Effect of hydroxy groups and microtopography generated by a nanosecond-pulsed laser on pure Ti surfaces.

In this paper, we study a process for modifying the surface microtopography of the Ti oxide layer using a nanosecond-pulsed laser (NPL). Even now, the mechanism by which hydroxyl groups are generated on the titanium surface treated by NPL is not clear. Hence, we evaluated the surface properties of the NPL defocus distances on pure titanium surfaces, and investigated the relationship between the generation of hydroxyapatites/cell viability and the titanium surface characteristics. The NPL defocus distance was varied from 0 to 4 mm. Defocus distances of 0 and 2 mm generated microtopographical features on the titanium surface, and the resulting surfaces exhibited a greater density of OH groups than the surface treated with a defocus distance of 4 mm. The surfaces treated using defocus distances of 0 and 2 mm were found to be coated with microspherical hydroxyapatite composed of coexisting plate- and needle-like crystals after immersion in simulated body fluid, and alkaline phosphatase activity assays indicated improved cell compatibility. The improvements in biocompatibility and cell compatibility were due to the pocket-like microtopographical structures formed along the processing trace. These pockets contained a large amount of OH groups, and promoted the growth of hydroxyapatite.

Phase behavior of medium and high internal phase water-in-oil emulsions stabilized solely by hydrophobized bacterial cellulose nanofibrils.

Water-in-oil emulsions stabilized solely by bacterial cellulose nanofibers (BCNs), which were hydrophobized by esterification with organic acids of various chain lengths (acetic acid, C2-; hexanoic acid, C6-; dodecanoic acid, C12-), were produced and characterized. When using freeze-dried C6-BCN and C12-BCN, only a maximum water volume fraction (ϕw) of 60% could be stabilized, while no emulsion was obtained for C2-BCN. However, the maximum ϕw increased to 71%, 81%, and 77% for C2-BCN, C6-BCN, and C12-BCN, respectively, 150 h after the initial emulsification, thereby creating high internal phase water-in-toluene emulsions. The observed time-dependent behavior of these emulsions is consistent with the disentanglement and dispersion of freeze-dried modified BCN bundles into individual nanofibers with time. These emulsions exhibited catastrophic phase separation when ϕw was increased, as opposed to catastrophic phase inversion observed for other Pickering emulsions.

Ion-Specific Modulation of Interfacial Interaction Potentials between Solid Substrates and Cell-Sized Particles Mediated via Zwitterionic, Super-Hydrophilic Poly(sulfobetaine) Brushes.

Zwitterionic polymer brushes draw increasing attention not only because of their superhydrophilic, self-cleaning capability but also due to their excellent antifouling capacity. We investigated the ion-specific modulation of the interfacial interaction potential via densely packed, uniform poly(sulfobetaine) brushes. The vertical Brownian motion of a cell-sized latex particle was monitored by microinterferometry, yielding the effective interfacial interaction potentials V(Δh) and the autocorrelation function of height fluctuation. The potential curvature V″(Δh) exhibited a monotonic increase according to the increase in monovalent salt concentrations, implying the sharpening of the potential confinement. An opposite tendency was observed in CaCl2 solutions, suggesting that the ion specific modulation cannot be explained by the classical Hofmeister series. When the particle fluctuation was monitored in the presence of free sulfobetaine molecules, the increase in [sulfobetaine] resulted in a distinct increase in hydrodynamic friction. This was never observed in all the other salt solutions, suggesting the interference of zwitterionic pairing of sulfobetaine side chains by the intercalation of sulfobetaine molecules into the brush layer. Furthermore, poly(sulfobetaine) brushes exhibited a very low V″(Δh) and hydrodynamic friction to human erythrocytes, which seems to explain the excellent blood repellency of zwitterionic polymer materials.

[Interlaboratory study on migration test of antimony and germanium for food-contact polyethylene terephthalate].

An interlaboratory study was performed to evaluate a migration test method of antimony (Sb) and germanium (Ge), based on the Japanese Food Sanitation Law for food- contact polyethylene terephthalate. Eighteen laboratories participated, and quantified Sb and Ge in three test solutions as blind duplicates using graphite furnace atomic absorption spectrometry (GF-AAS), inductively coupled plasma-optical emission spectrometry (ICP-OES) or induced coupled plasma-mass spectrometry (ICP-MS). Statistical analysis revealed that the trueness, repeatability and reproducibility were 98-107%, 1.7-7.5% and 2.0-18.8% by using GF-AAS and ICP-OES. The performance of these methods is sufficient for testing the specifications. The performance parameters of ICP-MS were 99-106%, 0.7-2.2% and 2.2-10.5%, respectively. ICP-MS is available as an alternative measuring method. However, in some laboratories, the quantitative values of Sb were higher than the addition levels. We found that Sb in working solutions is absorbed on glass vessels. Careful control of concentration in working solutions is required for Sb analysis.

[Performance comparison of material tests for cadmium and lead in food contact plastics].

Based on the Japanese Food Sanitation Law, the performances of official and alternative material test methods for cadmium (Cd) and lead (Pb) in food contact plastics were compared. Nineteen laboratories participated to an interlaboratory study, and quantified Cd and Pb in three PVC pellets. in the official method, a sample is digested with H2SO4, taken up in HCl, and evaporated to dryness on a water bath, then measured by atomic absorption spectrometry (AAS) or inductively coupled plasma-optical emission spectrometry (ICP-OES). Statistical treatment revealed that the trueness, repeatability (RSDr) and reproducibility (RSDr) were 86-95%, 3.1-9.4% and 8.6-22.1%, respectively. The values of the performance parameters fulfilled the requirements , and the performances met the test specifications. The combination of evaporation to dryness on a hot plate and measurement by AAS or ICP-OES is applicable as an alternative method. However, the trueness and RSDr were inferior to those of the official method. The performance parameters obtained by using the microwave digestion method (MW method) to prepare test solution were better than those of the official method. Thus, the MW method is available as an alternative method. Induced coupled plasma-mass spectrometry (ICP-MS) is also available as an alternative method. However, it is necessary to ensure complete digestion of the sample.