Search

Tissue engineering is based on the association of cultured cells with structural matrices and the incorporation of signaling molecules for inducing tissue regeneration. Despite its enormous potential, tissue engineering faces a major challenge concerning the maintenance of cell viability after the implantation of the constructs. The lack of a functional vasculature within the implant compromises the delivery of nutrients to and removal of metabolites from the cells, which can lead to implant failure. In this sense, our investigation aims to develop a new strategy for enhancing vascularization in tissue engineering constructs. This study's aim was to establish a culture of human adipose tissue-derived stem cells (hASCs) to evaluate the biocompatibility of electrospun fiber mesh made of polyhydroxybutyrate (PHB) and its copolymer poly-3- hydroxybutyrate-co-3-hydroxyvalerate (PHB-HV) and to promote the differentiation of hASCs into the endothelial lineage. Fiber mesh was produced by blending 30% PHB with 70% PHB-HV and its physical characterization was conducted using scanning electron microscopy analysis (SEM). Using electrospinning, fiber mesh was obtained with diameters ranging 300 nm to 1.3 μm. To assess the biological performance, hASCs were extracted, cultured, characterized by flow cytometry, expanded and seeded onto electrospun PHB/PHB-HV fiber mesh. Various aspects of the cells were analyzed in vitro using SEM, MTT assay and Calcein-AM staining. The in vitro evaluation demonstrated good adhesion and a normal morphology of the hASCs. After 7, 14 and 21 days of seeding hASCs onto electrospun PHB/PHB-HV fiber mesh, the cells remained viable and proliferative. Moreover, when cultured with endothelial differentiation medium (i.e., medium containing VEGF and bFGF), the hASCs expressed endothelial markers such as VE-Cadherin and the vWF factor. Therefore, the electrospun PHB/ PHB-HV fiber mesh appears to be a suitable material that can be used in combination with endothelial-differentiated cells to improve vascularization in engineered bone tissues. [ABSTRACT FROM AUTHOR]

Abstract: The radiation-induced graft polymerization of hydrophilic [sodium p-styrene sulfonate (SSS), acrylic acid (AAc)] and hydrophobic [styrene (St), methyl acrylate (MAAc)] monomers onto microbial poly(3-hydroxybutyrate) (PHB) powder was performed and the characteristics of the both grafting films obtained after remolding were compared. The grafting of various monomers onto the PHB powder increased with reaction time. The degree of grafting (X g) onto the PHB by these various monomers followed the order St, SSS, MAAc and AAc. The PHB films onto which were grafted St, SSS, MAAc and AAc were characterized by measuring the contact angle, the adsorption of enzyme PHB depolymerase, and the biodegradability, as well as by differential scanning calorimetry. Both hydrophobic and hydrophilic monomers affected the contact angle of grafted PHB film with St, SSS, MAAc and AAc monomers. However, the adsorption of enzyme on the grafted PHB film increased with the amount of hydrophilic monomer and degree of grafting. Consequently, the enzyme PHB depolymerase easily approached the PHB film when the hydrophilic groups were grafted onto its surface. The enzymatic degradation of grafted PHB films with hydrophilic monomer proceeded more quickly than that of hydrophobic monomers. [Copyright &y& Elsevier]

Composite gels based on polyacrylamide and poly(N-isopropyl acrylamide) with incorporated sodium bentonite particles are synthesized. It is shown that the presence of hydrophobic isopropyl groups in a polymer molecule promotes the subsequent formation of highly ordered aggregates of clay and cetylpyridinium chloride in a gel composite. An increase in temperature results in the collapse of composite gels based on poly(N-isopropyl acrylamide); however, no marked changes in the structure of lamellar aggregates of clay and surfactant are observed. It is revealed that the gel can stabilize lamellar structures formed in organoclay suspension prior to the incorporation into swollen polymer network. [ABSTRACT FROM AUTHOR]

Abstract  A new salicylate-selective electrode based on the complex (2,3;6,7;10,11;14,15-tetraphenyl-4,9,13,16-tetraoxo-1,5,8,12-tetraazacyclohexadecane) copper(II) [CuL] as the membrane carrier was developed. The electrode exhibits a good Nernstian slope of −60.9 ± 1.0 mV/decade and a linear range from 1.0 × 10−6 to 1.0 × 10−1 M for salicylate. The detection limit is 5.0 × 10−7 M. The electrode has a fast response time (5–15 s) and can be used for more than three months. The selective coefficients were determined by the fixed interference method (FIM) and separate solution method (SSM). The salicylate-selective electrode could be used in the pH range 3.5–10.5. It was employed as an indicator electrode for direct determination of salicylate in pharmaceutical samples. [ABSTRACT FROM AUTHOR]

Abstract  New silicon-containing poly(salicylidene azomethines) were prepared by polycondensation of di-or tetrasalicylidene derivatives of aromatic di- or tetraamines. The spectral data suggest the occurrence of noncovalent transannular donor-acceptor interaction N→Si providing “nonclassical” conjugation. [ABSTRACT FROM AUTHOR]

Abstract: The cellular adhesion and motility have direct implications in the tumoral-metastatic cells development or in the tissue engineering mechanisms for instance. Our work aims at knowing the impact of substrate mechanical properties on those adhesion and motility mechanisms by modifying bulk rigidity, surface energy and composition of a bio-compatible poly-di-methyl-siloxane (PDMS) substrate. We show how a wide range of PDMS rigidity can be obtained and how Ar/O2-based plasmas turn PDMS surface to hydrophilic. A correlation between surface energy, bulk rigidity, cells adhesion and growth is finally shown. [Copyright &y& Elsevier]

Abstract: Well-controlled methods of nanopattern definition in SiO2 and Si have been developed: Lateral Pattern Definition technique in SiO2 (LPD) and Pattern Definition by Edge Oxidation technique, suitable for mono-Si and poly-Si paths (PADEOX). SEM examinations of the patterns of width of several tens of nm have been presented. Dependence of width of the pattern on parameters of the process has been discussed. Application of the PADEOX technique in FinFET technology has been described. [Copyright &y& Elsevier]

Cells sustain high rates of actin filament elongation by maintaining a large pool of actin monomers above the critical concentration for polymerization. Profilin–actin complexes constitute the largest fraction of polymerization-competent actin monomers. Filament elongation factors such as Ena/VASP and formin catalyze the transition of profilin–actin from the cellular pool onto the barbed end of growing filaments. The molecular bases of this process are poorly understood. Here we present structural and energetic evidence for two consecutive steps of the elongation mechanism: the recruitment of profilin–actin by the last poly-Pro segment of vasodilator-stimulated phosphoprotein (VASP) and the binding of profilin–actin simultaneously to this poly-Pro and to the G-actin-binding (GAB) domain of VASP. The actin monomer bound at the GAB domain is proposed to be in position to join the barbed end of the growing filament concurrently with the release of profilin. [ABSTRACT FROM AUTHOR]

The effect of the molecular mass of poly(ethylene oxide) (PEO) on lignin-PEO blends was studied using thermal analysis and FT-IR. Differential scanning calorimetry (DSC) analysis revealed miscible blends over the entire blend ratio. A negative deviation in Tg from a simple weighted average was observed, indicating the existence of relatively weak favorable interactions between blend components. Analysis of the data revealed no difference in the magnitude or propensity of intermolecular interactions with increasing PEO molecular mass in the kraft lignin-PEO blends. By contrast, the fitting parameters obtained for organosolv lignin were substantially different; the higher molecular mass PEO had a higher propensity to form slightly stronger intermolecular inter-actions than the lower molecular mass PEO. Low molecular mass poly(ethylene glycol) dimethylether (M-PEG)-lignin blends had a much higher degree of crystallinity than the PEO blends, resulting in an increase in Tg at high PEG content. FT-IR analysis revealed the presence of strong intermolecular hydrogen bonding between lignin and PEO. However, the band shape of the OH region of the M-PEG blends was slightly different from the PEO blends; some of the original lignin inter- and intramolecular hydrogen bonding was still present in the M-PEG-lignin blends. [ABSTRACT FROM AUTHOR]

Abstract: Two kinds of poly(3-hexylthiophene) films with identical chemical compositions are prepared. One of the films is obtained by electropolymerization of 3-hexylthiophene (as-grown film) and the other is prepared by casting a solution dissolving the as-grown film (cast film). A clear difference is found in the mobility vs. doping level plots between the as-grown and cast films and its reason is discussed. [Copyright &y& Elsevier]

Double-stranded RNA (dsRNA) is produced upon viral infection and can activate innate immunity. Polyinosinic:polycytidylic acids [poly(I:C)] is a synthetic mimetic of dsRNA and functions through an endosomal receptor, Toll-like receptor (TLR) 3 or cytosolic receptors. Another type of dsRNA, polyadenylic:polyuridylic acids [poly(A:U)], can also act as an immune adjuvant, but it remains unclear how it exhibits its adjuvant effects. Here, we have characterized the adjuvant effects of poly(A:U). Poly(A:U) could induce both IFN-α and IL-12p40 from murine bone marrow dendritic cells (DCs). Poly(A:U)-induced IFN-α production depended on a DC subset, plasmacytoid dendritic cell (pDC), and required TLR7. IL-12p40 was also produced by poly(A:U)-stimulated pDC in a TLR7-dependent manner. In addition to pDC, conventional dendritic cell (cDC) also produced IL-12p40 in response to poly(A:U). This IL-12p40 induction resulted from two cDC subsets, CD24high cDC and CD11bhigh cDC in a TLR3- and TLR7-dependent manner, respectively. In vivo injection of poly(A:U) with antigen led to clonal expansion of and IFN-γ production from antigen-specific CD8+ T cells. Consistent with the in vitro findings, TLR3 and TLR7 were required for the clonal T-cell expansion. Notably, TLR3, rather than TLR7, was critical for generating IFN-γ-producing CD8+ T cells. CD8+ T-cell responses induced by poly(A:U) were independent of type I IFN signaling. Our results demonstrate that poly(A:U) functions as an in vivo immunoadjuvant mainly through TLR3 and TLR7. [ABSTRACT FROM AUTHOR]