Detection of interfacial phenomena with osteoblast-like cell adhesion on hydroxyapatite and oxidized polystyrene by the quartz crystal microbalance with dissipation

The adhesion process of osteoblast-like cells on hydroxyapatite (HAp) and oxidized polystyrene (PSox) was investigated using a quartz crystal microbalance with dissipation (QCM-D), confocal laser scanning microscope (CLSM), and atomic force microscope (AFM) techniques in order to clarify the interfacial phenomena between the surfaces and cells. The interfacial viscoelastic properties (shear viscosity (η(ad)), elastic shear modulus (μ(ad)), and tan δ) of the preadsorbed protein layer and the interface layer between the surfaces and cells were estimated using a Voigt-based viscoelastic model from the measured frequency (Δf) and dissipation shift (ΔD) curves. In the ΔD-Δf plots, the cell adhesion process on HAp was classified as (1) a mass increase only, (2) increases in both mass and ΔD, and (3) slight decreases in mass and ΔD. On PSox, only ΔD increases were observed, indicating that the adhesion behavior depended on the surface properties. The interfacial μ(ad) value between the material surfaces and cells increased with the number of adherent cells, whereas η(ad) and tanδ decreased slightly, irrespective of the surface. Thus, the interfacial layer changed the elasticity to viscosity with an increase in the number. The tan δ values on HAp were higher than those on PSox and exceeded 1.0. Furthermore, the pseudopod-like structures of the cells on HAp had periodic stripe patterns stained with a type I collagen antibody, whereas those on PSox had cell-membrane-like structures unstained with type I collagen. These results indicate that the interfacial layers on PSox and HAp exhibit elasticity and viscosity, respectively, indicating that the rearrangements of the extracellular matrix and cytoskeleton changes cause different cell-surface interactions. Therefore, the different cell adhesion process, interfacial viscoelasticity, and morphology depending on the surfaces were successfully monitored in situ and evaluated by the QCM-D technique combined with other techniques.     

Effect of interfacial proteins on osteoblast-like cell adhesion to hydroxyapatite nanocrystals

A quartz crystal microbalance with dissipation (QCM-D) technique was employed to detecting the protein adsorption and subsequent osteoblast-like cell adhesion to hydroxyapatite (HAp) nanocrystals. The interfacial phenomena with the preadsorption of three proteins (albumin (BSA), fibronectin (Fn), and collagen (Col)), the subsequent adsorption of fetal bovine serum (FBS), and the adhesion of the cells were investigated. The QCM-D measured the frequency shift (Δf) and dissipation energy shift (ΔD), and the viscoelastic properties of the adlayers were evaluated using ΔD-Δf plot and Voigt-based viscoelastic model. The Col adsorption significantly showed higher Δf, ΔD, elasticity, and viscosity values as compared to the BSA and Fn adsorption, and the subsequent FBS adsorption depended on the preadsorbed proteins. The ΔD-Δf plot of the cell adhesion also showed a different behavior depending on the surfaces, and the Fn- and Col-modified surfaces showed the rapid mass and ΔD changes by forming the viscous interfacial layers with cell adhesion, indicating that the processes were affected by the cellular reaction through the extracellular matrix (ECM) proteins. The confocal laser scanning microscope images of adherent cells showed a different morphology and pseudopod on the surfaces. The cells adhered to the surfaces modified with the Fn and Col had significantly uniaxially expanded shapes and fibrous pseudopods, and those modified with the BSA had a round shape. Therefore, the different cell-protein interactions would cause the arrangement of the ECM and the cytoskeleton changes at the interfaces, and these phenomena were successfully detected by the QCM-D and Voigt-based model.     

Immobilization of folic acid on Eu3+-doped nanoporous silica spheres

Folic acid (FA) was immobilized on Eu(3+)-doped nanoporous silica spheres (Eu:NPSs) through mediation of the 3-aminopropyltriethoxysilane adlayer. The ordered nanopores of Eu:NPS were preserved by the immobilization. The FA-immobilized Eu:NPSs showed the characteristic photoluminescence peak due to interactions between the FA molecules and Eu(3+) ions, and highly dispersed stability in phosphate buffered saline.     

Growth rate predictions of single- and multi-mode Richtmyer�CMeshkov instability with reshock

The single- and multi-mode Richtmyer–Meshkov instabilities (RMI) with reshock are numerically analyzed in two- and three-dimensional domains. Four different types of air/SF ₆ interface shapes are investigated in a shock tube configuration, and the predicted post-reshock growth rates are compared with available empirical models of Mikaelian’s (Physica D 36(3):343–347, 1989) and Charakhch’an’s (J Appl Mech Tech Phys 41(1):23–31, 2000). The simulation of 3D multi-mode RMI shows good agreement with a past experimental study, but other interface types (2D single-mode, 2D multi-mode and 3D single-mode) result in different growth rates after reshock. Parametric studies are therefore performed to investigate the sensitivities of the post-reshock growth rates to model the empirical parameters. For single-mode RMI configurations, the interface shape is found to be only a weak function of the post-reshock growth rate, as also predicted by previous reshock models. The post-reshock growth rate shows a linear correlation to the velocity jump due to reshock; however, it is only about a half of the prediction of Charakhch’an’s model even though the growth before reshock compares well with pre-reshock models. The 3D single-mode post-reshock RMI growth rate is nearly 1.6 times larger than the 2D single-mode RMI. The parametric studies of multi-mode RMI show two distinctly different growth rates depending on the mixing conditions at reshock. If the interface remains sharp at the time of reshock, the post-reshock growth rate is as large as the single-mode cases. However, if the interface is mixed due to non-linear interactions of bubbles and spikes, the growth rates becomes slow and independent of the interface shapes. Overall, this study provides new insights into the flow features of reshocked RMI for different initial perturbation types.     

Preferential Alignment of Hydroxyapatite Crystallites in Nanocomposites with Chemically Disintegrated Silk Fibroin

Hydroxyapatite (HAp) nanocrystals were prepared at room temperature by a coprecipitation method from Ca(OH)₂ and H₃PO₄, in the presence of chemically disintegrated silk fibroin (SF). Adsorbed amounts of cations on SF and crystallinity of HAp in the composite were increased by the chemical disintegration of SF higher order structure. Preferential alignment of c-axis of HAp crystallites along the longitudinal direction of ca. 150nm SF fibril was observed. These changes due to disintegration of SF were discussed in terms of the chemical interaction between HAp and SF. The resulted composite with preferential alignment of HAp nanocrystals is a good candidate as a starting material for bone substitutes.     

A novel synthesis of alkyl phenylsulfinates

Alkyl phenylsulfinates (Ph-SO-OR) were prepared from thiophenol (or diphenyldisulfide) by electrolysis in acetic acid with alcohols and sodium acetate in satisfactory yields.     

Measurement of polarized target asymmetry in γd → pn in the photon energy region between 0.3 and 0.7 GeV

The target asymmetry in γd → pn has been measured at proton c.m. angles of 70°, 100° and 130° in the photon energies between 0.3 and 0.7 GeV. Results show relatively small asymmetry values in contrast to large proton polarizations. A phenomenological analysis by Ikeda et al. does not reproduce the present data, especially in the lower energy region.