A new approach to assembling 3-D cell cultures is being pursued by Thomas Killian, Ph.D., and his collaborators at Rice University and Nano3D Biosciences. “Magnetic levitation through the use of magnetic nanoparticles is a new paradigm, providing the advantages of a simple platform that can easily be incorporated into existing protocols and diagnostics,” Dr. Killian asserted.
While there are a number of studies under way using biodegradable porous scaffolds, protein matrices, protein-based gels, or rotational-based bioreactors as a basis for three-dimensional in vitro structures, Dr. Killian argued that there are significant advantages to his approach.
He described a three-dimensional Bio-Assembler™ that relies on cellular uptake of a biocompatible gel containing magnetic iron oxide and gold nanoparticles.
Dr. Killian pointed out that the biological application of magnetic forces is well recognized. Magnetic resonance imaging is widely used in clinical diagnostic radiology, and magnetic nanoparticles have been employed in the manipulation of surface patterns, cell sorting, mechano-conditioning of cells, and cellular micromanipulation, among other applications.
Under the conditions used for creating levitated 3-D cell culture, magnetic iron oxide nanoparticles are well tolerated by mammalian cells, a result consistent with previous reports.
To form levitated 3-D cultures, Dr. Killian and his coworkers incubate the cells with the gel, allowing the cells to absorb the magnetic nanoparticles. Excess gel is then washed away. Application of an external magnet causes the treated cells to rise to the air-medium interface, and within 12 hours multicellular structures assemble themselves.
In experiments with neural stem cells, levitated structures formed branching configurations consistent with aggregated cell clusters. Human glioblastoma cells displayed certain biochemical functions (N-cadheren production) similar to in vivo tissue.
Finally, Dr. Killian argued that magnetic field manipulation may provide new opportunities for culturing and manipulating mixed populations of cells. When human glioblastoma cells and normal human astrocytes were separately cultured and then guided together by external magnetic fields, a clear interface separating the cell structures was initially evident.
By 12 hours, the populations began to fuse, lose their individual spherical shapes, and coalesce into a single spheroid with the human glioblastoma cells invading the structure composed of normal human astrocytes.
“These results illustrate the potential of this methodology for analysis of brain tumor invasiveness in co-culture assays, suggesting that 3-D culturing through magnetic levitation of cells is a useful biotechnology,” Dr. Killian concluded.