Figure 1.

Schematic diagram. Schematic diagram of the thermal response of cells on PNIPAAm immobilized on PCL surfaces (a) as well as the reactions to immobilize PNIPAAm on PCL (b). At 37 °C the conformation of PNIPAAAm is like a random coil which provides a hydrophobic surface on PCL macrocarriers. When the temperature is dropped down to 30 °C, the conformation changes to globular causing the surface to be hydrophilic in nature. A hydrophobic surface attracts cells whereas a hydrophilic surface repels the cells as shown in figure (a). In order to immobilize PNIPAAm on PCL surfaces a simple amidation reaction was carried out following the introduction of both carboxylic and amine groups on PCL surfaces and in PNIPAAm respectively (b). The amine group (NH₂) was introduced to PCL-COO- whereas carboxylic groups on PCL were activated by using EDC/NHS.