Actin-microtubule dynamic composite forms responsive active matter with memory

Active cytoskeletal materials in vitro demonstrate self-organising properties similar to those observed in their counterparts in cells. However, the search to emulate phenomena observed in the living matter has fallen short of producing a cytoskeletal network that would be structurally stable yet possessing adaptive plasticity. Here, we address this challenge by combining cytoskeletal polymers in a composite, where self-assembling microtubules and actin filaments collectively self-organise due to the activity of microtubules-percolating molecular motors. We demonstrate that microtubules spatially organise actin filaments that in turn guide microtubules. The two networks align in an ordered fashion using this feedback loop. In this composite, actin filaments can act as structural memory and, depending on the concentration of the components, microtubules either write this memory or get guided by it. The system is sensitive to external stimuli suggesting possible autoregulatory behaviour in changing mechanochemical environment. We thus establish artificial active actin-microtubule composite as a system demonstrating architectural stability and plasticity.

Collagen polarization promotes epithelial elongation by stimulating locoregional cell proliferation

Epithelial networks are commonly generated by processes where multicellular aggregates elongate and branch. Here we focus on understanding cellular mechanisms for elongation, using an organotypic culture system as a model of mammary epithelial anlage. Isotropic cell aggregates broke symmetry and slowly elongated when transplanted into collagen 1 gels. The elongating regions of aggregates displayed enhanced cell proliferation that was necessary for elongation to occur. Strikingly, this loco-regional increase in cell proliferation occurred where collagen 1 fibrils reorganized into bundles which were polarized with the elongating aggregates. Applying external stretch as a cell-independent way to reorganize the ECM, we found that collagen polarization stimulated regional cell proliferation to precipitate symmetry-breaking and elongation. This required b1-integrin and ERK signaling. We propose that collagen polarization supports epithelial anlagen elongation by stimulating loco-regional cell proliferation. This could provide a long-lasting structural memory of the initial axis that is generated when anlage break symmetry.

Nanosensors Based on Structural Memory Carbon Nanodots for Ag+ Fluorescence Determination

Ag+ pollution is of great harm to the human body and environmental biology. Therefore, there is an urgent need to develop inexpensive and accurate detection methods. Herein, lignin-derived structural memory carbon nanodots (CSM-dots) with outstanding fluorescence properties were fabricated via a green method. The mild preparation process allowed the CSM-dots to remain plentiful phenol, hydroxyl, and methoxy groups, which have a specific interaction with Ag+ through the reduction of silver ions. Further, the sulfur atoms doped on CSM-dots provided more active sites on their surface and the strong interaction with Ag nanoparticles. The CSM-dots can specifically bind Ag+, accompanied by a remarkable fluorescence quenching response. This “turn-off” fluorescence behavior was used for Ag+ determination in a linear range of 5–290 μM with the detection limit as low as 500 nM. Furthermore, findings showed that this sensing nano-platform was successfully used for Ag+ determination in real samples and intracellular imaging, showing great potential in biological and environmental monitoring applications.

Nanosensors Based on Structural Memory Carbon Nanodots for Ag+ Fluorescence Determination

Ag+ pollution is great of harm to the human body and the biology. Therefore, it is an urgent need to develop inexpensive and accurate detection methods. Herein, lignin-derived structural memory carbon nanodots (CSM-dots) with outstanding fluorescence property were fabricated via a green method, which reserve functional and structural units of the precursor molecules. The CSM-dots could specifically bind Ag+, accompanied with a remarkable fluorescence quenching response. This “turn-off” fluorescence behavior was used for Ag+ determination in a linear range of 5-290 μM with the detection limit as low as 500 nM. Furthermore, the finding showed that this sensing nano-platform was successfully used for Ag+ determination in real samples and intracellular imaging, showing great potential in biological and environmental monitoring applications.

Collagen polarization provides a structural memory for the elongation of epithelial anlage

Branched epithelial networks are fundamental features of many organs in the body. The biogenesis of these networks involves distinct processes where multicellular aggregates elongate and branch. In this report we focus on understanding how the extracellular matrix contributes to the process of elongation. Using mammary epithelial organotypic cultures we found that collagen 1, but not a basement membrane extract, induces the formation of elongated multicellular aggregates. Indeed, isotropic aggregates, used as models of epithelial anlage, broke symmetry and elongated when transplanted into collagen 1 gels; this was accompanied by reorganization of collagen fibrils into bundles that were polarized around the elongating aggregates. By applying external stretch as a cell-independent way to reorganize the ECM gels, we found that collagen polarization itself can induce and guide the direction of aggregate elongation. This critically involves cell proliferation, which is selectively enhanced in the regions of anlage that elongate, and requires β1-integrin and ERK signaling. We propose that collagen polarization promotes anlage elongation by providing a structural memory of the initial axis that is generated when aggregates break symmetry.