Structure-skin permeability relationship of dendrimers.

Purpose: To investigate skin penetration of poly (amidoamine) (PAMAM) dendrimers as a function of surface charge and molecular weight in presence and absence of iontophoresis.

Methods: Dendrimers were labeled with fluoroisothiocynate (FITC); skin penetration of dendrimers was studied using excised porcine skin in-vitro. Skin penetration of FITC-labeled dendrimers was quantified using confocal laser scanning microscope (CLSM). G2-G6 NH(2), G3.5-COOH and G4-OH dendrimers were used.

Results: Cationic dendrimers showed higher skin penetration than neutral and anionic dendrimers. Skin penetration of cationic dendrimer increased linearly with increase in treatment time. Iontophoresis enhanced skin penetration of cationic and neutral dendrimers. Increase in current strength and current duration increased skin transport of dendrimers. Passive and iontophoretic skin penetration of cationic dendrimers was inversely related to their molecular weight. Dendrimer penetrated the skin through intercellular lipids and hair follicles. With iontophoresis, dendrimer was also found in localized skin regions.

Conclusions: The study demonstrates that the physicochemical properties of dendrimers influence their skin transport. Findings can be used to design dendrimer-based nanocarriers for drug delivery to skin.