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Page 16 of 27 He et al. Soft Sci 2024;4:37 https://dx.doi.org/10.20517/ss.2024.32

Photocatalysis can promote skin wound healing by facilitating certain reactions. Deng et al. introduced
injectable double-network MOF-based hydrogels (Au@ZIF-8) that generate reactive oxygen species (ROS)
[98]
under light irradiation . Compared to traditional ZIF-8, the composite hydrogels exhibit enhanced light
absorption and improved charge carrier separation, leading to more efficient ROS generation. These
hydrogels demonstrate bactericidal activity, remain stable and safe, and promote wound healing
[Figure 8A], highlighting their potential as wound dressing materials. Han et al. developed photo-
responsive hydrogels strengthened with Prussian blue nanoparticles (PBNPs) . These hydrogels capture
[99]
bacteria via electrostatic adsorption, disrupting the bacterial membrane surface potential and respiration.
Combined with their photothermal properties, the hydrogels effectively eliminate bacteria. Additionally,
they exhibit excellent mechanical strength, biocompatibility in vitro, and antibacterial properties in vivo.
Despite the development of many wound dressings, achieving effective bacterial prevention, efficient release
of bactericidal agents, and avoiding overhydration remains challenging. Yao et al. addressed these
[100]
challenges by loading ZIF-8 into a porous PVA hydrogel membrane . This composite hydrogel exhibits
antibacterial and anti-inflammatory properties while maintaining a large contact angle (120°) for
physiological fluids, preventing the absorption of unwanted liquids. The MOFs release Zn(II) ions slowly,
while the PVA membrane protects the MOFs from degradation in physiological fluids. For diabetic patients,
delayed wound healing often leads to diabetic foot ulcers, affecting about 15% of patients. Huang et al.
developed a curcumin-based MOF hydrogel coated with quaternary ammonium salt CS to enhance diabetic
[101]
wound healing . The inclusion of Zn(II) ions and vancomycin strengthens the hydrogel’s antibacterial
properties, rapidly killing captured bacteria. Anti-inflammatory properties of curcumin and photothermal
performance of the hydrogel create an immune microenvironment that accelerates healing. Li et al. created
an injectable hydrogel with antibacterial and antioxidant properties by incorporating α-lipoic acid, which
helps reverse oxidative stress-induced cell damage and promotes cell proliferation and migration . Zhang
[102]
et al. designed a zinc MOF-based hydrogel with alginate and poly(propylene glycol) to integrate
photodynamic therapy, enhancing the antibacterial effect by disrupting bacterial membranes and increasing
[103]
ROS production . Qiu et al. developed a Zn-MOF-based hydrogel with high ROS scavenging capacity and
sustained antibacterial activity, making it suitable for regulating ROS-dominated inflammatory
[104]
environments .

Collectively, these studies showcase the remarkable progress in developing MOF-based hydrogels as
versatile and effective materials for antibacterial applications in wound healing. These hydrogels hold great
promise for enhancing therapeutic outcomes and addressing challenges in wound care.

Wound healing and drug delivery
There are other ways to promote the healing of diabetic foot ulcers. Copper ions are reported to be active
for wound healing, but the copper ions concentration in the healing is proven as toxic level. Xiao et al.
synthesized a Cu-based MOF with polymer hydrogels and fabricated a MOF-hydrogel system that can
release copper ions in an appropriate concentration . Through the reference experiment, the pure MOF
[105]
nanoparticles which will degrade in the protein solution are protected well from degradation by the
hydrogels. The copper ions are released but the concentration is kept at a safe level, and the wound healing
is accelerated. Yang et al. reported a MOFs-based hydrogel hybrid system that can continuously release
hydrochloride, curcumin, and Cu(II) ions, while also maintaining a moist microenvironment that promotes
wound healing in diabetic mice . Via the experiment to the two call lines (HaCat and HSF cells), the
[106]
cytotoxicity and healing effects of MOFs-based hydrogels are demonstrated, with in vivo local treatment
showing excellent therapeutic efficacy in enhancing the healing of diabetic wounds. Via a simple
solvothermal reaction, Wang et al. fabricated donut-like MOFs and furthermore fabricated a light-
responsive hydrogel . The tough surface of the CuNA facilitates the loading and release of basic fibroblast
[107]