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32 PCB007 MAGAZINE I NOVEMBER 2018 Researchers have developed a three-dimen- sional (3D) organ-on-a-chip that enables con- tinuous real-time monitoring of cells and could be used to develop new treatments for disease while reducing the number of animals used in research. The device—which incorporates cells inside a 3D transistor made from a soft sponge-like material inspired by native tissue structure— gives scientists the ability to study cells and tissues in new ways. By enabling cells to grow in three dimensions, the device more accurate- ly mimics the way that cells grow in the body. Led by the University of Cambridge, the re- searchers say their device could be modified to generate multiple types of organs—such as a liver-on-a-chip or a heart-on-a-chip—ultimate- ly leading to a body-on-a-chip that would sim- ulate how various treatments affect the body as a whole. Their results are reported in the journal Science Advances. Traditionally, biological studies were (and still are) done in Petri dishes where specif- ic types of cells are grown on a flat surface. While many of the medical advances made since the 1950s—including the polio vaccine— have originated in Petri dishes, these two-di- mensional (2D) environments do not accurate- ly represent the native 3D environments of hu- man cells and can lead to misleading informa- tion and failures of drugs in clinical trials. 3D Organ-on-a-chip Could Accelerate Search for New Disease Treatments ic parts connected by spring-shaped wires. Each island contains electrodes and devices called piezoelectric transducers that produce ultrasound waves when electricity passes through them. The bridges connecting them are made of thin, spring-like copper wires. The island-bridge structure allows the entire patch to conform to the skin and stretch, bend, and twist without compromising electronic func- tion. The patch uses ultrasound waves to contin- uously record the diameter of a pulsing blood vessel located as deep as four centimeters be- low the skin. This information then gets trans- lated into a waveform using customized soft- ware. Each peak, valley, and notch in the wave- form—as well as the overall shape of the wave- form—represents a specific activity or event in the heart. These signals provide detailed infor- mation to doctors assessing a patient's cardio- vascular health. They can also be used to pre- dict heart failure, determine if the blood sup- ply is fine, etc. Next Steps Researchers note that the patch still has a long way to go before it reaches clinics. Im- provements include integrating a power source, data processing units, and wireless communi- cation capability into the patch. "Right now, these capabilities have to be delivered by wires from external devices. If we want to move this from benchtop to bed- side, we need to put all these components on board," said Xu. The team is looking to collaborate with ex- perts in data processing and wireless technolo- gies for the next phase of the project. The paper, "Monitoring of the Central Blood Pressure Waveform via a Conformal Ultrasonic Device," is published in the journal Nature Bio- medical Engineering. Joint co-authors include Xiaoshi Li, Hongjie Hu, Lin Zhang, Zhenlong Huang, Muyang Lin, Zhuorui Zhang, Zhenan Yin, Hua Gong, Shubha Bhaskaran, Yue Gu, Mitsutoshi Makihata, Yuxuan Guo, Yusheng Lei, Yimu Chen, Yang Li, Tianjiao Zhang, Al- bert P. Pisano, and Liangfang Zhang (UC San Diego); Chunfeng Wang (Zhengzhou Universi- ty); and Zeyu Chen and Qifa Zhou (University of Southern California). This project was supported by the National Institutes of Health and the Center for Wearable Sensors at UC San Diego. PCB007