Introductory Overview of Plastic Product for Use in PCR
The use of genetic material has almost boundless applicability from diagnostics to genetic engineering. Genetic information obtained from samples is purified and then amplified for use. This amplification is most typically done by PCR.
In PCR a polymerase, an enzyme responsible for reading the information in a strand of DNA and creating a complementary strand, is used to replicate DNA in successive cycles. Of course, the enzyme can’t do this alone - unpolymerized triphosphate base pairs are the substrate that are polymerized by the enzyme into the new strands of DNA. Primers are used to facilitate the polymerase coming together with the template DNA. The PCR mix has other components and buffering agents as well. However, one thing that is not included in the mix are enzymes responsible for unwinding the two strands of the DNA ladder so that the polymerase can access the them. The reason is not included in the mix is that this is done by heating the mix to around the mid 90s Celsius (the optimal temperature can vary depending on several considerations), a temperature at which the two strands separate. At the end of replication, the reaction is cooled so that strands can come back together setting up the next round of replication. This cycling of temperatures is the reason that devices responsible for running PCR reactions are called thermocyclers.
Aside from merely amplifying the amount DNA present, PCR can be linked to simultaneous detection in a process called real time PCR. The basic idea is the amplification is linked to a florescence signal that increases in intensity as the amount DNA increases. This can be used to quickly determine whether a specific DNA sequence is present in a sample or else to determine the relative expression of a gene if the PCR reaction also involves the reverse transcription of RNA.
Because of these considerations the vessel a PCR reaction is carried out in needs to meet a number of exacting criteria. The tube or plate’s interior needs to be free of contaminates or substances degradative to DNA/RNA. The surface of the plate needs to be sufficiently low binding that a significant amount of reaction product or reagents will not adsorb to it. Finally, it needs to be able to tolerate and facilitate the rapid temperature cycling. Regarding real time PCR it is important that a clear signal can be detected, therefore the plastic needs should be highly transparent.
Greiner PCR plates and tubes meet these criteria. In addition to being free of detectable DNAse, RNAse and human DNA they are made of polypropylene whose hydrophobic character means that it is comparatively low binding. Extra thin plastic used for the tubes and plates facilitates thermocycling by enabling rapid thermal conduction. Furthermore, optically clear caps and plate sealers are available for Real Time PCR.
