26 research outputs found
Tissue fusion over non-adhering surfaces
Tissue fusion eliminates physical voids in a tissue to form a continuous
structure and is central to many processes in development and repair. Fusion
events in vivo, particularly in embryonic development, often involve the
purse-string contraction of a pluricellular actomyosin cable at the free edge.
However in vitro, adhesion of the cells to their substrate favors a closure
mechanism mediated by lamellipodial protrusions, which has prevented a
systematic study of the purse-string mechanism. Here, we show that monolayers
can cover well-controlled mesoscopic non-adherent areas much larger than a cell
size by purse-string closure and that active epithelial fluctuations are
required for this process. We have formulated a simple stochastic model that
includes purse-string contractility, tissue fluctuations and effective friction
to qualitatively and quantitatively account for the dynamics of closure. Our
data suggest that, in vivo, tissue fusion adapts to the local environment by
coordinating lamellipodial protrusions and purse-string contractions
Failure mechanisms of graphene under tension
Recent experiments established pure graphene as the strongest material known
to mankind, further invigorating the question of how graphene fails. Using
density functional theory, we reveal the mechanisms of mechanical failure of
pure graphene under a generic state of tension. One failure mechanism is a
novel soft-mode phonon instability of the -mode, whereby the graphene
sheet undergoes a phase transition and is driven towards isolated benzene rings
resulting in a reduction of strength. The other is the usual elastic
instability corresponding to a maximum in the stress-strain curve. Our results
indicate that finite wave vector soft modes can be the key factor in limiting
the strength of monolayer materials
Perspective: The promise of multi-cellular engineered living systems
Recent technological breakthroughs in our ability to derive and differentiate induced pluripotent stem cells, organoid biology, organ-on-chip assays, and 3-D bioprinting have all contributed to a heightened interest in the design, assembly, and manufacture of living systems with a broad range of potential uses. This white paper summarizes the state of the emerging field of "multi-cellular engineered living systems," which are composed of interacting cell populations. Recent accomplishments are described, focusing on current and potential applications, as well as barriers to future advances, and the outlook for longer term benefits and potential ethical issues that need to be considered.National Science Foundation (U.S.) Science Technology Center. Emergent Behaviors of Integrated Cellular Systems (Grant CBET0939511)National Cancer Institute (U.S.) (Grant U01 CA202177