Development of soft nanocomposite materials and their applications in cell culture and tissue engineering

Novel soft nanocomposite materials with unique organic/inorganic network structures have been developed by extending the strategy of "organic/inorganic nanocomposites" to the field of soft materials. The structures described here were synthesized by in-situ free-radical polymerization of various monomers in the presence of exfoliated clay (hectorite) in aqueous media. The nanocomposite hydrogels (NC gels) and soft nanocomposites (M-NCs) obtained were flexible and transparent soft materials, regardless of the clay content, that could be prepared in various shapes and surface forms, each consisting of individually different polymer/clay network structures. Owing to these unique network structures, both NC gels and M-NCs showed extraordinary mechanical properties such as ultrahigh elongation at break and widely controlled modulus and strength, which could overcome the problems (e.g., mechanical fragility, optical turbidity, poor processing ability) associated with conventional chemically crosslinked materials. In addition, the NC gels and M-NCs exhibited a number of new characteristics related to optical anisotropy, morphology, biocompatibility, stimulus sensitivity and cell culture. In the present review, we outline the novel features of these soft nanocomposites, and demonstrate their potential as soft culture substrates useful for tissue engineering as well as soft, transparent, absorbing, and mechanically tough biomaterials for many bio-applications.