Reversible attachment on soft substrates is useful in a range of applications, including soft robotics and soft‐tissue surgical instrumentation. On rigid substrates, the use of micropatterned ...adhesives has been extensively explored. It has been shown that surface micropatterns provide conformability, thereby enabling the formation and preservation of contact with the substrate. On soft, deformable substrates, on the other hand, surface micropatterns largely lose their functionality. Alternative mechanisms have to be explored to maximize conformability and thus formation and preservation of contact on soft substrates. 3D‐printing is used to fabricate adhesives with internal cylindrical pores of various configurations leading to different combinations of high/low normal/shearing stiffness, and shear forces are measured on glass and on soft elastomeric substrates. On the glass substrate, shear forces are highest for the adhesives with the lowest normal stiffness, independently from their shear stiffness. On the soft substrates, the highest shear forces are achieved for the adhesives combining low normal stiffness, enabling contact formation, with high shear stiffness, promoting contact preservation. The beneficial effect of such anisotropic stiffness on shear forces increased with the deformability of the substrate.
3D‐printing is used to fabricate a series of anisotropic adhesives with internal cylindrical pores of various configurations leading to different combinations of high/low normal/shearing stiffness and measured shear forces on glass and on soft elastomeric substrates. The beneficial effect of such anisotropic stiffness on shear forces increased with the deformability of the substrate.
Dynamic covalent chemistry (DCC) has proven to be a valuable tool in creating fascinating molecules, structures, and emergent properties in fully synthetic systems. Here we report a system that uses ...two dynamic covalent bonds in tandem, namely disulfides and hydrazones, for the formation of hydrogels containing biologically relevant ligands. The reversibility of disulfide bonds allows fiber formation upon oxidation of dithiol‐peptide building block, while the reaction between NH−NH2 functionalized C‐terminus and aldehyde cross‐linkers results in a gel. The same bond‐forming reaction was exploited for the “decoration” of the supramolecular assemblies by cell‐adhesion‐promoting sequences (RGD and LDV). Fast triggered gelation, cytocompatibility and ability to “on‐demand” chemically customize fibrillar scaffold offer potential for applying these systems as a bioactive platform for cell culture and tissue engineering.
Here we report functionalized peptides that can participate in disulfide and acyl‐hydrazone chemistry. DCLs of such molecules yield self‐assembling fibres. We incorporated cell adhesion‐promoting sequences into the scaffold that can undergo hydrogelation to obtain materials that present biologically relevant ligands. The importance of this work lies in the methodology for fabricating tailor‐made materials through a modular approach.
A series of novel 3,4-diarylpyrazolines was synthesized and evaluated in cannabinoid (hCB1 and hCB2) receptor assays. The 3,4-diarylpyrazolines elicited potent in vitroCB1 antagonistic activities and ...in general exhibited high CB1 vs CB2 receptor subtype selectivities. Some key representatives showed potent pharmacological in vivo activities after oral dosing in both a CB agonist-induced blood pressure model and a CB agonist-induced hypothermia model. Chiral separation of racemic 67, followed by crystallization and an X-ray diffraction study, elucidated the absolute configuration of the eutomer 80 (SLV319) at its C4 position as 4S. Bioanalytical studies revealed a high CNS−plasma ratio for the development candidate 80. Molecular modeling studies showed a relatively close three-dimensional structural overlap between 80 and the known CB1 receptor antagonist rimonabant (SR141716A). Further analysis of the X-ray diffraction data of 80 revealed the presence of an intramolecular hydrogen bond that was confirmed by computational methods. Computational models and X-ray diffraction data indicated a different intramolecular hydrogen bonding pattern in the in vivo inactive compound 6. In addition, X-ray diffraction studies of 6 revealed a tighter intermolecular packing than 80, which also may contribute to its poorer absorption in vivo. Replacement of the amidine -NH2 moiety with a -NHCH3 group proved to be the key change for gaining oral biovailability in this series of compounds leading to the identification of 80.
Linear shear in a model granular system Ren, Jie; Dijksman, Joshua A; Behringer, Robert P
Chaos (Woodbury, N.Y.),
12/2011, Letnik:
21, Številka:
4
Journal Article
Atomic force microscopy provides direct atomic-scale access to friction. In this paper, unexpected and potentially dramatic consequences of the tip elasticity are discussed. Under certain natural ...conditions an essentially new, nontrivial regime can be entered. Although the tip appears to perform typical stick-slip motion, the tip-surface contact is fully "lubricated" by fast thermal motion of the tip apex. The interpretation of the observations needs to be changed completely in this case.
Astringency is one of the most complex oral sensations. This dry, puckering mouthfeel occurs when consuming wine, tea, or other foods containing polyphenols. The exact mechanism behind this dry ...mouthfeel is not completely understood. Here, we describe a systematic tribological approach to measure model and real saliva to understand the specific role of the salivary proteins (mucins and proline-rich proteins (PRPs)) on lubrication-based astringency. Our approach reveals that there are two routes towards lubrication losses, partly involving irreversible molecular mechanisms for which the order of reactivity matters. For human saliva, we find two lubrication mechanisms: (I) Using phenolic compounds, we find aggregation-induced lubrication losses due to hydrogen bond formation, which depend critically on phenol size: large polyphenols allow for aggregation-induced lubrication losses, but small phenols do not. (II) For metal salts combined with saliva, we observe aggregation without lubrication losses as a result of electrostatic interactions. We find that lubrication losses are caused by the specific removal of the salivary PRP layer, whereas mucin aggregation in the presence of PRPs does not lead to lubrication losses. Additionally, we show that the addition of solvents that are able to reduce protein-polyphenol hydrogen bonding (e.g. ethanol) can prevent lubrication losses. Lubrication losses can also be compensated by the addition of highly viscous fluids (glycerol) that can provide viscous lubrication.
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•Large polyphenols aggregate PRPs leading to salivary lubrication losses related to astringency perception.•Mucin aggregation does not cause salivary lubrication losses when PRPs remain unaffected.•Salivary lubrication losses can be prevented by the addition of hydrogen-bond donors or highly viscous fluids.
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