Light-Based Tissue Bioprinting Method Cuts Reliance on Animals

A light-based 3D bioprinting technique could soon be used to produce tissue models for testing and basic research. The approach is poised to reduce reliance on animals in laboratory testing.

BRIGHTER, a European Union-funded project coordinated by the Institute for Bioengineering of Catalonia (IBEC), is developing a 3D bioprinting technology that uses light-sheet lithography to accurately generate and mold complex tissues like the human skin with high spatial resolution and speed.

The new technology is based on a top-down lithography approach, in contrast to current bottom-up, layer-by-layer bioprinting methods.

To begin, researchers placed a hydrogel composed of living human cells and photosensitive molecules in a cuvette. All the necessary components to reproduce the tissue, including different types of cell populations, were combined in the mixture of hydrogel, cells, and light-sensitive molecules.

Using a light-sheet microscope, the researchers illuminated the hydrogel mixture with a thin laser light sheet that followed a programmed pattern. The cells in the hydrogel were patterned in a specific way, leading to the formation of 3D microstructures that reproduced the tissue architecture and function. The remaining hydrogel was washed out after the printing process.

The approach allowed the researchers to mold the engineered tissue to create a specific 3D structure on demand; they could control the stiffness, shape, and dimensions of the structure, and they generated 3D tissues with complex geometries. In addition to providing localized control of the shape required for the 3D structure, the light-sheet bioprinting technique increased resolution.

A small square of a matrix containing skin cells. The European project consortium, BRIGHTER, is developing a new 3D bioprinting technology to produce artificial skin using light. It could significantly reduce animal use in pharmaceutical, cosmetics, and biomedical research. Courtesy of the Institute for Bioengineering of Catalonia (IBEC).

As the tissue was being built, the researchers observed the process in real time, as well as in 3D, since entire planes can be polymerized at the same time.

Because the approach is much faster than bottom-up bioprinting, cell viability is preserved, the researchers reported.

“We hope to be able to print a skin sample with an area of 1 cm² and a thickness of 1 mm in approximately 10 min and with a cell viability of more than 95%, greatly improving current bioprinting conditions,” IBEC researcher Núria Torras said.

The ability to mold bioprinted skin tissue is important, because human skin is composed of several layers, each with different cell types. The technology also enabled the researchers to generate vascularization of the tissue and include appendages such as the sebaceous and sweat glands and the hair follicles.

The tissues generated using this technique could be sent to hospitals and pharmaceutical labs, where they could be used for performing preclinical tests, developing medicines, or testing new chemicals and cosmetics. Because the tissues are constructed from human cells, they would not only reduce the need for animal experimentation — they would produce more reliable results than animal testing.

Bioprinted tissue could also be used in medical interventions for burn patients or people with dermatological diseases or wounds. In the future, the light-based bioprinting technique could even be used to produce organs in the laboratory. The process of molding the bioprinted tissue can be customized, since patient cells can be used to construct the tissue.

The light-based 3D bioprinting technology, based on patterning 3D cell cultures using laser light-sheet microscopy, also overcomes many of the technical obstacles that currently limit the fabrication of complex human tissues. “Our innovative 3D bioprinting system not only achieves tissues that are closer to the real ones, but it is also much faster than current systems, a fundamental factor to ensure the viability of the new tissues,” said professor Elena Martínez, the project’s coordinator.

For its proof-of-concept application, the research team will bioprint viable engineered skin tissues that demonstrate the key features of the BRIGHTER device: skin appendix (hair follicles, sweat glands), stem cell niches, and a vascular network. According to the team, vascularized bioengineered skin constructs that contain not only the epidermis, but also skin appendages (hair follicles and sebaceous and sweat glands), are a huge unmet need.

The BRIGHTER consortium includes scientists from three research institutions: IBEC, Goethe Universität Frankfurt, and Technion. It also includes researchers from the biotechnology companies Mycronic and Cellendes.