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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)

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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).

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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).

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DOI: 10.1177/0022034516629400
WoS: 000374580000013
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Multiphoton confocal microscopy and nonlinear spectroscopy are used to investigate the caries process in dentin. Although dentin is a major calcified tissue of the teeth, its organic phase comprises type I collagen fibers. Caries drive dentin demineralization and collagen denaturation. Multiphoton microscopy is a powerful imaging technique: the biological materials are transparent to infrared frequencies and can be excited to penetration depths inaccessible to 1-photon confocal microscopy. The laser excitation greatly reduces photodamage to the sole focal region, and the signal-to-noise ratio is improved significantly. The method has been used to follow pathologic processes involving collagen fibrosis or collagen destruction based on their 2-photon excited fluorescence (2PEF) emission and second harmonic generation (SHG). Combining multiphoton imaging with nonlinear spectroscopy, we demonstrate that both 2PEF and SHG intensity of human dentin are strongly modified during the tooth caries process, and we show that the ratio between SHG and 2PEF signals is a reliable parameter to follow dental caries. The ratio of the SHG/2PEF signals measured by nonlinear optical spectroscopy provides valuable information on the caries process, specifically on the degradation of the organic matrix of dentin. The goal is to bring these nonlinear optical signals to clinical application for caries diagnosis.

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Casein micelles (CMs) are colloidal protein-mineral complexes in equilibrium in the milk serum. Their enzymatic cross-linking by transglutaminase (TGase) allow a modification of their characteristics. The aim of this work is to determine the impact of this modification on their characteristics (size and elastic properties) in a native liquid environment by atomic force microscopy (AFM). The challenge is to immobilize the particles on a surface in their natural state in order to investigate the effect of covalent cross-linking in a simulated milk ultrafiltrate (SMUF).

Commentaires: le titre est différent sur site de la conférence Elsevier "Investigation of properties of casein micelles depleted in beta casein by atomic force microscopy performed in liquid environment"