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International Journal of Bioprinting Magnetic (Bio)inks for tissue engineering

Figure 2. Overview of the techniques for the incorporation of MNPs in hydrogels. (A) Blending method: MNPs are blended in the pre-crosslinked
hydrogel (i), which is then crosslinked (ii), with the particles being embedded in the matrix. (B) Grafting-onto method: the functionalized MNPs (i) are
mixed with the pre-crosslinked hydrogel (ii), which is then crosslinked (iii) with MNPs being an integral part of the network. (C) In situ method: the
crosslinked hydrogel (i) is dipped into a solution with iron ions (ii), which diffuse into the matrix (iii) and then put in contact with precipitating agents
(iv), promoting the formation of MNPs (v).

achieving a high stability of hydrogel after the MNPs were generating abilities. Additionally, Tang et al. also
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integrated into the matrix’s structure. 46 created a poly(2-acrylamido-2-methylpropane sulfonic
acid)/polyacrylamide hydrogel with the same type of
3.3. In situ precipitation nanoparticles. This hydrogel presented hyperthermic
In this method, hydrogels are crosslinked prior to the properties when exposed to an external magnetic field in
incorporation of the magnetic component and subsequently four different types of porcine tissue, both in solution and
immersed in a solution containing Fe and Fe ions
2+
3+
(Figure 2C). This allows them to disperse throughout the exposed to air. Moreover, the magnetic hydrogel effectively
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entire hydrogel’s network in a uniform manner and then promoted a controllable and sustained drug release.
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precipitate, resulting in the formation of MNPs. Despite
allowing for a better entrapment of the particles within the 4. 3D (bio)printing of magnetic hydrogels
hydrogel, the use of harsh precipitation agents might limit This section provides a brief description of 3D extrusion
this approach’s compatibility with natural biomaterials and printing, which is the additive manufacturing technique
cells, restricting its use to materials that can withstand more commonly used for printing magnetic hydrogels
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these agents without getting degraded. 41 aiming at tissue engineering applications. 3D extrusion
This technique has been used by Miyazaki et al., who bioprinting is a nomenclature only reserved for approaches
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developed a chitosan hydrogel by in situ precipitation of where live cells are incorporated inside the inks, while 3D
magnetite nanoparticles in order to assess their heat- extrusion (bio)printing is a broader nomenclature applied

Volume 10 Issue 1 (2024) 7 https://doi.org/10.36922/ijb.0965