Updated: Apr 7, 2021
The dermocosmetic industry is extremely lucrative, representing one of the largest growing global markets and continuously innovating in the field of beauty and hygiene. With the rise of animal welfare concerns, the need to create new skin model alternatives to assess the efficacy of pharmaceutical, skincare, and cosmetic products through in vitro techniques has emerged. The use of human skin is the gold standard when it comes to product evaluation and testing, since this approach can ensure that the results will be less variable and more accurate . The field of dermocosmetology needs tissue models that mimic the native skin with high fidelity, thus being able to prove the effectiveness of bioactive principles or finished products . Skin tissue engineering and 3D bioprinting are extremely important tools to meet these new demands in the cosmetics and skincare market, as they provide innovative technologies that make it possible to fabricate complex structures with living cells.
The potential of tissue engineering in the treatment of several skin diseases and lesions is already known, however, tissue engineering and 3D bioprinting also have a huge potential in dermocosmetology. As engineered tissues are typically designed in different patterns and can be biofabricated by distinct methods, they can originate several types of skin models, including epidermal and dermal, which can be specifically selected depending on the intended dermocosmetic application . This outstanding alternative to replacing tests in animal models and improving product accuracy and efficacy has been the focus of a large number of investments. Global cosmetic brands such as Proctor & Gamble (P&G) and L’Oréal are currently into research and development of 3D bioprinted skin models. P&G has become the latest household name to explore 3D bioprinting, claiming it to be definitely a very strong emerging area for dermocosmetic innovations .
Figure 1: Reconstructed human epidermis by L’Oréal. 
A living skin equivalent was the first in vitro model of human skin, which was developed using normal keratinocytes (NHKs) that proliferated and differentiated on a de-epidermized dermis . More recently, tissue engineering approaches originated full-thickness skin models from ﬁbroblast-populated collagen matrices (dermal equivalents) overlaid by stratiﬁed NHKs. These models were designed to allow evaluation of the potential of sunscreens to protect the skin from UV-associated damage . An efficient path to achieving a satisfactory bioprinted model system for treating different structural and cosmetic skin conditions is using different combinations of keratinocytes and fibroblasts, melanocytes, and stem cells. Skin equivalents usually consist of populations of allogeneic skin cells growing in layers and seeded on scaffolds derived from ECM proteins .
Inkjet deposition, laser-assisted, and extrusion bioprinting are some of the main approaches to obtain tissue-engineered skin for dermocosmetical purposes. The extrusion-based technique is more cell-friendly and allows great incorporation of biological molecules using mechanical force to generate and deposit a continuous cylindrical stream of bioink. By using inkjet deposition or laser-assisted bioprinting, which uses an energy-absorbing donor layer that responds to laser stimulation, it is possible to achieve a tight control over microstructures and spatiotemporal deposition of biomaterials and cells, particularly stem cells, facilitating studies of biomimicry and miniaturization [7,9].
Figure 2: Categories of bioprinting techniques .
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8- Bob Woods. Companies are making human skin in labs to curb animal testing of products. 2017. CNBC.com
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