Sunday, February 17, 2013

Towards a Human Body on a Chip - Part I

How can we accelerate the current drug development model?

Before a pharmaceutical company will test a new drug on humans, it is most commonly tested on small animals. However, these animals may not react on the drug the same way as humans do. It would be much more reliable to test theses drugs directly on humans, but this would be too dangerous as the not yet approved drug might harm the person.

To overcome these issues, researchers are developing human-like systems to mimik parts of our body, like the lung, human intestine or a kidney. These device are called body on a chip or organ on a chip. The major technique behind these chip is microfluidics (check out my post on microfluidics to get a nice intro). One can see these chips as building blocks for something bigger. The aim of this research area is to connect the devices together to create a human on a chip, a human-like working system which is able to mimik parts of our body for drug testing purposes. This way we might even eliminate the use of animals for drug testing to avoid ethical issues. In my next few posts, I will introduce body-on-a-chip platforms which have been developed already and will explain how they work. I would like to start with a very important organ, our lung.

How can you mimik a human lung?

The lung is the crucial respiratory organ in our body. It's main function is to bring fresh oxygen from the air you breath in to the blood and get rid of carbon dioxide or other waster gases that your body does not need when you breath out. In June 2010, researchers from the Wyss Institute at Harvard have developed the very first lung on a chip. The microfluidic device is made using a flexible see-through polymer. The device features one main channel in the center which is divided by a thin membrane into two parts (see picture below). The membrane has small holes inside to let oxygen and other particles flow between the two compartments. On the top side of the membrane, lung cells are attached to the membrane whereas on the bottom side, human capillary cells are attached. Air flows through the top part and human blood through the bottom part. The two channels labeled "vacuum" on the sides are pressurized periodically and will deform the center channel to mimik breathing. 

Principle of the lung on a chip device.
Image courtesy of the Wyss Institute. 
What can you test with a lung on a chip?

The testing spectrum of the lung on a chip device is wide. For instance, one can analyze the influence of environmental pollutions on the lung. One can also model diseases which occur in the lung to see how a drug is affecting the lung cells and how it is healing the system. One major advantage is the transparency of the device, as you can see in the image below. The lung function can be directly monitored under a microscope in real-time. Traditionally, a biopsy is needed in order to see the direct effect of a drug on the body.  

Actual microfluidic lung on a chip device.
Image courtesy of the Wyss Institute. 
With this lung on a chip, pharmaceutical companies can directly test their drugs on a human like lung without the need of testing it on animals. The current drug development model is in a crisis, as it costs millions of dollar and takes many years to pass a drug from the animal testing phase to the human trial phase. The animal model is poor and most of the drugs fail the human test. The lung on a chip device could prevent animal testing and would allow the pharmaceutical companies to directly test on a human model which would be less time-consuming, much cheaper and eliminate the use of animals for testing.