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loaded curcumin into 3D bioprinting gel hydrogel to create a suitable microenvironment

for ADSCs and confirmed that curcumin effectively regulated the repair effect of

ADSCs on diabetic wounds by targeting the AGE/AGER/p65 signaling pathway.
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Yingshan Zhou et al. synthesized modified HAs including MHA and Shha with highly
substituted acrylate groups. MHA/Shha hydrogels were prepared by blending modified

HA with mercaptoacrylate via Michael addition precross-linking, followed by

subsequent covalent cross-linking through mercaptoacrylate and acrylate-acrylate

photopolymerization. These hydrogels represented promising hydrogel scaffold

candidates for diabetic wound.

2.2.2. Schiff base reaction

The Schiff base reaction, a mild and efficient condensation reaction between -

CHO and -NH2 groups that formed an imine bond (C=N), were played a crucial role in

hydrogel preparation, which could adjust the proportion of reactants and precisely

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controlling the reaction conditions, such as temperature, pH value, reaction time, etc.
After introducing 3D printing technology into the hydrogel, it was possible to precisely

print the appropriate hydrogel by layer-by-layer stacking based on the pre-designed
model. By precisely controlling the printing parameters and the conditions of the Schiff

base reaction, the hydrogel scaffolds with complex 3D structures could be directly

fabricated. Moreover, by adjusting the degree of schiff base reaction on cross-linking,

the mechanical properties and pore structure of 3D printed hydrogel can be optimized

to better match the specific requirements of different tissue engineering.

Commonly employed crosslinkers for Schiff base reaction included genipin,

dialdehyde cholesterol modified starch (DACS), and oxidized Konjac glucomannan

(OKGM), which could react with different polymer matrices, offering a wide range of

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options for tailoring the properties of 3D-printed hydrogels. Jianxi Xiao et al. used
multi-crosslinking strategies, including free radical polymerization, Michael addition,

Schiff base reaction, and hydrogen bonding, to fabricate a cell-loaded collagen-based

bio-ink consisting of methacrylated collagen (CMA) and dihydromyricetin (DHM). As

a polyphenolic antioxidant, the aldehyde groups formed after the oxidation of DHM

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