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covalent bond interactions, including H bonding, electrostatic attraction, and
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hydrophobic effects, to build a 3D porous network structure of hydrogels. This

method not only preserved the natural structure and biological activity of the raw
material, but also avoided the damage that may be caused by chemical cross-linking

agents, which was of great significance for tissue engineering, drug delivery, and the

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treatment of diabetic wounds and gastrointestinal surgical incisions. However,
hydrogels obtained by physical cross-linking also have some shortcomings, such as

relatively poor uniformity, mechanical strength, and long-term stability. The

introduction of 3D printing technology has made a big breakthrough in this area, which

was very important for developing better diabetic wound repair materials.

Temperature-induced cross-linking method was an important method in the

physical cross-linking methods. It regulated the non-covalent interactions between

molecules to achieve gelation through temperature changes. At low temperatures, the

raw materials existed stably in a soluble state, and when the temperature rise to

physiological temperature, they spontaneously assembled to form fibers networks
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through non-covalent forces. Kathryn E. Drzewiecki et al. used microbiota to modify
collagen to obtain managed collagen (CMA). This hydrogel retained the self-

assemblability, biodegradability, and natural biological activity of collagen. Under the

physiological temperature and pH conditions, CMA exhibited rapid and temperature-

29
dependent reversible self-assembly. Wolf H. Rombouts et al. prepared a silk fibroin-
collagen hydrogel that achieved reversible state changes by temperature switching

(Figure 2A). When the temperature was increased to 40°C, the silk proteins self-

assembled, whereas upon cooling to 20°C, the self-assembly process became

synchronized with the formation of the triple helices structures. Moreover, the

introduction of anionic polypeptide poly(γ-glutamic acid) (γ-PGA) into the CMA

hydrogel effectively improveed the temperature-dependent phase transition behavior of

collagen, resulting in a low-viscosity solution at room temperature and a non-flowing
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gel near 37℃, respectively. However, it was still difficult to accurately control the

gelation time, porosity and mechanical properties of collagen hydrogels. Through the

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