8.5.1.2　Dendrimers

Dendrimers are a class of synthetic hyperbranched polymers.Their core and highly functional branches can carry hydrophilic and lipophilic drugs through host-guest interactions and chemical conjugation，consequently developing a universal platform with high drug loading and high monodispersity.Polyamide dendrimer（PAMAM），a chemical penetration enhancer，has been used for transdermal administration researches of various small molecular drugs（e.g.，tamsulosin hydrochloride（a selective alpha 1A adrenergic receptor antagonist for urinary retention），ketoprofen and diflunisal，8-methoxypsoralen，riboflavin（vitamin B2），5-fluorouracil）in the skin of rat or pig.The mechanisms by which different dendrimers promote drug transdermal delivery depend on their sizes（determined by branch algebra）and charge.①The relatively small dendrimers can quickly diffuse through the stratum corneum and change the solubility，polarity and structural integrity of the lipid bilayer to act as a fluid for drug penetration.②The cationic dendrimers can form nanopores to destroy the lipid bilayer and promote drug penetration.③Certain dendrimers can participate in drug penetration through transcellular pathway.(https://www.daowen.com)