Sweet Spots

Doctors commonly diagnose infectious diseases by checking patients’ blood for evidence of proteins or genes unique to different bacteria and viruses. Soon, they may be able to look instead for pathogen-specific sugars, thanks to a glass chip developed by biologist Denong Wang at Columbia University’s Genome Center. The technology could ultimately be less cumbersome than DNA-based tests and more accurate than protein-based tests for certain pathogens, allowing physicians to quickly screen for thousands of different infectious diseases at once using a small sample of blood.

When a person is exposed to a bacterium or virus, his or her body produces antibodies that bind to specific sugar molecules on the pathogen’s surface. Wang dotted glass chips with some of those same sugars, from bacteria such as Pneumococcus or Haemophilus influenza. He then washed blood samples over the chips; if people had been exposed to Pneumococcus, for example, antibodies from their blood stuck to the corresponding sugars on the chips and were then detected through a microscope.

One of the biggest challenges in making sugar chips has been getting the sugars to stick to glass. Wang discovered a relatively simple method: he coated the chip surface with nitrocellulose, which holds the sugars in place. Each of Wang’s first chips contains just 48 different sugars, but, he says, “We could spot up to 20,000 different sugars on a single chip, which would allow us to target all the most common pathogens.” Wang’s goal, in fact, is to create a diagnostic tool that could detect pathogens such as HIV, anthrax and smallpox. He is in discussion with a number of drug companies about commercializing his technology.