Wound healing is a complex process with different stages: First, the bleeding is stopped. Then, in the the inflammatory phase, debris and bacteria are removed from the wound. In the following proliferative phase, new tissue is formed and closes the wound. Finally, the new tissue remodels, matures, and becomes mechanically stronger. Several nanomaterials have been investigated as candidates for speeding up wound healing. However, most of them only help in a single stage of the healing process.

Yan Cheng, Xi Li, Haiyuan Zhang, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, and colleagues have developed hollow CeO₂ nanoparticles (NPs) with a rough surface and filled with L‐arginine, which can promote multiple stages of wound healing. The hollow CeO₂ NPs were synthesized using silica NPs as templates. The surface of the silica NPs coated with a CeO₂ layer through a calcination method and the silica cores were removed using a sodium hydroxide solution. The particles were suspended in a buffer solution and mixed with L-arginine to load them with the amino acid.

As tests in mice showed, the resulting CeO₂ NPs can promote wound healing: They first form “nanobridges” which help to close the wound. The porous shell of the NPs promotes the production of reactive oxygen species under sunlight, which can help to prevent infection during the inflammation stage. In addition, the L-arginine inside the NPs acts as a source of nitric oxide (NO) under the conditions in a wound. NO promotes wound healing in the proliferation stage. Thus, the NPs are promising for sequentially promoting multiple stages of the wound healing process.

• Hollow, Rough, and Nitric Oxide-Releasing Cerium Oxide Nanoparticles for Promoting Multiple Stages of Wound Healing,
  Xiaomin Ma, Yan Cheng, Hui Jian, Yanlin Feng, Yun Chang, Runxiao Zheng, Xiaqing Wu, Li Wang, Xi Li, Haiyuan Zhang,
  Adv. Healthcare Mater. 2019.
  https://doi.org/10.1002/adhm.201900256