Development of Three-Dimensional Tissue Models Based on Hierarchical Cell Manipulation Using Nanofilms

The creation of artificial three-dimensional (3D) tissues possessing structure and function similar to natural tissue is a key challenge for implantable tissues in tissue engineering, and for model tissues in pharmaceutical assays. This account is a summary of our current research toward this challenge. We have developed a simple and unique bottom-up approach, hierarchical cell manipulation technique, using nanometer-sized layer-by-layer films consisting of fibronectin and gelatin (FN–G) as a nano-extracellular matrix (nano-ECM). The FN–G nanofilms were prepared directly on the cell surface, and we discovered that at least 6 nm thick FN–G films acted as a stable adhesive surface for adhesion of the second cell layer. Various 3D-layered constructs consisting of single or multiple types of cells were successfully fabricated, and the higher cellular activities induced from the 3D-structures as compared to monolayer structure were observed. Furthermore, the multilayered constructs like a blood vessel wall structure indicated almost the same drug response as in vivo natural blood vessels, suggesting the possibility to use as an in vitro blood vessel model to analyze drug response. Recently, we also developed a rapid bottom-up approach by a single cell coating using FN–G nanofilms, because the fabrication of two-layers (2L) is limited through the above technique due to the time required for stable cell adhesion. This rapid approach easily provided approximately eight-layered (8L) 3D-tissues after only one day of incubation. The layer number, cell type, and location were all successfully controlled by altering the seeding cell number and order. Moreover, fully and homogeneously vascularized tissues of 1 cm width and 50 µm height were obtained by a sandwich culture of the endothelial cells. These hierarchical cell manipulations will be promising to achieve one of the dreams of biomedical field, in vitro creation of artificial 3D-tissue models.