11.2.3　Antibacterial dressings

During the use of the hydrogel wound dressings，the hydrogel dressings directly contact the surface of the tissue，which can reduce the loss of body fluids，and it is also necessary to prevent secondary infection of the wound.Therefore，hydrogel dressings should have good antibacterial properties，which can inhibit the growth of bacteria on the wound surface during use，and at the same time prevent the infection of microorganisms outside the body.In order to meet this requirement，antibacterial hydrogel dressings have emerged，which can be obtained by loading antibacterial agents or modifying hydrogel with the antibacterial motif.

The antibacterial agents loaded hydrogels refer to the hydrogels that directly load the antibacterial agent into the hydrogels.According to different types of antibacterial agents，hydrogels loaded with antibacterial agents can be roughly divided into three types.They are hydrogels loaded with metal ions or metal NPs（such as Ag+，Fe3+，Ag NPs），antibiotics，and non-antibiotics antibacterial drugs.For example，Chen et al.used ferric ethylenediaminetetraacetate（EDTAFe3+）to crosslink hyaluronic acid（HA）to obtain antibacterial hydrogels.When being applied to wounds，HA can be degraded at the site of infection，and the hydrogels can locally release Fe3+complexes.These Fe3+complexes can be rapidly absorbed by surrounding bacteria and reduced to Fe2+.Fe2+reacts with hydrogen peroxide（H2O2）produced by bacteria and inflammatory cells to form hydroxyl radicals through Fenton reaction to destroy the bacterial structure，thereby achieving sterilization（Figure 11-5）.(https://www.daowen.com)

Unlike hydrogels loaded with antibacterial agents，inherent antibacterial hydrogels refer to hydrogels with inherent antibacterial properties prepared by introducing components with antibacterial functional groups.Inherent antibacterial hydrogels can be divided into cationic polymer hydrogels and antimicrobial peptide-based hydrogels.The inherent antibacterial hydrogels mainly kill the bacteria by interacting with the negatively charged bacterial cell membrane，and the cell membrane structure is destroyed and the intercellular substance flows out.Lei et al.prepared an antibacterial hydrogel based on monodisperse PDAfunctionalized bioactive glass NPs and antibacterial polypeptide F127-e-poly-L-lysine.The nanocomposite hydrogel exhibited highly effective antibacterial properties against bacteria with multidrug resistance and effectively promoted the formation of collagen tissue and the regeneration of blood vessels.