11.2.6 Wound dressings for controlled active ingre...
The treatment of chronic wounds sometimes requires appropriate supplementation of active ingredients，such as growth factors or certain gas stimulation to facilitate wound healing.Therefore，the development of wound dressings containing the controlled release of active ingredients will play an increasingly important role in the treatment of chronic wounds.The growth factor is a kind of polypeptide substance that regulates cell growth and other cell functions by binding to specific，high-affinity cell membrane receptors.It is used in signal transduction，regulation of cell proliferation and differentiation，and tissue maintenance.Recombinant human epidermal growth factor（rhEGF）is widely used clinically in wound treatment as a biological agent that strongly promotes cell regeneration and tissue repair，but its direct use faces the challenge of requiring long-term low-temperature storage.To this end，Han et al.inserted dopamine into clay nanosheets with partial oxidation and incorporated the nanocomposites into polyacrylamide hydrogels.The hydrogels exhibited repeatable and long-lasting adhesion.In addition，the rhEGF could be loaded into the hydrogels，and the rat full-thickness skin defect experiment showed that the hydrogels can be excellent dressings for accelerating wound healing.
The development of effective yet economical methods to improve wound healing is always highly desirable.Due to the advantages of high treatment efficiency and good biocompatibility，gas therapy by using O2，NO，H2S，and others have been proved to have the potential to promote wound healing.Studies have shown that adequate oxygen supply is a prerequisite for wound tissue growth and remodeling.However，insufficient microcirculation at the wound can lead to hypoxia，which is not beneficial for the healing of skin wounds.Therefore，increasing the oxygen content around the wound is one of the most important strategies to promote wound healing.Current oxygen therapies，including hyperbaric oxygen（HBO）and local gaseous oxygen（TGO），mainly use gaseous oxygen delivery，which is not effective in penetrating the skin.Wu et al.developed an oxygengenerating patch made of living microalgae hydrogel，which could generate dissolved oxygen（Figure 11-10）.The transport performance of the dissolved oxygen generated by the patch is more than 100 times than TGO.The patch could promote cell proliferation and migration，and tube formation in vitro，and improve chronic wound healing and skin graft survival in diabetic mice.
In addition，according to the principle of the Bohr effect，CO2 can be used instead of direct use of O2 for skin wound treatment to promote healing.When CO2 dissolves in the tissue surrounding the wound，the decrease in pH will trigger the hemoglobin to release more O2 locally at the site，thereby effectively promoting the healing of the wound.Compared with the direct use of O2，CO2 has a high solubility in body fluids，thus it is more convenient for controlled delivery.In particular，the strategy of accurately releasing CO2 gas on the wound on demand has attracted more and more attention.(https://www.daowen.com)
Yeh et al.designed a metal ion-ligand coordination NP and used NIR to trigger CO2 release for wound healing.Zhang et al.developed a photothermal hydrogel for on-demand and local delivery of CO2 by combining thermally responsive block copolymer（BCP）of Pluronic F127 and carbon NP（CNP）with amino groups to accelerate the healing of skin wounds.When the hybrid hydrogel was irradiated with light，CNP can convert light energy into heat energy，triggering the decomposition of bicarbonate and local release CO2 at the wound site，which speeded up wound healing by improving local microcirculation and increasing tissue oxygen concentration.In addition，gas delivery can also be combined with photothermal therapy（Figure 11-11）.