Receptor mediated adhesion under external stimuli.

Abstract

Poly (N-isopropylacrylamide) (PIPAAm) is a natural thermoresponsive polymer (TRP) that is widely used in tissue engineering and drug delivery [5-14]. Studies have found that PIPAAm can change its hydrophilicity by altering temperature. At temperatures above its lower critical solution temperature (LCST) of 32°C [7, 12], PIPAAm changes its conformation from expanded coil to a condensed globule; water molecules leaves the polymer [6-14] and hence displaying hydrophobic character. At this condition, cell adhesion is favourable; cells will adhere to the surface, spread and multiply in numbers [7, 10]. As the surface is cooled below its LCST, the polymer becomes hydrated and displays a hydrophilic character. Cells do not like this environment and they will reduce their contact area with the surface by becoming more spherical in shape and eventually get detached from the surface. With this intrinsic characteristic of PIPAAm, cells can be extracted from the surface via alterations in temperature without the use of enzymes [6- 10, 12, 14]. This can prevent damage to the cell surface proteins as well as the cell itself [7, 10, 14]. This study has successfully shown the evolution of cell de-adhesion on PIPAAm surface under confocal reflection interference and contrast microscopy (CRICM) and immunostaining and fluorescence microscopy.