Page 355 - IJB-10-5

International Journal of Bioprinting Printing organoids in peptide matrices

Table 2. Diameter, periodicity, and helicity of peptide fibers measured by atomic force microscopy (AFM)
Peptide Diameter (nm) Periodicity (nm) Helicity
Parent 8.9 ± 1.1 53.1 ± 1.9; 82.5 ± 3.1; 24.4 ± 1.4; 65.9 ± 2.9 LH
FIB (low) 8.4 ± 1.6; 11.6 ± 2.3 32.6 ± 2.5; 55.5 ± 2.4; 64.2 ± 2.3 LH
FIB (high) 9.5 ± 1.7 22.6 ± 1.7 LH
LAM (low) 5.8 ± 1.1 37.5 ± 1.2; 58.7 ± 0.1 LH
LAM (high) 4.7 ± 0.2; 5.8 ± 0.1 41.0 ± 0.8; 94.1 ± 0.2; 108.4 ± 1.1; 147.5 ± 2.2 LH; RH
FIB-LAM 6.8 ± 1.1 52.3 ± 0.6; 41.3 ± 0.8; 47.6 ± 0.9 LH
Abbreviations: FIB, fibrinogen-derived peptide containing the RGD motif; LAM, laminin-derived peptide containing YIGSR; LH, left-handed; RH,
right-handed.

spectrum is detailed in Table 3. FWHM indicates a less length for any of the conditions, suggesting various
ordered packing of the β-turn secondary structure, which assembling structures that depend on the peptides’ ratio
points to multiple arrangements of the nanofibers. 48–50 On and concentration. In an earlier publication, we reported
the contrary, the FIB (high) peptide in the Raman spectrum that the parent peptide IIFK single fibers (via AFM) had
displayed a prominent left-shifted β-turn at 1661 cm , a diameter of 3.2 nm and were composed primarily of
−1
36
which indicates a high curvature of the sheet, accompanied β-turns at the minimal gelation concentration. However,
by a low FWHM, which supports the AFM periodicity the diameter and periodicity of mixed ultrashort peptides
data where we only observed one main periodicity. When have not been reported until now.
the ratio of this combination is increased in favor of the We also evaluated the hydrogel-forming properties of
parent peptide, we again observed several periodicity these materials by rheology and inverted vial test (Figure
types, similar to the case of having only the parent peptide S1, Suporting Information). Storage and loss modulus
fibers. Notably, there is no exact matching of any period obtained for LAM and FIB at various concentrations were

Table 3. Raman shift, full width at half maximum (FWHM), and area of each peak for α-helix, β-turn, and unordered structures for
each peptide condition

Peptide Secondary structure Raman shift (cm ) FWHM (cm ) Area (%)
−1
−1
Parent (low) α-helix 1658 - 4.5
β-turn 1665 17 68.5
Unstructured 1684 - 27.0
FIB (low) α-helix 1658 - 30.0
β-turn 1666 16 42.4
Unstructured 1684 - 27.6
FIB (high) α-helix 1652 - 11.6
β-turn 1661 16 62.4
Unstructured 1679 - 26.0
LAM (low) α-helix 1658 - 13.5
β-turn 1666 16 58.5
Unstructured 1686 - 28.0
LAM (high) α-helix 1658 - 17.4
β-turn 1666 21 54.7
Unstructured 1690 - 27.3
FIB-LAM α-helix 1656 - 4.2
β-turn 1664 17 59.7
Unstructured 1681 - 36.1
Abbreviations: FIB, fibrinogen-derived peptide containing the RGD motif; LAM, laminin-derived peptide containing YIGSR.

Volume 10 Issue 5 (2024) 347 doi: 10.36922/ijb.3033