Volcano-Shaped Scanning Probe Microscopy Probe for Combined Force-Electrogram Recordings from Excitable Cells.

Atomic force microscopy based approaches have led to remarkable advances in the field of mechanobiology. However, linking the mechanical cues to biological responses requires complementary techniques capable of recording these physiological characteristics. In this study, we present an instrument for combined optical, force, and electrical measurements based on a novel type of scanning probe microscopy cantilever composed of a protruding volcano-shaped nanopatterned microelectrode (nanovolcano probe) at the tip of a suspended microcantilever. This probe enables simultaneous force and electrical recordings from single cells. Successful impedance measurements on mechanically stimulated neonatal rat cardiomyocytes in situ were achieved using these nanovolcano probes. Furthermore, proof of concept experiments demonstrated that extracellular field potentials (electrogram) together with contraction displacement curves could simultaneously be recorded. These features render the nanovolcano probe especially suited for mechanobiological studies aiming at linking mechanical stimuli to electrophysiological responses of single cells.

Intracellular Recording of Cardiomyocyte Action Potentials with Nanopatterned Volcano-Shaped Microelectrode Arrays.

Micronanotechnology-based multielectrode arrays have led to remarkable progress in the field of transmembrane voltage recording of excitable cells. However, providing long-term optoporation- or electroporation-free intracellular access remains a considerable challenge. In this study, a novel type of nanopatterned volcano-shaped microelectrode (nanovolcano) is described that spontaneously fuses with the cell membrane and permits stable intracellular access. The complex nanostructure was manufactured following a simple and scalable fabrication process based on ion beam etching redeposition. The resulting ring-shaped structure provided passive intracellular access to neonatal rat cardiomyocytes. Intracellular action potentials were successfully recorded in vitro from different devices, and continuous recording for more than 1 h was achieved. By reporting transmembrane action potentials at potentially high spatial resolution without the need to apply physical triggers, the nanovolcanoes show distinct advantages over multielectrode arrays for the assessment of electrophysiological characteristics of cardiomyocyte networks at the transmembrane voltage level over time.

[A new approach to the biomechanics of the normal and pathologic lumbar disk using the finite element method]. / Une nouvelle approche de la biomécanique du disque lombaire normal et pathologique à l'aide de la méthode des éléments finis.

The model was created based on the L2-L3 intervertebral disc considering it to be symmetrical on a longitudinal axis and a mid-transverse plane and could be subjected to a longitudinal load of 400 N in compression. The analysis of this two-dimensional problem by using the finite element program S.A.M.C.E.F. utilizes a quadrangular isoparametric and axi-symmetric element. The results took into account the vertical deflection and radial displacement of the nodal points and also the deformation diagram and stress distribution (Von Mises comparison) of the three regions studied: nucleus pulposus, annulus fibrosus and the end plate. This model has been applied to three pathological states: fissuring of the annulus and nucleus herniation, simulation of an enucleation, and a fracture of the central area of end plate with Schmörl's nodule formation. In each case, a deformation and a stress distribution modified relatively to those observed in normal discs were obtained. For instance, in the case of herniation the maximum stress equals 3.700 N/mm2 in comparison with 1.350 N/mm2 found in normal cases. This simplified model is one of the first which reproduces some pathological states of intervertebral discs and facilitates the understanding of the biomechanics of these states.