A team of engineers and biologists at California Institute of Technology in Pasadena have designed a petri dish that can continuously capture images of growing cell cultures. Called ePetri, the developers describe the device online this week in the journal Proceedings of the National Academy of Sciences.
Petri dishes, used to grow cell cultures such as those to identify bacteria, normally require that the cells being cultured be placed in an incubator to grow. As the sample grows, researchers need to remove the dish — often numerous times — from the incubator to study the culture under a microscope.
The Caltech team designed a new device that can track the cell or bacteria culture while in the incubator, without removing the dish and using a separate microscope. “The data from the ePetri dish automatically transfers to a computer outside the incubator by a cable connection,” says the paper’s lead author Guoan Zheng. “Therefore, this technology can significantly streamline and improve cell culture experiments by cutting down on human labor and contamination risks.”
The team used a commercially available cell-phone image sensor, Lego building blocks, and and a Google smartphone for the prototype device. The lab technician places the culture on the image-sensor chip (pictured at top), while the phone’s LED screen provides the scanning light source. The technician then places the device in an incubator with a wire running from the chip to a laptop outside the incubator.
As the image sensor records images of the culture, that information is sent out to the laptop, making it possible for researchers to acquire and save images of the cells as they grow in real time. The device’s designers say the technology is particularly helpful at imaging cells that grow close to one another, called confluent cells, and typically cover the entire petri dish.
Imaging confluent cells has up to now been a particularly labor-intensive process. Changhuei Yang, senior author of the study and engineering professor, says the technology creates “a system in which you can do wide field-of-view microscopy imaging of confluent cell samples,” an improvement on the microscope, which he characterizes as “an expensive and suboptimal workhorse.”
Caltech biologist Michael Elowitz, a coauthor on the study, tested the device with observations of embryonic stem cells. In different parts of a petri dish, stem cells often behave differently, changing into various types of other, more specialized cells.
A conventional microscope with its lens limitations cuts a researchers effective field of view and can only focus on one region of the traditional petri dish at a time, says Elowitz. With the ePetri, however, Elowitz says he could follow the stem-cell changes over the entire surface of the device.
The ePetri technology is designed as a platform, which allows it to be supplemented with and connected to other devices. For example, ePetri could provide microscopy-imaging capabilities for other portable diagnostic lab-on-a-chip tools.
The team is also planning a self-contained system that would include its own small incubator, which would enable physicians to conduct their own tests of bacterial cultures, without sending them to an outside lab.
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