Cell sheet engineering: intelligent polymer patterned surfaces for tissue engineered liver

We describe a new culture system utilizing the temperature-responsive polymer grafted surface for designing of cell position and layered tissue reconstruction. Organizing of the hepatic tissue structure by controlling the culture system, that is patterned co-culture and layered cell sheet co-culture achieved by moving the cultured cells from the culture surface, resulted in regulation of the hepatocyte function. The technique for cell sheet manipulation would promote the liver tissue engineering in quality.     

Temperature-responsive,polymer-modified surfaces for green chromatography

Thermoresponsive poly(N-isopropylacrylamide) (PIPAAm) and its derivatives were utilized as chromatography column matrix modifiers to develop novel supports for thermoresponsive hydrophobic chromatography with aqueous mobile phase. In the column, matrix surfaces show thermoresponsive hydrophilic/hydrophobic property alterations, which alter interaction with and retention of solutes to be separated. We have also demonstrated that the electrostatic interaction of ionic solutes and charged, thermoresponsive polymer-modified surfaces can be modulated temperature changes in the aqueous mobile phase alone.     

Fast swelling/deswelling kinetics of comb-type grafted poly(N-isopropylacrylamide) hydrogels

The synthesis and characterization of comb-type grafted thermo-sensitive hydrogels is presented. These hydrogels were synthesized by polymerization of N-isopropylacrylamide (IPAAm) with a PIPAAm macromonomer. This process leads to a crosslinked IPAAm backbone polymer, copolymerized with highly mobile comb-type PIPAAm chains. These new thermo-responsive copolymers displayed higher equilibrium swellings at lower temperatures and rapid deswelling kinetics at elevated temperatures. The swelling/deswelling for comb-type gels is dependent on the graft chain lengths, in contrast to normal PIPAAm gel lacking the graft chains. As the temperature is increased above the critical temperature, the dehydrated graft chains aggregated due to hydrophobic attraction. Rapid and reversible kinetics of the graft-type gel were observed in response to stepwise temperature changes within short time cycles: phenomena not observed in normal crosslinked thermo-sensitive gels. The influence of freely mobile graft chains on both the equilibrium and dynamic properties of comb-type PIPAAm gel is demonstrated. Possible application of graft-type gel is discussed for actuator systems.