Microscale adhesion patterns for the precise localization of amoeba

In order to get a better understanding of amoeba-substrate interactions in the processes of cellular adhesion and directional movement, we engineered glass surfaces with defined local adhesion characteristics at a micrometric scale. Amoeba (Dictyostelium dicoideum) is capable to adhere to various surfaces independently of the presence of extracellular matrix proteins. This paper describes the strategy used to create selective adhesion motifs using an appropriate surface chemistry and shows the first results of locally confined amoeba adhesion. The approach is based on the natural ability of Dictyostelium to adhere to various types of surfaces (hydrophilic and hydrophobic) and on its inability to spread on inert surfaces, such as the block copolymer of polyethylene glycol and polypropylene oxide, named Pluronic. We screened diverse alkylsilanes, such as methoxy, chloro and fluoro silanes for their capacity to anchor Pluronic efficiently on a glass surface. Our results demonstrate that hexylmethyldichlorosilane (HMDCS) was the most appropriate silane for the deposition of Pluronic. A complex dependence between the physicochemistry of the silanes and the polyethylene glycol block copolymer deposition was observed. Using this method, we succeed in scaling down the micro-fabrication of pluronic-based adhesion motifs to the amoebaComment: Microelectronic Engineering (2008) in pres

On the Influence of Discrete Adhesive Patterns for Cell Shape and Motility: A Computational Approach

International audienc

Mathematical Modelling of Fibroblast shape Transition on Arrays of Adhesive Micropatterns with Varying Pitch

Cell adhesion to the extracellular matrix is crucial to many physiological events since it underlies cell motility and cell proliferation. Cell shape and cell migration depend on the forces developed within the cytoskeleton. These forces are highly regulated at the adhesion site through feedback mechanisms. The observation of cells plated on culture dishes shows continuous membrane oscillations with recurring patterns. In that experimental case, the cell cytoskeleton dynamics never reaches a steady state since adhesion is homogeneous and never strong enough for forces to develop and to stabilize the cell shape. Engineered micrometric adhesive patches have therefore been used to discretize and limit the surface for cell adhesion. With these new adhesive conditions, the cell becomes able to develop stronger adhesions through a mechanism of integrin clustering and to develop competing stress fibers ultimately converging to stable geometrical cell shapes. Arrays of adhesive micropatches with different pitches have been considered. Fibroblast cells have been shown to adapt their shape according to the pitch length. For small pitches, fibroblasts adopt their characteristic " starry " shape. Transition from square to triangular and then to bipolar shapes are then observed when increasing the pitches of the adhesive arrays from 4 up to 20µm. A mathematical model has been developed to describe the observed cell shape transitions. The model describes the cell membrane deformations in connection with the intracellular actin dynamics. A discrete extension to the continous model formulation allows to take into account the process by which the adhesions form and mature through integrin recruitement and stimulate the formation of actin stress fibres. The intensity and distribution of the tension forces developed in the actin fibres ultimately determine the cell stable shape. The model is thus able to reproduce successively the observed shape transitions. Moreover, the model shows that the admissible level of membrane extension is conditionning the stable geometry of the cell for a given pitch. The main limitation of the model is the use of phenomenological rules to describe the maturation of the adhesion and stress fibres. In a future work we aim to refine the model by taking explicitly into account the regulation mechanisms of the most important cystoskeletal proteins (Arp2/3, cofilin, gelsolin)

Mathematical Modelling of Fibroblast shape Transition on Arrays of Adhesive Micropatterns with Varying Pitch

Cell adhesion to the extracellular matrix is crucial to many physiological events since it underlies cell motility and cell proliferation. Cell shape and cell migration depend on the forces developed within the cytoskeleton. These forces are highly regulated at the adhesion site through feedback mechanisms. The observation of cells plated on culture dishes shows continuous membrane oscillations with recurring patterns. In that experimental case, the cell cytoskeleton dynamics never reaches a steady state since adhesion is homogeneous and never strong enough for forces to develop and to stabilize the cell shape. Engineered micrometric adhesive patches have therefore been used to discretize and limit the surface for cell adhesion. With these new adhesive conditions, the cell becomes able to develop stronger adhesions through a mechanism of integrin clustering and to develop competing stress fibers ultimately converging to stable geometrical cell shapes. Arrays of adhesive micropatches with different pitches have been considered. Fibroblast cells have been shown to adapt their shape according to the pitch length. For small pitches, fibroblasts adopt their characteristic " starry " shape. Transition from square to triangular and then to bipolar shapes are then observed when increasing the pitches of the adhesive arrays from 4 up to 20µm. A mathematical model has been developed to describe the observed cell shape transitions. The model describes the cell membrane deformations in connection with the intracellular actin dynamics. A discrete extension to the continous model formulation allows to take into account the process by which the adhesions form and mature through integrin recruitement and stimulate the formation of actin stress fibres. The intensity and distribution of the tension forces developed in the actin fibres ultimately determine the cell stable shape. The model is thus able to reproduce successively the observed shape transitions. Moreover, the model shows that the admissible level of membrane extension is conditionning the stable geometry of the cell for a given pitch. The main limitation of the model is the use of phenomenological rules to describe the maturation of the adhesion and stress fibres. In a future work we aim to refine the model by taking explicitly into account the regulation mechanisms of the most important cystoskeletal proteins (Arp2/3, cofilin, gelsolin)

Control of cell morphodynamic and displacement orientation by precise tuning between substrate nanopatterning and rigidity

International audienc

The motility of normal and cancer cells in response to the combined influence of substrate rigidity and anisotropic microstructure

International audienceCell adhesion and migration are strongly influenced by extracellular matrix (ECM) architecture and rigidity, but little is known about the concomitant influence of such environmental signals to cell responses, especially when considering cells of similar origin and morphology, but exhibiting a normal or cancerous phenotype. Using micropatterned polydimethylsiloxane substrates (PDMS) with tuneable stiffness (500kPa, 750kPa, 2000kPa) and topography (lines, pillars or unpatterned), we systematically analyse the differential response of normal (3T3) and cancer (SaI/N) fibroblastic cells. Our results demonstrate that both cells exhibit differential morphology and motility responses to changes in substrate rigidiy and microtopography. 3T3 polarization and spreading are influenced by substrate microtopography and rigidity. The cells exhibit a persistent type of migration, which depends on the substrate anisotropy. In contrast, the dynamic of SaI/N spreading is strongly modified by the substrate topography but not by substrate rigidity. SaI/N morphology and migration seem to escape from extracellular cues: the cells exhibit uncorrelated migration trajectories and a large dispersion of their migration speed, which increases with substrate rigidity