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3D freeform printing of nanocomposite hydrogels
A

B C

Figure 5. In vitro enzymatic degradation behavior of three-dimensional-printed scaffolds. (A) Remaining
weight over incubation time after the hydrogel scaffolds were immersed in hyaluronidase solution,
and optical images of the scaffolds before and after enzymatic degradation. (B) Fourier-transform
infrared spectra of (a) glycidyl methacrylate-hyaluronic acid (HAc) hydrogel, (b) alginate hydrogel,
(c) HAc-alginate (HAc-Alg) after degradation, and (d) HAc-Alg/30 wt% calcium phosphate (CaP) after
degradation. (C) X-ray diffractometer pattern of HAc-Alg/30 wt% CaP scaffolds after degradation.

of hyaluronidase through a 7-day immersion Our results indicate that Alg and minerals were
study (Figure 5A). We found that approximately the main components of the remaining scaffolds
85% of HAc in the HAc-Alg scaffolds was after hyaluronidase-mediated degradation, as
rapidly degraded after 2 days, whereas >50% of confirmed by the FT-IR spectra (Figure 5B).
HAc remained in HAc-Alg/CaP, indicating that The FT-IR spectra of GM–crosslinked HAc and
the nanocomposite hydrogels exhibited higher Alg hydrogels had the following characteristic
resistance against enzymatic degradation. The peaks: For GM–crosslinked HAc, amide N-H
complete degradation of HAc in HAc-Alg and stretch from 3200 to 3600 cm , C=O stretching
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HAc-Alg/CaP took 6 and 12 days, respectively and N–H bending in the 1595 – 1710 cm range,
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(Supplementary Figure 8). The optical images of C–H bending peak between 1350 and 1480 cm ,
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the remnant hydrogels after degradation confirmed and C–O stretch of the proteoglycan sugar ring
the outstanding biostability of the HAc-Alg/CaP from 985 to 1140 cm ; and for Alg, stretching
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hydrogels. The precipitation of nanocrystals on vibrations of the hydroxyl groups at 3430 cm
−1
the HAc chains effectively blocked the access and stretching vibrations of the asymmetric and
of enzyme molecules to HAc and enhanced its symmetric bands of carboxylate anions at 1619
resistance to enzymatic degradation [5,31] . and 1416 cm , respectively [32,33] . The FT-IR
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40 International Journal of Bioprinting (2020)–Volume 6, Issue 2