Fluctuation-Based Super-Resolution Traction Force Microscopy

Cellular mechanics play a crucial role in tissue homeostasis and are often misregulated in disease. Traction force microscopy is one of the key methods that has enabled researchers to study fundamental aspects of mechanobiology; however, traction force microscopy is limited by poor resolution. Here, we propose a simplified protocol and imaging strategy that enhances the output of traction force microscopy by increasing i) achievable bead density and ii) the accuracy of bead tracking. Our approach relies on super-resolution microscopy, enabled by fluorescence fluctuation analysis. Our pipeline can be used on spinning-disk confocal or widefield microscopes and is compatible with available analysis software. In addition, we demonstrate that our workflow can be used to gain biologically relevant information and is suitable for fast long-term live measurement of traction forces even in light-sensitive cells. Finally, using fluctuation-based traction force microscopy, we observe that filopodia align to the force field generated by focal adhesions

Effective Delivery of the CRISPR/Cas9 System Enabled by Functionalized Mesoporous Silica Nanoparticles for GFP-Tagged Paxillin Knock-In

In this study, direct and effective intracellular delivery of CRISPR/Cas9 plasmids for homology-directed repair is achieved by functionalized mesoporous silica nanoparticles (MSNs). The functionalized MSNs (Cy5.5-MSNs-NLS) are synthesized by in situ labeling of a fluorescent dye (Cy5.5) and surface conjugation of nuclear localization sequence (NLS, PKKKRKV), showing a high loading efficiency (50%) toward the plasmids (PXN cutdown plasmid: GFP-Cas9-paxillin_gRNA and repair plasmid: AICSDP-1: PXN-EGFP). Subsequently, a polymeric coating of the poly(dimethyldiallylammonium chloride) (PDDA) is electrostatically deposited onto the plasmid-loaded Cy5.5-MSNs-NLS by microfluidic nanoprecipitation. The coating layer offers effective protection against the denaturation of plasmids by EcoRV restriction enzymes, and is shown to prevent premature release. Moreover, owing to the positive charge and pH-responsive disaggregation of PDDA, enhanced cellular internalization (16 h) and endosomal escape (4 h) of the nanocarrier are observed. After escape of nanocarrier system into the cytoplasm, the NLS on the surface of MSNs facilitates nuclear transport of the CRISPR/Cas9 plasmids, achieving successful GFP-tag knock-in of the PXN genomic sequence in U2OS cells. This intracellular delivery system thus offers an attractive method to overcome physiological barriers for CRISPR/Cas9 delivery, showing considerable promise for paxillin-associated focal adhesion and signaling regulator investigation

Effect of microstructure on the stability of retained austenite in transformation-induced-plasticity steels

Two Fe-0.2C-1.55Mn-1.5Si (in wt pet) steels, with and without the addition of 0.039Nb (in wt pet), were studied using laboratory rolling-mill simulations of controlled thermomechanical processing. The microstructures of all samples were characterized by optical metallography, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The microstructural behavior of phases under applied strain was studied using a heat-tinting technique. Despite the similarity in the microstructures of the two steels (equal amounts of polygonal ferrite, carbide-free bainite, and retained austenite), the mechanical properties were different. The mechanical properties of these transformation-induced-plasticity (TRIP) steels depended not only on the individual behavior of all these phases, but also on the interaction between the phases during deformation. The polygonal ferrite and bainite of the C-Mn-Si steel contributed to the elongation more than these phases in the C-Mn-Si-Nb-steel. The stability of retained austenite depends on its location within the microstructure, the morphology of the bainite, and its interaction with other phases during straining. Granular bainite was the bainite morphology that provided the optimum stability of the retained austenite.<br /

Exact essential norm of generalized Hilbert matrix operators on classical analytic function spaces

We compute the exact value of the essential norm of ageneralized Hilbert matrix operator acting on weightedBergman spaces Apv and weighted Banach spaces H∞v ofanalytic functions, where v is a general radial weight. Inparticular, we obtain the exact value of the essential normof the classical Hilbert matrix operator on standard weightedBergman spaces Apα for p &gt; 2 + α, α ≥ 0, and on Korenblumspaces H∞α for 0 &lt; α &lt; 1. We also cover the Hardy spaceHp, 1 &lt; p &lt; ∞, case. In the weighted Bergman space case, theessential norm of the Hilbert matrix is equal to the conjecturedvalue of its operator norm and similarly in the Hardy spacecase the essential norm and the operator norm coincide. Wealso compute the exact value of the norm of the Hilbert matrixon H∞wα with weights wα(z) = (1 − |z|)α for all 0 &lt; α &lt; 1. Also in this case, the values of the norm and essential normcoincide