By Harrison York
3D printing has become increasingly popular in recent years. At its core, 3D printing is a process where a machine manufactures a three-dimensional object layer by layer. It is the process of incrementally building a product out of a viscous stock material by following a digital plan. This stock material (the “ink” of the 3D printer) can be made of materials ranging from plastic to metal, and in recent years, developments in 3D printing technology have led to the printing of materials like ceramics, sand, wood, stone, and even organic material like human tissues.
Applications for 3D printing are rapidly growing, as the cost, ease-of-use, and capabilities of these machines improves each year. Currently, concrete is being 3D printed for use in low-cost and efficient construction projects. The average consumer can fabricate items made of wood by using a filament that consists of wood particles and plastic. Polylactic Acid (PLA), is an extremely popular and easy to use plastic filament that enables newcomers and veterans alike to print a wide range of items—hundreds of thousands of plans for which can be accessed for free through online databases and entered into a home 3D printer.
While certain types of 3D printing are becoming more accessible, others are still loosely limited to companies, universities, and labs because of the cost and experience required to use them. 3D bioprinting, or the use of 3D printing technology to create multicellular tissue, is a novel form of 3D printing that is being tested for use in biological research, experimentation, and eventual medical utility.
Despite the complexity of 3D bioprinting technology, developments are being made to make it more practical and widely applicable to healthcare scenarios.
Last year, researchers at the Wyss Institute at Harvard University devised a method of generating vascular—or blood vessel—tissue that was almost ten times thicker than previous bioprinted vascular tissue. They achieved this by using a multi-material process that involves taking endothelial cells (cells that line the inner wall of blood vessels) and placing them inside a silicone mold. Later, a layer of mesenchymal stem cells (which are found in connective tissue like blood vessels) is printed on top of the stem cells and a liquid composed of extracellular material (a soup of proteins and other organic chemicals) is applied to fill gaps and connect the cells in the system, adding stability. This new process results in a stability that has been proven to give this tissue a lifespan of over six weeks under laboratory conditions.
This tissue is living, meaning that the cells function and behave like normal cells in an organism, and so it offers hope that such tissue can be used medically. The current intended use of such biomaterial is in regenerative medicine and further research, especially in drug tests.
Another exciting breakthrough in bioprinting occurred earlier this year, when a team at Rensselaer Polytechnic Institute in New York created a way to print living skin that can be used in skin grafts and can adapt to a patient’s tissue type.
“Right now, whatever is available as a clinical product is more like a fancy Band-Aid,” Pankaj Karande, associate professor of chemical and biological engineering and leader of the research team, said on the real-world applications their lab-grown tissue could one day have. Their new bioprinting technique promises to produce manufactured tissue at the level required for integration into the body. “Once we start approaching that complexity,” Karande explained, “biology takes over and starts getting closer and closer to what exists in nature.”
Living biomaterial like that offered in this process brings hope that more complex organs may be artificially produced and used in transplants, compatible with the natural human body.
In November 2020, engineers from Carnegie Mellon University’s College of Engineering announced their successful printing of a realistic human heart, strong enough to be used by surgeons for practice performing heart surgery.
This is a significant development because bioprinted organ models have been too stiff or too soft for any practical use. Knowing this, the team at Carnegie Mellon used a process called Freeform Reversible Embedding of Suspended Hydrogels (FRESH) to create the heart. FRESH involves a bioprinter extruding soft biomaterial a layer at a time into a hydrogel gelatin, which serves to prevent the artificial organ from collapsing during printing. The hydrogel is in a liquid-like state, and some of the material bonds to the extruded substance as it holds the product together. After the model is complete, heat is applied, and the extra hydrogel melts away.
For this specific heart, the team used alginate as their soft organic material. It is an affordable biomaterial made from seaweed with similar properties to cardiac tissue. The team is attempting to model other organs like the kidneys and liver.
While the heart model is not a living bioprint, the FRESH method may one day be able to print functional, living tissue, like the skin and vascular examples previously explored.
3D bioprinting is an industry budding with growth and potential. Teams around the world are working to advance this technology, which can provide accurate models for surgical practice, living tissue for drug testing, and supplements for healing existing tissue. In the future, bioprinting could produce functional organs for transplants, which would save lives and solve the current shortage of donated organs.
1. Why is bioprinting useful?
3D bioprinting is useful for creating models and living tissue for use in many areas. Model organs can be used to train medical students and give them realistic surgical practice. Living tissue can be used by people who need skin grafts or similar procedures after suffering from burns, as epithelial (skin) tissue is being bioprinted more effectively. In the future, bioprinting could produce real, working organs for transplants and solve problems with certain diseases.
2. How can you learn more about bioprinting and 3D printing in general?
3D printing is becoming increasingly accessible as the cost of machines and materials is falling. If you want to be able to fabricate your own designs and print models from a vast internet of free content, you should consider buying a 3D printer. Today, you can purchase a capable machine for less than three hundred dollars, such as the popular Ender 3 Pro, and be able to use this technology in your own home. 3D printing opens up doors for creativity, engineering, and STEM fields in general.