— Heart cells squeeze the polymer sphere, causing it to act like a pump (Image: Royal Society of Chemistry)
A tiny pump driven by living heart cells has been developed by researchers in Japan. Future versions could perhaps power medical implants or devices that analyse biological samples, the researchers say.
The pump is made from a hollow sphere of flexible polymer with tubes connected to opposite sides. The sphere is coated with a sheet of cultured rat heart muscle cells and these cells drive the pump with pulsing contractions.
The device was developed by Takehiko Kitamori at the University of Tokyo, Japan, and colleagues at the Japan Science and Technology Agency. The team liken their invention to the simple one-chamber heart of an earthworm.
The pump has no need for a battery, just a ready supply of nutrients for the cells. The researchers say similar pumps could someday drive small amounts of fluid around chips for biological analysis or through medical implants that release drugs inside the human body.
Pump and power
"The device could be useful for many medical situations where pump and power source cannot easily be combined," says Paul Kenis, an expert in micro-chemical systems based at the University of Illinois in the US.
The main part of the pump is made from a flexible polymer sphere 5 millimetres in diameter. Teflon capillary tubes measuring 400 microns in diameter are inserted into opposite sides of this sphere.
A cell-friendly protein coating is then added to the sphere followed by a sheet of pulsing cultured heart cells. After just an hour the cells are firmly attached and begin driving the pump.
To test the pump, the researchers placed it in a nutrient medium at human body temperature (37°C). They watched through a microscope as small polystyrene balls contained with a fluid moved through the pump's tubes. The pump operated continuously for six days in testing.
Chambers and valves
"The next step is to add chambers and valves to the device, so it can pump the liquid in one direction only," says Kitamori. These could be made by using UV laser light to selectively harden parts of the polymer material used to make the pump, he suggests.
"It sounds like a crazy idea," says Steve Haswell, who researches micro-fluidics at Hull University, UK, "but they're trying to address a big issue for micro-fluidics."
Haswell explains that it is hard to control tiny volumes of liquid accurately: "A chip the size of a thimble is often surrounded by a whole bench full of equipment."
Tiny pumps undoubtedly provide a better way to control fluid on this scale, Haswell says, but he believes other approaches to be more promising. "Small pumps actuated by polymers that respond to electric fields or chemicals are becoming quite good," he told New Scientist. "Heart cells make effective pumps when in the structure of a heart, but it will be harder to make sheets of them perform."
Journal reference: Lab on a Chip (DOI: 10.1039/b612082b)