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International Journal of Bioprinting 3D printed hydrogels for tumor therapy

formation. The EDS mapping images shown in Figure 6D GelMA, and MgHAp/GelMA-PDA hydrogels in the wet
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indicate the element distribution in the cross-sectional state were 0.114 ± 0.005, 0.195 ± 0.033, 0.211 ± 0.019, and
area of the printed MgHAp/GelMA hydrogel. It clearly 0.111 ± 0.059 MPa, respectively. While in the dry state,
showed the distribution of MgHAp nanocomposites in the Young’s modulus of GelMA, HAp/GelMA, MgHAp/
MgHAp/GelMA hydrogel. Also, EDS pattern in Figure S3, GelMA, and MgHAp/GelMA-PDA hydrogels were 10.020
Supporting Information reveals the presence of Mg in the ± 3.343, 28.750 ± 9.248, 36.190 ± 11.186, and 31.913 ±
printed MgHAp/GelMA-PDA hydrogel. Furthermore, the 10.770 MPa, respectively. Notably, the mechanical strength
thermogravimetric analysis (TGA) results in Figure S4, of 3D-printed MgHAp/GelMA-PDA hydrogels was still far
Supporting Information shows the thermal degradation behind that of the native bone. Hydrogel scaffolds usually
behavior of 3D-printed GelMA, HAp/GelMA, MgHAp/ possess insufficient mechanical strength for bone tissue
GelMA, and MgHAp/GelMA-PDA hydrogels. This regeneration. To reinforce the mechanical properties of
indicates that due to the addition of HAp and MgHAp hydrogels, ceramic particles have been widely used. In the
nanocomposites, the remained weight percentages of current study, the addition of 10% of MgHAp significantly
HAp/GelMA, MgHAp/GelMA, and MgHAp/GelMA-PDA increased the modulus of hydrogels in both dry and wet
scaffolds increased after sintering at 800°C in comparison state. To further improve the mechanical properties,
to that of GelMA hydrogel. However, the fastest thermal more MgHAp nanocomposites could be incorporated
degradation temperature stayed nearly the same for into hydrogels. However, a higher percentage of MgHAp
GelMA (333.6°C), HAp/GelMA (324.1°C), MgHAp/ can lead to the formation of a compact network within
GelMA (333.5°C), and MgHAp/GelMA-PDA (337.8°C) hydrogels, thereby impacting the swelling and degradation
hydrogels. Overall, HAp and MgHAp nanocomposites behavior of MgHAp/GelMA-PDA hydrogels as well as
were well-dispersed in the printed hydrogels. influencing DOX release and cellular metabolism. Hence,
striking a balance among the mechanical properties of
Generally, GelMA hydrogels have poor mechanical
properties. For example, Rizwan et al. found that the hydrogels is critical.
compression modulus of 15% GelMA hydrogels was below The swelling behavior of hydrogels is related to their
50 kPa. O’connell et al. showed that the peak storage structural and dimensional stability as hydrogels tend
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modulus of 10% GelMA hydrogels could not exceed 10 to swell upon interaction with biological fluids, leading
kPa, even with a high photoinitiator concentration and to changes in weight and size. Therefore, the swelling
light intensity and a long exposure time of UV light. behavior of hydrogels is essential for diffusion/migration
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Consequently, ceramic particles were encapsulated of encapsulated small biomolecules, drugs, and cells.
in GelMA hydrogels to reinforce their mechanical As shown in Figure 8A, printed hydrogels reached their
strength. In the current study, the mechanical properties swelling equilibrium after being immersed in PBS for 12
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of 3D-printed GelMA, HAp/GelMA, MgHAp/GelMA, h. The swelling ratios of GelMA, HAp/GelMA, MgHAp/
and MgHAp/GelMA-PDA hydrogels were investigated GelMA, and MgHAp/GelMA-PDA hydrogels were 328.05
through compression tests. As shown in Figures 7 and ± 9.01%, 326.64 ± 3.97%, 322.01 ± 3.77%, and 307.59 ±
S5, Supporting Information the compression strength of 7.41%, respectively. The degradation of a hydrogel could
3D-printed GelMA hydrogels in the wet and dry states facilitate the formation of extracellular matrix (ECM),
was 0.124 ± 0.014 and 2.590 ± 0.475 MPa, respectively. thereby creating an optimal microenvironment for cell
The combination of GelMAH and GelMAL significantly growth. Moreover, the biodegradation rate of hydrogels
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increased the mechanical strength because GelMAH should be compatible with the rate at which new tissue
could be efficiently crosslinked by UV light and GelMAL is formed. Figure 8B displays the in vitro degradation
had a high sol–gel transition temperature and thus behavior of the printed hydrogels. Printed GelMA, HAp/
could be efficiently thermally crosslinked. On the other GelMA, and MgHAp/GelMA hydrogels manifested
hand, the addition of 10% HAp or MgHAp in GelMA similar degradation behavior. Following an immersion in
hydrogels significantly increased mechanical strength. PBS for 4 weeks, the degradation rates of GelMA, HAp/
The compression strength of 3D-printed HAp/GelMA and GelMA, and MgHAp/GelMA hydrogels were 50.41 ±
MgHAp/GelMA hydrogels in the wet state was 0.171 ± 1.27%, 54.40 ± 0.85%, and 60.87 ± 0.99%, respectively.
0.011 and 0.182 ± 0.023 MPa, respectively. However, the However, MgHAp/GelMA-PDA hydrogels exhibited a
compression strength of MgHAp/GelMA-PDA hydrogels higher degradation rate. After 4 weeks of degradation, the
in the wet state decreased to 0.099 ± 0.012 MPa, which degradation rate of MgHAp/GelMA-PDA hydrogels was
could be attributed to the addition of PDA particles 84.32 ± 0.79%. The relatively high degradation rate was
decreasing the UV crosslinking efficiency. As a result, attributed to the addition of PDA particles, which reduced
the Young’s modulus of GelMA, HAp/GelMA, MgHAp/ the UV crosslinking efficiency.

Volume 10 Issue 5 (2024) 244 doi: 10.36922/ijb.3526