17,762 research outputs found
Endometriosis: A Rare Cause of Large Bowel Obstruction.
Large bowel obstruction can result in significant morbidity and mortality, especially in cases of acute complete obstruction. There are many possible causes, the most common in adults being colorectal cancer. Endometriosis is a benign disease, and the most affected extragenital location is the bowel, especially the rectosigmoid junction. However, transmural involvement and acute occlusion are very rare events. We report an exceptional case of acute large bowel obstruction as the initial presentation of endometriosis. The differential diagnosis of colorectal carcinoma may be challenging, and this case emphasizes the need to consider intestinal endometriosis in females at a fertile age presenting with gastrointestinal symptoms and an intestinal mass causing complete large bowel obstruction.info:eu-repo/semantics/publishedVersio
Viscoelastic monitoring of starch-based biomaterials in simulated physiological conditions
Dynamic mechanical analysis (DMA) was used to investigate the solid-state rheological behaviour in a starch-based thermoplastic aimed to be used in different biomedical applications. The tested samples were processed by different injection moulding procedures. The dry samples were immersed in a simulated physiological solution and the relevant viscoelastic parameters were monitored against time. The decrease
of stiffness due to swelling can be followed in real time, being less pronounced for the composite sample with hydroxyapatite (HA). The temperature control of the liquid bath was found to be very good. Frequency scans were also performed in wet conditions in samples previously immersed during different times, indicating that DMA is a suitable method to control in-vitro the changes on the viscoelastic properties of biomaterials during degradation
Finite-size effects in roughness distribution scaling
We study numerically finite-size corrections in scaling relations for
roughness distributions of various interface growth models. The most common
relation, which considers the average roughness . This illustrates how
finite-size corrections can be obtained from roughness distributions scaling.
However, we discard the usual interpretation that the intrinsic width is a
consequence of high surface steps by analyzing data of restricted
solid-on-solid models with various maximal height differences between
neighboring columns. We also observe that large finite-size corrections in the
roughness distributions are usually accompanied by huge corrections in height
distributions and average local slopes, as well as in estimates of scaling
exponents. The molecular-beam epitaxy model of Das Sarma and Tamborenea in 1+1
dimensions is a case example in which none of the proposed scaling relations
works properly, while the other measured quantities do not converge to the
expected asymptotic values. Thus, although roughness distributions are clearly
better than other quantities to determine the universality class of a growing
system, it is not the final solution for this task.Comment: 25 pages, including 9 figures and 1 tabl
Some trends on how one can learn from and mimic nature in order to design better biomaterials
Chemistry and applications of phosphorylated chitin and chitosan
Chitin and chitosan are natural based non-toxic,
biodegradable and biocompatible polymers and have been used in
biomedical areas in the form of sutures, wound healing materials and
artificial skin, and for the sustained release of drugs as well as in various
industrial applications. However, practical use of these polymers has
been mainly confined to the unmodified forms. Recently, there has been
a growing interest in chemical modification of chitin and chitosan to
improve their solubility and widen their applications. Among them,
phosphorylated chitin and chitosan have attracted considerable interest
because of their various advantages: anti-inflammatory property, ability
to form metal complexes, blood compatibility and formation of anionic
polyelectrolyte hydrogels. The purpose of this review is to take a closer
look of different synthetic methods of phosphorylated chitin and chitosan
and their potential applications in environmental, food, fuel cell, and
biomedical fields. Based on current research and existing products,
some new and futuristic approaches in this context area are discussed.R. Jayakumar acknowledges the Portuguese Foundation for Science and Technology for providing him a Post-Doc scholarship (SFRH/BPD/14670/2003). This work was partially supported by FCT Foundation for Science and Technology, through funds from the POCTI and/or FEDER program. This work was partially supported by the European Union funded STREP Project HIPPOCRATES (NMP3-CT-2003-505758)
Synthesis and characterization of N-methylenephenyl phosphonic chitosan
Chitosan is a natural based polymer obtained by alkaline deacetylation of chitin, exhibiting excellent properties such as nonâtoxicity, biocompatibility and biodegradability. NâMethylenephenyl phosphonic chitosan (NMPPC) is synthesized from chitosan by reacting with phenyl phosphonic acid using formaldehyde. The NMPPC was characterized by FTIR, 31PâNMR, Xâray diffraction, scanning electron microscopy, thermogravimeteric analysis and solubility studies. A significant decrease of molecular weight was observed in the NMPPC. The TGA studies suggested that NMPPC has less thermal stability than chitosan. The Xâray diffraction analysis showed that NMPPC was amorphous in nature. The solubility property of the polymer was improved after the incorporation of a phenyl phosphonic grou
Innovative approach for producing injectable, biodegradable materials using chitooligosaccharides and green chemistry
Although there are a number of injectable biomaterials currently under development, they present some drawbacks
such as being based on synthetic polymers, needing toxic or aggressive synthesis procedures or using raw materials
with low availability and/or high production costs. Having this in mind, a novel injectable biomaterial using
chitooligosaccharides as starting materials was developed. This system uses a widely available and cheap polymer
from marine biomass (chitosan), which can be turned into an injectable material by water-based and ecologically
friendly reactions. Chitooligosaccharides were functionalized with methacrylic groups, to allow in situ crosslinking.
The degree of substitution, as determined by 1H NMR, varied between 5 and 50%. The system was
characterized in terms of kinetics of gel formation, rheology, degradation behavior and in vitro cytotoxicity. The
gelation time could be easily tailored between 1.5 and 60 min by changing the conditions of the methacrylation
reaction, and the final gel presented rheological properties typical of strong gels, that is, shear stresses in the kPa
range. The cross-linked gel was degradable and nontoxic, presenting indeed an interesting cytokinetic effect.
Injectable materials based on chitooligosaccharides are, therefore, an innovative system combining adequate
biological performance, ease of preparation, and an ecologically friendly concept of production.The authors thank Dr. Mar Fernandez for the cytotoxicity tests. L.F.B. thanks the European Commission for supporting this work through a Marie Curie-IIF fellowship
Surface properties of extracts from cork black condensate
The insulation corkboard production generates black condensate
(BC), a paste-like solid waste. It is hydrophobic and
has the potential to be used as protective coating. To evaluate
this potential, coatings were prepared from BC extracts and
their surface behavior was evaluated by contact angle (CA)
measurements. The CA dynamics were recorded as a function
of time; advancing CAs were also registered; the
approaches were applied according to Fowkes, Owens-
Wendt-Rabel-Kaelble (OWRK), and Van Oss to determine
the surface energy (SE) for each coating. Depending on the
liquid probe, three phenomena were observed: water evaporation,
diiodomethane diffusion into the coating, and rearrangement
of the chemical groups on the coating surface,
when glycerol was dropped onto the surface. Based on the
results from the CA dynamics, the applicability of the coatings
against hydrophobic environments was limited owing to
its affinity to apolar compounds. The results show that the
coating prepared by the toluene BC extract was the best coating.
The key data were: water CA of 99.38, total SE (between
37.4 mN m-1 and 40.1 mN m-1), SE polar component
(0.1 mN m-1), and the acidic and basic characters were negligible.
It can be concluded that the BC extracts have potential
for coatings.R.P. acknowledges a post-doc research grant BPD/39333/2007 from the Portuguese Foundation for Science and Technology (FCT). We gratefully acknowledge Amorim Isolamentos S.A. for the supply of black condensate
Wetspun poly-L-(lactic acid)-borosilicate bioactive glass scaffolds for guided bone regeneration
We developed a porous poly-L-lactic acid (PLLA) scaffold compounded with borosilicate bioactive glasses (BBGs) endowing it with bioactive properties. Porous PLLA-BBG fibre mesh scaffolds were successfully prepared by the combination of wet spinning and fibre bonding techniques. Micro-computed tomography (ÎŒCT) confirmed that the PLLA-BBG scaffolds containing â 25% of BBGs (w/w) exhibited randomly interconnected porous (58 to 62% of interconnectivity and 53 to 67% of porosity) with mean pore diameters higher that 100 ÎŒm. Bioactivity and degradation studies were performed by immersing the scaffolds in simulated body fluid (SBF) and ultrapure water, respectively. The PLLA-BBG scaffolds presented a faster degradation rate with a constant release of inorganic species, which are capable to produce calcium phosphate structures at the surface of the material after 7 days of immersion in SBF (Ca/P ratio of ~ 1.7). Cellular in vitro studies with human osteosarcoma cell line (Saos-2) and human adipose-derived stem cells (hASCs) showed that PLLA-BBGs are not cytotoxic to cells, while demonstrating their capacity to promote cell adhesion and proliferation. Overall, we showed that the proposed scaffolds present a tailored kinetics on the release of inorganic species and controlled biological response under conditions that mimic the bone physiological environment.JSF acknowledges the Portuguese Foundation for Science and Technology (FCT) for his PhD grant BD/73162/2010. This work was partially supported by the European Research Council grant agreement ERC-2012-ADG20120216-321266 - project ComplexiTE
Study of the fosfosal controlled permeation through glutaraldehyde crosslinked chitosan membranes
Advanced material forum III : proceedings of the III International Materials Symposium, Aveiro, 2005Fosfosal, a phosphate derivative of salicylic acid, which presents both analgesic and antiinflammatory
properties, was used as a model drug to study the potential of recently developed
chitosan membranes (with different crosslinking degrees) to be used as drug release rate-controlling
membranes. The fosfosal permeation across these membranes was studied using an in-house built
developed diffusion cell with online automatic monitoring. Experiments were performed using
phosphate buffer saline (PBS) solution at 37ÂșC. Different flow properties of the detection set up
were determined in order to estimate the errors introduced by the automatic online monitoring
system. For increasing crosslinking degrees the permeability initially decreased, and then increased,
likely as a consequence of the crosslinking influence on a variety of properties like crystallinity and
hydrophilicity that have opposite influence on permeability. In summary, it was possible to control
the drug release profile by means of changing the degree of crosslinking of chitosan membranes and
to follow the respective release kinetics by means of using the developed diffusion cell(undefined
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