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Elemoso, et al.
not tenable for experimental determination. in moderate concentrations are not toxic and are
Structure prediction depends on protein recovered by binding iron ions in the body .
[22]
crystallography, which allows us to create a Demirci et al. were the first who have used the
mathematical model of the protein in question. method of magnetic levitation of cells without
• Biomaterial research its saturation with magnetic nanoparticle .
[23]
The calcium phosphate particles can be used Diamagnetic objects ranging in size from several
for bone defect regeneration. Microgravity millimeters to centimeters were used in these
allows obtaining biocompatible octocalcium experiments. Their final equilibrium configuration
phosphate phase rapidly in the final product. depended on the balance of magnetic and gravitational
Thus, magnetic levitation of calcium forces (in special paramagnetic environment, in the
phosphate particles is a promising approach gradient magnetic field created by special magnets,
for rapid 3D fabrication in the field of bone and in the absence of direct contacts between its
tissue engineering. components). Such approach allows to manage
More companies plan to participate in space building blocks in paramagnetic environments to
experiments. Cellink, a Swedish 3D bioprinter fabricate 3D construct . Gadolinium salts were
[24]
manufacturer, has announced a strategic collaboration added as the additional agent to enhance the medium
with Made In Space, a microgravity manufacturing paramagnetic properties in their experiments [25,26] .
specialist, to identify bioprinting opportunities for Gadolinium salts can be included in some contrast
the ISS (https://cellink.com/cellink-partners-with- mediums used in magnetic resonance imaging
made-in-space-for-microgravity-bioprinting/). US (e.g., Omniscan), so they are allowed for clinical
companies such as Allevi and Made In Space are use. Nevertheless, gadolinium salts in high
also developing 3D bioprinter for space . concentrations can cause toxic effect on cells and
[18]
In space, companies try to use two main tissue spheroids. This approach also creates certain
approaches: (i) Using classical extrusion bioprinting risk of osmotic pressure imbalance due to excessive
technology (main challenge to overcome ion concentration in the paramagnetic medium.
microgravity, and especially using hydrogels for Another approach in the development of
scaffold material printing) and magnetic/acoustic “scaffold-free” technology is the management
approach, and (ii) using novel technology that of cell material (including tissue spheroids)
applies microgravity as an additional trigger for using ultrasonic waves or so-called acoustic
biofabrication (main challenge to design 3D model bioprinting . One of the approaches in acoustic
[27]
of the printed construct). bioprinting is to control cells using so-called
These technologies are compared in Figure 1. “acoustic tweezers.”
Here, we would like to discuss in detail the The mode of action of “acoustic tweezers”
acoustic and magnetic bioprinting technologies as is as follows: Piezoelectric substrate and
the new directions of bioprinting. two transversely-spaced pairs of interdigital
The use of magnetic forces in tissue engineering transducers generate standing acoustic-surface
has begun with a series of studies by Ito et al. . waves that capture and move cells. The change of
[19]
The developed approach was defined as “magnetic the cell position occurs due to the change in acoustic
force-driven tissue engineering.” Magnets and amplitude and transducers pair phase. Since phase
magnetic fields were used to place cells with and amplitude can be set and changed easily, the
magnetic nanoparticles on various scaffolds in accuracy of cell movement will be limited only
initial series of experiments. The next step in by the equipment resolution. Whereby, the cell
the development of this approach was the use of movement speed can reach 5 µm/s . Some studies
[28]
magnetic forces to control the movement of tissue have illustrated that such manipulation with cell
spheroids containing magnetic nanoparticles in material does not affect its viability, functionality,
2D space [20,21] . Recent works have shown that and genes expression [29,30] . Moreover, it has variety
superparamagnetic nanoparticles of iron oxide of advantages in comparison with approaches

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