| Living sensors: At the heart of a new system for detecting airborne bioterror agents is a CD-size disc with 16 chambers at its perimeter. Particles from the air are collected in the chambers, where they’re exposed to immune cells with antibodies specific to particular agents. If the target agents are present, the cells emit blue light. The light in this image is a simulation; light emitted by cells in the chambers is too faint to be picked up by conventional photography, but it is picked up by light meters in the device. |
Credit: MIT Lincoln Laboratory
A sensor system that can rapidly detect six potential airborne bioterror agents, including anthrax, is now on the market. The detector relies on living immune-system cells genetically engineered to emit light when exposed to a particular contaminant. From sampling the air to getting a readout from the cells, the detection process takes only three minutes. The company selling the sensor, Innovative Biosensors, of Rockville, MD, is marketing it for use in airports and other buildings, including laboratories where research on dangerous pathogens is performed.
Time is of the essence when detecting bioterror agents. Bacteria like anthrax are infective within two to three minutes of exposure, so the faster a building can be evacuated and the agent contained, the better. "We're harnessing the fastest pathogen identification system there is," says James Harper, a researcher at MIT Lincoln Laboratory, where the technology was developed by Todd Rider beginning in the late 1990s. "In the body, B cells bind to pathogens and respond in a second," says Harper.
The mouse B cells at the heart of the Lincoln Lab detection system can be engineered to detect any agent for which an antibody exists. But the six agents that Innovative Biosensors is initially targeting are the smallpox virus, the toxins botulinum and ricin, anthrax, and two other bacteria. The B cells are loaded into pockets in a disc the size of a CD. These discs in turn are loaded into a one-cubic-foot detector containing fans, an imaging system, and a computer processor.
When the detector is turned on, fans suck air into it. Particles in the air are collected in 16 chambers at the perimeter of the disc. Then the disc is spun at high speed to release the cells from their pockets and transport them to the collected particles. If the agent the cells are designed to detect is present, they emit blue light. The detector uses software to analyze light levels from the disc's chambers to determine whether a bioterror agent is present. The raw data about light peaks and reaction kinetics is complex, says Lincoln Lab researcher Joseph Lacirignola, but algorithms process it to arrive at a yes or no answer.
The system can run 16 tests simultaneously, one in each chamber of the disc. Harper says that when at least two chambers are devoted to each pathogen, there are no false positives. The Lincoln Lab system can detect anthrax and other agents at concentrations as low as 10 individual particles per 30 liters of air. Each disc can be used only once.
The Innovative Biosensors detector can automatically load a fresh disc after taking a reading, but it need not run continually. It comes packaged with another, less accurate detection device, also developed at Lincoln Lab. This device uses ultraviolet light and triggers the cell-based system if it detects a potential biomolecule.