Design of novel biointerfaces (I). Blood compatibility of poly(2-methoxyethyl acrylate)

We have reported that poly(2-methoxyethyl acrylate) (PMEA) shows excellent blood compatibility with respect to the coagulation, complement, leukocyte and platelet systems in vitro and ex vivo when compared with other polymer surfaces. In this study, to clarify the reasons for this good compatibility, the structure of water in the hydrated PMEA were investigated and compared to water structure of poly(2-hydroxyethyl methacrylate) (PHEMA) and polyacrylate analogs as references. The hydrated water in PMEA could be classified into three types; free water, freezing-bound water, and non-freezing water. Cold crystallization of water in the heating process was clearly observed at -42 degrees C. This cold crystallization is interpreted as the phase transition from the amorphous ice to the crystal ice that belongs to the freezing-bound water in PMEA. On the other hand, the cold crystallization peak (freezing bound water; which prevents the biocomponents from contacting the polymer surface or non-freezing water on the polymer surface) was not observed for hydrated PHEMA and PMEA analogous polymers. We hypothesized that the freezing-bound water layer between free water and non-freezing water was an important factor for the excellent blood compatibility of PMEA.