Synopsis

Hydrogel films can be useful carriers of active ingredients into the skin for cosmetic or pharmaceutical purposes. The preparation of hydrogel films often involves a crosslinking step where the soluble gel converts to an insoluble but reversibly swellable film. With my research group I successfully developed hydrogel films, initially with a synthetic polymer, using UV radiation for the crosslinking reaction; we then continued with natural polymers, such as hyaluronic acid. The use of UV radiation can be high-risk and expensive for large scale manufacture. We therefore explored alternative sources of energy for the crosslinking reaction; we found that the crosslinking reaction is feasible also via thermal (oven-assisted) and microwave energy. The oven-assisted method (~80℃) was most efficient in terms of hydrogel film properties, safety, and cost-effectiveness. We subsequently uploaded active ingredients into the hydrogel films and studied their in vitro release kinetics; the crosslinked hyaluronic acid hydrogel films allowed high percentage loading of the active ingredients and enabled their complete immediate release within 10 min. Therefore, these crosslinked hydrogel films are a promising cosmetic and pharmaceutical immediate-release delivery system and also a sustainable formulation in terms of manufacturing cost-effectiveness, simplicity and safety.