Paper Organs

Schematic of paper organs highlighting its artificial blood vessel

Yu Shrike Zhang/Zhang Lab

An important step in developing a new medicine is to discover how it might affect individual cells. Typically, this is done in a petri dish, but that hardly captures the nuance of a living body, in which medicines interact with live tissue. Now, scientists have pioneered a solution that may allow for testing drugs in an environment more similar to the human body: a paper model of organ tissues created with a 3D printer.

As a proof-of-concept demonstration, researchers in the Division of Engineering in Medicine at Harvard Medical School and in the School of Chemistry and Chemical Engineering at Harbin Institute of Technology in China created a breast cancer tumor model. First, they printed a paper organ out of bacterial cellulose, a relatively inexpensive compound made naturally by some bacteria as a layer of protection around cells, with fibers that can be manipulated at the nanoscale. Next, they injected the organ with a petroleum-jelly paraffin ink to create channels in the paper. After the cellulose dried, they heated the ink to remove it, leaving behind hollow microchannels. To simulate blood vessels, they inserted endothelial cells (which typically line blood vessels) in those channels. Finally, they added breast cancer cells onto the top and bottom of the model organ, which distributed themselves across the structure and stayed viable for two weeks. With such a “living” model, researchers could then, in theory, add medicines and observe cell behavior.

The major benefits of this new method are its affordability and long shelf life. “We calculated each piece of the device to be only three to four cents,” said Yu Shrike Zhang, assistant professor of medicine at Harvard University, and co-author of the study. “These devices can be very stable when dry, so that they can be stored indefinitely.” Researchers can rehydrate a paper model when needed to test a new medicine. “Imagine we have these in the hospital on the shelf,” said Zhang. “When the patient materials are available, we make tissue models, then test them with drugs. Within a short period, you could get personalized results on which drugs may work best for that particular patient.” (Nano Letters)