By Akshita Nair
In the world of healthcare education, physical models of organs and structures have always been essential. Because of the sheer complexity of the human body, the ability to see, move, and manipulate models has always benefited medical students, allowing them to learn more efficiently and effectively. Easily customizable and readily accessible, 3D printed models of organs have always been a practical choice. However, the rigid materials that are used to make them, such as plastic and rubber, have never been able to stimulate the feel of the body’s soft tissues. This creates a problem for aspiring surgeons, who have to practice surgeries on models that feel nothing like actual organs. In the case of heart surgeons, not knowing what to expect during their first surgery can be disastrous, making the need for accessible, lifelike heart models clear. Fortunately, it looks like we’re one step closer to making this a reality.
In November 2020, a team of researchers led by Adam Feinberg at Carnegie Mellon University were able to create the first full-sized, lifelike 3D printed model of the human heart. It’s the product of two years of research, and is extremely detailed, with a squishy texture similar to that of real cardiac tissue. Scientists had previously agreed on using collagen, a protein that helps provide structure to most biological tissues, to stimulate the feel of cardiac tissue. However, trying to 3D print a model made of collagen using the traditional method always causes it to melt into a puddle, since the model is unable to withstand the pressure of the air around it until the collagen is able to gel. To make sure that the model is able to solidify without collapsing, the researchers instead used a new method of 3D printing: Freeform Reversible Embedding of Suspended Hydrogels, or FRESH.
FRESH involves using a fine, precise needle to inject “ink” (the liquid that will be solidified to become the model) into a hydrogel bath. The hydrogel supports the delicate structures inside the model heart, allowing it to maintain its shape as it’s printed. Once the printing is complete, the hydrogel, which is mostly made of water, is melted at 37˚C, leaving just the fully formed and solidified model, which can be handled in open air. While this method has been used to create small objects in the past, Feinberg and his team had to modify the printer to be able to print larger objects like the full-sized model heart. Next, they had to choose a protein to use as an “ink” for the 3D printer. They decided on alginate, an inexpensive, seaweed-derived substance that gels very easily. It’s also commonly used to deliver drugs directly into tissues, making it a good choice to start experimenting with.
One the printer was ready, the team performed an MRI scan of a patient’s heart, which the FRESH 3D printer used as a basis to create the model heart. The same technology was used to print a section of coronary artery, which can be filled with fake blood and dissected. The team hopes that surgeons can use the models to practice dissecting and suturing, and that the technology can be used to make models of other organs, such as kidneys and lungs. As the heart model can be made out of collagen, it could even be used as an extracellular matrix to contain and support cells of a working 3D printed heart. The possibilities that this fresh new method provides really are endless.
References:
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