(475j) Enhanced Cell-Seeding into 3-D Scaffolds by Use of Magnetite Nanoparticles for Tissue Engineering

Tissue engineering is a promising technology for solving the organ transplantation crisis caused by donor shortage. One approach to tissue engineering is to isolate cells from a small tissue biopsy, expand the cells in vitro, and seed them into three-dimensional (3-D) porous biodegradable scaffolds that allow the cells to reconstruct tissues, via cell adhesion, proliferation and deposition of extracellular matrix (ECM). In these processes, cell seeding is the first step in constructing the 3-D tissue-like structures, and it is known that cell seeding into scaffolds at high density is closely associated with enhancement of tissue formation in 3-D constructs. However, technical difficulties in cell seeding are caused by the complex structure of the scaffold and insufficient migration into the scaffolds due to pore size and material. Therefore, numerous methodologies for cell seeding into 3-D scaffolds have been investigated, but the establishment of conclusive and effective seeding method is still remaining. We previously proposed a methodology for tissue engineering using magnetite nanoparticles and magnetic force, which we termed ?Mag-TE? (Ito A et al. Tissue Eng 2004;10(5-6):833-840). In the present study, we applied the Mag-TE technique to a cell seeding process and have termed the technique ?Mag-seeding?. The cell-seeding efficiency of NIH/3T3 fibroblasts by Mag-seeding was investigated using 6 types of commercially available scaffold which were 5 collagen sponges and 1 D,D-L,L polylactic acid sponge having various pore sizes. NIH/3T3 fibroblasts were magnetically labeled with our original magnetite cationic liposomes (MCLs), which have a positive surface charge in order to improve adsorption onto the cell surface. NIH/3T3 fibroblasts labeled with MCLs were seeded onto a scaffold, and a magnet (4 kG) was placed under the scaffold. Mag-seeding facilitated successful cell seeding into the deep internal space of the scaffolds. Cell-seeding efficiency increased significantly in all scaffolds when compared to those without magnetic force. The highest cell-seeding efficiency of 70.0% was achieved when cells were seeded into PLA by Mag-seeding, while only 40% of cells were seeded by ordinary static seeding without magnet. Moreover, when a high-intensity magnet (10 kG) was used, cell-seeding efficiency was significantly enhanced. These results suggest that Mag-seeding is a promising approach for tissue engineering.