October 07, 2013
BehindTheMedspeak — Coming soon: Use your phone to take a picture of a single virus
Below, Daniel Akst's Wall Street Journal story.
Smartphone cameras are getting better and better. But how about one that can photograph a single virus?
It won't come with the latest iPhones but it does exist, thanks to electrical engineer Aydogan Ozcan and his team at the University of California, Los Angeles. Using 3-D printing, they've created a portable smartphone attachment weighing less than eight ounces that can capture images of things 1,000 times slimmer than a human hair.
Why rig up smartphones to perform the kind of scientific work other equipment can already do? Because smartphones are cheap and ubiquitous. Enabling them to detect viruses and bacteria could project sophisticated biomedical testing into remote locations where bulky lab equipment and reliable electricity might not be available.
Getting clear pictures of things as tiny as viruses isn't easy, and a smartphone user couldn't just aim, magnify and shoot. The Ozcan team used a laser diode to illuminate superthin samples at a 75° angle, thereby avoiding the detection of scattered light that would interfere with a clear image. Viral samples were prepared by applying dyes that would cause telltale viral proteins to emit fluorescent light.
These steps enabled the scientists to capture legible images of human cytomegalovirus (a common virus that can cause illness and even death in the immuno-compromised) measuring around 150 to 300 nanometers. The attachment was able to detail other particles as small as 90 to 100 nanometers. By contrast, a human hair is around 100,000 nanometers thick.
The smartphone images were verified through the use of more conventional equipment, such as an electron microscope.
Dr. Ozcan, who has also invented smartphone attachments that can detect food allergens and conduct kidney tests, used a Nokia PureView 808 smartphone, but he says that the new smartphone microscope could easily be customized to work with an iPhone or Android device.
Below, the abstract of the scientific paper cited above, published in the September 9 issue of ACS NANO.
Fluorescent Imaging of Single Nanoparticles and Viruses on a Smart Phone
Optical imaging of nanoscale objects, whether it is based on scattering or fluorescence, is a challenging task due to reduced detection signal-to-noise ratio and contrast at subwavelength dimensions. Here, we report a field-portable fluorescence microscopy platform installed on a smart phone for imaging of individual nanoparticles as well as viruses using a lightweight and compact opto-mechanical attachment to the existing camera module of the cell phone. This hand-held fluorescent imaging device utilizes (i) a compact 450 nm laser diode that creates oblique excitation on the sample plane with an incidence angle of 75°, (ii) a long-pass thin-film interference filter to reject the scattered excitation light, (iii) an external lens creating 2× optical magnification, and (iv) a translation stage for focus adjustment. We tested the imaging performance of this smart-phone-enabled microscopy platform by detecting isolated 100 nm fluorescent particles as well as individual human cytomegaloviruses that are fluorescently labeled. The size of each detected nano-object on the cell phone platform was validated using scanning electron microscopy images of the same samples. This field-portable fluorescence microscopy attachment to the cell phone, weighing only 186 g, could be used for specific and sensitive imaging of subwavelength objects including various bacteria and viruses and, therefore, could provide a valuable platform for the practice of nanotechnology in field settings and for conducting viral load measurements and other biomedical tests even in remote and resource-limited environments.
October 7, 2013 at 08:01 PM | Permalink
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