Magnetic separation of cells in coculture systems using magnetite cationic liposomes

In tissue engineering, coculture systems have been employed for two major purposes: (1) construction of tissue and organ substitutes (e.g., coculture of parenchymal and nonparenchymal cells in liver tissue engineering) and (2) maintenance of cellular functions (e.g., coculture of embryonic stem cells with embryonic fibroblasts as the feeder cells). For the characterization and recovery of specific cell types, however, target cells have to be isolated from other cells. We report here a novel magnetic separation method to isolate target cells in coculture systems. In this method, target cells were cocultured with nontarget cells labeled with magnetite cationic liposomes (MCLs). Thus, when necessary, the MCL-labeled nontarget cells were magnetically removed from the coculture, resulting in negative isolation of the target cells. As the separation models, three deferent types of coculture systems were examined: rat hepatocytes with various MCL-labeled cells (mouse NIH3T3, STO, or human umbilical vein endothelial cells), human keratinocyte HaCaT cells with MCL-labeled NIH3T3 cells, and mouse embryonic stem cells with MCL-labeled STO cells. In these cocultures, target cells were separated with 94% purity and 98%recovery yield on average. This technique provides a promising approach to isolate and recover target cells for further analysis and application.