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

cartilage matrix. By adding anisotropic fillers, such as and the strut thickness of the engineered constructs were
nanocellulose, into alginate solution, the printability of the optimized to provide sufficient strength and induce the
bioink was significantly improved. 130,131 The nanocellulose- osteoinductive effect as well.
incorporated bioink exhibited enhanced cell spreading, Byambaa et al. fabricated pyramidal microstructured
proliferation, and ECM formation, demonstrating its bone-like tissue constructs that mimic the architecture of
great potential in 3D printing of living tissue and organs. natural bone tissue. Rapidly degradable GelMA hydrogel
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Researchers have also demonstrated that the anisotropic encapsulated with HUVECs and human mesenchymal
gradient-structured cartilage exhibited better cartilage stem cells (hMSCs) was printed in the center of the
repair effect both in vivo and in vitro as the anisotropic construct, which was surrounded by gelatin methacryloyl
structure can provide desirable mechanical characteristics (GelMA)/silicate nanoplatelets hydrogel (Figure 5a). The
and signaling pathway required for chondrogenic vessel was formed via the degradation of GelMA overtime
differentiation. 132,133 To closely resemble the anisotropic (Figure 5b). The encapsulated hMSCs and HUVECs could
heterogeneous multilayered structure of natural cartilage, migrate and proliferate in the constructs, and the hMSCs
a novel strategy combining microfluidic and 3D printing promoted vasculogenesis. In addition, hMSCs in silicate
technique to construct engineered zonal cartilage was nanoplatelets hydrogels differentiated into osteoblasts.
developed. 134,135 The technology relies on a microfluidic Chiesa et al. also developed vascularized bone model
printing head connected to a coaxial needle extruder with controlled pore geometry, size, and interconnectivity
to print muscle precursor cells onto hydrogel fibers in a by printing gelatin-nanohydroxyapatite hydrogel in a
high-resolution 3D bioprinting process. The advanced supporting bath composed of Pluronic F127 (Figure 5c–f).
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approach enables the deposition of chemical, physical, A wood-pile scaffold was first printed and kept in the
and biological cues, making it possible to fabricate supporting bath. Gelatin was crosslinked with genipin,
scaffolds with exceptionally high shape fidelity and cell followed by removing sacrificial materials. Cylinders with
viability. Zone-specific matrix was observed after human a diameter of 4 mm were cut from the scaffolds for further
articular chondrocytes and human bone marrow-derived investigation, including pore connectivity, compressive
mesenchymal stem cells were cultured for 3 weeks modulus, osteogenic differentiation, and vascularization.
in vitro. 134 The engineered bone model exhibited robust
vascularization and HUVECs-supported osteogenesis,
6.3. Bone tissues indicating that vascularized bone model could be readily
Bone is one of the rigid body tissues and composed of two fabricated via 3D bioprinting.
main components, i.e., collagen and calcium phosphate.
Bone tissue constructs that are hierarchically porous are 6.4. Cardiac tissues
helpful for vascularization and cell proliferation. To treat Similar to chondrocytes, cardiomyocytes have limited
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bone defects, tough but light, biocompatible substitutes regenerative capacity. This signals a crucial need to
endowed with the capability of preventing any allergic regenerate cardiac tissues. The cardiomyocytes are aligned
reactions are required. Traditional fabrication methods, in cardiac tissues to execute spontaneous, synchronous,
such as freeze-casting, foam replica, high-pressure and rhythmic contractions. The hierarchical property of
pressing, and injection molding, cannot control the native myocardium and complicated blood vessels are the
porous structure, but the recently developed 3D printing main challenges in fabricating cardiac tissues.
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techniques could overcome the limitations to fabricate
customized scaffolds. Lee et al. had attempted to fabricate a model of
left ventricle of human heart via embedded printing.
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As one of the main bone components, calcium Collagen was crosslinked by changing the pH of supporting
phosphate supports osteoblast adhesion, proliferation, bath, and the geometry could be maintained for over 28
and osteoinduction. Additionally, it regenerates bone days. Cell viability achieved 96%, and the ventricular
marrow stromal cells to induce bone formation. Besides contraction was noticed after 4 days of culturing.
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calcium phosphate, other nanomaterials, such as silicate Moreover, wall thickening, an evidence of ventricular
nanoplatelets and hydroxyapatite, are commonly used contraction, was observed during peak systole. They also
in bone tissue engineering. Nyberg et al. fabricated PCL printed a functional robust tri-leaflet heart valve that was
scaffolds functionalized with tricalcium phosphate, mounted to a pulsatile pump. Cyclical opening and closing
hydroxyapatite, or decellularized bone matrix and co- of the valve leaflets were observed under the pulsatile
cultured with adipose-derived stromal/stem cells. The flow. Further, a monolayer of HUVECs was formed on the
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addition of minerals increased the viscosity of the PCL leaflets. However, the limitation of this study is that the cell
melts. By tuning the 3D printing parameters, the porosity density was too low to mimic the real tissue as it requires

Volume 10 Issue 2 (2024) 91 doi: 10.36922/ijb.1637