Electronic Structure of BiFe1−xMnxO3 Thin Films Investigated by X-Ray Absorption Spectroscopy

Multiferroic polycrystalline BiFe1-xMnxO3 (0≤x≤0.3) thin films have been prepared on the Pt(111)/Ti/SiO2/Si(100) substrates by pulsed laser deposition method. The influence of Mn substitution on the electronic structure and magnetic properties has been studied. X-ray diffraction spectroscopy shows that Mn substitution slightly modulates crystal structure of the BiFe1-xMnxO3 system within the same structural phase. According to Fe L edge X ray absorption spectroscopy, Fe ions are found to be formally trivalent for doping amount x in BiFe1-xMnxO3. The enhanced magnetization by increasing Mn content is attributed to an alternation degree of hybridization between Fe 3d-O 2p and Mn 3d-O 2p orbitals, basing on the carefully examined Fe L and O K edge X-ray absorption spectroscopy. The crystal structural and the electronic structural results show a causal relation between them by demonstrating intrinsic mutual dependence between respective variations

A microfluidic-based multi-shear device for investigating the effects of low fluid-induced stresses on osteoblasts.

Interstitial fluid flow (IFF) within the extracellular matrix (ECM) produces low magnitude shear stresses on cells. Fluid flow-induced stress (FSS) plays an important role during tissue morphogenesis. To investigate the effect of low FSS generated by IFF on cells, we developed a microfluidic-based cell culture device that can generate multiple low shear stresses. By changing the length and width of the flow-in channels, different continuous low level shear stresses could be generated in individual cell culture chambers. Numerical calculations demonstrate uniform shear stress distributions of the major cell culture area of each chamber. This calculation is further confirmed by the wall shear stress curves. The effects of low FSS on MC3T3-E1 proliferation and differentiation were studied using this device. It was found that FSS ranging from 1.5 to 52.6 µPa promoted MC3T3-E1 proliferation and differentiation, but FSS over 412 µPa inhibited the proliferation and differentiation of MC3T3-E1 cells. FSS ranging from 1.5 to 52.6 µPa also increased the expression of Runx2, a key transcription factor regulating osteoblast differentiation. It is suggested that Runx2 might be an important regulator in low FSS-induced MC3T3-E1 differentiation. This device allows for detailed study of the effect of low FSS on the behaviors of cells; thus, it would be a useful tool for analysis of the effects of IFF-induced shear stresses on cells

Numerical modeling.

<p>(a) Simplified microfluidic network. (b) The equivalent circuit diagram corresponding to the microfluidic network of (a), where <i>Ri</i> is the hydraulic resistance of the microchannel, and <i>R</i> is the hydraulic resistance of the identical culture chamber.</p

The proliferation index of MC3T3-E1 cells in chambers 1, 2, 3, and 4.

<p>The proliferation index of MC3T3-E1 cells in chamber 4 was lower, compared to cells in chambers 1 and 2. The single asterisk indicates <i>p</i><0.05 and the couple asterisk indicates <i>p</i><0.001.</p

Shear stress calculations in four chambers.

<p>(a) Flow streamlines at the middle height plane. (b) Shear stress at the bottom wall. (c) Distributions of the wall shear stress in the y-direction.</p

MC3T3-E1 cells in four chambers with perfusion culture for 48 h.

<p>(a–d) MC3T3-E1 cells in chambers 1, 2, 3, and 4, respectively, before perfusion culture (bright field). (e–h) MC3T3-E1 cells in chambers 1, 2, 3, and 4, respectively, with perfusion culture for 48 h, then stained by Rh123-Hoechst-PI. Scale bar = 100 µm.</p

The differentiation of MC3T3-E1 cells in chambers 1, 2, 3, and 4.

<p>The expression of ALP, Col I, and osteocalcin increased gradually from chambers 1 to 3, then decreased in chamber 4. Runx2 expression showed a similar pattern to that of ALP and osteocalcin.</p

Primers used for RT-PCR.

<p>Primers used for RT-PCR.</p