Physical Concepts Toward Cell–Material Integration

“Integration” of biological cells and materials has been discussed over the past 10–15 years. Several institutions, including iCeMS of Kyoto University, have been trying to achieve this ambitious goal. One of the major problems that is often overlooked is physical roles of interfaces, where cells meet materials. Ample evidence, both experimental and theoretical, has suggested that “interface” is not merely a boundary between two bulk phases but possesses distinct structures and functions under or out of equilibrium. In biological systems, the characteristic length scale ranges from several nm up to sub-μm (called mesoscopic). Unfortunately, the importance of science in mesoscopic length scale has not been well understood/appreciated neither by biologists nor chemists until very recently. For example, “biocompatibility of material” is frequently discussed only in terms of hydrophilicity/hydrophobicity, charge, or chemical functionality of the surface, ignoring the presence of hydration repulsion, long-range van der Waals interaction, and passive and active fluctuation of cells and biomacromolecules. This chapter aims to provide with a comprehensive overview on the basic physical principles “how cells meet materials in mesoscopic space” from the viewpoint of physics, which may help us improve the strategy for cell–material fusion.