'3D printed' human skin pigmentation created

Scientists have developed a new method for controlling pigmentation in fabricated human skin using 3D bio-printing. The method developed by researchers at Nanyang Technological University in Singapore has the potential to produce pigment-correct skin grafts. It could also be used to develop skin constructs for toxicology testing and fundamental cell biology research.

The team controlled the distribution of melanin-producing skin cells (melanocytes) on a biomimetic tissue substrate, to produce human-like skin pigmentation. While current engineered skin constructs are successfully used in skin repair and grafting, toxicology, and chemical testing, they lack complex features such as skin pigmentation, sweat glands or hair follicles.

"3D bio-printing is an excellent platform for the precise deposition of biomaterials and living cells to make biomimetic skin, in large volumes with great repeatability," said Wei Long Ng from Nanyang Technological University. However, non-uniform skin pigmentation is often seen, and this remains a huge challenge to be solved.

"Our aim with this project was to use this method to demonstrate the feasibility of making 3D in-vitro pigmented human skin constructs, with uniform skin pigmentation," said Wei Long, lead author of the study published in the journal Biofabrication. To make the pigmented skin constructs, the team used three different types of skin cells - keratinocytes, melanocytes, and fibroblasts - and a two-step 'drop on demand' bio-printing method.

"The two-step bio-printing strategy involves the fabrication of hierarchical porous collagen-based structures (that closely resembles the skin's dermal region)," said Wei Long. "When we compared the 3D bio-printed skin constructs to those made using a manual-casting method, we found two distinct differences between the two fabrication approaches - the cell distribution on top of the dermal regions, and the microstructures within the dermal regions.

"The two-step bio-printing strategy enables the standardised distribution of printed cells in a highly- controlled way, as compared to the manual casting approach," Wei Long said. The bio-printing technique allows the manipulation of pore sizes within the 3D collagen-fibroblast matrices, to fabricate hierarchical porous structures that are clearly seen in the native skin tissues, researchers said. In contrast, tuning the skin microstructure within the 3D collagen-fibroblast matrices using the manual-casting approach is extremely challenging, they said.