A research team from TU Graz and the Vellore Institute of Technology in India is developing a 3D-printed skin imitation equipped with living cells in order to test nanoparticles from cosmetics without animal testing.

Directive 2010/63/EU laid down restrictions on animal testing for the testing of cosmetics and their ingredients throughout the EU. Therefore, there is an intense search for alternatives to test the absorption and toxicity of nanoparticles from cosmetics such as sun creams. A team of researchers from Graz University of Technology (TU Graz) and the Vellore Institute of Technology (VIT) in India is working on the development of skin imitations that mimic the native three-layer tissue structure and biomechanics of human skin. Such imitations can be produced using 3D printing and consist of hydrogel formulations that are printed together with living cells. The first skin models are now ready for nanoparticle testing.

Hydrogels in which skin cells survive and grow

“The hydrogels for our skin imitation from the 3D printer have to fulfil a number of requirements,” says Karin Stana Kleinschek from the Institute of Chemistry and Technology of Biobased Systems at TU Graz. “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.” The starting point for stable and 3D-printable structures are hydrogel formulations developed at TU Graz. Hydrogels are characterised by their high-water content, which creates ideal conditions for the integration and growth of cells. However, the high-water content also requires methods for mechanical and chemical stabilisation of the 3D prints.

TU Graz is working intensively on cross-linking methods for stabilisation. Ideally, following nature’s example, the cross-linking takes place under very mild conditions and without the use of cytotoxic chemicals. After successful stabilisation, the cooperation partners in India test the resistance and toxicity of the 3D prints in cell culture. Only when skin cells in the hydrogel survive in cell culture for two to three weeks and develop skin tissue can we speak of a skin imitation. This skin imitation can then be used for further cell tests on cosmetics.

Successful tests

The first tests of 3D-printed hydrogels in cell culture were very successful. The cross-linked materials are non-cytotoxic and mechanically stable. “In the next step, the 3D-printed models (skin imitations) will be used to test nanoparticles,” says Karin Stana Kleinschek. “This is a success for the complementary research at TU Graz and VIT. Our many years of expertise in the field of material research for tissue imitations and VIT’s expertise in molecular and cell biology have complemented each other perfectly. We are now working together to further optimise the hydrogel formulations and validate their usefulness as a substitute for animal experiments.”