50 research outputs found
Properties of melt processed chitosan and aliphatic polyester blends
The activities (at pH 7 and 50°C) of purified EGV (Humicola insolens) and CenA (Cellulomonas fimi) were determined on cotton fabrics
at high and low levels of mechanical agitation. Similar activity measurements were also made by using the core domains of these cellulases.
Activity experiments suggested that the presence of cellulose binding domains (CBDs) is not essential for cellulase performance in the
textile processes, where high levels of mechanical agitation are applied. The binding reversibilities of these cellulases and their cores were
studied by dilution of the treatment liquor after equilibrium adsorption. EGV showed low percentage of adsorption under both levels of
agitation. It was observed that the adsorption/desorption processes of cellulases are enhanced by higher mechanical agitation levels and that
the binding of cellulase with CBD of family I (EGV) is more reversible than that of CBD of the cellulase of family II (CenA)
Osteogenic differentiation of human bone marrow mesenchymal stem cells seeded on melt based chitosan scaffolds for bone tissue engineering applications
The purpose of this study was to evaluate the growth patterns and osteogenic differentiation of human bone
marrow mesenchymal stem cells (hBMSCs) when seeded onto new biodegradable chitosan/polyester scaffolds.
Scaffolds were obtained by melt blending chitosan with poly(butylene succinate) in a proportion of 50% (wt)
each and further used to produce a fiber mesh scaffold. hBMSCs were seeded on those structures and cultured for
3 weeks under osteogenic conditions. Cells were able to reduce MTS and demonstrated increasing metabolic
rates over time. SEM observations showed cell colonization at the surface as well as within the scaffolds. The
presence of mineralized extracellular matrix (ECM) was successfully demonstrated by peaks corresponding to
calcium and phosphorus elements detected in the EDS analysis. A further confirmation was obtained when carbonate
and phosphate group peaks were identified in Fourier Transformed Infrared (FTIR) spectra. Moreover, by reverse
transcriptase (RT)-PCR analysis, it was observed the expression of osteogenic gene markers, namely, Runt related
transcription factor 2 (Runx2), type 1 collagen, bone sialoprotein (BSP), and osteocalcin. Chitosan-PBS (Ch-
PBS) biodegradable scaffolds support the proliferation and osteogenic differentiation of hBMSCs cultured at
their surface in vitro, enabling future in vivo testing for the development of bone tissue engineering therapies.Ana Costa-Pinto was supported by a grant (SFRH/24735/2005) from the Portuguese Foundation for Science and Technology "Fundacao para a Ciencia e a Tecnologia" (FCT). This work was partially supported by the EU Integrated Project GENOSTEM (Adult Mesenchymal Stem Cells Engineering for connective tissue disorders: from the bench to the bedside, LSHB-CT-2003-5033161), and the European Network of Excellence EXPERTISSUES (NMP3-CT-2004-500283). The authors would like to acknowledge to the School of Health Sciences of the University of Minho for the opportunity of using its facilities
Growth of SiO2 microparticles by using modified Stober method: Effect of ammonia solution concentration and TEOS concentration
The unique structural features and suitability of the SiO2 microparticles in different application areas have mobilized a worldwide interest in the last few decades. In this report a classical method known as the Stober method has been used to synthesize silica microspheres. These microparticles have been synthesized by the reaction of tetraethyl orthosilicate (Si(OC2H5)(4), TEOS)(silica precursor)with water in an alcoholic medium (e.g. ethanol) in the presence of KCl electrolyte and ammonia as a catalyst. It has been observed that the size of the microparticles closely depends on the amount of the TEOS and ammonia. A decrease in the size of micro particles from 2.1 mu m to 1.7 mu m has been confirmed as the amount of TEOS increases from 3.5ml to 6.4ml respectively. In similar way a decrease in the diameter of the micro particles from 2.1 mu m to 1.7 mu m has been observed with increase in the ammonia content from 3ml to 9ml
Melt-based compression-molded scaffolds from chitosan-polyester blends and composites: Morphology and mechanical properties
Blends of chitosan and synthetic aliphatic polyesters
(polybutylene succinate, polybutylene succinate adipate,
polycaprolactone, and polybutylene terepthalate adipate)
were compounded with and without hydroxyapatite,
a bioactive mineral filler known to enhance osteoconduction.
The blends and composites were compression molded
with two different granulometric salt sizes (63–125 lm and
250–500 lm) having different levels of salt content (60, 70,
and 80%) by weight. By leaching the salt particles, it was
possible to produce porous scaffolds with distinct morphologies.
The relationship between scaffold morphology and
mechanical properties was evaluated using scanning electron
microscopy, microcomputed tomography, compression
testing, differential scanning calorimetry, small-angle X-ray
scattering (SAXS), and wide-angle X-ray scattering. The produced
scaffolds are characterized by having different morphologies
depending on the average particle size and the
amount of NaCl used. Specimens with higher porosity level
have a less organized pore structure but increased interconnectivity
of the pores. The stress–strain curve under compression
displayed a linear elasticity followed by a plateau
whose characteristics depend on the scaffold polymer composition.
A decrease in the salt particle size used to create
the porosity caused in general a decrease in the mechanical
properties of the foams. Composites with hydroxyapatite
had a sharp reduction in yield stress, modulus, and strain
at break. The melting temperature decreased with increased
chitosan content. SAXS results indicate no preferential crystalline
orientation in the scaffolds. Cytotoxicity evaluation
were carried out using standard tests (accordingly to ISO/
EN 10993 part 5 guidelines), namely MTS test with a 24-h
extraction period, revealing that L929 cells had comparable
metabolic activities to that obtained for the negative control.Contract grant sponsor: Fundacao Luso-Americana para Desenvolvimento (FLAD
Adhesion, proliferation, and osteogenic differentiation of a mouse mesenchymal stem cell line (BMC9) seeded on novel melt-based chitosan/polyester 3D porous scaffolds
The aim of the present work was to study the biological behavior of a mouse mesenchymal stem cell line
when seeded and cultured under osteogenic conditions onto novel processed melt-based chitosan scaffolds.
Scaffolds were produced by compression molding, followed by salt leaching. Scanning electron microscopy
(SEM) observations and lCT analysis showed the pore sizes ranging between 250 and 500 lm and the
interconnectivity of the porous structure. The chitosan–poly(butylenes succinate) scaffolds presented high
mechanical properties, similar to the ones of trabecular bone (E1%*75 MPa). Cytotoxicity assays were
carried out using standard tests (accordingly to ISO/EN 10993 part 5 guidelines), namely, MTS test with a
24 h extraction period, revealing that L929 cells had similar metabolic activities to that obtained for the
negative control. Cell culture studies were conducted using a mouse mesenchymal stem cell line (BMC9).
Cells were seeded onto the scaffold and allowed to proliferate for 3 weeks under osteogenic conditions.
SEM observations demonstrated that cells were able to proliferate and massively colonize the scaffolds
structure. The cell viability assay MTS demonstrated that BMC9 cells were viable after 3 weeks of culture.
The cells clearly evidenced a positive differentiation toward the osteogenic lineage, as confirmed by the
high ALP activity levels. Moreover, energy dispersive spectroscopy (EDS) analysis revealed the presence of
Ca and P in the elaborated extracellular matrix (ECM). These combined results indicate that the novel
melt-based chitosan/polyester scaffolds support the adhesion, proliferation, and osteogenic differentiation
of the mouse MSCs and shows adequate physicochemical and biological properties for being used as
scaffolds in bone tissue engineering–related strategies
Assessment of the suitability of chitosan/polybutylene succinate scaffolds seeded with mouse mesenchymal progenitor cells for a cartilage tissue engineering approach
In this work, scaffolds derived from a new biomaterial originated from the combination of a natural
material and a synthetic material were tested for assessing their suitability for cartilage tissue engineering
applications. In order to obtain a better outcome result in terms of scaffolds’ overall properties,
different blends of natural and synthetic materials were created. Chitosan and polybutylene succinate (CPBS)
50/50 (wt%) were melt blended using a twin-screw extruder and processed into 5 5 5mm scaffolds
by compression moulding with salt leaching. Micro-computed tomography analysis calculated an
average of 66.29% porosity and 92.78% interconnectivity degree for the presented scaffolds. The salt
particles used ranged in size between 63 and 125 lm, retrieving an average pore size of 251.28 lm.
Regarding the mechanical properties, the compressive modulus was of 1.73 ± 0.4MPa (Esec 1%). Cytotoxicity
evaluation revealed that the leachables released by the developed porous structures were not
harmful to the cells and hence were noncytotoxic. Direct contact assays were carried out using a mouse
bone marrow–derived mesenchymal progenitor cell line (BMC9). Cells were seeded at a density of 5 105
cells/scaffold and allowed to grow for periods up to 3 weeks under chondrogenic differentiating conditions.
Scanning electron microscopy analysis revealed that the cells were able to proliferate and colonize
the scaffold structure, and MTS test demonstrated cell viability during the time of the experiment.
Finally, Western blot performed for collagen type II, a natural cartilage extracellular matrix component,
showed that this protein was being expressed by the end of 3 weeks, which seems to indicate that the
BMC9 cells were being differentiated toward the chondrogenic pathway. These results indicate the
adequacy of these newly developed C-PBS scaffolds for supporting cell growth and differentiation toward
the chondrogenic pathway, suggesting that they should be considered for further studies in the cartilage
tissue engineering field.J. T. Oliveira would like to acknowledge the grant (SFRH/ BD17135/2004) from Portuguese Foundation for Science and Technology (FCT). The authors would like to thank Fernanda Marques, at the Institute for Health and Life Sciences (ICVS), University of Minho, Braga, Portugal, for her help with the Western blot analysis, as well as the staff at ICVS for allowing to use their facilities. The monoclonal antibody for collagen type II was obtained from the Developmental Studies Hybridoma Bank developed under the auspices of the NICHD and maintained by the Department of Biological Sciences, University of Iowa (Iowa City, IA). This work was carried out under the scope of the European NoE EXPERTISSUES (NMP3-CT-2004-500283), and partially supported by the European Project GENOSTEM (LSHB-CT-2003-503161) and the FCT Project CartiScaff (POCTI/SAU-BMA/58991/2004)
Polymer Nanocomposites—A Comparison between Carbon Nanotubes, Graphene, and Clay as Nanofillers
Nanofilled polymeric matrices have demonstrated remarkable mechanical, electrical, and thermal properties. In this article we review the processing of carbon nanotube, graphene, and clay montmorillonite platelet as potential nanofillers to form nanocomposites. The various functionalization techniques of modifying the nanofillers to enable interaction with polymers are summarized. The importance of filler dispersion in the polymeric matrix is highlighted. Finally, the challenges and future outlook for nanofilled polymeric composites are presented
MODELING MEAT FREEZING
The effects of frozen storage on rancidity, color and selected textural properties (drip loss, cooking loss and shear strength) of ground beef patties was studied. The parameters included storage temperatures of (-12.2, -23.3 or -34.4 C), fat levels (15 or 30%) and packaged in polyvinyl chloride vacuum packaged or polyethylene overwrap. The samples were analyzed for rancidity, and textural and color degradation at 4 wk intervals for a period of 20 weeks. The effect of the independent variables were observed and the most significant parameters identified. Time-temperature effects as a function of fat levels and package type are presented in the form of response surfaces. Additionally, a finite difference model was developed to predict transient temperature response during freezing and thawing of food-stuffs. The model was tested against slab-shaped ground beef patties. The model accounted for three different boundary conditions encountered during freezing heat transfer as well as variable thermophysical properties below the initial freezing point