Use of magnetic nanoparticles to monitor alginate-encapsulated betaTC-tet cells.

Noninvasive monitoring of tissue-engineered constructs is an important component in optimizing construct design and assessing therapeutic efficacy. In recent years, cellular and molecular imaging initiatives have spurred the use of iron oxide-based contrast agents in the field of NMR imaging. Although their use in medical research has been widespread, their application in tissue engineering has been limited. In this study, the utility of monocrystalline iron oxide nanoparticles (MIONs) as an NMR contrast agent was evaluated for betaTC-tet cells encapsulated within alginate/poly-L-lysine/alginate (APA) microbeads. The constructs were labeled with MIONs in two different ways: 1) MION-labeled betaTC-tet cells were encapsulated in APA beads (i.e., intracellular compartment), and 2) MION particles were suspended in the alginate solution prior to encapsulation so that the alginate matrix was labeled with MIONs instead of the cells (i.e., extracellular compartment). The data show that although the location of cells can be identified within APA beads, cell growth or rearrangement within these constructs cannot be effectively monitored, regardless of the location of MION compartmentalization. The advantages and disadvantages of these techniques and their potential use in tissue engineering are discussed.