Magnesium alloys have been investigated by many researchers as a new absorbable biomaterial owing to their excellent degradability with non-maleficence or low-maleficence in living tissues. In the present work, the in vitro cytocompatibility of an Magnesium alloy was investigated by culturing cells directly on it. Investigations were carried out in terms of the cell viability along with the use of scanning electron microscopy to observe its morphology. The cell lines used were derived from fibroblast, endothelial, and smooth muscle cells. Pure magnesium and AZ31 alloy composed of magnesium (96 %), aluminum (3 %), and zinc (1 %) were adopted as models. The viability of cells on the metal samples and on the margin area of a multi-well plate was investigated. For direct culturing on metal, a depression in the viability and morphologically stressed cells were observed. In addition, the cell viability was also depressed for the margin area. To clarify the factors causing the negative effects, the amount of eluted metal ions and pH changes in the medium because of the erosion of the Magnesium samples were investigated, together with the cytotoxicity of sole metal ions corresponding to the composition of the metals. It was found that Mg(2+), Zn(2+), and Al(3+) ions were less toxic at the investigated concentrations, and that these factors will not produce negative effects on cells. Consequently, these factors cannot fully explain the results.

Th1 and Th2 cells, which were induced from naive T cells of TCR-transgenic mice, showed differential sensitivity to activation-induced cell death (AICD) triggered by stimulation with anti-CD3 monoclonal antibody. The Th1 cells showed more rapid AICD than Th2 cells. This accelerated AICD of Th1 cells was strongly blocked by protein kinase C (PKC) inhibitors (H-7 or GF 109203X). Moreover, long-term treatment of Th1 cells with phorbol 12-myristate 13-acetate (PMA) caused the abrogation of anti-CD3-induced AICD in parallel with the disappearance of PMA-sensitive PKC isoforms such as PKC alpha, gamma, epsilon and theta. Therefore, it was clearly demonstrated that PMA-sensitive PKC isoforms are essential for AICD of Th1 cells. The different susceptibility to AICD between Th1 and Th2 cells was not due to their differential expression levels of PMA-sensitive PKC isoforms but appeared to be due to their differential requirement for PMA-sensitive isoforms in the up-regulation of Fas ligand which is involved in suicide killing of activated Th1 cells.

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Poly(2-methoxyethyl acrylate) is known to exhibit good blood compatibility. This study was designed to understand the effect of methoxyethyl ester groups on the platelet compatibility of polymers. Polymers bearing either methoxyethyl ester or methyl ester groups, such as poly(acrylate)s, poly(methacrylate)s, and poly(vinyl benzoate)s, were prepared and a comparative study of the ester groups was performed. Polymers bearing methoxyethyl ester groups and poly(methyl acrylate) exhibited good and approximately equal platelet compatibility, regardless of their chemical structure, as estimated using flow cytometry and scanning electron microscopy. To understand these results, the static properties (namely, surface wettability by contact angle and water structure by differential scanning calorimetry) and a dynamic property (13 C-NMR relaxation time of the functional groups) were analyzed. The results showed that platelet compatibility could be interpreted from the water structure and dynamic property.

It is well known that polyether-based copolymers have good blood compatibility, although many mechanisms have been proposed to explain their favorable performance. Our objective in carrying out the present study was to obtain a better understanding of the effect of the (poly)ether segment on blood compatibility. Therefore, we synthesized poly(propylene glycol) (PPG)-based initiators for atom transfer polymerization, where the number of propylene glycol (PG) units in the PPG (Pn(PG) was varied from 1 to 94. Methyl methacrylate (MMA) was polymerized using the initiators, resulting in the formation of polyMMAs with a PG-based ether part at the polymer terminal. We mainly investigated the effects of Pn(PG) on the surface properties and platelet compatibility of the PPG-polyMMA. X-ray photoelectron spectroscopy and surface contact angle (CA) analysis revealed the exposure of the PG units at the surface of the polymer. The platelet compatibility of the polymers was improved compared with a commercial polyMMA, even when Pn(PG) = 1. These results suggest that PG units have an important influence on favorable blood compatibility, regardless of the Pn(PG) value. We also investigated protein adsorption behavior in terms of the amount and deformation of fibrinogen adsorbed on the polymer surface.

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Metals and metal alloys are widely used in medical devices that contact blood and/or tissue, and various coating materials for the metal parts have been proposed to improve surface properties such as biocompatibility. This study aims to understand the performance of new coating materials, copolymers of methyl acrylate and acrylic acid, in terms of their biocompatibility and adhesive strength to a metal surface. Blood compatibility was investigated through platelet and coagulation system responses. Cytocompatibility was studied in three cell-line types (endothelium, smooth muscle, and fibroblasts) in terms of cell viability and morphology; these tests showed that compatibility depended on the cell types and acrylic acid content of the copolymers. Because of their blood compatibility and adhesion strength, the methyl acrylate and acrylic acid copolymers containing 10–24 mol% acrylic acid were found to be excellent candidates as potential coating materials for devices contacting blood.