Peripheral nerve injuries are serious traumas resulting in loss of motor and sensory functions of nerves. The post-traumatic neuropathies are often chronic and mostly resistant to current treatments. Our objective is to develop new strategies to regenerate nerve after trauma by biomimetic approaches and go towards in vitro neurogenesis. For this we use neural crest derived human multipotent dental pulp stem cells (hDPSC) in co-culture with sensory neurons from mice dorsal root ganglia (DRG), and an in vitro neurogenic differentiation of hDPSC [3].In order to explore nanomechanical and morphological characteristics of human DPSC and mouse DRG neurons atomic force microscopy was employed. We have shown that the mechanical properties of the soma and sub cellular growth cone regions correlate well with the amount, organization and dynamics of the underlying cytoskeletal structure [1,2]. Here we present preliminary data about hDPSC in co-culture, with mDRG neurons and during an in vitro neurogenic differentiation gathered by nanomechanical mapping.[1] O. Benzina, V. Szabo, O. Lucas, M-b. Saab, T. Cloitre, F. Scamps, C. Gergely and M. Martin (2013) Changes induced by peripheral nerve injury in the morphology and nanomechanics of sensory neurons, J. Biomedical Optics 18(10)[2] M. Martin, O.Benzina, V. Szabó, A. G. Végh, O. Lucas, T. Cloitre, F. Scamps and C. Gergely (2013) Morphology and Nanomechanics of Sensory Neurons Growth Cones following Peripheral Nerve Injury, Plos One , 8 (2)[3] M. Király, B. Porcsalmy, A. Pataki, K. Kádár, M. Jelitai, B. Molnár, P. Hermann, I. Gera, WD. Grimm, B. Ganss, A. Zsembery, G. Varga, (2009) Simultaneous PKC and cAMP activation induces differentiation of human dental pulp stem cells into functionally active neurons, Neurochem. Int. 55 (323-332)

Fluorescent nano-diamonds (fND) are attractive tools for nanoscale biological cellular imaging allowing both photoluminescence and magnetic resonance imaging [1]. Recent technological developments enable to fabricate bright fND particles of various sizes with high content of nitrogen-vacancy (NV) centres [2]. In this work we study internalization processes of NDs in the breast cancer MCF7 1DIV cell line using Atomic Force Microscopy imaging and force spectroscopy. fND particles of size range from 5 to 60 nm were used, prepared from Ib synthetic diamond, electron irradiated, annealed and plasma oxidized to create NV centers.Changes of cells stiffness were detected by AFM force measurements after introducing the fNDs into the cell medium. We observed an oscillating variation of cell membrane Young's modulus while the cells become stiffer. We believe that repetitive uptake/release processes of fNDs are responsible for these mechanical changes. Contrarywise, more confluent MCF7 cells (3DIV) did not show any significant change in Young’s Modulus, as compare with control ones. Indeed, it has been shown that differences in nanoparticle uptake can arise from how close the cells are to one another (confluence) [3] and how old they are.Moreover, our results suggest that studies on fNDs uptake should consider the cell cycle, as in a cell population, the dose of internalized nanoparticles in each cell varies as the expression of membrane proteins vary during the cell cycle [4]. The cell cycle is a series of events that lead to cell division and replication, consisting of four phases: G1 (when the cell increases its size), S (the cell synthesizes DNA), G2 (the cell synthesizes proteins for cell division) and M (the cell divides and the two daughter cells enter the G1 phase). During each event, cellular processes can vary; meaning that the rate at which a cell takes up foreign material, as for instance nanoparticles, may depend on the phase the cell is in [4-6], modifying accordingly their elasticity. When nanoparticle internalization is studied, it is therefore crucial to resolve how the state of the different cells affects the uptake. [1] L. Moore, M. Nesladek et al., Nanoscale (2014).[2] J. Havlik, M. Gulka, M. Nesladek et al., Nanoscale (2013).[3] B. Snijder, et al. Nature 461, 520–523 (2009). [4] E. Boucrot and T. Kirchhausen, Proc. Natl Acad. Sci. USA 104, 7939–7944 (2007). [5] D. Raucher and M. P. Sheetz, J. Cell Biol. 144, 497–506 (1999). 
[6] J. K. Schweitzer, E. E. Burke, H. V Goodson and C. D’Souza-Schorey. J. Biol. Chem. 280, 41628–41635 (2005).

Spectroscopic ellipsometry is increasingly used for investigation of biofilms and biological materials because of its non-invasive manner. In case of biofilms, the investigated material might be present on the surface only in small amounts forming an island-like coating. In this work we investigate the applicability of different ellipsometric models for such discontinuous biofilms. We used various types of peptides for which adhesion differences in the case of deposition to n- and p-type silicon were theoretically determined in [1]. Since the adhesion of these types of peptides to differently doped silicon significantly differs, resulting in selective deposition of peptides from liquid solutions, the applicability of the ellipsometric models can be tested sufficiently. [1] S. K. Ramakrishnan, M. Martin, T. Cloitre, L. Firlej, C. Gergely, Molecular Mechanism of Selective Binding of Peptides to Silicon Surface. J. Chem. Inf. Model. 54, 2117 (2014).

We studied the oxygen etching of individual single-walled carbon nanotubes on silicon oxide substrates using atomic force microscopy and high-temperature environmental scanning electron microscopy. Our in situ observations show that carbon nanotubes are not progressively etched from their ends, as frequently assumed, but disappear segment by segment. Atomic force microscopy, before and after oxidation, reveals that the oxidation of carbon nanotubes on substrates proceeds through a local cutting that is followed by a rapid etching of the disconnected nanotube segment. Unexpectedly, semiconducting nanotubes appear more reactive under these conditions than metallic ones. We also show that exposure to electron and laser beams locally increases the chemical reactivity of carbon nanotubes on such substrates. These results are rationalized by considering the effect of substrate-trapped charges on the nanotube density of states close to the Fermi level, which is impacted by the substrate type and the exposure to electron and laser beams.

Agricultural spraying involves atomizing a liquid stream through a hydraulic nozzle, thus forming a liquid sheet that is subsequently destabilized into drops. Standard adjuvants such as dilute oil-in- water emulsions are known to influence the spray drop size distribution. Although being documented, the physical mechanisms at the origin of the size increase remain unclear. To elucidate the mechanisms causing the changes on the drop size distribution, we investigate the influence of dilute emulsions on the destabilization mechanisms of liquid sheets. Model laboratory experiments based on the collision of a liquid tear on a small solid target are used to produce and characterize liquid sheets. With dilute oil-in-water emulsions, the liquid sheet is destabilized during its expansion by the nucleation of holes that perforate the sheet and grow. The emulsion concentration and the size of the oil droplet of the emulsion are varied to rationalize their influence on the sheet destabilization mechanisms. The results obtained with the model laboratory experiments are compared to the measurement of the drop size distribution resulting from a conventional agricultural spray. The very good correlation between the number of perforation events and the volume fraction of small drops in the spray suggests (i) that the model experiment on liquid sheet is appropriate to investigate and gain an understanding of the physical mechanisms governing the spray drop size distribution and (ii) that the perforation destabilization mechanism of liquid sheets, which dominates for dilute emulsions, is at the origin of the increase of the size of the spray drops.

Principles of formation of viral capsids with double protein shells