Page 93 - IJB-9-1

International Journal of Bioprinting Progress in bioprinting of bone

was produced with a HAp-containing phase and a tubular storage and loss moduli, and compressive modulus of
structure filled with alginate/gelatin to represent bone hydrogels. Hydrogels containing 2% nSi were used for
tissue and vascular structure, respectively. bioprinting and cells could retain their viability and
Different from the blending of alginate and gelatin, proliferation, accompanied by increased ALP activity and
alginate/gelatin composite hydrogel has been bioprinted increased gene expression of Runt-related transcription
using an in situ cross-linking mechanism, which is factor 2 (RUNX2), osterix, ALP, collagen type I alpha 1
attributed to the Schiff-base reaction between aldehyde (COL1A1), OCN, and osteopontin (OPN). Critical-sized
groups of oxidized alginate and amino groups of cranial defects of Sprague Dawley (SD) rats were also
gelatin [114] . When gelatin was extruded into a support bath transplanted with scaffolds, and micro-CT, Van Gieson,
that contained oxidized alginate, freeform fabrication of histochemistry, and Masson’s trichrome staining results
complex 3D structures can be obtained [121] . demonstrated that the MSCs-loaded 2% nSi scaffold
showed better outcomes than the control groups (without
3.1.4. Photocurable bioinks scaffolds or nSi). Using a nanoengineered bioink consisting
Modification of biomaterials (such as gelatin, alginate, and of GelMA, kappa-carrageenan, and nSi, which formed
HA) with methacrylate enables chemically cross-linking an ionic-covalent entanglement network, Chimene
using UV radiation [122] , which overcomes the above- et al. [124] succeeded in bioprinting a hollow cylinder with
mentioned limitations, such as low viscosity and slow 150 layers (3 cm in height). The presence of nSi resulted
gelation. Photopolymerization has also been integrated in the increased compression modulus and the significant
into EBB processes to enhance the stability and complexity deposition of GAGs, proteoglycans, Ca, and phosphate in
of the bioprinted bone. In the work by Poldervaart et human MSCs post-bioprinting, demonstrating that the
al. , MeHA has been investigated for bone bioprinting, bioink could induce endochondral differentiation of MSCs.
[72]
where UV light exposure enhanced the storage modulus In a study by Demirtaş et al. , chitosan, chitosan-
[74]
and elastic modulus of the MeHA, and hBMSCs residing HAp composite, and MC3T3-E1 cells were printed using
in MeHA hydrogels retained 64% viability after a 21-day an EBB, in which alginate and alginate-HAp hydrogels
culture. Despite the absence of additional osteogenic were used as comparisons. With the incorporation of
stimuli, Ca deposition in hydrogels with higher MeHA HAp, both chitosan and alginate hydrogels had 3 – 6
concentrations (2.5 – 3%) was significantly greater folds greater elastic modulus. Spherical morphology
than that observed in hydrogels with lower MeHA of cells was seen in alginate and chitosan hydrogels on
[52]
concentrations (1.5%). Byambaa et al. used GelMA day 7 of culture, whereas spread cells were observed in
hydrogels containing different concentrations of VEGF to alginate-HAp and chitosan-HAp hydrogels, indicating
produce a gradient structure, and a gel rod in the center a positive effect of HAp on cellular morphology. Cells
was bioprinted with GelMA, forming a perfusable vascular within chitosan-HAp hydrogel expressed higher levels of
lumen with an endothelial lining. Cocultured HUVECs osteogenic proteins and Ca deposition as compared to
and hMSCs reached 93% cell viability after 7 days, and other groups. Using BMSCs, RAW264.7 macrophages,
MSCs in the inner fibers differentiated into smooth gelatin, GelMA, polyethylene glycol (PEG), and BMP-
muscle cells, which promoted vascular vessel formation. 4-loaded mesoporous silica nanoparticles (MSNs) as
In the three outer layers, the MSCs and bioactive silicate bioinks, Sun et al. [125] demonstrated that MSNs improved
nanoplatelets were embedded in GelMA-VEGF bioink, the mechanical and shear-thinning properties of the
which induced osteogenic differentiation in vitro. The hydrogel. In vitro and in vivo (implantation in calvarial
Alizarin Red S staining, immunostaining, and RT-qPCR defects of DM rats) tests were conducted using RAW/
results demonstrated that a mature bone with angiogenesis BMP-4 scaffolds, where BMP-4-loaded MSNs induced
was generated after 21 days of culture.
macrophage polarization and inhibited the inflammatory
3.1.5. Bioinks with particle reinforcement response. Moreover, the BMSC/RAW/BMP-4 group was
tested in vitro, which indicated that the expression of
As biomaterials such as silicate and calcum phosphates RUNX2, OPN, and ALP was up-regulated. The in vivo
are well-known for their roles in increasing mechanical
properties and mineralization of bone scaffolds, such results, further, highlighted the superiority of the BMSC/
materials in the form of particles are supplemented in RAW/BMP-4 group over others regarding new bone
volume and degree of neovascularization.
bioinks. A recent study by Liu et al. [123] encapsulated rat
BMSCs in a bioink containing nanosilicate (nSi), gelatin, In light of the fact that amorphous magnesium
and alginate, in which the addition of nSi resulted in low phosphates (AMPs) stimulate rapid differentiation and
hydrogel swelling and improved shear-thinning character, mineralization of pre-osteogenic cells, a shear-thinning and

Volume 9 Issue 1 (2023) 85 https://doi.org/10.18063/ijb.v9i1.628