Skin penetration-inducing gelatin methacryloyl nanogels for transdermal macromolecule delivery

In this study, the suitability of gelatin methacryloyl (GelMA) nanogels for transdermal delivery of macromolecules was demonstrated. The synthesis of GelMA nanogels (GNs) and fluorescein isothiocyanate labelled bovine serum albumin (FITC-BSA) loaded GelMA nanogels (FGNs) were implemented when confined in water-in-oil nanoemulsion droplets via the photopolymerization of the methacryloyl substituents to create crosslinked nanogels. Both GNs and FGNs existed as fine particles in aqueous condition (pH 7.4) for 7 days. No distinct aggregation of nanogel particles were observed. In the MTT assay, high percentage of cell viability indicated that GNs did not exhibit any growth inhibitory effect or significant cytotoxicity. The skin penetration study results showed that FGNs permeated across the epidermis and into the dermis of a porcine model when compared to the FITC-BSA dissolved in PBS. Possible penetration routes of FITC-BSA through the stratum corneum (SC) were illustrated by visualizing the SC structure with fluorescent signals of FITC-BSA. The penetration mechanism of FGNs across the SC layer was successfully demonstrated by explaining three penetration routes (intercellular, follicular, and transcellular route). The results suggest that GNs have a potential as a transdermal delivery carrier for hydrophilic macromolecules.