How to Prevent Aerosol Contamination in PCR Labs

The application and development of PCR (polymerase chain reaction) technology has led to more effective evidence for disease diagnosis, especially the promotion and application of fluorescent quantitative PCR, which has greatly improved the sensitivity and accuracy of the test. However, with the widespread use of this technology in pathogen detection laboratories, the problem of aerosol contamination in PCR laboratories has gradually aroused concern. In order to effectively avoid PCR laboratory DNA / RNA aerosol contamination, to obtain stable and reliable test results, to prevent false positives, PCR laboratory to establish strict anti-pollution measures and the corresponding pollution monitoring system to prevent aerosol contamination pollution, once found aerosol contamination, to promptly find the cause and the corresponding solution to the pollution problem.

Zoning of Laboratories

The PCR laboratory should be divided into four sections according to the relevant regulations: reagent preparation section, specimen preparation section, PCR amplification section, and product analysis section, with the first two sections being the pre-amplification section and the last two sections being the post-amplification section. The pre-amplification area and post-amplification area should be strictly separated and equipped with ventilation and purification to form a pressure difference between the sections. Workflow, including experimental materials, reagents, recording paper, pens, cleaning materials, etc., can only flow from the pre-amplification zone to the post-amplification zone, i.e. from the reagent preparation zone → specimen processing zone → amplification zone → product analysis zone, and shall not flow in the reverse direction. It is strictly forbidden to reverse the flow in the clean corridor while forming different gradient pressure differences between each section, corresponding buffer room, and clean corridor so that the air flow is the same as the working direction.

Setting up Controls

Two negative controls (both using water as a template, one with the sample involved in nucleic acid extraction and the other not involved in the extraction, added only when configuring the amplification system) are prepared each time before conducting the experiment, in order to monitor the aerosol contamination in the laboratory and determine whether there is contamination and what causes it, so that measures can be taken to prevent and eliminate it. A positive control should also be set for monitoring the reliability and accuracy of the experimental results.

Monitoring Laboratory Aerosols

Laboratory air is regularly purified using a home air purifier, and the filter in the purifier is dipped into water, mixed, and the mixed water is used as a sample for corresponding testing in order to keep abreast of the contamination of aerosols in the air. Regularly collect samples of cotton swabs from the interior and surface of pipette guns, extractors, amplifiers and other instruments for testing in order to understand the contamination in experimental instruments.

Strict Workflow

Each section of PCR is equipped with its own work clothes, which can be distinguished by color, and the corresponding work clothes must be changed when entering each section; meanwhile, the entrance of the clean corridor is equipped with special shoes for PCR room, which must be changed when entering, and felt mats are equipped in front of each section. Laboratory personnel in the clean corridor can only go from the direction of the reagent preparation area to the direction of the result analysis area, and each section is equipped with different personnel for operation if conditions permit, so as to avoid the personnel of each section from moving around each other.

Enhance Cleaning and Disinfection

Good cleaning and disinfection of the laboratory is an effective way to prevent aerosol contamination in the laboratory. The scope of laboratory cleaning includes the cleaning of work surfaces (test benches, ultra-clean benches and storage cabinets, etc.), surfaces of instruments and equipment (rotating heads of centrifuges, heating blocks for DNA extraction, sample slots of amplifiers, pipette rods for pipetting, spiking slots of genetic analyzers, etc.), reused tools or utensils, etc.

Before and after the start of the experiment, the surfaces of the above-mentioned areas and instruments are wiped repeatedly with freshly prepared 10% sodium hypochlorite solution, and then scrubbed with 75% ethanol to remove residues, and the experiment can only be performed after the alcohol has evaporated. This can effectively remove the various pollutants attached to their surfaces. At the same time, the laboratory is regularly disinfected by UV light irradiation.