Fabrication of Tunable 3D Cellular Structures in High Volume Using Magnetic Levitation Guided Assembly

Abstract

Tunable and reproducible size with high circularity is an important limitation to obtain three-dimensional (3D) cellular structures and spheroids in scaffold free tissue engineering approaches. Here, we present a facile methodology based on magnetic levitation (MagLev) to fabricate 3D cellular structures rapidly and easily in high-volume and low magnetic field. In this study, 3D cellular structures were fabricated using magnetic levitation directed assembly where cells are suspended and self-assembled by contactless magnetic manipulation in the presence of a paramagnetic agent. The effect of cell seeding density, culture time, and paramagnetic agent concentration on the formation of 3D cellular structures was evaluated for NIH/3T3 mouse fibroblast cells. In addition, magnetic levitation guided cellular assembly and 3D tumor spheroid formation was examined for five different cancer cell lines: MCF7 (human epithelial breast adenocarcinoma), MDA-MB-231 (human epithelial breast adenocarcinoma), SH-SY5Y (human bone-marrow neuroblastoma), PC-12 (rat adrenal gland pheochromocytoma), and HeLa (human epithelial cervix adenocarcinoma). Moreover, formation of a 3D coculture model was successfully observed by using MDA-MB-231 dsRED and MDA-MB-231 GFP cells. Taken together, these results indicate that the developed MagLev setup provides an easy and efficient way to fabricate 3D cellular structures and may be a feasible alternative to conventional methodologies for cellular/multicellular studies.

Biomedical Applications of Magnetic Levitation

“…[ 64 ] Another similar setup was used to find the effects of paramagnetic medium concentration, culture time, and cell seeding density on 3D cell culturing using mouse fibroblast cells and five different types of cancer cells (HeLa [human epithelial cervix adenocarcinoma], PC‐12 [rat adrenal gland pheochromocytoma], SH‐SY5Y [human bone marrow neuroblastoma], MDA‐MB‐231 [human epithelial breast adenocarcinoma], and MCF7 [human epithelial breast adenocarcinoma]). [ 131 ] It was reported that the circularity, area, and size of the spheroids could be controlled by manipulating cell culturing time, paramagnetic agent concentration, and cell seeding density. An increase of culture time resulted in the formation of a spheroid with larger diameters, ultimately decreasing cell viability due to the diffusion limitation (i.e., cell viability decreased from 92%, on day 3, to 58%, on day 7).…”

“…Overall, the platform provided an easy‐to‐use and low‐cost method to form 3D cell cultures for 3D bioprinting, regenerative medicine, and drug screening applications. [ 131 ]…”

“…Overall, the platform provided an easy-to-use and low-cost method to form 3D cell cultures for 3D bioprinting, regenerative medicine, and drug screening applications. [131] MagLev was used to culture a scaffold-free 3D breast cancer model in vitro in order to investigate homotypic as well as heterotypic cell-cell interactions, tumor-fibroblast interactions, and effects of tumor microenvironment on drug efficacy. [132] Doxorubicin (100 nM), a chemotherapy drug, was applied to the coculture of cancer cells and fibroblast, which resulted in an 80% and 45% decrease in the area and density of cancer cell culture, respectively, resembling in vivo findings and demonstrating the suitability of MagLev cell cultures for cancer drug studies.…”

In Vitro Magnetic Techniques for Investigating Cancer Progression

“…In this way, the aggregates levitate to a certain equilibrium height based on the balance of magnetic, gravitational, and buoyancy forces [52]. Magnetic levitation may occur with magnets sandwiching individual wells, where each well will form one spheroid, or sandwiching the length of a capillary channel, where multiple spheroids will form along the tube, sharing culture media [52,53]. Additionally, a paramagnetic media (media containing a known concentration of paramagnetic agent) can be used to suspend the cells rather than incorporating paramagnetic beads [53,54].…”

“…In principle, magnetic levitation improves kinetic imaging abilities because the spheroids can be spatially manipulated without direct contact and these spheroids should not undergo translational movement after reaching equilibrium. Successful traditional imaging has been demonstrated in a few studies [52,53,57]. However, for many magnetic levitation platforms, only side-view images are accessible due to the sandwiched magnets around the dish, which are not compatible with standard microscope objective positioning.…”