Transiently thermally responsive surfaces: Concepts for cell sheet engineering

Abstract

Stimuli-sensitive or smart polymers are a most important class of soft materials which transiently adapt their physical and/or chemical properties upon small changes in the external environment. Given that, these polymers increasingly utilize in biorelated applications such as drug and gene delivery, biosensing, tissue regeneration and cell sheet engineering. Based on the type of response stimulus, smart polymers are divided into pH, temperature, electric or magnetic force, ionic strength and light responsive materials. In their midst, fast coil-to-globule transition of temperature-responding or thermo-responsive polymers about certain critical temperature has rendered these polymers very attractive especially from the biomedical point of view. Among lower critical solution temperature (LCST) and upper critical solution temperature (UCST) smart polymers, LCSTs are highly regarded in regenerative medicine, thanks to similarity of their critical point with physiological temperature of human body. Generally, LCST polymers are divided into synthetic and natural sub-groups with different exclusive properties. As the overwhelming majority of previously reported LCST polymers are based on poly (N-isopropyl acrylamide) (PNIPAm), we attempt to address other types of LCST polymers and discuss about their biorelated applications, especially cell sheet engineering at two-dimensional or three-dimensional states. By highlighting recent examples of newly developed LCST polymeric systems, we hope to address the development of new generations of smart materials as well.