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International Journal of Bioprinting 3D-printed nanocomposites: Synthesis & applications

Figure 4. (a) Schematic representation of the fabricated artificial skin with microstructure and (b) the cross-sectional views. Reproduced with the
permission from ref. Copyright © 2018 John Wiley & Sons, Inc.
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hydrogel and then deposited a second confluent monolayer thereby constructing a desirable anisotropic artificial skin.
of hydrogels encapsulating keratinocytes. Both in vitro and The oriented IS-MMT in turn facilitates PVDF dipoles
in vivo experiments were conducted on the artificial skin alignment, which greatly improved the piezoelectric
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through histological and immunohistological methods. properties of electronic skin. Lackner et al. fabricated
The encapsulated cells exhibited high cell viability, and the anisotropic structures, composed of nanocellulose and
in vivo differentiation property of the skin, which grafted alginate, with gradient mechanical properties. Controlling
onto the back of mice, was examined. Orthkeratotic the fiber orientation through the printing path allowed
stratum corneum was generated, implying stratification for fine-tuning of the mechanical performance. The
and terminal differentiation of the printed skin. The fast engineered structure could be applied to the production of
fabrication speed, together with the high resemblance to different tissues, such as skin, cartilage, and cardiovascular
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the natural human skin, corroborates the application of tissues.
microextrusion-based bioprinting in fabricating artificial 6.2. Cartilage tissues
skin. Kim et al. replicated skin anatomy by constructing Cartilage is an avascular tissue containing only 10–15% of
vascularized dermis and hypodermis and the topical chondrocytes, which justifies its limited self-regenerative
epidermal layer via extrusion (Figure 4a and b). The capability. Several techniques have been developed
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functional biomarkers in each compartment, such as to repair defective cartilage, but the repaired cartilage
filaggrin, laminin, keratin 10, fibronectin, collagen type I, exhibits fibrocartilaginous phenomena and is not able to
and CD31, were examined and expressed in specific regions, withstand the intense mechanical pressure. Therefore, it
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indicating the successful formation of matured skin. The is crucial to regenerate cartilage-like tissue endowed with
bioengineered vessel provided nutrition and oxygen and mechanical property that can induce chondrogenesis and
promoted the physiological interaction with epidermis replace damaged cartilage.
during the differentiation of keratinocyte, presenting a
novel strategy used to fabricate physiologically human- Antich et al. deposited PLA with superior mechanical
mimetic skin that serves as a more reliable experimental strength in grid-like structure to support hyaluronic acid-
platform for evaluating the cytotoxicity of drug and based hydrogel. They mixed hyaluronic acid and alginate
cosmetic and investigating skin-related diseases. and discovered that adding hyaluronic acid increased the
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expression of chondrogenic gene markers. Schipani
Skin tissues are anisotropic with varied mechanical et al. fabricated anisotropic articular cartilage constructs
characteristics depending on their location. Flexible with interpenetrating network composed of alginate
anisotropic electronic skin was engineered by Pei et al. and GelMA. The constructs are soft in compression
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via 3D printing strategy. The strong shear and tensile and stiff in tension, which simulated human cartilage.
stress generated at the nozzle walls assisted the alignment In addition, the bioprinted artificial articular cartilage
of the ionic salt-montmorillonite (IS-MMT) in poly promoted chondrogenesis, and the encapsulated bone
(vinylidene fluoride) (PVDF) inks along the printing path, marrow-derived stromal cells produced hyaline-like

Volume 10 Issue 2 (2024) 90 doi: 10.36922/ijb.1637