Handheld Advanced Nucleic Acid Analyzer (HANAA)
About the size of a brick, the HANAA biodetection system can be held in one hand and weighs less than a kilogram. The system was designed for emergency response groups, such as firefighters and police, who are often first on the scene at sites where bioterrorism may have occurred. Each handheld system can test four samples at once-either the same test on four different samples or four different tests on the same sample. HANAA can provide results in less than 30 minutes, compared with the hours to days that regular laboratory tests typically take.
The way HANAA works is that the operator prepares the samples by putting them in a liquid buffer and adding chemicals. A tiny disposable plastic tube holding about 0.02 milliliter of the prepared liquid is then inserted into the system. Many copies of a sample's DNA are needed to analyze it and identify its makeup. HANAA uses a technique called the polymerase chain reaction (PCR), which amplifies agent-specific DNA fragments to a detectable level. In PCR, an aqueous sample is heated close to the boiling point and then cooled many times (40 times in HANAA). Every time the DNA is heated, the two intertwined strands of DNA unwind and come apart. As the sample cools down, the DNA makes a copy of itself. Thus, at the end of each cycle, the amount of DNA is doubled.
To detect the DNA in a sample, a synthesized DNA probe tagged with a fluorescent dye is introduced into the sample before it is inserted into the heater chamber. Each probe is designed to attach to a specific organism, such as anthrax or plague. Thus, the operator must have an idea of what substances might be involved. The system doesn't test for all unknowns, a responder has to decide what kinds of pathogens to test for ahead of time and set up the system accordingly. If that organism is present in the sample, the probe attaches to its DNA, which is then amplified during the PCR process, releasing the fluorescent tag. HANAA measures the sample's fluorescence and the presence (or absence) of the targeted organism.
One of the big breakthroughs for the handheld system involved the design of a small silicon heater chamber for the heating and cooling cycle, a concept developed at Livermore by Allen Northrup, a former Laboratory scientist. The commercial thermocyclers used for standard laboratory tests are pretty big, ranging from the size of a microwave oven to a large desk. A typical large thermocycler takes about 3 minutes to cycle through one heating and cooling cycle, so a complete analysis requires 2 to 3 hours. In the HANAA system, the thermal cycling process occurs in tiny silicon heater chambers, micromachined by Livermore's Center for Microtechnology. Each chamber has integrated heaters, cooling surfaces, and windows through which detection takes place. Because of the low thermal mass and integrated nature of the chambers, they require little power and can be heated and cooled more quickly than conventional units. The mini-chambers typically cycle from about 55°C to 95°C and back to 55°C in about 30 seconds.
Using this technique, the HANAA system could, in principle, detect as few as 10 individual bacteria in one-hundredth of a milliliter in less than 30 minutes. The system has the potential of saving many lives by saving time-anthrax, for example, is highly treatable if detected early.
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