October 8, 2021

Let There Be Light! How the Lumen X+ is redefining bioprinting capabilities

By better replicating the in vivo cellular environment, the transition from 2D cell culturing to 3D set off a chain reaction of scientific advances in many research fields, including tissue engineering. Tissue engineers quickly adopted 3D bioprinters to extrude cells in defined spatial arrangements that were more physiologically relevant. Although extruded filaments were revolutionary, when scaling up to the size of human organs, it was the Lumen X+™ light-based bioprinter, powered by Volumetric, that precipitated a paradigm shift by enabling the higher resolutions needed to recreate the complex vasculature of organs such as the lung.

Form follows function

In biology, everything from a protein’s conformation to an organ’s structure to an organism’s overall form is an evolutionary consequence of its function. Armed with today’s advanced imaging technology and an unprecedented understanding of the form of organs, tissue engineers are asking if function will follow form. If they can push the science and technology to approximate a living tissue’s form or structure, will the engineered construct function like the original?

Although scientists can grow and fit billions of cells in a 15 mL conical tube, keeping them alive is still a challenge. Just as it would be difficult to bring home groceries or remove trash if civil engineers forgot to design streets for a city. When cells no longer have access to nutrients, oxygen and waste removal, they start dying off. In the in vivo human lung, a multiscale vasculature transports nutrients and removes waste produced by cells to keep them alive. Consider this vasculature the body’s equivalent to city streets. Tissue engineers need to replicate these in order to make bioprinted tissue a reality. The extrusion-based BIO X6™ bioprinter, which offers the versatility of interchangeable printheads and makes it possible to work with a variety of materials, is one option. By incorporating a sacrificial biomaterial, the BIO X6 can even be used to create the hollow cavities of tubular structures.

Shedding new light

The Lumen X+ goes further, using lumens of light to make vascular lumens and create even more intricate vasculature. Shining the light-based bioprinter’s visible light into a vat of photosensitive liquid, or PhotoInk™, triggers a localized chemical reaction. Each point of light represents a pixel and can convert small volumes of liquid into a solid. Images are projected onto the hydrogel for polymerization layer by layer, achieving very intricate, complex structures, millions of points of light at a time.

As the vasculature in a human lung branches out, the airways and blood vessels get smaller and move closer together but never touch. A functional model of the lung needs to achieve that proximity to allow for the diffusion of gases to the blood vessels. Researchers do not want these vessels to ever fluidically connect, so they have to design a topology of entangled vessels that allow for the diffusional transport of nutrients from one vascular network to another.

To control how much of the bioink gets polymerized, Dr. Jordan Miller’s lab at Rice University tried including yellow food-safe additives as biocompatible photo absorbers of blue light, adding color to the otherwise transparent hydrogel. At the right concentration, the yellow additives restrict the effective polymerization range along the z axis, letting researchers fine-tune their hollow vessels.

Future direction

Researchers are pushing the boundaries of what is possible with hydrogels and light-based bioprinting. They are actively working on smaller vessel diameters and narrower inter-vessel distances to enable more efficient diffusion. Creating these complex topologies was unthinkable just 5 years ago but can now be made with the Lumen X+. Armed with such advanced technologies, researchers are expected to see exponential progress in the next few years. They aim to achieve bioprinted organs that get even 10% of function. For someone who has total organ failure, 10% functionality could be a lifesaver.

The Lumen X+

The first DLP printer specifically designed for bioprinting is the premier choice when constructing microscopic features with speed, fidelity and precision.

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