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

Figure 1. Cyclohexyl alanine-based self-assembling ultrashort peptide hydrogels. (A) IIZK and IZZK peptides start to self-assemble to form hydrogels at
relatively low concentration of 1 mg/mL in 1× PBS. (B) Mechanical characterization of ultrashort peptide hydrogels using oscillatory shear measurement.
The gels were prepared based on the flow rate ratio of peptide solution and PBS from the printing parameter. (C) SEM micrographs of printed IIZK and
IZZK hydrogels.

these two promising ultrashort peptides, IIZK and IZZK, a porous nanofiber network similar to the extracellular
[40]
as bioinks for cartilage development in vivo. matrix .
The mechanical properties of these cyclohexyl 3.2. Printability and shape fidelity assessment
alanine-based peptide hydrogels were characterized 3D bioprinting experiments were conducted with IIZK
using oscillatory rheological measurement (Figure 1B). and IZZK peptides to assess printability and shape fidelity.
To mimic the same condition as the printed ultrashort A fidelity assessment rubric was developed to quantify
peptide bioink, the gel samples were prepared by mixing observations. Table 1 displays the rubric with a score of
peptide solution and PBS in two to one ratio. Frequency 1–5 awarded to each printed construct, depending on
sweep experiments were performed by applying angular performance in terms of gelation, consistency, thread
frequency from 100 to 0.1 rad/s at 0.1% strain. The results continuity, print resolution, and shape fidelity (Table 2).
show an almost linear profile of both ultrashort peptides’ Several constructs were printed with IZZK and were
storage moduli (G′) and loss moduli (G″), suggesting that observed to have quick gelation and maintain thread
both have frequency-independent behavior. This property consistency and continuity (Figure 2A). In terms of
is also commonly observed in other types of hydrogels . print resolution and fidelity, the constructs have sharp
[39]
The stiffness of both ultrashort peptides was then resolution with solid walls, indicating strong mechanical
determined by the storage modulus at 0.1% strain and stability. Hence, a score of 5 was awarded to IZZK
1 rad/s angular frequency. The stiffness of IIZK hydrogel constructs. The hollow cylinder was printed with 54 layers
was found to be around 149.06 kPa, which was nearly without observing any gaps or clogs during printing.
double of IZZK hydrogel (82.38 kPa). From the amplitude Likewise, several samples of IIZK were printed and
sweep measurement, we observed almost similar observed (Figure 2B). While the peptide powder took
deformation behavior between two hydrogels based on slightly longer to dissolve and achieve gelation, IIZK was
their linear viscoelastic (LVE) region. The nanostructure able to maintain consistent gelation and thread continuity
morphology of the ultrashort peptide hydrogels was throughout printing. Structure shape was fabricated with
characterized using a SEM (Figure 1C). The SEM images very good print resolution and shape fidelity. However,
of both ultrashort peptide gels showed the formation of when constructing the hollow cylinder, it was observed

Volume 9 Issue 4 (2023) 67 https://doi.org/10.18063/ijb.719