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Silk Fibroin and Calcium Phosphate 3D Scaffolds Promote in vitro Osteogenesis
A B

C

D E

Figure 3. Conformation and crystalline structure of SF scaffolds. (A) Infrared spectra of extrusion-printed SF scaffolds from the three
inks and pure SA. (B) XRD patterns of hybrid SF scaffolds with various pH conditions. (C) Crystalline morphology of calcium phosphate
minerals under varied pH conditions and organic solvent/aqueous environments. (D) Crystalline morphology of calcium phosphate minerals
at 50°C and 80°C. (E) XRD patterns of hybrid SF scaffolds with various temperature conditions.

conformation gradually increased from 38.7% for Ink 1 At pH 10–11, an amorphous calcium phosphate phase
to 52.1% for Ink 2. The β–sheet content of mineralized (ACP) of calcium phosphate also appeared. Figure 3D
scaffolds was maintained, suggesting that no changes reveals that the morphology of CaHPO (monetite
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were induced in the conformation of SF scaffolds during or DCP) prepared at two temperatures was similarly
the post-mineralization. The peak at 1030 cm for the irregular particles, and Figure 3E confirms that both
-1
mineralized SF scaffold was characteristic of PO 4 3-[47,48] , were the same DCP crystalline phase compared to the
which further proved the formation of calcium phosphate DCPD phase at room temperature. Table S2 summarizes
in the scaffold. the results from the XRD of SF scaffolds under various
Figure 3B compares the XRD patterns of three mineralization conditions. For the aqueous environment,
mineralized SF scaffolds under aqueous conditions. The at pH 4 – 5, DCPD was the only calcium phosphate
wide peak at 20.96° denotes the crystalline phase of phase; at pH 7, it changed to a combination of DCPD
SF [49,50] . The rest of sharp peaks were identified as two and DCP; at pH 10–11, it reverted to a completely
crystalline phases of calcium phosphate, CaHPO ·2H O different amorphous phase of ACP. Such mineralization
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2
(Brushite or DCPD) and CaHPO (monetite or DCP). results agreed well with previously reports without using
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8 International Journal of Bioprinting (2022)–Volume 8, Issue 4