Lipid nanocarriers and 3D printed hollow microneedles as strategies to promote drug delivery via the skin

The skin represents an interesting site for the administration of active pharmaceutical ingredients. It offers several advantages over the most conventionally used routes of administration such as the oral and the parental route. Indeed, it bypass the 1st pass metabolism, avoids variables that affect drug absorption in the gastrointestinal tract (i.e. pH, enzymatic activity and drug-food interactions), it is a convenient and non-invasive means of drug delivery and does not require specialized healthcare staff for drug administration. However, due to the structural properties of the skin, only drugs with selected physicochemical features are suitable to be delivered via this administration route. In order to facilitate skin drug delivery various strategies have been studied over the years such as the use of chemical enhancers, external energy or nanodelivery systems. In this thesis lipid nanocarriers combined with the penetration enhancer Transcutol® P and 3D printed microneedles are employed as strategies to promote drug delivery via the skin. Specifically, Part 1 investigates the combination of the penetration enhancer Transcutol® P with two different lipid nanocarriers, solid lipid nanoparticles (Chapter 1) and phospholipid vesicles (Chapter 2), as tools to promote the skin accumulation of 8-methoxypsoralen (8-MOP). In Part 2, 3D printing is employed as an innovative method for the manufacturing of solid and hollow microneedles (MNs) patches.