Novel ultra-high molecular weight polyethylene (UHMWPE)/zirconia composites were previously prepared by the in situ polymerization of ethylene using a Ti-based Ziegler-Natta catalyst supported on to the surface of zirconia, as a bearing material for artificial joints. Tribological tests revealed that a uniform dispersion of zirconia in UHMWPE markedly increased the wear resistance. The effects of zirconia content on the oxidation behavior of the γ-ray-treated UHMWPE/zirconia composite surfaces were examined. The oxidation index that estimates the oxidation degree as the content of total carbonyl compounds was monitored using Fourier transform infrared spectroscopy-attenuated total reflectance. The changes in the surface composition due to the oxidation were confirmed by electron spectroscopy for chemical analysis. The extent of oxidation decreased with increasing zirconia content, which was attributed to the increased crystallinity as well as the decreased polymer portion of the UHMWPE/zirconia composites.
The present study demonstrated that covalently galactosylated poly(D,L-lactic-co-glycolic acid) (PLGA) surface encourages hepatocyte adhesion and growth to form a dense cell network. Galactosylation of the PLGA surface was accomplished by grafting allylamine (AA) using inductively coupled plasma-assisted chemical vapor deposition (ICP-CVD) and conjugating lactobionic acid (LA) with AA via 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide (EDC/NHS) activation. The modified surface was characterized by Fourier transform infrared spectroscopy in the attenuated total reflectance, electron spectroscopy of chemical analysis, atomic force microscopy, and contact angle measurement. For evaluation of cell affinity in vitro, primary rat hepatocytes were prepared and seeded onto the modified PLGA surfaces. The galactosylated PLGA surface showed more pronounced hepatocyte adhesion and growth compared to those on the control PLGA surface. The hepatocytes seeded on galactosylated substrates exhibited a radial migration with filopodial growth to form multicellular aggregates, whereas those on control PLGA showed slowly adhered rounded shapes. Moreover, galactosylation increased metabolic hepatocyte activities such as albumin secretion and urea synthesis.
The mixtures of non-conjugated dienes, 4-methyl-1,4-hexadiene and 5-methyl-1,4-hexadiene (MHD), were successfully synthesized by the reaction of isoprene with ethylene using Fe(III)-based catalyst in toluene. The conversion was over 96 mol% on the basis of the initial amount of isoprene used. The production yield for MHD was nearly 50 mol%, the other was polyisoprene. The mixtures were successfully copolymerized with ethylene by using zirconium-based metallocenes. The products were characterized by the combinations of gas chromatography, high temperature gel permeation chromatography, 1 H NMR, 13 C NMR, high temperature 1 H NMR, UV/Visible spectroscopy, and differential scanning calorimetry. It was found that 5-methyl-1,4-hexadiene was active enough to be incorporated into the copolymer chain but the corresponding isomeric material, 4-methyl-1,4-hexadiene, was inactive in metallocene-catalyzed copolymerizations. Specifically, in the zirconocene-catalyzed copolymerizations of ethylene with MHD, ansa-structure catalysts seem to be more efficient than non-bridged type zirconocene. The degree of incorporation of MHD in the resulting copolymers was able to be controlled by the amount of non-conjugated dienes used initially.
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