3D-printed hydrogel patch for controlled topical release: Gelatin/tannic acid formulation meets additive manufacturing

Prolonged use of protective masks can cause skin issues like rosacea and "maskne," particularly among healthcare workers. Poorly fitting commercial dressings often worsen these problems. A novel solution involves 3D-printing personalized hydrogel patches with active ingredients, with customizable designs, concentrations, and controlled release rates. This study explores customizable 3D-printed gelatin/ tannic acid hydrogel patches containing metronidazole for rosacea or salicylic acid for maskne treatment. Rheological properties, including gelation temperature, viscosity at gelation temperature, gelation time, and viscosity during printing, were analysed. Optimal printing conditions were determined using a Quality by Design approach with Design of Experiments framework. Three patch designs-occlusive, grid, and triangular infill-were 3D-printed. Mechanical properties were assessed via tensile strength tests, and in vitro studies evaluated the release profiles and permeation of the active ingredients. The gelatin/tannic acid and gelatin/tannic acid-metronidazole hydrogels had similar gelation temperatures, while the salicylic acid hydrogel gelled at a lower temperature. All formulations had comparable viscosities at gelation, and gelation times (∼20 s). Optimal print conditions were 42 °C, 25 Psi, and 30 mm/s gelatin/tannic acid and metronidazole hydrogels, and 36 °C and 30 Psi for the salicylic acid formulation. Infill patterns affected mechanical properties and drug release, with grid patterns showing stronger structures and higher drug release rates compared to triangular patterns. In vitro permeation tests revealed salicylic acid penetrated the epidermal barrier and accumulated within the skin, despite low overall retention of both active ingredients. These findings highlight the potential of personalized 3D-printed patches for treating mask-related skin conditions.