Everyone is surrounded by DNA in their daily lives, and any activity of human beings may leave DNA and cause pollution to DNA testing. Some DNA contamination can be corrected by re-inspection, and some pollution (such as contamination of a very small amount of physical evidence) may cause irreparable damage, so how to implement the forensic DNA laboratory anti-pollution measures for DNA contamination.
1 Laboratory environment and facilities
The forensic DNA laboratory strictly controls the environment and facilities, and implements sub-regional management and regular cleaning systems, which is an effective means to avoid DNA contamination.
1.1 Laboratory partition
Due to the high sensitivity of forensic DNA testing, in order to prevent cross-contamination during the testing process, the forensic DNA laboratory should establish a laboratory partition and authorization entry system. The ventilation and exhaust systems between the regions should not be mixed, and unrelated personnel should not enter the experimental area. Experimental equipment and equipment in different areas shall not be mixed.
The sub-regional management of the DNA laboratory ensures that different tests are performed in different experimental areas, and the unidirectional flow of the sample and the sample is achieved in order of decreasing DNA content. The DNA laboratory must set up the case acceptance and sample storage area, the sample DNA extraction area, the DNA amplification area, and the DNA detection area. The conditional laboratory should also set the initial inspection area, the result analysis area, the preparation area, etc. A buffer zone should also be set up in the extension zone and the detection zone for the technician to change the overalls. For the examination of trace DNA, such as contact with DNA, since the amount of DNA contained in the sample is small, there is a danger of contamination, and a special DNA extraction region is required.
PCR contamination is a feature of forensic DNA laboratories and a focus of laboratory contamination prevention. In the PCR amplification product or the allelic standard control, a high concentration of the DNA target fragment is detected, and a very small amount is detected. Once such contamination occurs in the laboratory, it will be difficult to remove, and the consequences are serious. Partition management of the laboratory and strict operation according to requirements can effectively prevent pollution, and the key point is to strictly manage the DNA detection area. The centrifuge tube containing the amplification product or the control can only be opened in the DNA detection area, and the area is not allowed to be taken out; the waste in the detection area should be tightly packed; the technician should change the overalls when entering or leaving the area.
1.2 Laboratory cleaning
Doing a good job in laboratory cleaning is an effective way to prevent cross-contamination in DNA laboratories. There are various reasons for DNA cross-contamination, mainly due to mutual contamination between material samples or between samples and physical evidence. The way of DNA cross-contamination can be caused by direct contact, or it can be caused by the transfer of foreign DNA through a certain carrier, which makes the DNA test result wrong; the former is easy to find and prevent, the latter is difficult to find and prevent, which requires experiment The room should be cleaned and disinfected regularly.
Laboratory cleaning includes cleaning of work surfaces, equipment surfaces, reusable tools or utensils. The key parts of the work surface include the counter for the laboratory to accept the sample, the DNA extraction workbench, the ultra-cleaning platform for extracting DNA, and the sample storage cabinet, all of which are easy to contact and leave DNA; the equipment mainly has the rotor of the centrifuge, The heating block for extracting DNA, the sample tank of the amplification instrument, the suction hole of the pipette rod, the sample introduction tank of the genetic analyzer, etc.; the reusable tools or utensils mainly include scissors and tweezers used for cutting the sample of the sample, A reagent bottle for preparing a reagent, and the like.
The laboratory cleaning is mainly by wiping and cleaning. Firstly, the surface of the object to be cleaned is repeatedly wiped with freshly prepared 10% bleach (7 mM sodium hypochlorite solution), and then scrubbed with 75% ethanol to remove the residue, which can effectively remove the surface. Adhere to various pollutants and, if conditions permit, UV disinfection at regular intervals. In addition to establishing a regular cleaning system, the laboratory should clean and clean it in time if it is found that DNA contamination may occur during the inspection process.
Today, the laboratory anti-pollution has been introduced to you here. There are many considerations for the construction and use of the laboratory. We need to keep learning from our builders and users. I hope that today's article will help you.