pinecone/core-2020-05-10-deduplication huggingface dataset:
Preparation and in vitro characterization of novel bioactive glass ceramic nanoparticles

SiO2-CaO-P2O5 ternary bioactive glass ceramic
(BGC) nanoparticles with different compositions were
prepared via a three-step sol-gel method. Polyethylene
glycol was selected to be used as the surfactant to
improve the dispersion of the nanoparticles. The morphology
and composition of these BGC nanoparticles
were observed by ESEM and EDX. All the BGC particles
obtained in this method were about 20 nm in diameter.
XRD analysis demonstrated that the different compositions
can result in very different crystallinities for the
BGC nanoparticles. Bioactivity tests in simulated body
fluid solution (SBF), and degradability in phosphate
buffer solution (PBS), were performed in vitro. SEM, EDX, and XRD were employed to monitor the surface variation
of neat poly(L-lactic acid), PLLA, foam and PLLA/BGC
porous scaffolds during incubation. The BGC nanoparticles
with lower phosphorous and relative higher silicon
content exhibited enhanced mineralization capability in
SBF and a higher solubility in PBS medium. Such novel
nanoparticles may have potential to be used in different
biomedical applications, including tissue engineering or
the orthopedic field.Contract grant sponsor: FCT; contract grant numbers: POCTI/FIS/61621/2004, SFRH/BPD/25828/2005, PTDC/QUI/69263/200
Synthesis, characterization, bioactivity and biocompatibility of nanostructured materials based on the wollastonite-poly(ethylmethacrylate-co-vinylpyrrolidone) system

Composite materials are very promising biomaterials\ud
for hard tissue augmentation. The approach assayed\ud
in this work involves the manufacturing of a composite\ud
made of a bioactive ceramic, natural wollastonite (W) and a\ud
nanostructured copolymer of ethylmethacrylate (EMA) and\ud
vinylpyrrolidone (VP) to yield a bioresorbable and biocompatible\ud
VP–EMA copolymer. A bulk polymerization was\ud
induced thermally at 508C, using 1 wt % azobis(isobutyronitrile)\ud
(AIBN) as free-radical initiator. Structural characterization,\ud
compressive strength, flexural strength (FS), degradation,\ud
bioactivity, and biocompatibility were evaluated in\ud
specimens with a 60/40 VP/EMA ratio and ceramic content\ud
in the range 0–60%. A good integration between phases\ud
was achieved. Greater compression and FS, in comparison\ud
with the pure copolymer specimens was obtained only\ud
when the ceramic load got up to 60% of the total weight.\ud
The soaking in NaCl solution resulted in the initial swelling\ud
of the specimens tested. The maximum swelling was\ud
reached after 2–3 h of immersion and it was significantly\ud
greater for lower ceramic loads. This result makes the polymer\ud
component the main responsible for the interactions\ud
with the media. After soaking in SBF, microdomains segregation\ud
can be observed in the polymer component that can\ud
be related with a dramatic difference in the reactivity of\ud
both monomers in free radical polymerization, whereas the\ud
formation of an apatite-like layer on the W surfaces can be\ud
observed. Biocompatibility in vitro studies showed the absence\ud
of cytotoxicity of all formulations. The cells were able\ud
to adhere on the polystyrene negative control and on specimens\ud
containing 60 wt % wollastonite forming a monolayer\ud
and showing a normal morphology. However, a low cellular\ud
growth was observed.   2008 Wiley Periodicals, Inc.\ud
J Biomed Mater Res 88A: 53–64, 2009Peer reviewe
Mono-functional aminosilanes as primers for peptide functionalization

When covalently attaching biomolecules to surfaces such as titanium, trifunctional silanes are commonly used as primers to produce surface amine groups. However, these primed surfaces are rarely uniform in structure due to networking of the silane. Mono-functional aminosilanes may result in more uniform structures, although their long-term stability and effect on osteoblast cell responses are possible issues for orthopedic applications. This study examines for the first time the optimization of peptide coupling to titanium using mono-functional aminosilane reaction chemistry. The resultant surface topography, chemistry, and thicknesses were characterized showing improved surface uniformity compared with trifunctional silanized surfaces. The stability of the coatings was examined over a period of 8 days in environments of varying pH, temperature, and humidity. In addition, human osteosarcoma (HOS) cell adhesion and spreading on the samples was examined; adhesion was minimal on silanized surfaces, but after functionalization with cysteine the cell density was greater than the titanium control and showed no overall detrimental effect on initial cell responses
Macroporous hydroxyapatite scaffolds for bone tissue engineering applications : physicochemical characterization and assessment of rat bone marrow stromal cell viability

In this work, a new methodology is reported
for developing hydroxyapatite (HA) scaffolds using an
organic sacrifice template. The novelty of work consists of
possibility of obtaining porous and highly interconnected
scaffolds mimicking the sacrificial component. Our purpose
consisted of evaluating the physicochemical properties
of the HA scaffolds by means of Fourier transform
infra-red spectroscopy, X-ray diffraction analysis, and
scanning electron microscopy (SEM) attached with an Xray
detector. The HA scaffolds obtained possess a porosity
of !70%, and macropores diameter in the range of
50–600 lm. In contrast, results regarding the microcomputed
tomography analysis have demonstrated both high
pore uniformity and interconnectivity across the scaffolds.
The compressive strength of the HA scaffolds was found
to be 30.2 6 6.0 MPa. Bioactivity of the HA scaffolds was
assessed by immersion into a simulated body fluid solution,
in vitro. SEM observations have showed a deposition
of apatite on the surface of the HA scaffolds, with a ‘‘cauliflower-
like’’ morphology after 1 day, and tend to be
more pronounced with the immersion time. The changes
in calcium and phosphorus concentration were monitored
by inductively-coupled plasma optical emission spectrometry.
Cytotoxicity of the HA scaffolds was preliminarily
investigated by carrying direct observation of mouse
fibroblasts cells (L929 cell-line) death in the inverted
microscope, and then cell viability was determined by
means of carrying out a MTS assay. Complementarily, a
luminescent cell viability assay based on the quantification
of adenosine triphosphate was performed using rat
bone marrow stromal cells (RBMSCs). A LIVE/DEAD
assay and SEM analysis allowed the visualization of the
RBMSCs adhesion and proliferation on the surface of the
HA scaffolds. According to the results obtained from 3D
architecture, mechanical properties, biocompatibility, and
adhesion tests, it is suggested that HA scaffolds has
potential to find applications in bone tissue engineering
scaffolding.Contract grant sponsor: European NoE EXPERTISSUES; contract grant number: NMP3-CT-2004-50028
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
Improving the affinity of fibroblasts for bacterial cellulose using carbohydrate-binding modules fused to RGD

The attachment of cells to biomedical materials can be improved by using adhesion sequences, such as Arg-Gly-Asp (RGD), found in several extracellular matrix proteins. In this work, bifunctional recombinant proteins, with a Cellulose-Binding Module (CBM), from the cellulosome of Clostridium thermocellum and cell binding sequences - RGD, GRGDY - were cloned and expressed in E.coli. These RGD-containing cellulose binding proteins were purified and used to coat bacterial cellulose fibres. Its effect on the cell adhesion/biocompatibility properties was tested using a mouse embryo fibroblasts culture. Bacterial cellulose (BC) secreted by Gluconacetobacter xylinus (=Acetobacter xylinum) is a material with unique properties and promising biomedical applications. CBMs adsorbs specifically and tightly on cellulose. Thus, they are a useful tool to address the fused RGD sequence (or other bioactive peptides) to the cellulose surface, in a specific and simple way. Indeed, fibroblasts exhibit improved ability to interact with bacterial cellulose sheets coated with RGD-CBM proteins, as compared with cellulose treated with the CBM, that is, without the adhesion peptide. The effect of the several fusion proteins produced was analyzed.Fundação para a Ciência e a Tecnologia (FCT)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES, Brazil
A new route to produce starch-based fiber mesh scaffolds by wet spinning and subsequent surface modification as a way to improve cell attachment and proliferation

This study proposes a new route for producing fiber mesh scaffolds from a starch-polycaprolactone (SPCL) blend. It was demonstrated that the scaffolds with 77% porosity could be obtained by a simple wet-spinning technique based on solution/precipitation of a polymeric blend. To enhance the cell attachment and proliferation, Ar plasma treatment was applied to the scaffolds. It was observed that the surface morphology and chemical composition were significantly changed because of the etching and functionalization of the fiber surfaces. XPS analyses showed an increase of the oxygen content of the fiber surfaces after plasma treatment (untreated scaffolds O/C:0.32 and plasma-treated scaffolds O/C:0.41). Both untreated and treated scaffolds were examined using a SaOs-2 human osteoblast-like cell line during 2 weeks of culture. The cell seeded on wet-spun SPCL fiber mesh scaffolds showed high viability and alkaline phosphatase enzyme activity, with those values being even higher for the cells seeded on the plasma-treated scaffolds.Contract grant sponsor: FCT Foundation for Science and Technolog
Development of new chitosan/carrageenan nanoparticles for drug delivery applications

The use of polymeric nanoparticles, especially those composed of natural polymers, has become a very interesting approach in drug delivery., mainly because of the advantages offered by their small dimensions. The aim of this work was to develop a novel formulation of nanoparticles comprised of two natural marine-derived polymers, namely chitosan and carrageenan, and to evaluate their potential for the association and controlled release of macromolecules. Nanoparticles were obtained in a hydrophilic environment, under very mild conditions, avoiding the use of organic solvents or other aggressive technologies for their preparation. The developed nanocarriers presented sizes within 350-650 run and positive zeta potentials of 50-60 mV. Polymeric interactions between nanoparticles' components were evaluated by Fourier transform infrared spectroscopy. Using ovalbumin as model protein, nanoparticles evidenced loading capacity varying from 4% to 17%, and demonstrated excellent capacity to provide a controlled release for up to 3 weeks. Furthermore, nanoparticles have demonstrated to exhibit a noncytotoxic behavior in biological in vitro tests performed using L929 fibroblasts, which is critical regarding the biocompatibility of those carriers. In summary, the developed chitosan-carrageenan nanoparticles have shown promising properties to be used as carriers of therapeutic macromolecules, with potential application not only strictly in drug delivery, but also in broader areas, such as tissue engineering and regenerative medicine. (C) 2009 Wiley Periodicals, Inc. J Biomed Mater Res 92A: 1265-1272, 2010Contract grant sponsor: Portuguese Foundation for Science and Technology (FCT) (POCTI/FEDER programmes)Contract grant sponsor: European Union STREP Project HIPPOCRATES; contract grant number: NMP3-CT-2003505758Contract grant sponsor: European NoE EXPERTISSUES; contract grant number: NMP3-CT-2004-50028
Characterization of dextrin-based hydrogels : rheology, biocompatibility, and degradation

A new class of degradable dextrin-based hydrogels (dextrin-HEMA) was developed. The hydroxyethyl methacrylate ester (HEMA) hydroxyl groups were activated with N,N' carbonyldiimidazole (CDI), followed by their coupling to dextrin, yielding a derivatized material that can be polymerized in aqueous solution to form hydrogels. A comparative study of the stability of the dextrin-HEMA hydrogels and dextrin-vinyl acrylate (dextrin-VA, produced in previous work) revealed that only the firsts are effectively hydrolyzed under physiological conditions. A severe mass loss of dextrin-HEMA gels occurs over time, culminating in the complete dissolution of the gels. Rheologic analysis confirmed that physical structuring is less pronounced when dextrin is modified with methacrylate side groups. The biocompatibility results revealed that the dextrin hydrogels have negligible cell toxicity, irrespective of the hydrogel type (HEMA and VA), allowing cell adhesion and proliferation. Gathering the biocompatibility and the ability to tailor the release profiles, we consider dextrin a promising biomaterial for biomedical applications, namely for controlled release
Changes in the physical structure and chain dynamics of\ud
elastin network in homocysteine-cultured arteries

The thermal and dielectric properties of the elastin network were investigated in arteries cultured with\ud
physiological and pathological concentrations of homocysteine, an aminoacid responsible of histological impairments in human arteries. The physical structure of this amorphous protein was investigated by differential scanning calorimetry (DSC). To explore the molecular dynamics of the elastin network in the nanometer range, we used thermally stimulated currents (TSC), a dielectric technique running at low frequency, and measuring the dipolar reorientations in proteins subjected to a static electrical field. Combining DSC and TSC experiments reveals the molecular mobility of the proteins, both in the glassy state and in the liquid state. Significant differences are evidenced in the physical structure and relaxation behavior of elastin network in cultured arteries (physiological and pathological concentrations of homocysteine) and discussed
Gellan gum : a new biomaterial for cartilage tissue engineering applications

Gellan gum is a polysaccharide manufactured
by microbial fermentation of the Sphingomonas paucimobilis
microorganism, being commonly used in the food and
pharmaceutical industry. It can be dissolved in water, and
when heated and mixed with mono or divalent cations,
forms a gel upon lowering the temperature under mild
conditions. In this work, gellan gum hydrogels were
analyzed as cells supports in the context of cartilage regeneration.
Gellan gum hydrogel discs were characterized
in terms of mechanical and structural properties.
Transmission electron microscopy revealed a quite homogeneous
chain arrangement within the hydrogels matrix,
and dynamic mechanical analysis allowed to characterize
the hydrogels discs viscoelastic properties upon compression
solicitation, being the compressive storage and loss
modulus of !40 kPa and 3 kPa, respectively, at a
frequency of 1 Hz. Rheological measurements determined
the sol-gel transition started to occur at approximatel 368C, exhibiting a gelation time of !11 s. Evaluation of
the gellan gum hydrogels biological performance was
performed using a standard MTS cytotoxicity test,
which showed that the leachables released are not
deleterious to the cells and hence were noncytotoxic.
Gellan gum hydrogels were afterwards used to encapsulate
human nasal chondrocytes (1 3 106 cells/mL) and
culture them for total periods of 2 weeks. Cells viability
was confirmed using confocal calcein AM staining.
Histological observations revealed normal chondrocytes
morphology and the obtained data supports the claim
that this new biomaterial has the potential to serve as a
cell support in the field of cartilage regeneration.Contract grant sponsor: The Portuguese Foundation for Science and Technology (FCT); contract grant number: SFRH/BD17135/2004Contract grant sponsor: The European NoE EXPERTIS-SUES; contract grant number: NMP3-CT-2004-500283Contract grant sponsor: The European Project HIPPO-CRATES; contract grant number: STRP 505758-
Biomimetic PEG hydrogels crosslinked with minimal plasmin-sensitive tri-amino acid peptides

Semi-synthetic, proteolytically degradable polymer hydrogels have proven effective as scaffolds to augment bone and skin regeneration in animals. However, high costs due to expensive peptide building blocks pose a significant hurdle towards broad clinical usage of these materials. Here we demonstrate that tri-amino acid peptides bearing lysine (or arginine), flanked by two cysteine residues for crosslinking, are adequate as minimal plasmin-sensitive peptides in poly(ethylene glycol)-based hydrogels formed via Michael-type addition. Substitution of lysine (or arginine) with serine rendered the matrices insensitive to the action of plasmin. This was demonstrated in vitro by performing gel degradation experiments in the presence of plasmin (0.1 U/mL), and in the in vivo situation of regeneration of critical-sized bone defects. When placed as implants into rat calvaria, gels formed from the minimal plasmin substrates showed clear signs of cell infiltration and gel remodeling that coincided with extensive bone formation. (c) 2009 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
In vivo evaluation of acellular human dermis for abdominal wall repair

Limitations of synthetic biomaterials for abdominal wall repair have led investigators to seek naturally derived matrices, such as human acellular dermis, because of their excellent biocompatibility and their ability to naturally interface with host tissues with minimal tissue response. In this study, we investigated two different biomaterials derived from human dermis (FlexHD acellular dermis and FlexHD acellular dermis-thick) in a rabbit abdominal hernia repair model. One quarter of the abdominal wall was replaced with each biomaterial, and the animals were followed for up to 24 weeks. Rabbit hernias repaired with AlloDerm(R), a commercially available acellular dermal matrix, and sham operated animals served as controls. Retrieved samples of these implants were assessed grossly and histologically. Collagen production measurements and tension studies were performed. FlexHD acellular dermis, FlexHD acellular dermis-thick, and AlloDerm(R) maintained their strength in the rabbit hernia repair model with no incidence of hernia formation or bowel adhesion. The exact size measurements at 24 weeks were 217.0 +/- 20.9% for FlexHD acellular dermis, 200.8 +/- 23.5% for FlexHD acellular dermis-thick, and 209.7 +/- 32.9% for AlloDerm(R). Macroscopic and microscopic evaluation showed excellent integration and tissue formation. All biomaterials studied harbored cells that produced new collagen fibers, and a six-fold increase in these fibers was observed at 24 weeks. This study shows that acellular biomaterials derived from human dermis are suitable for abdominal hernia repair. (c) 2009 Wiley Periodicals, Inc. J Biomed Mater Res 2010
Changes on surface morphology of corn starch blend films

This study aims at evaluating the influence of enzymatic degradation solution on the surface morphology and thermal properties of a poly(ethylene-vinyl alcohol) copolymer-corn starch thermoplastic blend (SEVA-C), as a function of immersion time. To perform this study, three different batches were assessed using SEVA-C samples of different thicknesses and a fixed weight of 1.6 g, immersed in alpha-amylase (50 u/L) up to 90 days at 37 degrees C. TGA, contact angle measurements, scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques were used. Three degradation mechanisms are considered in these systems: namely, mass loss due to plasticizer leaching (glycerol), starch enzymatic cleavage, and synthetic polymer fractions degradation. Enzymatic hydrolysis of the starch fraction and subsequent leaching from the internal bulk structure led to an increase in surface porosity, pore size, roughness, and to the development of small pits throughout the surface, as observed by SEM and AFM