Smartphone-driven, lensless Petri dish images cell cultures in real time

Researchers at the California Institute of Technology (Caltech) have developed a Petri dish that uses a smartphone camera image sensor chip and LED screen to image cell cultures in real time, enabling cheaper, faster medical diagnostics.

Researchers at the California Institute of Technology (Caltech; Pasadena, CA) have developed a Petri dish that uses a smartphone camera image sensor chip and LED screen to image cell cultures in real time, enabling cheaper, faster medical diagnostics.

The team's 'smart' Petri dish—known as ePetri—is a compact, small, lens-free microscopy imaging platform that can directly track cell or bacteria cultures within the incubator, explains Guoan Zheng, lead author of the study and a graduate student in electrical engineering at Caltech. The data from ePetri then automatically transfers to a computer outside the incubator by a cable connection, significantly streamlining and improving cell culture experiments by cutting down on human labor and contamination risks, he says.

The team built the ePetri prototype using a Google smartphone, a commercially available cell-phone image sensor, and Lego building blocks. The culture is placed on the image-sensor chip, while the phone's LED screen is used as a scanning light source. The device is placed in an incubator with a wire running from the chip to a laptop outside the incubator. As the image sensor takes pictures of the culture, that information is sent out to the laptop, enabling researchers to acquire and save images of the cells as they are growing in real time. The technology is particularly adept at imaging confluent cells—those that grow very close to one another and typically cover the entire Petri dish—something that has required a costly traditional microscope until now, says Changhuei Yang, senior author of the study and professor of electrical engineering and bioengineering at Caltech.

Caltech biologist Michael Elowitz, a co-author on the study, used the ePetri system to observe embryonic stem cells. Stem cells in different parts of a Petri dish often behave differently, changing into various types of other, more specialized cells. By using the ePetri platform, Elowitz was able to follow the stem-cell changes over the entire surface of the device.

"Instead of a large, heavy instrument full of delicate lenses, Yang and his team have invented a compact lightweight microscope with no lens at all, yet one that can still produce high-resolution images of living cells. Not only that, it can do so dynamically, following events over time in live cells, and across a wide range of spatial scales from the subcellular to the macroscopic," says Elowitz.

Yang and his team believe the ePetri system is likely to open up a whole range of new approaches to many other biological systems as well. Since it is a platform technology, it can be applied to other devices. For example, ePetri could provide microscopy-imaging capabilities for other portable diagnostic lab-on-a-chip tools. The team is also working to build a self-contained system that would include its own small incubator. This advance would make the system more useful as a desktop diagnostic tool that could be housed in a doctor's office, reducing the need to send bacteria samples out to a lab for testing.

In addition to medical diagnostic tests, the ePetri platform may be useful in drug screening and the detection of toxic compounds. It has also proved to be practical for use in basic research.

The device is described in a paper that appears online this week in the Proceedings of the National Academy of Sciences (PNAS). Funding support was provided by the Coulter Foundation.

For more information, please visit http://www.pnas.org/content/108/41/16889.abstract.

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