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Two-photon polymerization (2PP) allows precise 3D printing at the micrometer scale, and by associating it with magnetic materials, the creation of remotely actuatable micro-structures. Such structures attract a growing interest for biomedical applications, thanks to their size and to the biocompatibility of some photoresist materials. Gelatin methacryloyl (Gel-MA) is one such material, and can be used to create physiological scaffolds for cell culture. Here, the physico-chemical properties of two resins are exploited, the first being a silica-based hybrid polymer, the OrmoComp, and the second a Gel-MA-based hydrogel.....
Little is known about the contribution of 3D surface geometry on the development of multi-layered tissues containing fibrous extracellular matrix components such as those found in bone. Here we elucidate the role of curvature in the formation of chiral, twisted plywood-like structures. Tissues consisting of murine pre-osteoblast cells (MC3T3-E1) were grown on 3D scaffolds with constant mean curvature and negative Gaussian curvature for up to 32 days. Using 3D fluorescence microscopy, the influence of surface curvature on actin stress-fiber alignment and chirality was investigated...
Protrusions at the leading-edge of a cell play an important role in sensing the
extracellular cues during cellular spreading and motility. Recent studies provided
indications that these protrusions wrap (coil) around the extracellular
fibers. However, the physics of this coiling process, and the mechanisms that
drive it, are not well understood. We present a combined theoretical and
experimental study of the coiling of cellular protrusions on fibers of different
geometry. Our theoretical model describes membrane protrusions that are
produced by curved membrane proteins that recruit the protrusive forces of
actin polymerization, and identifies the role of bending and adhesion energies
in orienting the leading-edges of the protrusions along the azimuthal (coiling)
One ubiquitous cellular structure for performing various tasks, such
as spreading and migration over external surfaces, is the sheet-like
protrusion called a lamellipodium, which propels the leading edge of
the cell. Despite the detailed knowledge about the many components
of this cellular structure, it is not yet fully understood how these
components self-organize spatiotemporally to form lamellipodia. We
review here recent theoretical works where we have demonstrated
that membrane-bound protein complexes that have intrinsic curvature
and recruit the protrusive forces of the cytoskeleton result in a simple,
yet highly robust, organizing feedback mechanism that organizes the
cytoskeleton and the membrane...
B.Schamberger, R. Ziege, K. Anselme, M. Ben Amar, M. Bykowski, A. P. G. Castro, A. Cipitria, R. A. Coles, R. Dimova, M. Eder, S. Ehrig, L. M. Escudero, M. E. Evans, P. R. Fernandes, P. Fratzl, L. Geris, N. Gierlinger, E. Hannezo, A. Iglič, J. J. K. Kirkensgaard, P. Kollmannsberger, Ł. Kowalewska, N. A. Kurniawan, I. Papantoniou, L. Pieuchot, T. H. V. Pires, L. D. Renner, A. O. Sageman-Furnas, G. E. Schröder-Turk, A. Sengupta, V. R. Sharma, A. Tagua, C. Tomba, X. Trepat, S. L. Waters, E. F. Yeo, A. Roschger, C. M. Bidan, J. W. C. Dunlop
Surface curvature both emerges from, and influences the behavior of, living objects at length scales ranging from cell membranes to single cells to tissues and organs. The relevance of surface curvature in biology is supported by numerous experimental and theoretical investigations in recent years. In this review, first, a brief introduction to the key ideas of surface curvature in the context of biological systems is given and the challenges that arise when measuring surface curvature are discussed. Giving an overview of the emergence of curvature in biological systems, its significance at different length scales becomes apparent...
Curvature is a geometric feature widely observed in the epithelia and critical to the performance of fundamental biological functions. Understanding curvature-related biophysical phenomena remains challenging partly owing to the difficulty of quantitatively tuning and measuring curvatures of interfacing individual cells. In this study, we prepared confluent wild-type Madin–Darby canine kidney cells on a torus structure presenting positive, zero, and negative Gaussian curvatures with a tubule diameter of 2–7 cells and quantified the mechanobiological characteristics of individual cells. Cells on the torus surface exhibited topological sensing ability both as an individual cell and collective cell organization. Both cell bodies and nuclei, adapted on the torus, exhibited local Gaussian curvature-dependent preferential orientation...
Generation of tissue curvature is essential to morphogenesis. However, how cells adapt to changing curvature is still unknown because tools to dynamically control curvature in vitro are lacking. Here, we developed self-rolling substrates to study how flat epithelial cell monolayers adapt to a rapid anisotropic change of curvature. We show that the primary response is an active and transient osmotic swelling of cells. This cell volume increase is not observed on inducible wrinkled substrates, where concave and convex regions alternate each other over short distances; and this finding identifies swelling as a collective response to changes of curvature with a persistent sign over large distances...
The early development of many organisms involves the folding of cell monolayers, but this behaviour is difficult to reproduce in vitro; therefore, both mechanistic causes and effects of local curvature remain unclear. Here we study epithelial cell monolayers on corrugated hydrogels engineered into wavy patterns, examining how concave and convex curvatures affect cellular and nuclear shape. We find that substrate curvature affects monolayer thickness, which is larger in valleys than crests. We show that this feature generically arises in a vertex model, leading to the hypothesis that cells may sense curvature by modifying the thickness of the tissue...
Resealing of membrane pores is crucial for cell survival. Membrane surface charge and medium composition are studied as defining regulators of membrane stability. Pores are generated by electric field or detergents. Giant vesicles composed of zwitterionic and negatively charged lipids mixed at varying ratios are subjected to a strong electric pulse. Interestingly, charged vesicles appear prone to catastrophic collapse transforming them into tubular structures. The spectrum of destabilization responses includes the generation of long-living submicroscopic pores and partial vesicle bursting ...
This review presents the different physical descriptions of cell assemblies. After a short
presentation of discrete models, very popular in studies of epithelial tissues, we focus
more on multi-cellular spheroids containing a variety of components. In particular, we
highlight both an approach based on the Smoluchowski theory of aggregation that does
not consider the spatial structure of the aggregates and a continuous model for cell
mixtures based on the Onsager formalism combined with the Rayleigh principle for the
dynamics of dissipative systems. We show how ...
Bone Tissue Engineering has been focusing on improving the current methods for bone repair, being the use of scaffolds presented as an upgrade to traditional surgery techniques. Scaffolds are artificially porous matrices, meant to promote cell seeding and proliferation, being these properties influenced by the permeability of the structure. This work employed experimental pressure drop tests and Computational Fluid Dynamics models to assess permeability (and fluid streamlines) within ...
Mechanobiology of the Mitotic Spindle
N. Pavin and I. M. Tolic
The mitotic spindle is a microtubule-based assembly that separates the chromosomes during cell division. As the spindle is basically a mechanical micro machine, the understanding of its functioning is constantly motivating the development of experimental approaches based on mechanical perturbations, which are complementary to and work together with the classical genetics and biochemistry methods. Recent data emerging from these approaches in combination with theoretical modeling led to novel ideas and ...
3D interrelationship between osteocyte network and forming mineral during human bone remodeling
M. Ayoubi, A. F. van Tol, R, Weinkamer, P. Roschger, P. C. Brugger, A. Berzlanovich, L. Bertinetti, A. Roschger, P. Fratzl
Advanced Healthcare Materials
During bone remodeling, osteoblasts are known to deposit unmineralized collagenous tissue (osteoid), which mineralizes after some time lag. Some of the osteoblasts differentiate into osteocytes, forming a cell network within the lacunocanalicular network (LCN) of bone. To get more insight into the potential role of osteocytes in the mineralization process of osteoid using focused ion beam‐scanning electron microscopy...
Too rigid to fold: Carotenoid-dependent decrease in thylakoid fluidity hampers the formation of chloroplast grana
M. Bykowski, R. Mazur, J. Wójtowicz, S. Suski, M. Garstka, A. Mostowska, L. Kowalewska
In chloroplasts of land plants, the thylakoid network is organized into appressed regions called grana stacks and loosely arranged parallel stroma thylakoids. Many factors determining such intricate structural arrangements have been identified so far, including various thylakoid-embedded proteins, and polar lipids that build the thylakoid matrix...
Polyelectrolyte substrate coating for controlling biofilm growth at solid–air interface
N. V. Ryzhkov, A. A. Nikitina, P. Fratzl, C. M. Bidan, E. V. Skorb
Advanced Materials Interfaces
Because bacteria–surface interactions play a decisive role in bacteria adhesion and biofilm spreading, it is essential to understand how biofilms respond to surface properties to develop effective strategies to combat them. Polyelectrolyte coating is a simple and efficient way of controlling surface charge and energy. Using polyelectrolytes of various types, with different molecular weights and polyelectrolyte solutions of various pH...
Hierarchical self-assembly of a striped gyroid formed by threaded chiral mesoscale networks
J. J. K. Kirkensgaard, M. E. Evans, L. de Campo, and S. T. Hyde
Proceedings of the National Academy of Sciences
Chirality and hierarchical ordering are two fundamental properties found in many of nature’s most complex self-assembled structures such as living cells. Simultaneous control over these properties in synthetic systems is vital to mimic or even surpass nature’s designs. Via numerical simulations, we describe a class of complex morphologies that afford radically new architectures for self-assembled shapes. Specifically, a mixture of two ...
Y. Guyot, F.P. Luyten, J. Schrooten, I. Papantoniou, L. Geris
Bone tissue engineering strategies use flow through perfusion bioreactors to apply mechanical stimuli to cells seeded on porous scaffolds. Cells grow on the scaffold surface but also by bridging the scaffold pores leading a fully filled scaffold following the scaffold's geometric characteristics. Current computational fluid dynamic approaches for tissue engineering bioreactor systems have been mostly carried out for empty scaffolds. The effect of 3D cell growth and extracellular matrix formation (termed in this study as ...
P. Bassereau, R. Jin, T. Baumgart, M. Deserno, R. Dimova, V. A. Frolov,
P. V. Bashkirov, H. Grubmüller, R. Jahn, H. J. Risselada, L. Johannes, M. M. Kozlov, R. Lipowsky, T. J. Pucadyil, W. F. Zeno, J. C. Stachowiak, D. Stamou, A. Breuer, L. Lauritsen, C. Simon, C. Sykes, G. A. Voth and T. R. Weik
The importance of curvature as a structural feature of biological membranes has been recognized for many years and has fascinated scientists from a wide range of different backgrounds. On the one hand, changes in membrane morphology are involved in a plethora of phenomena involving the plasma membrane of eukaryotic cells, including endo- and exocytosis, phagocytosis and filopodia formation. On the other hand, a multitude of intracellular processes at the level of organelles rely on generation, modulation, and maintenance of membrane curvature to maintain the organelle shape and functionality...
R. Dasgupta, M. S. Miettinen, N. Fricke, R. Lipowsky, and R. Dimova
The ganglioside GM1 is present in neuronal membranes at elevated concentrations with an asymmetric spatial distribution. It is known to generate curvature and can be expected to strongly influence the neuron morphology. To elucidate these effects, we prepared giant vesicles with GM1 predominantly present in one leaflet of the membrane, mimicking the asymmetric GM1 distribution in neuronal membranes. Based on pulling inward and outward tubes, we developed a technique that allowed the direct measurement of the membrane spontaneous curvature ...