Shear-Induced Detachment of Polystyrene Beads from SAM-Coated Surfaces

Abstract

In this work we experimentally and theoretically analyze the detachment of microscopic polystyrene beads from different self-assembled monolayer (SAM) surfaces in a shear flow in order to develop a mechanistic model for the removal of cells from surfaces. The detachment of the beads from the surface is treated as a thermally activated process applying an Arrhenius Ansatz to determine the activation barrier and attempt frequency of the rate determing step in bead removal. The statistical analysis of the experimental shear detachment data obtained in phosphate-buffered saline buffer results in an activation energy around 20 kJ/mol, which is orders of magnitude lower than the adhesion energy measured by atomic force microscopy (AFM). The same order of magnitude for the adhesion energy measured by AFM is derived from ab initio calculations of the van der Waals interaction energy between the polystyrene beads and the SAM-covered gold surface. We conclude that the rate determing step for detachment of the beads is the initiation of rolling on the surface (overcoming static friction) and not physical detachment, i.e., lifting the particle off the surface.

Tuning the Cell Adhesion on Biofunctionalized Nanoporous Organic Frameworks

“…As demonstrated by the results shown in Figure B, the critical shear stress τ 50 was significantly higher on RGD‐functionalized substrates in comparison to nonfunctionalized SURGELs. This finding of a stronger adhesion of the CAL72 cells due to the RGD functionalization correlates well with the observed increased mean cell area on the RGD functionalized substrates . These experiments show that by functionalization of the SURGEL substrates with biomolecules, such as RGD, we can tune the cell–material interaction.…”

Optimization of mechanical properties of glass‐spheres‐filled polypropylene composites for extrusion‐based additive manufacturing

“…This results in strong covalent bonds between the E‐glass and its coating and, thus, in improved mechanical properties. Furthermore, a strong interface prevents the peel‐off of the coating during processing at elevated temperatures and shear conditions, which has been reported to occur for weak matrix–filler interfaces , such as the combination of A‐glass and the aminosilane coating. Moreover, E‐glass exhibits a smaller surface contact angle with water than A‐glass , which is an indication for a more reactive surface.…”

“…a) and with the weak interfacial bonding between the coating and the A‐glass (see “ Tensile Properties ”). During shear deformation, the spheres can detach from the coating , resulting in an increased tendency to agglomerate and, hence, an elevated viscosity at low shear rates . Contrary to this, the compound PP/MA/E‐C reaches a Newtonian plateau for frequencies lower than 50 rad s −1 .…”

Modulating wall shear stress gradient via equilateral triangular channel for in situ cellular adhesion assay

“…In a recent work by Cho et al, there are no exact correlations between the normal adhesion force and the shear adhesion strength, but it has been elucidated that the required activation energy to peeling-off detachment of particles through applying shear stress is small compared to the energy to normal lift-off detachment. 21 Although there remains whether the normal adhesion force or shear adhesion strength is a suitable parameter for quantification of the cell adhesion, the cell adhesion strength with the shear stress term has been widely reported with the various cell types on the different substrates. [6][7][8][9][10][11][12][13][14]22,23 Besides, there have been attempts to demonstrate the mechanical model to estimate the magnitude of the normal force when the WSS is applied to the adhered cells to evaluate the binding force of the integrin receptors to extracellular ligands.…”