Page 47 - IJB-10-4

International Journal of Bioprinting 3D bioprinting in otorhinolaryngology

cannot effectively eliminate the complications related to 4.4. Mechanical properties
early extrusion. In vivo experiments have demonstrated The application of 3D bioprinting in otorhinolaryngology
that the mechanical strength of silk resulted in pressure often involves bioprinting bones or cartilage. Thus, it is
maintenance in the middle ear, high durability of the necessary to use bioinks that can produce similar hardness
scaffold, alleviation of extrusion-related complications, and strength to ensure the vitality of cells and promote their
and accelerated tissue healing. 119 proliferation, differentiation, and function. Consequently,
materials with similar mechanical properties to tissues in
4.3. Biocompatibility vivo or adjusted by crosslinking and other methods are
Biocompatibility is defined as a material’s capacity to often used to ensure that the hardness of printed tissues
work in tandem with the host response in a specific is similar to that of the target tissues. Consequently, this
application. Therefore, it is essential to consider the mediates the original functions of the tissues and organs
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biological environment in the host and the material and stimulates the maturity and integrity of the overall
when formulating and designing bioinks to ensure good structure and interconnection. 71,125 Currently, dECM is the
biocompatibility and non-toxicity to the host. The bioink with mechanical properties closest to those of native
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cytotoxic effects of bioinks may be due to the formation tissues. In addition, the diffusion and permeability of the
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of leaching or extractable substances during degradation original tissue must be considered during the bioprinting
and other processes. Common leaching and extractable process. Materials with higher viscosities often have
substances generated by polymers include additives, fewer pores and can form more stable structures, thereby
processing aids, and small amounts of monomers and allowing for lower levels of diffusion and permeability.
oligomers. Winkler et al. successfully developed a Kim et al. used glycidyl methacrylate (GMA) to make a
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novel heat-resistant polyacrylate material (VisiJet M2S- silk fibroin (SF)-based bioink (Sil-MA) and evaluated its
HT90), which displayed good biocompatibility in mouse performance. In a light-curing experiment, different Sil-
fibroblasts (L929), human embryonic kidney cells (HEK MA concentrations affected the mechanical properties
293E), and yeast (S. cerevisiae) in vitro. Additionally, the of hydrogels, including stiffness and pore size. Increasing
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printed structure should have sufficient porosity to enable the Sil-MA concentration could enhance the mechanical
the exchange of nutrients, oxygen, and metabolites for the properties, improve the flexibility of the material, and
nascent tissues. Yan et al. reported a biodegradable scaffold generate a stretchable structure. The data indicated that
with a controlled release of deferoxamine fabricated by 30% Sil-MA had the strongest mechanical strength and
3D bioprinting. The scaffold significantly accelerated the excellent elasticity after deformation, and its compressive
vascular patterning of human umbilical vein endothelial resistance was 10 times higher than that of the PCL-mixed
cells (HUVECs) and promoted the production of a gelatin hydrogel scaffold. The experimental data revealed
mineralized matrix and expression of osteogenic- that 30% Sil-MA had good mechanical integrity when used
related genes during the osteogenic differentiation of to simulate organ tissues in vivo (such as brain and ear).
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MSCs. In an in vivo rat model, the cells seeded on the Li et al. identified in vitro differentiation of human bone
3D printed scaffold exhibited good cell viability and marrow stromal cells (hBMSCs) in 3D-printed silicon/
proliferation, and the cells adhered and grew along the polytetrahydrofuran/PCL hybrid scaffolds with specific
surface of the scaffold, further highlighting the scaffold’s channel sizes. The hBMSCs in the hybrid scaffolds (with a
biocompatibility. Nedunchezian et al. constructed pore width of 200–250 μm) were observed to preferentially
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hydrogel scaffolds from ADSCs and HA hydrogel bioinks support chondrogenic differentiation and matrix
to promote chondrogenic differentiation. The hydrogel generation. A low porosity scaffold would correspond to
scaffold of this formulation exhibited an ideal geometry a lack of space for cell-matrix synthesis, and consequently,
and visible pores, indicating good biocompatibility. inhibiting the growth and differentiation of the cells.
Continuous secretion of chondrogenic marker genes was Likewise, a highly porous scaffold would limit the interaction
observed in subsequent in vitro experiments, indicating and dedifferentiation between cells. Therefore, the design
successful cartilage differentiation. Therefore, the of scaffolds requires precise control of the structure, taking
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successful application of a particular 3D-bioprinting into account the porosity for optimal cell activity (e.g.,
process is dependent on the biocompatibility of the proliferation and differentiation) and mechanical strength
materials used, and this criterion is more stringent in the for optimal tissue support. Moreover, the mechanical
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field of otorhinolaryngology to ensure high cell activity properties of scaffolds have been found to weaken with
after transplantation and avoid undesired inflammation. increased porosity, indicating that a balance between the
At present, most studies explore the effects of bioinks on two should be the focus of scaffold design. 127,128 During the
biocompatibility, and this could be an important direction bioprinting process, researchers must comprehensively
for clinical applications. consider the characteristics of the target tissue, reducing

Volume 10 Issue 4 (2024) 39 doi: 10.36922/ijb.3006