Haemostasis occurs at sites of vascular injury, where flowing blood forms a clot, a dynamic and heterogeneous fibrin-based biomaterial. Paramount in the clot’s capability to stem haemorrhage are its changing mechanical properties, the major driver of which are the contractile forces exerted by platelets against the fibrin scaffold 1. However, how platelets transduce microenvironmental cues to mediate contraction and alter clot mechanics is unknown. This is clinically relevant, as overly softened and stiffened clots are associated with bleeding 2 and thrombotic disorders 3. Here, we report a high-throughput hydrogel based platelet-contraction cytometer that quantifies single-platelet contraction forces in different clot microenvironments. We also show that platelets, via the Rho/ROCK pathway, synergistically couple mechanical and biochemical inputs to mediate contraction. Moreover, highly contractile platelet subpopulations present in healthy controls are conspicuously absent in a subset of patients with undiagnosed bleeding disorders, and therefore may function as a clinical diagnostic biophysical biomarker.
This study introduces an extremely stable attractive nanoscale emulsion fluid, in which the amphiphilic block copolymer, poly(ethylene oxide)-block-poly(ϵ-caprolactone) (PEO-b-PCL), is tightly packed with lecithin, thereby forming a mechanically robust thin-film at the oil-water interface. The molecular association of PEO-b-PCL with lecithin is critical for formation of a tighter and denser molecular assembly at the interface, which is systematically confirmed by T relaxation and DSC analyses. Moreover, suspension rheology studies also reflect the interdroplet attractions over a wide volume fraction range of the dispersed oil phase; this results in a percolated network of stable drops that exhibit no signs of coalescence or phase separation. This unique rheological behavior is attributed to the dipolar interaction between the phosphorylcholine groups of lecithin and the methoxy end groups of PEO-b-PCL. Finally, the nanoemulsion system significantly enhances transdermal delivery efficiency due to its favorable attraction to the skin, as well as high diffusivity of the nanoscale emulsion drops.
An attractive nanoemulsion fluid system with a drop‐percolated network is depicted in the image, in which dipole–dipole interaction between phosphorylcholine groups of lecithin and methoxy end groups of poly(ethylene oxide)‐block‐poly(ϵ‐caprolactone) leads to a gel‐like rheological behavior. This intriguing emulsion system significantly enhances transdermal delivery efficiency due to its favorable attraction to the skin as well as high diffusivity of the nanoscale emulsion drops. More information can be found in the Full Paper by Y. Lee, A. Fernandez‐Nieves, J. W. Kim et al. on page 4292 ff.
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