Having roamed the seas for at least 500 million years and holding the title of the oldest multi-organ animal on the planet, jellyfish have certainly stood the test of time. So it’s probably not surprising to see various research groups looking to the gelatinous, umbrella-shaped animals for inspiration in a number of areas, including the development of ocean-going robots. Now researchers at Harvard University and the California Institute of Technology (Caltech) looking to gain a better understanding of how biological pumps such as the heart work, have created an artificial jellyfish from rat heart muscle and silicon.
Jellyfish propel themselves through the water by pulsing their bell-shaped bodies and it is this pumping motion, which is similar to the way in which the human heart moves blood throughout the body, that the researchers sought to emulate with their artificial jellyfish. By reverse engineering the motor function of a jellyfish, the team hoped to gain new insights into how such biological pumps work.
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“It occurred to me in 2007 that we might have failed to understand the fundamental laws of muscular pumps,” said Parker, Tarr Family Professor of Bioengineering and Applied Physics at the Harvard School of Engineering and Applied Sciences (SEAS) and a core faculty member at the Wyss Institute for Biologically Inspired Engineering at Harvard. “I started looking at marine organisms that pump to survive. Then I saw a jellyfish at the New England Aquarium, and I immediately noted both similarities and differences between how the jellyfish and the human heart pump.”
To create the artificial jellyfish, which has been dubbed “Medusoid,” Parker teamed with Janna Nawroth, a doctoral student in biology at Caltech, and Nawroth’s advisor, John Dabrini, a professor of aeronautics and bioengineering at Caltech and authority on biological propulsion.
Using analytical tools borrowed from the fields of law enforcement biometrics and crystallography, the team made maps of the alignment of subcellular protein networks in all of the jellyfish’s muscle cells. They then studied the electrophysical triggering of the jellyfish propulsion and the biomechanics of the propulsive stroke itself.
They hit upon the idea of using a sheet of cultured rat heart muscle tissue as the raw material for their artificial jellyfish after finding it would contract when electrically stimulated in a liquid environment. They then used a silicone polymer to fashion the body of their creation into a thin membrane with eight arm-like appendages.
Using the aforementioned analytical tools, the team then matched the subcellular, cellular, and supercellular architecture of the jellyfish musculature with the rat heart muscle cells.
When their creation was placed in a container of ocean-like saltwater, they applied an electrical current to shock the jellyfish into swimming with synchronized muscle contractions that mimic the movements of a real jellyfish. The team says the muscle cells actually started to contract slightly on their own before the electrical current was applied.
“I was surprised that with relatively few components - a silicone base and cells that we arranged - we were able to reproduce some pretty complex swimming and feeding behaviors that you see in biological jellyfish,” said Dabiri.
The researchers say Medusoid serves as a proof of concept for reverse engineering a variety of muscular organs and simple life forms and their approach is broadly applicable to the reverse engineering of muscular organs in humans.
“A big goal of our study was to advance tissue engineering,” said Nawroth. “In many ways, it is still a very qualitative art, with people trying to copy a tissue or organ just based on what they think is important or what they see as the major components - without necessarily understanding if those components are relevant to the desired function, or without analyzing first how different materials could be used.”
Parker adds that in developing Medusoid, he was also looking to challenge the traditional view of synthetic biology, which is “focused on genetic manipulation of cells.” Rather than just building a cell, Parker wanted to “build a beast.”
The next step for the researchers is to give the artificial jellyfish the ability to turn and move in a particular direction. They also hope to give it a simple “brain” so it can respond to its environment and replicate more advanced behaviors, such as heading towards a light source and seeking energy or food.
The team’s research was published in Nature Biotechnology on July 22.
Medusoid can be seen in action in the video below.
Source: Harvard University