Part human, part synthetic, a new microchip that imitates the inner workings of a lung could lead to new drug-testing methods that don’t involve animals.

The new device is a clear piece of rubber (the size of a quarter) covered with tiny channels made of a mesh-like membrane lined with human cells – lung cells on one side and blood cells on the other. When connected to a mechanical pump and regulator, the lung-on-a-chip mimics the breathing motion of a human lung. [Read "Breakthrough: Lab Lungs Live and Breathe."]

So far, the researchers have shown that the micro-lung accurately reproduces some lung functions in mice, such as how these organs respond to inhalation of nanoparticles – a good sign that this device could be used for both drug testing and toxicity testing.

Today’s technology for testing drugs comes in one of two flavors. One method is to use "oversimplified cell culture models," said study researcher Dan Huh, technology development fellow at the Wyss Institute for Biologically Inspired Engineering at Harvard University.

This involves growing cells in a static plastic dish and then exposing them to different types of drugs and measuring cell response.

The other way involves using expensive animal models, Huh said. In this method, scientists "use mice, rats to test efficacy and safety of drugs but this can cost a lot of money and takes a long time.”

Huh and his colleagues hope to ultimately link up various organs-on-a-chip, essentially getting rid of animals in drug testing all together.

Borrowing from computer technology

To model the small, delicate channels that make up a human lung, Huh and his team borrowed technology used to make computer chips.

“We don’t have electronic circuits in the system per se, but we use the technologies that people use to create electronic circuits,” Huh said. “Using the same technology, we can create microscopic structures that allow us to better manipulate living organisms like cells, and chemical and physical processes."

The channels in the miniature lung are about 400 microns in width and 70 microns in height. (For comparison, a human hair is about 100 microns in diameter.)

“We put lung cells and capillary cells into the microdevice, and we grow them inside the device to mimic the original structure found in the lungs,” Huh said.

Building organs in the lab

The results have implications for recreating human organs in the lab.

“We’re very ambitious about developing new drug-testing platforms,” Huh said. Researchers at the Wyss Institute are developing other organs-on-a-chip, such as guts, hearts and kidneys, which Huh hopes could some day be integrated into a single device.

“By integrating all of these miniaturized organ systems into a single device, eventually we might be able to completely replace animal testing,” Huh said.

The researchers don’t know how long until this miniaturized lung will be available for use.

“Right now this is a cool technology that’s been developed in a research lab,” Huh said. But "there are many hurdles along the way [before it can be used in the real world]."

These include making the chips more user-friendly and easier to operate, and integrating the pump and regulator, which are currently not on the chip.

The research appeared in the June 25 issue of the journal Science.