A European consortium is developing a lithography method for bioprinting tissue and organs that uses light sheet illumination and photosensitive hydrogels mixed with living cells. The project, coordinated by Elena Martinez from the Institute for Bioengineering of Catalonia (IBEC) and involving work taking place at the Goethe University Frankfurt, is called BRIGHTER for “bioprinting by light sheet lithography: engineering complex tissues with high resolution at high speed.” The lithography process for BRIGHTER works in a way similar to lithography in semiconductor technology, but instead of a semiconductor and photosensitive layer illuminated by a mask, the researchers use a hydrogel with photosensitive molecules. The hydrogel is exposed to a thin laser light sheet, leading to the formation of polymers that serve as a matrix for colonization by living cells. The remaining hydrogel, which is still in liquid form, is washed out. The specific properties of the polymer matrix can be used to introduce stem cells into well-defined compartments or to enable the formation of vessels. Light sheet bioprinting. A hydrogel composed of living cells and photosensitive molecules is deposited in a special cuvette. A thin laser light sheet illuminates the gel following a programmed pattern (green beam). This leads to the formation of 3D microstructures that reproduce the tissue architecture and function. The remaining, still-liquid hydrogel is washed out after the printing process. Courtesy of F. Pampaloni, BRIGHTER, 2019. “This method will enable us to adjust the spatial structure and the stiffness with an unprecedented resolution so that we can create the same heterogeneous microstructures that cells find in natural tissues,” said researcher Francesco Pampaloni. In contrast to bioprinting systems that build up structures layer by layer, taking a “bottom-up” approach, the BRIGHTER method takes a “top-down” approach to lithography. The researchers believe that this approach could reduce cell death during the bioprinting process and improve resolution, which would make it easier to successfully reproduce the delicate structures of natural tissue. Additional advantages over conventional 3D-printing systems could be faster speed and more cost-effective production. The BRIGHTER project will begin in July 2019 and will be funded for three years as part of the European Union’s Future and Emerging Technologies Open Horizon 2020 Programme.