We analyze the dynamics of paramagnetic particles on a paramagnetic substrate under a rotational magnetic field. When the paramagnetic particles are subjected to a rotational magnetic field, the rotational plane of which is perpendicular to the substrate surface, the particles form chain clusters caused by the dipole-dipole interaction between the particles and these clusters display a tumbling motion under certain conditions. In this case, the angular momentum of the clusters is converted to a translational one through the force of friction acting between the particles and substrate and, as a result, the clusters move along the surface of the substrate. We analyze the conditions under which the tumbling motion occurs and the dependence of the translational velocity of a cluster on the control parameters by the Stokesian dynamics method. Based on the dynamics of magnetic particles, we propose a method of manipulating nano- and microparticles using a rotational magnetic field. We demonstrate the manipulation of magnetic and nonmagnetic particles, a carbon nanotube, and a biological cell.

Pluripotent stem cells are central tools to many regenerative medicine strategies due to their ability to differentiate towards the three embryonic germ layers. One challenge remains in providing control over their differentiation into specific lineage, such as cardiac commitment. Here, the possibility of directing cardiomyogenesis of embryonic stem cells (ESCs) using a microfabricated magnetic pattern is demonstrated. The stem cells are labeled with magnetic nanoparticles, aggregated into embryoïd bodies (EBs) onto the pattern, and stimulated with a local magnetic force applied via the pattern. The EBs formed on this magnetic device experience the same differentiation profile than the ones created by the common hanging drop approach, while it allows high-throughput production of hundreds of EBs. Further on/off cyclic magnetic force stimulation mediated by the same device is sufficient to enhance cardiomyogenesis in a way that almost all EBs develop spontaneous beating, confirmed by the overexpression of -actin and troponin proteins, and by the upregulation (2 to 5-fold) of genes involved in mesoderm differentiation (Nkx2.5, Gata4, and Gata6), and more specifically cardiac lineage (Tnnt2, Myh6 and Myl-2). Beyond holding high application-level potential, this work confirms that physical forces, and specifically on/off dynamic ones can be sufficient to govern cell function. Received: ((will be filled in by the editorial staff)) Revised: ((will be filled in by the editorial staff))

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Cardiac tissue engineering (CTE) aims to generate potential scaffolds to mimic extracellular matrix (ECM) for recreating the injured myocardium. Highly porous scaffolds with properties that aid cell adhesion, migration and proliferation are critical in CTE. In this study, electrospun porous poly (l-lactic acid) (PLLA) porous scaffolds were fabricated and modified with different ECM derived proteins such as collagen, gelatin, fibronectin and poly-L-lysine. Subsequently, adult human cardiac fibroblasts (AHCF) were cultured on the protein modified and unmodified fibers to study the cell behavior and guidance. Further, the cytotoxicity and reactive oxygen species (ROS) assessments of the respective fibers were performed to determine their biocompatibility. Excellent cell adhesion and proliferation of the cardiac fibroblasts was observed on the PLLA porous fibers regardless of the surface modifications. The metabolic rate of cells was on par with the conventional cell culture ware while the proliferation rate surpassed the latter by nearly two-folds. Proteome profiling revealed that apart from being an anchorage platform for cells, the surface topography has modulated significant expression of the cellular proteome with many crucial proteins responsible for cardiac fibroblast growth and proliferation.

ABSTRACT:Chemical bonding and magnetic interaction of manganese dimer (Mn 2 ) are still in controversy in experimental and theoretical studies. In this work, we examined various exchange correlation functionals of Kohn-Sham density functional theory (DFT), together with hybrid-DFT, and Hartree-Fock plus DFT approaches on description of Mn 2 . We found that, in contrast to pure DFT functionals, the experimentally reported features of chemical bonding and antiferromagnetic interactions of Mn 2 can be reproduced by employing the Hartree-Fock exchange terms. Thus, it is recommended to employ HF plus DFT, or hybrid DFT with large HF portion approach for the case that the direct interactions among manganese atoms play a major role to determine the electronic structure, such as manganese clusters.