8.5.1　Penetration enhancers based on biomedical po...

Penetration enhancers are a kind of chemical substances that can reversibly reduce the resistance of the skin to drugs and accelerate the penetration of drugs through the skin.After removing them，the skin can restore the normal barrier function.Traditional small molecule chemical penetration enhancers include solvents（e.g.，ethanol，pyrrolidone（sodium pyrrolidone carboxylate），sulfoxides（dimethyl sulfoxide（DMSO）and decyl methyl sulfoxide）），fatty acids，surfactants，terpenes，azone，etc.They work in a variety of ways，including increasing solubility of drugs and penetration of drugs to the stratum corneum，liquidizing the stratum corneum crystal structure，and dissolving the lipid of the stratum corneum.The skin irritant penetration enhancers such as dimethyl sulfoxide（DMSO），dimethylformamide（DMF）and oxazolidinones are currently rarely utilized，while the more moderate penetration enhancers such as fatty acids，urea and pyrrolidone are still widely used.However，traditional chemical penetration enhancers are only suitable for small molecular weight drugs，and they are very limited for the penetration of macromolecular drugs such as biologicals.Comparatively，the polymer penetration enhancers（e.g.，hyaluronic acid，dendrimers，cyclodextrins，chitosan and its derivatives，and skinpenetrating peptides）have distinct advantages in promoting the penetration of macromolecular drugs and NPs.(https://www.daowen.com)