Preparation of thermoresponsive polymer brush surfaces and their interaction with cells

Poly(N-isopropylacrylamide) (PIPAAm) brush surfaces with different layer thickness on polystyrene substrates were prepared by surface-initiated atom transfer radical polymerization (ATRP). Surface characteristics of PIPAAm brushes and their influence on adhesion and detachment of bovine carotid artery endothelial cells (ECs) were controlled by PIPAAm layer thickness. Surface hydrophilicity increased with PIPAAm layer thickness at 37 °C because PIPAAm brush surfaces with higher thickness provide more extended chain conformations with relatively high chain mobility, and accompanying polymer chain hydration. These surface property alterations lead to negligible cell adhesion through minimal matrix protein adsorption and also modified surface modulus. By adjusting polymerization reaction conditions and time, polymer layers supporting confluent cultures of ECs were possible. Confluent EC monolayers spontaneously detached as contiguous cell sheets from PIPAAm brush surfaces at reduced temperatures. Thermoresponsive cell adhesion and detachment behavior were analyzed from the standpoint of surface physicochemical characteristics. Thermoresponsive surfaces prepared by surface-initiated ATRP techniques allow surface selection in preparing cell sheets from attachment-dependent cells having relatively strong adhesive property for tissue engineering applications.