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Dextran hydrogels were formed in situ by enzymatic crosslinking of dextran-tyramine conjugates (dex-TA)s using horseradish peroxidase (HRP) and hydrogen peroxide (H2O2). Depending on the molecular weight (Mn) of dextran and the degree of substitution (DS) of dextran with tyramine groups, the gelation time varied from about 20 s to a few minutes. Hydrogels prepared from dex-TA (Mn = 3.1 × 104 g/mol) with a DS of 10 had storage moduli up to 60 kPa. Moreover, hydrogels in which chondrocytes were encapsulated had moduli comparable to those without cells. The H2O2/TA mole ratio applied for the preparation of the hydrogels influenced the cell viability of chondrocytes cultured in the hydrogels. A live-dead assay revealed that almost all chondrocytes retained their viability when cultured in hydrogels prepared with a relatively low H2O2/TA mo...
Polysaccharide hybrids consisting of hyaluronic acid (HA) grafted with a dextran–tyramine conjugate (Dex–TA) were synthesized and investigated as injectable biomimetic hydrogels for cartilage tissue engineering. The design of these hybrids (denoted as HA-g-Dex–TA) is based on the molecular structure of proteoglycans present in the extracellular matrix of native cartilage. Hydrogels of HA-g-Dex–TA were rapidly formed within 2 min via enzymatic crosslinking of the tyramine residues in the presence of horseradish peroxidase and hydrogen peroxide. The gelation time, equilibrium swelling and storage modulus could be adjusted by varying the degree of substitution of tyramine residues and polymer concentration. Bovine chondrocytes incorporated in the HA-g-Dex–TA hydrogels remained viable, as shown by the Live–dead assay. Moreover, enhanced ch...
Clusters based on the mixed-valence gigantic inorganic ring [Mo154O462H14(H2O)(70)](14-) ({Mo-154}-ring) and dimethyldioctadecylammonium (DODA) were combined to form novel molecular assemblies of an inorganic-organic hybrid molecular system as Langmuir-Blodgett (LB) and cast films. (DODA)(20)[MO154O462H8(H2O)(70)] (2) was prepared by cation exchange and was characterized by a combination of thermogravimetry, IR, UV-vis-NIR, H-1 NMR, and XRD measurements. The salt 2 was soluble in common organic solvents, and the chemical stability Of {Mo-154}-ring encapsulated by DODA cationic surfactants in CHCl3 was found to be higher than that of the "native" sodium salt of the {Mo-154}-ring in H2O. Uniform spherical vesicle-like molecular assemblies of (DODA)(20)[Mo154O462H8(H2O)(70)] were observed in dilute THF, whose average diameter of 95 nm and...
We report synthesis and single crystal measurements of magnetic, transport and thermal properties of single crystalline BaCo$_2$As$_2$ as well as first principles calculations of the electronic structure and magnetic behavior. These results show that BaCo$_2$As$_2$ is a highly renormalized paramagnet in proximity to a quantum critical point, presumably of ferromagnetic character and that BaFeNiAs$_2$ behaves similarly. These results are discussed in relation to the properties of Ba(Fe,Co)$_2$As$_2$ and Ba(Fe,Ni)$_2$As$_2$, which are superconducting for low Co and Ni concentrations.
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