Communications of the ACM
Artificial Organs Evolve
A Madison, WI, company named InvivoSciences has developed micro-engineered heart tissues, which it calls NuHeart.
Credit: Biosense.com
One of the things that makes being human difficult is the realization that bodies fail over time. Hearts wear out, lung capacity diminishes, and other organs, such as ears, kidneys, and the pancreas, can't keep up. Even with state-of-the-art medical treatment, quality of life takes a hit or a person dies—sometimes prematurely.
As a result, scientists are now developing sophisticated synthetic organs that work inside, alongside, or outside the human body—and restore diminished or lost functionality. Of course, the challenges associated with creating replacement parts for the human body are steep, and over the last half-century progress has been painfully slow.
That is starting to change. Due to rapid advances in medicine, bioengineering, materials science, artificial intelligence (AI), and other areas, replacement organs are beginning to take shape. While early synthetic organs relied on mechanical functionality, advances in engineering and materials are now producing organs that incorporate natural or synthetic tissues.
"Scientists are developing and testing a wide variety of tools and devices," says Vakhtang Tchantchaleishvili, Editor-in-Chief of the journal Artificial Organs and Attending Cardiac Surgeon at Thomas Jefferson University in Philadelphia, PA. "There are a lot of challenges associated with getting to functional devices, but we are seeing continuing progress."
Adds Nigel Lovell, professor of biomedical engineering at the University of New South Wales in Australia, "In the coming years, artificial organs will blur the lines between technology and biology. They will improve and extend lifespans. They are the next step in humans becoming more like cyborgs."
And the Beat Goes On
The value of synthetic organs—ears, eyes, lungs, kidneys, and more—should not be underestimated. "Donor shortages and a lack of effective treatment methods for many conditions put a great number of people in peril," says Manisha Singh, a postdoctoral researcher in the Therapeutic Technology and Design Lab at the Massachusetts Institute of Technology (MIT). For example, about 50,000 people a year worldwide are candidates for a heart transplant. More than two million people annually die from liver disease, and about 540 million people globally have diabetes.
Drugs, dialysis, and other treatments can only go so far. For example, Lovell says, "Recreating the function of a biological heart or other organ is a remarkably difficult task. It requires a deep understanding of how the organ works, but it also involves a complex reengineering process that duplicates the organ's functionality. This typically involves mechanical, electrical, biochemical, and biological factors."
Artificial organs could change the equation. They include mechanical devices, systems that incorporate living or synthetic tissues, and hybrid biosynthetic systems that combine a mix of materials and technologies. Although much of the attention is on the human heart, researchers are also developing wearable kidneys, artificial lungs, synthetic livers, bionic eyes, and an artificial pancreas.
The field is now advancing rapidly due to a few factors, Lovell says. Materials science has introduced the possibility of creating artificial fibers and muscles, while reducing the risk of infection or rejection. At the same time, highly miniaturized electronics have made it possible to build smarter and more integrated devices. Recently, AI algorithms that can read, interpret, and react to data streaming in from a device have also fueled advances in the field.
Yet developing highly functional synthetic organs remains elusive. It is remarkably difficult to emulate complex body functions that can involve mechanical, electrical, and hormonal processes that scientists still do not fully understand. "Artificial organs must sense the metabolic demands of the body, and every person is different," Lovell says. "They must also be biocompatible and avoid serious side-effects."
Sensors placed inside the body can only do so much. They're useful for, say, monitoring and regulating blood sugar or hormonal levels. However, many systems that interface with excitable tissue such as the brain or retina function better with a large number of electrodes. Connecting these electrodes to neurons in the body allows the artificial organ to interact with the external environment in real time. The catch? "It's possible to use high numbers of electrodes in a system, but unless the electrodes are in close and intimate contact with the target neurons, the interface breaks down." Lovell explains.
The challenges don't stop there. There's also a need to power artificial organ systems, Tchantchaleishvili says. A device that uses a rechargeable or replaceable battery—such as a pacemaker—can work in some situations (and advances in battery size and density increasingly make this possible), but things get far more complicated when doctors implant a device that requires large amounts of energy inside a body, and it must operate for months or years without interruption.
For example, "Heart pumps consume much larger amounts of energy compared to many other types of devices," Tchantchaleishvili explains. "The ultimate goal is to develop devices that either don't require external energy sources or operate with minimal tethering."
Although the concept sounds far-fetched, it is not outside the realm of possibility. In the 1970s, researchers developed a way to use radioactive decay from an energy source such as plutonium 238 to create a lifetime supply of power. However, the idea has never caught on, due to public fears about radiation risks.
Moving Beyond Bionics
At MIT, Singh and a group of researchers working under the direction of professor Ellen Roche are attempting to push the science further. They have developed a robotic replica of the heart's right chamber. The robo-ventricle, which incorporates actual heart tissue as well as synthetic, balloon-like synthetic muscles, can be specifically tuned to different states ranging from healthy to diseased. In this way, researchers model factors such as pulmonary arterial hypertension and myocardial infarction. They can use the model to test and tune cardiac devices implanted in humans.
"The heart is a huge and complex muscle," Singh says. "A deeper understanding of how it functions is critical to designing and building devices that replicate essential functions and also adapt to a wide array of conditions and situations." The MIT group hopes to expand the project and their research to the entire heart, and eventually develop a soft robotic system that could be used to design and fine-tune future synthetic hearts.
The next couple of decades will see a lot of progress, Lovell says. "We are now on the path to understanding molecular biology far better, we are learning how to develop materials that can last a lifetime." Tchantchaleishvili believes that as various digital technologies converge and advance through materials science and tissue engineering, that sophisticated, elaborate, highly integrated synthetic organs will emerge.
Concludes Singe, "There are many areas where artificial organs can play an important role in improving people's lives—from the heart and lungs to the pancreas and the bladder. These systems will likely provide an alternative path for people needing a replacement organ."
Samuel Greengard is an author and journalist based in West Linn, OR, USA.
No entries found