the extracts of the materials were clearly non-toxic to L929 fibroblast cells. Analysis of cell adhesion and morphology of seeded osteoblastic-like cells in direct contact tests showed that at day 7 the number of cells on CS80-20 and CS60-40 was noticeably higher than that on C100, which suggests that starch containing materials may promote cell adhesion and proliferation. This combination of properties seems to be a very promising approach to obtain scaffolds with gradual in vivo pore forming capability for bone tissue engineering applications.This work was supported by the European NoE EXPERTISSUES (NMP3-CT-2004-500283), the European STREP HIPPOCRATES (NMP3-CT-2003-505758) and the Portuguese Foundation for Science and Technology (FCT) through POCTI and/or FEDER programmes

Adipose stem cell-derived osteoblasts sustain the functionality of endothelial progenitors from the mononuclear fraction of umbilical cord blood

Vascularization is the most pressing issue in tissue engineering (TE) since ensuring that engineered constructs are adequately perfused after in vivo transplantation is essential for the construct’s survival. The combination of endothelial cells with current TE strategies seems the most promising approach but doubts persist as to which type of endothelial cells to use. Umbilical cord blood (UCB) cells have been suggested as a possible source of endothelial progenitors. Osteoblasts obtained from human adiposederived stem cells (hASCs) were co-cultured with the mononuclear fraction of human UCB for 7 and 21 days on carrageenan membranes. The expression of vWF and CD31, and the DiI-AcLDL uptake ability allowed detection of the presence of endothelial and monocytic lineages cells in the co-culture for all culture times. In addition, the molecular expression of CD31 and VE-cadherin increased after 21 days of coculture. The functionality of the system was assessed after transplantation in nude mice. Although an inflammatory response developed, blood vessels with cells positive for human CD31 were detected around the membranes. Furthermore, the number of blood vessels in the vicinity of the implants increased when cells from the mononuclear fraction of UCB were present in the transplants compared to transplants with only hASC-derived osteoblasts. These results show how endothelial progenitors present in the mononuclear fraction of UCB can be sustained by hASC-derived osteoblast co-culture and contribute to angiogenesis even in an in vivo setting of inflammatory response.Financial support through the Ph.D. Grant SFRH/BD/44893/2008 to R.P. P. by the Portuguese Foundation for Science and Technology (FCT) and through the European Union NoE EXPERTISSUES (NMP3-CT-2004-500283) is acknowledged

Designing silk fibroin-based matrices with ionic liquids for tissue engineering strategies using human adipose stem cells

Silk (SF) is an attractive biomaterial to be used in tissue engineering applications because of its excellent mechanical properties and biocompatibility [1, 2]. In this work, the cellular response of silk hydrogels produced through dissolution of this protein in ionic liquids (ILs) was investigated. For that, degummed fibers obtained from the cocoons of mulberry silkworm (Bombyx mori) were dissolved in an IL and the solution was gelified in ethanol, followed by IL removal from gels using soxhlet extraction. The fabricated hydrogels were characterized biochemically and biophysically by detecting amino acid composition, FTIR, SEM and mechanical testing (DMA). For in vitro assessment, human adipose stem cells (hASCs) were seeded in the hydrogels and cultured for different time periods. The resulting hydrogels have a rubbery consistency, homogeneous surface and viscoelastic behavior. Additionally, no differences on amino acid composition were found, indicating that the silk composition was kept. Confocal images confirmed cell attachment and alignment of actin filaments within the hydrogel matrix with well-develop nuclei. The MTS assay demonstrated the metabolic activity of hASCs in contact with hydrogels up to 28 days. Furthermore, the results of DNA quantification showed that hASCs are able to proliferate during studied period. These results indicated that (i) the efficiency of IL removal resulted in hydrogels with minimal cytotoxicity; and (ii) positive cellular response of the materials surface for the adhesion and proliferation of hASCs. SEM observations corroborated with the results obtained from MTS and DNA suggested that cells are able to migrate at different levels within the structure. These findings indicated that silk hydrogels produced using ILs may be potential candidates for tissue engineering strategies, namely cartilage regeneration

Compostos bioativos em genótipos de mamão do banco ativo de germoplasma da Embrapa.

o consumo de frutas tropicais está aumentando no mercado nacional e internacional devido ao reconhecimento das suas propriedades nutricionais e terapêuticas. O mamão destaca-se por apresentar elevado valor nutricional, sendo rico em açúcares, minerais e compostos bioativos como os carotenoides, vitamina C e polifenóis

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)