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International Journal of Bioprinting Sr on GO enhances PLLA/PGA scaffold

was determined. In addition, BMSCs were fixed with 4% GPSr was similar to that of GP, which indicated that some
paraformaldehyde, washed with PBS, and permeated with functional groups, including N-H and C-N, still existed
0.1% v/v Triton X-100. After washing, non-specific binding after Sr was chelated onto GP. However, the peak of C-OH
was blocked by 10% goat serum solution (Invitrogen, at 1406 cm almost disappeared, probably caused by the
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Massachusetts, USA). )Osteocalcin polyclonal antibody chelation of Sr . XPS was employed to study the elemental
2+ 53
(OCN; 1:200 dilution; no. PA5-96529, Thermo Fisher compositions and chemical structures of GO, GP, and GPSr,
Scientific, Massachusetts, USA) and osteopontin (OPN; and the results are demonstrated in Figure 2b–f. Two typical
1:1000 dilution; ab8448, Abcam, Cambridge, England) were peaks of GO, i.e., C1s and O1s, could be observed in the
added and incubated overnight. Subsequently, a fluorescent full spectrum. Compared with GO, the full spectrum of GP
secondary antibody (ab150115, Abcam, Cambridge, and GPSr revealed a new peak of N1s and two of N1s and
England) was added, and the nuclei were stained with DAPI. Sr3d, respectively. The C1s spectrum was fitted, and the
Finally, BMSCs were observed with laser scanning confocal binding energies were determined at 289.68, 288.60, 286.73,
microscopy (LSCM; Zeiss, Jena, Germany) followed by 284.74, and 283.58 eV for GO, which correlated with C(O)
qualitative analysis using Image 6.0 software. OH, C=O, C-O, C=C/C-C, and C-H, respectively. 54,55 A new
peak was found at 287.44 eV, corresponding to C-N, which
2.7. Statistical analysis was formed due to the attached PDA for GPSr. The N1s in
In this study, all experiments were repeated five times, GPSr could be fitted to three peaks with binding energies at
unless otherwise noted, and the obtained data are expressed 401.85, 400.10, and 398.68 eV. The first two were associated
as mean ± standard deviation. The Statistical Product and with NH-C=O and N-H, respectively, which were generated
Service Solutions (SPSS) software was employed to analyze by the amine group in PDA. The peak at 398.68 eV
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the experimental data. Differences with p < 0.05 and p < corresponded to -N=, which was generated by the pyridine-
0.01 were regarded as statistically significant and very like structure in PDA. The above results indicated that PDA
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significant, respectively. was attached to GO in GPSr. In addition, high-resolution
XPS scans of Sr3d region in GPSr displayed Sr3d and
3. Results and discussion Sr3d peaks at 135.94 and 134.17 eV, respectively, which
3/2
5/2
The surface morphologies of GO, GP, and GPSr were further demonstrated the presence of GPSr. 58
visualized using SEM at the accelerated voltage of 20 kV. The scaffolds were fabricated by SLS, and the designed
As shown in Figure 1b–d, the smooth surface of GO was model with the fabricated scaffold is displayed in Figure
accompanied by an obvious wrinkled structure, while the 3a–c. The scaffolds were designed based on the hierarchical
GP surface was rough due to a layer of PDA attachment. porous structure of natural bone. 59,60 Specifically, the
Numerous particles were observed on the surface of GPSr, scaffold presented as a cylinder with a dimension of 11
possibly being the chelated Sr by PDA. In order to further mm (Φ) × 3 mm (h) combined with the interpenetrating
confirm the existence of PDA and Sr on GO, the element pores in a size ranging from 0.7 to 1.2 mm, which has been
analysis of GPSr was carried out by EDS. The corresponding reported to be beneficial for cell adhesion and growth.
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element mappings of C, O, N, and Sr elements were Tensile and compressive properties of LG scaffolds with
recorded, and the results are shown in Figure 1e–i. It could different content of GPSr were tested, as demonstrated
be found that N and Sr elements appeared in addition to in Figure 3c–h. LG scaffold exhibited 5.68 MPa in tensile
C and O elements, which GO originally had, and were strength and found that LG/GPSr0.5 scaffold exhibited
uniformly distributed in GPSr. This indicated that the Sr significantly higher tensile strength than the LG scaffold.
were successfully loaded on GO encapsulated by PDA. As the GPSr content increased, the tensile strength of
The chemical structures of GO, GP, and GPSr were scaffolds gradually increased until the GPSr content
evaluated by FTIR spectroscopy, as shown in Figure 2a. For reached 1.5 wt%. The LG/GPSr1.5 exhibited 9.49 MPa in
the spectrum of GO, a strong band at 3407 cm could be tensile strength, surpassing that of LG scaffold by 67.08%.
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indicative of O-H in GO, while peaks at 1728, 1630, 1406, But the tensile strength of LG/GPSr2 scaffold was 8.59
and 1080 cm correspond to C=O, C=C, C-OH, and C-O in MPa in tensile strength, which was lower compared with
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GO, respectively. 49,50 Regarding the spectrum of GP, the peak that of LG/GPSr 1.5 scaffold. Compressive properties of
of C=O in GO disappeared, indicating that the carboxyl scaffolds with different content of GPSr showed a similar
group in GO was consumed during the encapsulation trend to that of tensile properties. The LG/GPSr1.5
process of PDA. Two new peaks emerged at 1574 and 1192 exhibited 19.22 MPa in compressive strength, which was
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cm , indicating N-H shear vibration and C-N stretching 95.33% higher than that of the LG scaffold. It could be
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vibration in PDA, respectively. This proved that GO had concluded from the above test results that the addition
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been successfully encapsulated by PDA. The spectrum of of GPSr to the LG scaffold could significantly improve its

Volume 10 Issue 3 (2024) 201 doi: 10.36922/ijb.1829