A cyborg proto-jellyfish, a swimmer made of silicone whose electrified strokes are powered by rat heart cells, could hold the clues to heart tissue engineering and repair.
A team of engineers and biologists at Caltech and Harvard built the "medusoids" with the goal of replicating the movement of a jellyfish. Each swimmer, or medusoid, is an eight-limbed sheet of silicone rubber that can fold inwards like a floppy umbrella. The silicone mimics the elastic body of a living jellyfish, but that’s just a test case. The real goal of this project is to find a way to mimic the tissue of a living heart.
Placed in a tank and activated with a jolt of electricity, the medusoids swam along with jellyfish-like body contractions. The silicone body is patterned with a naturally occurring heart protein. When cells are first being grown on the rubber, the protein directs the growth of the heart cells that are seeded on it. "We need to have them neatly arranged in a row so they all pull in the same direction," says Janna Nawroth, the German designer of the mechanical marvel.
A live jellyfish swims and feeds by contracting and relaxing its elastic body. Those strokes are similar to the human heart’s pumping motion and the sloshing around of blood inside its chambers. The medusoid is a first step towards a long-term goal to grow a heart, parts of the heart, or a supporting pump for a weakened heart, says Nawroth.
While an artificial, tissue-engineered heart might be in our future, inspired in part by this work, a more immediate application of the team’s work could be in pathology. For example, a moving slice of lab-grown heart muscle is "much better than a [static] heart muscle that grows on the bottom of a dish because this actually pumps liquid," Nawroth says, and could serve as a test bed for heart drugs. The protein patterning that drew grooves for the growth of seeded heart cells could even be modified to recreate the weakened muscle seen in some heart conditions.
Nawroth has been studying the expanding and contracting motion of the jellyfish for five years. When she’s working in Boston (at the tissue engineering labs headed by Kevin Kit Parker), she bikes down to the New England Aquarium on Boston’s eastern shorefront to grab a jarful of the tiny swimmers, a few millimeters across. When she’s at her home research base at Caltech where she is a grad student, a Long Beach aquarium sends jarred samples of the tiny jellyfish by mail to her lab.
In her next chapter of jellyfish work, Nawroth will work on controlling the direction of movement of her medusoid creations. To her, the most exciting part of this work was seeing two seemingly different systems come together. "Now you see the similarities between the heart and the jellyfish, but originally no one thinks of it this way," she says. "There are these functions that both systems share—not that they look the same or have the same components, but they use similar design elements."