Thermocyclers or thermal cyclers are devices which have been developed for a cyclic temperature change of the polymerase chain reaction (PCR). PCR is an in vitro technique for the targeted amplification of deoxyribonucleic acid (DNA) sections. PCR requires a DNA matrix and two short known DNA sequences called oligonucleotides or primers.
The polymerase chain reaction (PCR)
In addition, the following deoxynucleoside triphosphates are required: dATP, dCTP, dGTP and dTTP, which are generally summarized as dNTPs. The reaction takes place in an aqueous buffered solution and is catalyzed by a thermostable DNA polymerase. Various thermostable polymerases have been isolated for this purpose and many are commercially available (Terpe 2016).
The amplification of the selected matrix is carried out in such a way that the DNA double strand is first melted into its two single strands in a denaturation step at 95-99 °C. This is followed by an annealing step at 45-65 °C. At these temperatures, the oligonucleotides are deposited on the matrix. And the third and last step is the elongation step at 68-75 °C. The polymerase fills the double strand. This cycle can be repeated 20 to 40 times depending on the process. As a result the product is exponentially amplified.
The applications of PCR
Today, the areas of application are manifold: Detection of pathogens such as retroviruses, viruses or bacteria, mapping of genomes, typing of HLA antigens, fingerprint analysis, cloning, gene synthesis, characterization or insertion of mutations, sequencing, genotyping are some of the applications.
The Labcycler of the company SensoQuest – here with a Thermoblock 96 made in gold-plated silver.
The important factor: the temperature
Temperatures are important for PCR. These must be adhered to by the thermal cyclers precisely. In addition, the temperature changes between the respective steps should take place quickly. Thermocyclers that use Peltier elements for heating and cooling have established themselves on the market. A block of thermally conductive metal, in which the sample carriers are placed, is tempered with the aid of these Peltier elements.
Silver or aluminium?
Aluminium and silver blocks have proven their worth. Silver with a thermal conductivity of 429 W/mK has better properties than aluminium with 237 W/mK. The silver blocks require less electricity, generate less waste heat and operating noise. In addition, block uniformity is achieved more quickly. The thermal cyclers with the name Labcycler are available with both a low-cost aluminium block and a high-quality silver block and guarantee reproducible work over a long period of time. SensoQuest GmbH offers a complete product portfolio around thermal cyclers.
The demands on the Thermocycler
From the Labcycler with Thermoblock 384 made of high-quality silver for high throughput to the low-cost Labcycler 48 made of aluminium for use in small research laboratories, every user can find a personal Thermocycler that meets all individual requirements.