Water structure of poly(2-methoxyethyl acrylate) observed by nuclear magnetic resonance spectroscopy.

Poly(2-methoxyethyl acrylate) (PMEA) is known to show excellent blood compatibility. The performance of PMEA has been attributed to the existence of cold-crystallizable water in it, as observed using differential scanning calorimetry (DSC). However, little is known on the property of the water in PMEA above 0 °C, especially at ambient temperature including the body temperature, because blood compatibility is observed at 37 °C. The present study was performed to clarify the state of water in PMEA in the temperature range 15-45 °C using solution nuclear magnetic resonance spectroscopy (NMR). In addition, water in poly(butyl acrylate) (PBA), which exhibited poor blood compatibility, was used as a control. In the NMR spectra of water in PMEA, two peaks appeared at 4.87 ppm and 3.71 ppm at 30 °C, showing the existence of two types of water structures. The peak intensity of the upfield water was considerably higher than that of the downfield water. On the other hand, the hydrated PBA showed only one peak at 4.98 ppm at 30 °C. The dynamic property of water in these polymers was estimated from the deuterium solution NMR spin-lattice relaxation time, T12H. The T12H values of peaks observed at 4-5 ppm were relatively high, denoting rapid motion, while those of water at 3.7 ppm in PMEA were small, denoting slow mobility. Thus, the states of water molecules in PMEA in terms of chemical shift and mobility were considered different from those in PBA at ambient temperature.

Platelet compatibility of magnesium alloys.

Lately, Mg alloys have been investigated as a new class of biomaterials owing to their excellent biodegradability and biocompatibility. It has previously been reported that the in vitro compatibility of a Mg alloy containing aluminum and zinc (AZ) alloy with the blood coagulation system is excellent due to Mg2+ ions eluting from the alloy. In this study, the compatibility of the AZ alloy with platelets was evaluated by scanning electron microscopy (SEM) and flow cytometry. In the flow cytometry analysis, the platelets were stained using PAC-1 and P-selectin antibodies. SEM images and PAC-1 analyses showed no negative effects on the platelets, whereas P-selectin analysis showed marked platelet activation. To understand these contradictory results, the amount of ß-thromboglobulin (ß-TG) released from the platelets was investigated. From that investigation, it was concluded that platelets are markedly activated by the alloys. In addition to clarifying divergent results depending on the analysis method used, the effects of Mg2+ ions and pH on platelet activation were studied. These results show that platelet activation is caused by an increase in pH at the alloy surface owing to the erosion of the alloy.

Effect of end segment on physicochemical properties and platelet compatibility of poly(propylene glycol)-initiated poly(methyl methacrylate).

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.

Cytocompatibility of magnesium and AZ31 alloy with three types of cell lines using a direct in vitro method.

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.