Biomaterial surface energy-driven ligand assembly strongly regulates stem cell mechanosensitivity and fate on very soft substrates.

Although mechanisms of cell-material interaction and cellular mechanotransduction are increasingly understood, the mechanical insensitivity of mesenchymal cells to certain soft amorphous biomaterial substrates has remained largely unexplained. We reveal that surface energy-driven supramolecular ligand assembly can regulate mesenchymal stem cell (MSC) sensing of substrate mechanical compliance and subsequent cell fate. Human MSCs were cultured on collagen-coated hydrophobic polydimethylsiloxane (PDMS) and hydrophilic polyethylene-oxide-PDMS (PEO-PDMS) of a range of stiffnesses. Although cell contractility was similarly diminished on soft substrates of both types, cell spreading and osteogenic differentiation occurred only on soft PDMS and not hydrophilic PEO-PDMS (elastic modulus <1 kPa). Substrate surface energy yields distinct ligand topologies with accordingly distinct profiles of recruited transmembrane cell receptors and related focal adhesion signaling. These differences did not differentially regulate Rho-associated kinase activity, but nonetheless regulated both cell spreading and downstream differentiation.

Qualification of a surface plasmon resonance assay to determine binding of IgG-type antibodies to complement component C1q.

Interaction of therapeutic antibodies with complement component C1q are frequently part of pharmaceutical characterization and production process comparability studies. Assays currently used to assess this interaction and/or the activation of the complement cascade are often cumbersome, time consuming or imprecise. We here report the further development, successful qualification and suitability evaluation of an SPR-based C1q binding assay for the characterization of IgG-C1q interactions. We evaluate different IgG subtypes and well-described mutants of IgG1. The assay offers a suitable alternative for extended characterization of interactions of IgG1 and IgG3 with complement component C1q.

Terrorist attacks sharpen the binary perception of "Us" vs. "Them".

Terrorist attacks not only harm citizens but also shift their attention, which has long-lasting impacts on public opinion and government policies. Yet measuring the changes in public attention beyond media coverage has been methodologically challenging. Here we approach this problem by starting from Wikipedia's répertoire of 5.8 million articles and a sample of 15 recent terrorist attacks. We deploy a complex exclusion procedure to identify topics and themes that consistently received a significant increase in attention due to these incidents. Examining their contents reveals a clear picture: terrorist attacks foster establishing a sharp boundary between "Us" (the target society) and "Them" (the terrorist as the enemy). In the midst of this, one seeks to construct identities of both sides. This triggers curiosity to learn more about "Them" and soul-search for a clearer understanding of "Us". This systematic analysis of public reactions to disruptive events could help mitigate their societal consequences.