Page 483 - IJB-9-6

International Journal of Bioprinting Bioprinting cell-laden protein-based hydrogel

leading to the weaker crosslinking, while for the other powder from porcine skin type A in 800 µL of silk fibroin
crosslinked ones, the cell release was deterred from the solution) loaded with human bone marrow-derived MSCs
strut owing to the stronger crosslinking. Among those (hBMSCs) (cell density: 1 × 10 cells/mL) were bioprinted.
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constructs with controllability (T-0.5 and T-1 ones), the In order to assess the cellular morphology and cartilaginous
T-0.5 scaffold with better cellular behaviors was chosen as matrices generated by cells after 21 days of chondrogenic
the optimum scaffold for further analyses in future studies. differentiation in constructs, scientists used histological
Table 2 summarizes the biophysical parameters influencing staining. They revealed that the GelMA structures displayed
PBHs’ bioprinting in the cartilage and bone TE. a sparse cells distribution, although the cells had spherical
morphology (Figure 3C(i, ii)). The silk fibroin/gelatin
3.2. Biochemical factors constructs showed a homogenous distribution of cells, and
3.2.1. Chemical structure some of these cells exhibited a spread morphology on day
Cells’ behaviors are impacted by diverse signals they 21 (Figure 3C(iii, iv)). The observed spread morphology
receive from the ECM and neighboring cells; indeed, could be owing to the adhesive sites in the silk fibroin/
[138]
these received signals are capable of promoting adherence, gelatin constructs .
morphogenesis, differentiation, and proliferation of 3.2.2. GFs and signaling molecules
cells [134] . Regarding the chemical structure as a biochemical Promoting cellular proliferation, inducing cell
cue, proteins in bioinks can exert effects in various ways, differentiation, or enhancing tissue regeneration via
one of which is that they are able to promote cell spreading, incorporating GFs or other signaling molecules into
survival, proliferation, and adhesion to the hydrogel matrix bioinks is another topic worthy of discussion [139-141] . The
via presenting adhesive sites and specific ligands like matrix desired cell/tissue-related properties of PBHs can be
metalloproteinase (MMP) sequence and RGD sequence, achieved by adding several GFs, such as insulin-like growth
which bind to the integrin receptors on cells surface [135] . factor [142] , vascular endothelial growth factor (VEGF)
Concerning this matter, cross-linker-free gelatin/silk [143] , stromal cell-derived factor-1α [144] , fibroblast growth
fibroin bioinks (1.5% and 7% w/v) encapsulating primary factor [145] , and BMP-2 [146] , as well as signaling molecules,
chondrocytes (cell density: 10 cells/mL) for the cartilage including exosomes, ECM granules, DNA, microRNA
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TE were printed by employing an extrusion printing (miRNA), cytokines, bioceramics, and bioactive polymers,
approach. They revealed enhanced cellular viability, to name a few [147] . For instance, these biochemical factors
improved cell adhesion, and increased ECM formation are capable of improving cell differentiation by presenting
compared to the control group, which could be attributed to cues that direct the differentiation of stem cells into specific
the RGD presence in both silk fibroin and gelatin proteins. cell types like bone or cartilage cells [148,149] . In this regard, a
Moreover, improved printability due to the shear-thinning team of scholars [150] worked on the functional vasculature
behavior of silk and the high viscosity of gelatin was and osteogenesis of GelMA-based bioinks for application
achieved [136] . Özenler et al. [137] designed mouse MC3T3-E1 as large-scale bone tissue constructs. Within this novel
preosteoblasts-loaded sodium alginate dialdehyde/gelatin study, GelMA bioinks (crosslinking approach: photo-
bioinks (7.5% and 15% w/v) containing fish scale (FS) crosslinking with 0.1% w/v Omnicure S2000 at 360–480
particles (1%, 3%, 5%, and 10% w/v) (cell density: 5 × 10 nm wavelength, UV light with 6.9 mW/cm , and exposure
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2
cells/mL) for bone regeneration. Then, they printed the time of 20 s) functionalized/loaded with VEGF and
bioinks using extrusion printing device and physically and silicate nanoplatelets that contained human umbilical vein
chemically crosslinked the structures employing CaCl and endothelial cells (HUVECs) and hBMSCs (cell densities:
2
microbial transglutaminase, respectively (Figure 3B). As 2 × 10 cells/mL) were bioprinted using extrusion-based
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one of the results, the promotion of cellular proliferation printing. To construct a pattern with both capabilities of
during 28 days of cultivation was reported due to the vascularization and osteogenesis, a HUVECs/hMSCs-
gelatin’s favorable RGD sequence. Another investigation encapsulated GelMA hydrogel (5% w/v) was bioprinted in
developed arch-like bioprinted constructs utilizing GelMA the central area so that a blood vessel could be formed, and
and silk fibroin/gelatin bioinks (crosslinking approaches: around this structure, they bioprinted silicate nanoplatelets-
photo-crosslinking with 0.25% w/v LAP at 365 nm loaded, VEGF-functionalized GelMA hydrogel (10% w/v)
wavelength (ultraviolet [UV] light with 700 mA) and embedded with hMSCs (cell density: 2 × 10 cells/mL) for
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exposure time of 2 min as well as enzymatic crosslinking inducing osteogenesis. It was revealed that a perfusable
with mushroom tyrosinase (800 units/mL), respectively) lumen possessing an endothelial lining at the construct’s
for cartilage regeneration. Employing extrusion printing, center was generated post-bioprinting. The hMSCs in the
two compositions of bioinks (GelMA bioink: 10% w/v of inner gel differentiated to the smooth muscle cells that
GelMA and silk fibroin/gelatin bioink: 80 mg of gelatin could promote the formation, stabilization, and maturation

Volume 9 Issue 6 (2023) 475 https://doi.org/10.36922/ijb.1089