Effect of PEG grafting density on surface properties of polyurethane substrata and the viability of osteoblast and fibroblast cells.

The surface of Tecoflex SG-80A Polyurethane (PU) films was modified by grafting polyethylene glycol (PEG) chains at three different molar amounts (0.05, 0.10, and 0.15 mmol). The resulting substrata were characterized by FTIR-ATR, TGA, AFM, SEM and contact angle to assess the surface modifications occurred during the grafting reactions. Osteoblasts and fibroblasts were cultured with PU extracts for 24 h, and their cell viability and morphology were evaluated by CellTiterBlue assay, Crystal Violet staining and Live/Dead assay. FTIR and TGA results indicated that PEG chains were successfully grafted onto PU surfaces, specifically in the hard segment of PU forming allophanate groups as the PEG grafting density increased. SEM and AFM images suggest that PU substrata were partially covered by PEG, increasing the dispersive and basic components of the PU surface energy. It was found that extracts from PEG-grafted polyurethanes increased the osteoblast viability, although fibroblasts viability remained constant regardless PEG grafting density; in spite of this both cells presented a more spread morphology at the lower PEG grafting density. Our results showed that surface energy of PU substrata can be tuned by PEG grafting density; also, the PEG leached tends to increase the pH of culture medium which leads to a higher viability of osteoblasts; nevertheless, PEG grafting density should be optimized to promote a healthy cell morphology as alterations in its morphology were detected at higher concentrations. Graphical abstract.

Synthesis and characterization of pH sensitive hydrogel nanoparticles based on poly(N-isopropyl acrylamide-co-methacrylic acid).

In this work, pH-sensitive hydrogel nanoparticles based on N-isopropyl acrylamide (NIPAM) and methacrylic acid (MAA) at various molar ratios, were synthesized and characterized in terms of physicochemical and biological properties. FTIR and 1HNMR spectra confirmed the successful synthesis of the copolymer that formed nanoparticles. AFM images and FE-SEM micrographs showed that nanoparticles were spherical, but their round-shape was slightly compromised with MAA content; besides, the size of particles tends to decrease as MAA content increased. The hydrogels nanoparticles also exhibited an interesting pH-sensitivity, displaying changes in its particle size when changes in pH media occurred. Biological characterization results indicate that all the synthesized particles are non-cytotoxic to endothelial cells and hemocompatible, although an increase of MAA content leads to a slight increase in the hemolysis percentage. Therefore, the pH-sensitivity hydrogels may serve as a versatile platform as self-regulated drug delivery systems in response to environmental pH changes.

Physicochemical characterization of several types of naturally colored cotton fibers from Peru.

Elemental composition, physical dimensions (length and apparent diameter), and crystallinity of different types of naturally colored cotton (NCCs) fibers from Peru were investigated using a CHNS organic elemental analyzer, optical microscopy and X-Ray Diffraction (XRD). Spectroscopic studies involving Fourier Transform Infrared Spectroscopy and X-Ray photoelectron spectroscopy (XPS) were conducted; and the thermal stability of cotton samples were also investigated. Results from organic elemental analyzer and XPS showed that cotton samples contain mainly carbon, oxygen and hydrogen, but darker color samples also presented nitrogen. It was also found that the white cotton sample exhibited the longest fibers whereas the darker color samples showed the shortest values in length. Interestingly, the crystallinity seems also decrease with color intensity of NCCs. Finally, the thermal stability of white cotton fibers was similar to those obtained for the NCCs.

Biosynthesis and characterization of polyhydroxyalkanoates produced by an extreme halophilic bacterium, Halomonas nitroreducens, isolated from hypersaline ponds.

AIMS: Morphological, biochemical and genotypic characterization of a halophilic bacterium isolated from hypersaline ponds located at Las Coloradas (Río Lagartos, Yucatán, Mexico). Characterization of polymer produced by this strain was also performed. METHODS AND RESULTS: Twenty strains were isolated from water samples of salt ponds and selected based on both morphological features and their PHA storage capacity, which were determined by SEM and staining methods with Nile red and Nile blue, respectively; strains were also analysed by the fluorescence imaging technique. Among them, JCCOL25.8 strain showed the highest production of PHA's reason why phenotypic and genotypic characterization was performed; this strain was identified as Halomonas nitroreducens. Polymer produced by this strain was characterized by FTIR, DSC, GPC and EDX spectroscopy. Results indicated that the biosynthesized polymer was polyhydroxybutyrate (PHB) which had a melting peak at 170°C and a crystallinity percentage of about 36%. CONCLUSIONS: Based on phenotypic and genotypic aspects, JCCOL25.8 strain was identified as H. nitroreducens and it was capable to accumulate PHB. SIGNIFICANCE AND IMPACT OF THE STUDY: To our knowledge, there is only one study published on the biosynthesis of PHA's by H. nitroreducens strains, although the characterization of the obtained polymer was not reported.

Synthesis and characterization of core-shell nanoparticles and their influence on the mechanical behavior of acrylic bone cements.

Core-shell nanoparticles consisting of polybutyl acrylate (PBA) rubbery core and a polymethyl methacrylate (PMMA) shell, with different core-shell ratios, were synthesized in order to enhance the fracture toughness of the acrylic bone cements prepared with them. It was observed by TEM and SEM that the core-shell nanoparticles exhibited a spherical morphology with ca. 120 nm in diameter and that both modulus and tensile strength decreased by increasing the PBA content; the desired structuring pattern in the synthesized particles was confirmed by DMA. Also, experimental bone cements were prepared with variable amounts (0, 5, 10 and 20 wt.%) of nanoparticles with a core-shell ratio of 30/70 in order to study the influence of these nanostructured particles on the physicochemical, mechanical and fracture properties of bone cements. It was found that the addition of nanostructured particles to bone cements caused a significant reduction in the peak temperature and setting time while the glass transition temperature (Tg) of cements increased with increasing particles content. On the other hand, modulus and strength of bone cements decreased when particles were incorporated but fracture toughness was increased.