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International Journal of Bioprinting 3D bioprinting of ultrashort peptides for chondrogenesis

Table 3. Characteristic comparison of IZZK and IIZK ultrashort peptide bioinks
IZZK peptide bioink IIZK peptide bioink
Stiffness (kPa) after 3D bioprinting 82.38 149.06
Biocompatibility (cell viability) High viability (92%) at day 24 postprinting High viability (91%) at day 24 postprinting
Printability and shape fidelity assessment score 5 (excellent resolution), 54-layer cylinder 4 (very good resolution), 45-layer cylinder
Printed structure stability Constructs were stable for at least 24 days Constructs were stable for at least 24 days

Figure 4. (A) The relative fold change of Sox-9, Col-II, Aggrecan, Col-I, and Col-X during in vitro chondrogenic differentiation was measured by RT-qPCR
analysis. **p < 0.005, ***p < 0.0001. (B) Col-II/Col-I and Col-II/Col-X ratios calculated based on relative fold change.

its level stayed the same at day 14 with no significant cartilage markers (Col-I and Col-X), IIZK peptide holds
upregulation (Figure 4A). Importantly, Col-II/Col-I potential. This could be envisioned by using the two
ratio was around 68 and 62 times higher with IZZK and ultrashort peptide bioinks to 3D-bioprint cartilage tissue
IIZK peptide bioinks, respectively (Figure 4B). On the mimics with different cartilaginous zones, i.e., hyaline
other hand, at day 14, both ultrashort peptides showed a cartilage zone and hypertrophic (calcified) cartilage
significant increase in Col-X expression levels compared zone. Such a combination is important, as calcified
to the control (Figure 4A). However, the Col-II/Col-X ratio cartilage is essential for engineered tissue integration
was around two times higher in IZZK and IIZK peptides, and function [50] .
respectively (Figure 4B). These results demonstrated that We observed differences in the mechanical stiffness
both ultrashort peptides fostered the differentiation of of printed versus manually formed 3D constructs.
MSCs into chondrocytes with hyaline phenotype and Upon manual casting, the stiffness of the IZZK peptide
hyaline cartilage formation. hydrogel was found to be higher than that of the IIZK
Taken together, the expression profile of Coll-II, Sox-9, peptide [29] . Interestingly, we found that the stiffness of the
and aggrecan suggest that the IZZK peptide is more printed IZZK peptide (82 kPa) hydrogel constructs was
suitable for cartilage tissue engineering applications. lower than that of the printed IIZK hydrogel constructs
However, considering the ratio of hyaline cartilage marker (149kPa) by nearly half a magnitude. This finding has
expression (Col-II) compared to fibro- and hypertrophic a significant implication for deciding the material and

Volume 9 Issue 4 (2023) 71 https://doi.org/10.18063/ijb.719