967 research outputs found
Novel genipin cross-linked chitosan-silk fibroin sponges for cartilage engineering strategies
The positive interaction of materials with tissues is an important step in regenerative medicine strategies. Hydrogels
that are obtained from polysaccharides and proteins are expected to mimic the natural cartilage environment and
thus provide an optimum milleu for tissue growth and regeneration. In this work, novel hydrogels composed of
blends of chitosan and Bombyx mori silk fibroin were cross-linked with genipin (G) and were freeze dried to
obtain chitosan/silk (CSG) sponges. CSG sponges possess stable and ordered structures because of protein
conformational changes from R-helix/random-coil to -sheet structure, distinct surface morphologies, and pH/
swelling dependence at pH 3, 7.4, and 9. We investigated the cytotoxicity of CSG sponge extracts by using L929
fibroblast-like cells. Furthermore, we cultured ATDC5 cells onto the sponges to evaluate the CSG sponges’ potential
in cartilage repair strategies. These novel sponges promoted adhesion, proliferation, and matrix production of
chondrocyte-like cells. Sponges’ intrinsic properties and biological results suggest that CSG sponges may be
potential candidates for cartilage tissue engineering (TE) strategies.S.S.S. and M.T.R. thank the Portuguese Foundation for Science and Technology (FCT) for Ph.D. scholarships (SFRH/BD/8658/2002 and SFRH/BD/30745/2006, respectively). A.F.M.P. thanks the FCT and FEDER for a grant (POCI/FIS/61621/2004). This work was partially supported by the European-Union-funded STREP project HIPPOCRATES (NMP3-CT-2003-505758) and was carried out under the scope of the European NoE EXPERTISSUES (NMP3-CT-2004-500283). We also acknowledge Adriano Pedro for his contribution to the micro-CT analysis
Novel genipin cross-linked chitosan-silk based sponges for the regeneration and repair of cartilage using a tissue engineering approach
Development of materials that can interactpositively with tissues is important to regenerative medicine strategies success. Cartilage tissue engineering (TE) scaffolding is a field of continuous evolution, and sponges derived from the combination of polysaccharides and proteins are expected to mimic the naturally
occurring environment in the articular cartilage matrix, providing an optimum environment for tissue growth and regeneration. Chitosan (Cht) and Bombyx mori silk fibroin (SF) are excellent candidates for sponges design due to their intrinsic characteristics. The present work aimed to improve the chitosan biocompatibility through blending with Cht-SF and genipin-cross-linking.
Hydrogels, produced by cross-linking of Cht-SF, were freeze-dryed to obtain the cross-linked chitosan/silk (CSG) sponges. Rheological and mechanical properties, structural aspects and morphological features of CSG sponges were evaluated. CSG sponges possess stable and ordered structures due to protein
conformation changes from alpha-helix/randomcoil to beta-sheet structure, porous and globular-like surface morphologies, and pH/swelling dependence at pH 3, 7.4 and 9. To evaluate sponges â suitability for cell studies, ATDC5 chondrocyte-like cells were seeded onto CSG sponges and ATDC5 viability (MTS assay), proliferation (DNA test), morphology (SEM analysis) and matrix production (GAGs quantification) were assessed after 14, 21 and 28 days of culture. ATDC5-sponge constructs showed a significant higher adhesion, proliferation and matrix production with the time of culture when compared to Cht, suggesting CSG sponges as potential candidates for cartilage TE strategies. Acknowledgements. Thanks to Portuguese Foundation for Science and Technology, STREP Project HIPPOCRATES (NMP3-CT-2003-505758) and European NoE EXPERTISSUES (NMP3-CT-2004-500283).info:eu-repo/semantics/publishedVersio
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Factors associated with smoking in pregnancy
The aim of this cross-sectional study was to identify factors related to smoking during pregnancy. The sample included 267 puerperae hospitalized in the maternity unit of a university hospital in Porto Alegre/RS. The data were collected through a self-applied instrument and statistically analyzed. The majority of the puerperae (51.3%) were between 18 and 25 years old, 55.4% were nonsmokers, 25.5% were smokers, 19.1% had recently ceased smoking (in abstinence). The nonsmokers had more consultations than the smokers and the abstinent smokers (p=0.025). The number of women who had more than one child was higher among smokers than among nonsmokers and abstinent smokers (p=0.002). Women were more likely to stop smoking before pregnancy when they had a partner who was a nonsmoker (p=0.007). Several factors influence smoking and smoking cessation and these are important in prenatal interventions aimed at pregnant women and their partners
Measurement of the muon anti-neutrino double-differential cross section for quasi-elastic scattering on hydrocarbon at~ GeV
We present double-differential measurements of anti-neutrino quasi-elastic
scattering in the MINERvA detector. This study improves on a previous single
differential measurement by using updated reconstruction algorithms and
interaction models, and provides a complete description of observed muon
kinematics in the form of a double-differential cross section with respect to
muon transverse and longitudinal momentum. We include in our signal definition
zero-meson final states arising from multi-nucleon interactions and from
resonant pion production followed by pion absorption in the primary nucleus. We
find that model agreement is considerably improved by a model tuned to MINERvA
inclusive neutrino scattering data that incorporates nuclear effects such as
weak nuclear screening and two-particle, two-hole enhancements.Comment: 47 pages, 31 figure
First evidence of coherent meson production in neutrino-nucleus scattering
Neutrino-induced charged-current coherent kaon production,
, is a rare, inelastic electroweak process
that brings a on shell and leaves the target nucleus intact in its ground
state. This process is significantly lower in rate than neutrino-induced
charged-current coherent pion production, because of Cabibbo suppression and a
kinematic suppression due to the larger kaon mass. We search for such events in
the scintillator tracker of MINERvA by observing the final state ,
and no other detector activity, and by using the kinematics of the final state
particles to reconstruct the small momentum transfer to the nucleus, which is a
model-independent characteristic of coherent scattering. We find the first
experimental evidence for the process at significance.Comment: added ancillary file with information about the six kaon candidate
Measurement of Total and Differential Cross Sections of Neutrino and Antineutrino Coherent Production on Carbon
Neutrino induced coherent charged pion production on nuclei,
, is a rare inelastic interaction in
which the four-momentum squared transfered to the nucleus is nearly zero,
leaving it intact. We identify such events in the scintillator of MINERvA by
reconstructing |t| from the final state pion and muon momenta and by removing
events with evidence of energetic nuclear recoil or production of other final
state particles. We measure the total neutrino and antineutrino cross sections
as a function of neutrino energy between 2 and 20 GeV and measure flux
integrated differential cross sections as a function of , and
. The dependence and equality of the neutrino and
anti-neutrino cross-sections at finite provide a confirmation of Adler's
PCAC hypothesis
Single neutral pion production by charged-current interactions on hydrocarbon at 3.6 GeV
Single neutral pion production via muon antineutrino charged-current
interactions in plastic scintillator (CH) is studied using the \minerva
detector exposed to the NuMI low-energy, wideband antineutrino beam at
Fermilab. Measurement of this process constrains models of neutral pion
production in nuclei, which is important because the neutral-current analog is
a background for appearance oscillation experiments. The
differential cross sections for momentum and production angle, for
events with a single observed and no charged pions, are presented and
compared to model predictions. These results comprise the first measurement of
the kinematics for this process.Comment: 6 pages, 5 figures, submitted to Physics Letters
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