Scientists have created the first artificial jellyfish -- a tiny blend of muscle tissue from a rat and thin, rubbery material from Dow Chemical Corporation – but with nary a jellyfish gene to its name.

The approaches used to build this "pseudo organism," as the researchers call it, may pave the way for more-effective ways to test new medicines, as well as new ways to repair or replace damaged organs in ways that use a patient's own tissue types – and no batteries for power, the team suggests.

Beyond the therapeutic lie other potential applications. The researchers say over the long term, their work could help lead to roving, autonomous sentinels that can measure pollution plumes in the ocean and perhaps even clean up the mess – while drawing nutrients from the ocean itself.

But the development also highlights the blurring line between life as it has evolved on Earth over the past 3.7 billion years and artificial forms that are beginning to emerge from labs, notes Kevin Parker, a physicist at Harvard University's Wyss Institute for Biologically Inspired Engineering, in Cambridge, Mass.

Initially, biologists identified organisms and their relationships to other organisms by their shapes and the functions various part of an organism performed. More recently, researchers have used genetics to define those relationships.

Here, looks alone suggest "this thing is a jellyfish, and functionally it's a jellyfish," Dr. Parker says. Yet the faux fish's biological material comes from a rat, so genetically, it's a rat."

"Everyone would agree that this is not an organism, although it's alive," he says. In effect, it's a tiny robot whose movements are controlled by living cells.

Some researchers have tried to mimic nature from the ground up, putting novel forms of DNA into DNA-free cells and activating the cells.

In this case, the research team – led by Dr. Parker and CalTech bioengineer John Dabiri – reverse-engineered a jellyfish's means of moving in the water. They then put the artificial and biological pieces together in the lab to produce a biomachine with the same shape and motions as its natural counterpart.

The results were published Monday in the journal Nature Biotechnology.

For years, Parker had been researching ways to use biological engineering to provide better ways to help patients diagnosed with heart disease, he says. On various visits to the New England Aquarium in Boston, he was struck by how similar the symmetrical undulations of a moving jellyfish was to the motions of a beating heart, he recalls.

Meanwhile, Dr. Dabiri gave a talk at Harvard on jellyfish propulsion.

Dabiri "was walking down the hall, and I pulled him over and said: 'Hey, man, I think I can build a jellyfish,' " Parker recalls. "He looked at me like I was off my rocker."

But not too far off, apparently, because a collaboration was born.

The two researchers and their graduate students made exquisite measurements of the electrical signals controlling muscles of juvenile jellyfish. And they mapped the locations of jellyfish muscle cells, paying particular attention to how key internal components of the cells were oriented as the cells made up the muscle strands. Surprisingly, they found the same internal orientations in strands of cells taken from the heart muscles of rats.

That allowed the team to use the rat-heart cells as a surrogate for cells from jellyfish muscles. In addition, the jellyfish muscles were set out in a unique pattern – a halo of muscle atop the jellyfish's crown, with other muscles radiating into lobe-shaped flaps extending outward from the crown.

When those muscles contract, the flaps uniformly close, ultimately forming a narrow bell, expelling water, and propelling the jellyfish forward. When those muscles relax, the lobes' natural elasticity returns the lobes to their original, outspread positions. In the process, this recoil sets up eddies along the edges of the lobes that draws tiny bits of food into the center of the bell, where the jellyfish's digestive system is.

For robo-jellyfish, the team used an elastic polymer in place of the jelly-like material a jellyfish hosts. And it used a machine criminologists use to match fingerprints to ensure that the muscle patterns they wanted for their “android” jellyfish matched as closely as possible those of a real jellyfish.

With pattern in hand, the researchers set down a protein on their faux fish's elastic "body" to which cultured rat-heart-muscle cells would bind and develop.

They set their faux jellyfish swimming by applying a small electrical current to the nutrient-laden solution in which the medusoids – a jellyfish variant of "humanoid" – were immersed. The critters swam with the same motion real jellyfish swim, and the team noticed that the muscles contracted slightly even before they applied electrical current. Moreover, the moving lobes on the faux jellyfish set up the same types of eddies that the researchers saw in real jellyfish movements.

With refinements, the approach could be used to build test subjects for new heart drugs, CalTech's Dabiri says. Tiny robo-jellyfish could provide an initial indication of whether a drug is likely to work as advertised. It also can give an initial indication of potential side effects – if, for instance, some of the faux-jellyfish lobes contract more strongly while others don't move much.

While medical uses provide an initial impetus, the approaches could eventually be used in manufacturing more broadly, researchers say. Cell-based manufacturing and bio-inspired robotics could produce useful materials at room temperatures, unlike human-made structural materials.

And they would be far more energy efficient. "We're imagining a system that because its made of biological components, it gets its energy the same way you and I do – by harvesting nutrients from the environment," Dabiri says.

Indeed, Parker suggests that this could be the real payback from decades of public spending on biological research.

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"If you take a look at how much money we've put into medical research since the 1990s, it has not resulted in lower costs for health care," he says, adding that "pharmaceutical companies will tell you that their pipelines are running dry and that they're heading for disaster because their patents are expiring."

After 20 years of funding, rising health-care costs, and promises of treatments that in some cases appear to perpetually lie just over the horizon, "We have to ask: What can we do besides medicine with all this biology we've learned?"