Taking a good picture of a cell is a critical skill for researchers in the lab and pathologists making a diagnosis, but it is easier said than done. Microscopy equipment purchasers make a trade-off between the size of the field of view, the resolution of the picture, and the price tag. It is possible to obtain a large field of view and a high resolution picture, but it involves expensive and bulky equipment.
In a new study in ACS Sensors, researchers at Wuhan University and the University of North Texas turned to a Blu-ray player to design a better setup for 3D microscopy (1). Their system relies on computational imaging, which provides high-resolution 3D reconstructions without traditional optical lenses. Computational imaging can be used with telescopes to view enormous celestial objects millions of light years away or with microscopes to accurately image microscopic objects such as bacteria. A repurposed, consumer-grade Blu-ray disc player imaged bacteria, performed urinalysis, and separated cells at a fraction of the cost of using traditional equipment.
Although Blu-ray technology had a short-lived success with consumers, the innovations of this technology have been embraced by the microscopy community. “The Blu-ray drive, in fact, is really an engineering masterpiece,” said, Guoan Zheng, a pharmaceutical scientist at Wuhan University and coauthor of the study.
A Blu-ray player contains key elements essential for microscopy. Lasers provide a light source; the disc tray acts a sample holder; and the rotational capability allows light to reflect off the object in all directions, giving a 3D map of optical signals. Thus, a Blu-ray player can be repurposed as a powerful microscopy tool.
A Blu-ray player reads a disc by assigning a value of “0” to small pits on the disc surface and a value of “1” if no pit is detected. To employ a similar computational method to read biological samples, Zheng and his team needed a way to create surface features that could translate the optical signal from the sample into something that the image sensor, and eventually the computer, could understand.
Modifying the surface of a disc can be achieved through surface patterning, which adds texture to surfaces, but usually involves expensive equipment as the size of the features decreases. Rather than using this approach, the researchers coated the image sensor in blood cells obtained with a simple prick of the finger. Blood cells happen to be the correct size to scatter the light into a pattern the processing unit recognizes, allowing it to generate a 3D reconstruction of an object.
The team first tested their repurposed Blu-ray player to image urine sediment. Detecting high levels of calcium oxalate crystals in urine can indicate kidney disease, but urinalysis is typically performed by counting crystals manually using microscopes with a small field of view, which can lead to unreliable results. Their device could identify the specific elements in the urine sediment in less than one minute. Coupled with an image processing algorithm they wrote, the images from the Blu-ray player gave 99.5% accuracy compared to manually counting the crystals under a traditional microscope.
To test their platform against typical laboratory equipment, the researchers used it to rapidly count red and white blood cells and Trypanosoma brucei parasites in a blood smear sample. The repurposed Blu-ray player achieved the same throughput (10,000 cells per second) as a cell-sorting flow cytometry instrument, but with a price tag of approximately $300, according to the researchers, about 300 times less expensive than a typical flow cytometer.
Finally, Zheng and his team used the Blu-ray player to monitor the growth of E. coli in a Petri dish in a 37ºC incubator without complicated microscope setups. The device collected an image of the entire dish, generating about two gigapixels of data in approximately five minutes. They used this image to estimate the dry mass of bacteria and track the bacterial growth.
This study illustrates the benefit of bringing old electronics to the lab instead of the dumpster, according to Edwin Hwu, a drug delivery and sensing scientist at the Technical University of Denmark who was not involved in the study. “We need to reuse these kinds of well-developed consumer electronics because if we throw it away, it is a waste,” said Hwu. “We can just use their function for a different application, just like this paper did.”
Zheng hopes to expand the availability of sophisticated microscopy capabilities to researchers and also provide citizen scientists with a means to fuel their own discoveries. “We can make the device widely available not only to researchers, but to every student or anyone who wants to build a high-throughput imaging device,” he said.
When it comes to the applications of this repurposed Blu-ray player, imaging urine, blood, and bacteria only scratches the surface.
Reference
- S. Jiang, C. Guo, T. Wang, J. Liu, P. Song, T. Zhang, R. Wang, B. Feng, G. Zheng, Blood-Coated Sensor for High-Throughput Ptychographic Cytometry on a Blu-ray Disc, Acs Sensors. (2022). https://doi.org/10.1021/acssensors.1c02704.
