Liposomes Enhance Dye Localization within the Mammary Ducts of Porcine Nipples

Transductal and transepidermal diffusion are two distinct penetration routes of molecules administered via the nipple. To improve the therapeutic potential of this drug administration technique, drug penetration into the mammary ducts should be maximized, which may be accomplished through design optimization of drug delivery vehicles. In this study, we evaluated liposomes, ranging in size from 100 to 3000 nm, to improve ductal penetration of model fluorescent dyes using fluorescence microscopy and image analysis. Liposomes encapsulating a model fluorescent lipophilic dye, nile red, or hydrophilic dye, sulforhodamine B, were applied topically on porcine nipples for 6 h in vitro. Liposome encapsulation of sulforhodamine B significantly reduced the total amount of dye penetrating the nipple, while penetration of liposome-encapsulated nile red varied depending on vesicle size, as compared to their solution controls. However, the fluorescence intensity localized at the ductal epithelium was higher at extended ...