•Plasma treatment was used as an adhesive tool for PDMS/collagen composite preparation.•Response surface methodology was used for statistical optimization.•A microscopic roughness can also lead to a ...mechanical interlocking between materials.•Hydroxyl groups on the PDMS surface contribute to the enhanced chemical interactions.•PDMS/collagen composite obtained by plasma treatment exhibited higher peel strength.
Direct chemical bonding of biomolecules to the surface of chemically inert polymers such as polydimethylsiloxane (PDMS) is not easily achieved. Therefore, pre-activation of such materials, followed by attachment of the biomolecule is necessary.
This paper describes a procedure to functionalize a PDMS surface by oxygen-based plasma followed by the adhesion of collagen type I for the preparation of adhesive-free bilayer composite intended as skin substitute. Plasma treatments between 40 and 120W for 5 to 15min were used and the extent of surface modification was followed by contact angle, Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM) and adhesion test. It was found that as the plasma power and time were increased, PDMS contact angle decreased while surface roughness increased as revealed by SEM and AFM. The formation of oxygen-containing functional groups at the surface was detected by FTIR. T-peel tests, performed on PDMS treated at 80W/13min and covered with collagen showed maximum peel strength of 0.1N/mm which was 3 times higher than that measured for the untreated bilayer composite. The observed enhancement in the adhesion strength was attributed to the increased mechanical interlocking driven by the increased roughness and the formation of hydrophilic functional groups.
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•Electrospun PCL nanofibers were superficially modified by air plasma treatment.•Effect of power level and discharge times on physicochemical properties was studied.•Surface changes ...were followed by FTIR, EDX, XPS, SEM, AFM, contact angle and o-TBO.•Carboxyl groups measured by XPS were correlated with those obtained by TBO analysis.
Polycaprolactone (PCL) is a biocompatible polymer approved by the FDA for using in medical devices but it is generally considered as hydrophobic material. In order to improve this drawback, electrospun PCL microfibers were superficially modified by air plasma treatments at three power levels (10, 20, 30W) and three discharge times (1, 3, 5min). The changes undergone by the microfibers were followed using spectroscopic and microscopic techniques such as Fourier Transform Infrared Spectroscopy (FTIR), Energy-dispersive X-ray spectroscopy (EDX), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM); contact angle and surface energy were also determined and the concentration of carboxylic groups was estimated by means of the o-toluidine blue method (TBO). SEM and AFM images demonstrated that the electrospun microfibers did not suffer morphological or topographical changes after the treatment. The contact angle in water diminished, whereas with diiodomethane, it increased after air plasma treatment. FTIR spectra did not show evidence that the plasma treatment modified the surface chemical composition of the microfibers, although the results from EDX and XPS showed an increase in oxygen–containing species and in the O/C ratio after treatment. Deconvolution of the O1s signals in the XPS spectra demonstrated that the carboxylic groups (COOH) increase with treatment time, which was confirmed and quantified with the TBO method. The percentage of the COOH groups measure by XPS was correlated with the concentration obtained in the TBO analysis.
The aim of this study was to gain some fundamental knowledge on the thermal degradation pathways of poly(
N
-vinyl pyrrolidone) using Thermogravimetry coupled with Fourier Transform Infrared ...Spectroscopy (TG–FTIR) in addition to IR and
1
H NMR spectroscopic studies of the partially degraded samples. It was found that the vinyl pyrrolidone is the main volatile products of the thermal degradation of PVP which implies that the predominant mechanism during thermal degradation of this polymer is the depolymerization to monomer of the polymeric main chain; however, it is evident that simultaneous reactions may be involved yielding oligomers. FTIR and
1
H NMR spectra of partially degraded samples of PVP exhibited very similar characteristics to that observed for undegraded samples although the
1
H NMR spectra suggest the presence of simultaneous reactions as the fragmentation of polymeric main chain.
Intestinal bacteria are an important indicator of the health of their host. Incorporating periodic assessment of the taxonomic composition of these microorganisms into management and conservation ...plans can be a valuable tool to detect changes that may jeopardize the survival of threatened populations. Here we describe the diversity and abundance of fecal bacteria for the black–tailed prairie dog (Cynomys ludovicianus), a threatened species, in the Janos Biosphere Reserve, Chihuahua, Mexico. We analyzed fecal samples through next generation massive sequencing and amplified the V3–V4 region of the 16S rRNA gene using Illumina technology. The results were analyzed with QIIME based on the EzBioCloud reference. We identified 12 phyla, 22 classes, 33 orders, 54 families and 263 genera. The phyla Firmicutes and Bacteroidetes were the most abundant groups and are associated with healthy intestinal communities and high efficiency in the energy diet. Most of the bacterial genera reported here for C. ludovicianus are not pathogenic and are normally found in mammalian feces. Some of the other bacteria are associated with soil, water and plants, possibly in relation to the habitat of the black– tailed prairie dog. This is the first study to report the fecal bacteria of C. ludovicianus in Mexico and it provides a baseline for determining this species' health for use in long–term conservation strategies.
Splanchnic venous thrombosis refers to the obstructive events of the abdominal venous system (portal, splenic, mesenteric, and suprahepatic) present with or without an underlying liver disease. These ...are rare disorders generally associated with both local risk factors, such as intra-abdominal infections, surgery or abdominal trauma, and systemic risk factors, represented by drugs (notably estrogen therapy) and some types of inherited or acquired thrombophilia, including myeloproliferative neoplasms associated with the V617F mutation of the JAK2 gene. The clinical presentation is heterogeneous, ranging from asymptomatic patients with incidental findings on abdominopelvic imaging to severe systemic compromise in sudden onset cases, with a high morbidity and mortality burden. Anticoagulation therapy is the current recommended treatment based on observational studies, with no consensus on management in the acute and long-term setting for both inmediate complications such as acute liver failure and intestinal ischemia or those arising from secondary portal hypertension over a longer period of time.
Bovine pericardium is a collagenous tissue commonly used as a natural biomaterial in the fabrication of cardiovascular devices. For tissue engineering purposes, this xenogeneic biomaterial must be ...decellularized to remove cellular antigens. With this in mind, three decellularization protocols were compared in terms of their effectiveness to extract cellular materials, their effect on glycosaminoglycan (GAG) content and, finally, their effect on tensile biomechanical behavior. The tissue decellularization was achieved by treatment with t-octyl phenoxy polyethoxy ethanol (Triton X-100), tridecyl polyethoxy ethanol (ATE) and alkaline treatment and subsequent treatment with nucleases (DNase/RNase). The quantified residual DNA content (3.0±0.4%, 4.4±0.6% and 5.6±0.7% for Triton X-100, ATE and alkaline treatment, respectively) and the absence of nuclear structures (hematoxylin and eosin staining) were indicators of effective cell removal. In the same way, it was found that the native tissue GAG content decreased to 61.6±0.6%, 62.7±1.1% and 88.6±0.2% for Triton X-100, ATE and alkaline treatment, respectively. In addition, an alteration in the tissue stress relaxation characteristics was observed after alkaline treatment. We can conclude that the three decellularization agents preserved the collagen structural network, anisotropy and the tensile modulus, tensile strength and maximum strain at failure of native tissue.
Molecular weight of isotactic polypropylene (iPP) and concentration of multi-walled carbon nanotubes (MWCNT) effects on the morphology, thermal stability, and electrical conductivity for iPP/MWCNT ...nanocomposites were evaluated. Nanocomposites were prepared by solution mixing followed by non-isothermal crystallization from the melt. The samples were characterized by different physical-chemical techniques. Electrical conductivity was obtained from electrical resistance measured using a source meter. It was determined that the morphology of the nanocomposites shows a change from spherulitic to fibrillar to undefined depending on the molecular weight of iPP and concentration of MWCNT. Morphology was correlated with thermal stability and electrical conductivity.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Nanocomposites prepared with segmented polyurethane (SPU) and commercially available nanoclays (Cloisite™ Na
+, Cloisite™ 15A, Cloisite™ 30B) were studied using thermogravimetric analysis coupled ...with Fourier Transform Infrared Spectroscopy (TGA/FTIR). The results showed that the thermal degradation of unfilled SPU and the 4, 6 and 10
wt% hand mixed nanocomposites occurred in two stages being the first due to degradation of hard segments and the second due to the degradation of soft segments. It was also found that the thermal stability of these nanocomposites was not improved by increasing nanoclay concentration except for SPU/Cloisite™ 15A nanocomposites were a 40
°C increase was observed. In a similar manner, FTIR spectra of the evolved gases obtained after the thermal degradation of these nanocomposites were qualitatively similar to the unfilled polymer except in those containing Cloisite™ 30B where isocyanate absorptions were detected. In contrast, SPU/Cloisite™ 30B nanocomposites prepared by
in-situ polymerization, exhibited higher thermal stability than the corresponding hand mixed nanocomposites. In addition, these nanocomposites exhibited the presence of carbon dioxide in the evolved gases during its second degradation stage which was not observed in the hand mixed nanocomposites. In this case, it can be said that the presence of clays in the nanocomposites has a significant effect on the thermal degradation pathways.
Structural and morphological properties of hydronium-potassium jarosite microstructures were investigated in this work, and their electrical properties were evaluated. All the microstructures were ...synthesized at a very low temperature of 70 °C with a reduced reaction time of 3 h. An increase in the pH from 0.8 to 2.1 decreased the particle sizes from 3 µm to 200 nm and an increase in the aging time from zero, three, and seven days resulted in semispherical, spherical, and euhedral jarosite structures, respectively. The Rietveld analysis also confirmed that the amount of hydronium substitution by potassium in the cationic site increased with an increase in pH. The percentages of hydronium jarosite (JH)/potassium jarosite (JK) for pH values of 0.8, 1.1, and 2.1 were 77.72/22.29%, 82.44/17.56%, and 89.98/10.02%, respectively. Microstructures obtained in this work were tested as alternative anode materials and the voltage measured using these electrodes made with hydronium-potassium jarosite microstructures and graphite ranged from 0.89 to 1.36 V. The results obtained in this work show that with reduced particle size and euhedral morphology obtained, modified jarosite microstructures can be used as anode materials for improving the lifetime of lithium-ion batteries.
Nowadays, the stability of antioxidant and color characteristics of minimally processed avocado puree during the storage is still unknown. Thus, this study aimed to evaluate the effect of adding ...natural extracts on the antioxidant capacity, color and consumer acceptance of avocado purees. Avocado pulp (
x
1
: 90–100%) was mixed with lemon (
x
2
: 0–10%) and onion (
x
3
: 0–5%) extracts following a constrained mixture design. Total phenolic compounds, reducing power, antioxidant capacity, color and consumer acceptance were measured at the beginning and after seven days of storage (4 °C). At the beginning of the storage, both reducing power and antioxidant capacity were affected by the proposed formulations, showing their maximum values (710 ± 9.0 mg AAE/100 g and 170.4 ± 8.6 Trolox/100 g, respectively) with the highest lemon extract level. Tested formulations did not exhibit a significant color difference among them (
p
> 0.05), showing values of
L
* = 70.1 ± 2.3,
a
* = − 21.7 ± 2.0 and
b
* = 52.1 ± 4.2. Reducing power was significantly affected after storage (
p
< 0.05). Moreover, a browning process was detected in all formulations, with a lesser effect on avocado puree formulated with 90, 5 and 5% and 90, 7.5 and 2.5% of
x
1
,
x
2
, and
x
3
, respectively, showing a total color change between 18.1 and 23.5 with respect to their initial state. The formulation
x
1
: 90%
x
2
: 7.5%, and
x
3
: 2.5% was the best accepted by the consumers at the beginning and end of the storage. The mixture design is an adequate tool for obtaining a natural avocado puree with high antioxidant properties and sensory acceptance.
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