3D Printed Skin Can Replace Animal Testing for Cosmetics

The skin is the largest organ we have in terms of surface area and whatever we apply to it is able to affect the body directly via the various layers. There it can fulfill its purpose, for example relieve pain and contribute to regeneration or even cause great harm. This is the case when ointments, cosmetics etc. contain toxic substances. To rule this out in advance, cosmetics are subjected to numerous tests for purity and compatibility. In order to protect us humans, animals are often used for such tests however, these are increasingly considered to be ethically reprehensible as they cause great suffering to animals. But what are the alternatives for testing sunscreen and other products and guaranteeing their safety? A team of researchers from Graz University of Technology and the Vellore Institute of Technology (VIT) in India created a 3D-printed skin that imitates the human model and is to be used for tolerance studies in the future.

The imitation skin was produced using 3D printing and is enriched with living cells. Like its biological counterpart, it has a three-layered tissue structure. In order to be able to print the imitation, hydrogel formulations had to be developed first. No easy task, as Karin Stana Kleinscek from the Institute of Chemistry and Technology of Biobased Systems at TU Graz points out. “The hydrogels for our skin imitation from the 3D printer have to fulfil a number of requirements,” she explained. “The hydrogels must be able to interact with living skin cells. These cells not only have to survive, but also have to be able to grow and multiply.”

3D-printed structure of the skin with human keratinocytes

Although hydrogels have a high water content, which is ideal for integrating cells and allowing them to grow, the high water content also leads to challenges. For example, the mechanical and chemical stability required for printing is impaired by the high water content. In order to solve the problem of stabilization, TU Graz worked on various cross-linking methods. The experiments were based on nature and the researchers aimed to avoid the use of cell-toxic chemicals.