New 3D printer creates complex biological tissues

Amir Miri

A 3D printer has been developed that uses a microfluidics chip to combine multiple cell-laden hydrogels into artificial tissue.

The printer uses a technique known as stereolithography, where a 3D object is printed layer-by-layer using UV light to polymerise a liquid prepolymer into a solid structure. The light is also used to create a pattern to guide the shape of each layer to be printed using an array of over a million tiny mirrors that move independently to change the light pattern. Conventional stereolithography bioprinters use only one material, but the newly-developed printer uses a microfluidics chip with four inlets to enable multi-material bioprinting.

“Tissues are wonderfully complex structures, so to engineer artificial versions of them that function properly, we have to recreate their complexity," said Ali Khademhosseini, professor of engineering at the UCLA Samueli school of engineering, who led the study. "Our new approach offers a way to build complex biocompatible structures made from different materials."

Each bio-ink is a stem cell-laden hydrogel that polymerises upon exposure to the UV light. The printed hydrogels then act as a scaffold that can mimic the extra-cellular matrix of tissue structure, allowing the “seeded” cells to grow and ultimately replace the scaffold. The microfluidics chip can rapidly switch between bio-inks, which decreases the printing time that might otherwise hinder cell viability.

The printer has been used to create complex tissue-like structures resembling tumours with networks of blood vessels, muscle strips, and musculoskeletal joints. The researchers also implanted bioprinted tissue into rodents, which was not rejected.

As actual tissues consist of multiple cell types, this process is a step towards printing artificial tissue for use in transplants and surgeries, and bioprinting could become a method for assisting in cancer research by helping to understand tumour progression. It will also be possible to accommodate as many different bio-inks as necessary by increasing the number of inlet channels in the microfluidic chip.

Advanced Materials http://doi.org/gdg7gx