Nucleic Acid Analyzer (HANAA)

Nucleic Acid Analyzer (HANAA)

Forensic analysis often involves the analysis of samples for the presence of disease-causing microorganisms (pathogens ). In the past, this analysis required the specialized media, incubators and other equipment housed in a laboratory. However, miniaturization of equipment has enabled some of the pathogen technology to be taken into the field in a portable form.

In the months preceding the 2003 war in Iraq, United Nations inspectors conducted forensic analyses throughout the country, searching for evidence of chemical, nuclear, and biological weapons. One of the portable devices utilized enabled detection of some bacterial pathogens based on the detection of target regions of nucleic acid.

The device used is a hand-held advanced nucleic acid analyzer (HANAA). It was developed by the Lawrence Livermore National Laboratory in 1999 based on a previous model of the nucleic acid analyzer ANAA produced in 1997.

HANAA is a real-time polymerase chain reaction (PCR)-based system for detecting pathogens. It is highly sensitive as it can detect 200 organisms per milliliter. Typical lab-based tests that require the growth of bacteria require the presence of millions of living bacteria.

The instrument takes advantage of real-time PCR technology that was developed in recent years. PCR amplification of DNA (deoxyribonucleic acid) requires repetitive sample heating (to approximately 203° F [95°C]) and cooling to a lower temperature specific for the sample (usually 122–161°F, or 50–72°C). Traditional instruments require two to three hours to complete a PCR run and additional time to run the products on a gel to detect positive samples. New real-time PCR instruments have heating and cooling systems allowing a reduction of the running time to less than 30 minutes. The same instruments also allow observation of product formation during the run. This is achieved by incorporation of fluorescent detection methods to visualize product formation.

The main part of the instrument is a sample module containing a miniaturized silicon thermal cycle of high heating and cooling efficiency. These small thermal units are a major breakthrough in technology, as batteries can efficiently support them. In comparison, most of the existing real-time systems are comparatively larger and heavier and cannot be operated in a field with ease, despite the similarly good technology for detection or time of analysis. HANAA also has an advantage over its predecessor ANAA, which was as big as a small suitcase. HANAA fits into the palm of a hand and weighs around two pounds (1 kg). It can operate 1.4–5.5 hours depending on the battery used. A run on the instrument is approximately 7–20 minutes depending on the program used for detection.

The PCR process used by HANAA is based on using TaqMan-type probes, which rely on a short DNA oligonucleotide being labeled by two fluorescent molecules, a quencher and a reporter. When a probe anneals to DNA, there is no signal as the short distance between the quencher and the reporter results in the reporter's fluorescence being quenched. However, during amplification, the reporter molecule is released and an increase in fluorescence is observed.

HANAA has four chambers for analysis and can perform two independent identifications in each chamber, therefore is able to test for up to eight pathogens at one time. Each of the sample units can be run independently, which makes the instrument highly flexible in use. The unit is operated by a keypad, with all the menu options and results displayed on a LCD (liquid crystal display) screen as text or bar charts. A positive sample is announced by an audible alarm.

The instrument and technology are still dependent on the quality of the sample and lack of any possible PCR inhibitors in the sample. However, sample preparation is relatively simple. A template for PCR is prepared by placing sample in a liquid buffer in a small (0.020 ml) test tube and reagents are added directly to the same tube.

see also Biological weapons, genetic identification; DNA fingerprinting; DNA recognition instruments; DNA sequences, unique; PCR (polymerase chain reaction).