Abstract
Interaction between polymers and soft-matter surfaces in the biological cell is a common yet incompletely understood phenomenon. This work investigates a generic situation where a thermoresponsive polymer gel is placed in the vicinity of an adsorbing surface, and starts contracting. The force is mediated by polymer chains that partially attach to the surface and partially to the contracting gel. The main goal was to understand how the force generated by the transforming polymer gel depends on key parameters that describe the system, most importantly, the concentration of the polymer, the length of the force-mediating polymer, and the the distance between the surface and the outer border of the contracting polymer gel. The key result of the paper is the Laplace transform (with regard to the polymer length) of the pulling force expression. Analytical approximations for the force have been obtained, and the exact expression for the pulling force is presented for the situation when the gel starts contracting. In depth analysis of the force behavior revealed several phases adopted by the polymer during the gel contraction.
Highlights
We had previously obtained direct experimental evidence for polymer-induced nanotube pulling from a self-assembled phospholipid membrane (Figure 1), that strongly suggests that the pulling action of polymer chains produces a significant force
Protein action on the cell membrane in combination with actin polymerization has been suggested as a mechanism driving lipid nanotube or exocytotic transport carrier formation,[6] polymer-membrane interactions might be involved in nanotube formation by means of pulling action.[7]
An intuitive expectation is that very long polymers should reduce their energy by leaving the membrane for the gel region
Summary
There are many instances in cell biology where polymers interact with soft-matter surfaces. We had previously obtained direct experimental evidence for polymer-induced nanotube pulling from a self-assembled phospholipid membrane (Figure 1), that strongly suggests that the pulling action of polymer chains produces a significant force. This force could could be an important factor in biomembrane transformations, such as deformation and tubulation. Apart from the in vivo examples discussed above, several engineering applications have been reported where polymer-decorated surfaces were used to control cell adhesion and release. We present a theoretical study of the forces that polymers can generate when they interact with a membrane surface. We investigate how the dynamics of polymer chains influences the force on a generic adsorbing membrane
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