Thermal Cycler (PCR)
With the Biometra thermal cyclers, we offer you a well-balanced selection of PCR instruments for a wide range of application requirements.
All Biometra thermal cyclers were developed for the highest quality and performance requirements and are manufactured in Germany according to these standards. In addition to the user-friendly thermal cyclers, optional thermal cycler management software ensures efficient and GMP-compliant, convenient laboratory work.
To ensure that you can rely on your PCR results for years, you can rely on our application support as well as our technical service with various service offerings and a specially developed high-precision temperature measurement system.
PCR thermal cycler
Thermocyclers are used to carry out the polymerase chain reaction (PCR). These devices are able to run through the different phases of the PCR independently and automatically. Analytik Jena's product portfolio includes a variety of PCR thermal cyclers for a wide range of requirements and applications. For laboratories that require devices for standard PCR applications, the powerful thermal cyclers of the Biometra series are ideally suited.
History and basics of PCR
It is somewhat disputed who exactly is responsible for the development of PCR. Norwegian Kjell Kleppe came up with the idea of amplifying DNA using primers – markers for specific DNA sequences – as early as the 1970s. However, it was not until 1983 that the idea really came to fruition thanks to biochemist Kary Mullis. Mullis developed a method for synthesizing DNA by cyclic duplication with the aid of the enzyme polymerase. Polymerase duplicates DNA in cells during the division process and is found in all organisms. To do this, it binds to a DNA strand and synthesizes a complementary strand by means of a primer. Mullis took up this natural principle and reproduced it artificially in the laboratory in order to duplicate the genetic material of e.coli bacteria. He heated the DNA to 96°C until it broke down into individual strands and then cooled it down again. The process had to be repeated several times to achieve sufficient amplification. The process was still very inefficient and the polymerase from e.Coli had to be added again and again with each heating cycle because the it was not stable at high temperatures. However, the basic mode of operation could be demonstrated. Mullis received the Nobel Prize for this in 1993. In the early days of PCR, water baths were used for heating and cooling, which made the entire process very lengthy and imprecise. Today, technologically sophisticated solutions exist in the form of PCR thermocyclers that deliver fast and precise results. Another decisive factor leading to the breakthrough of the PCR was the use of thermostable DNA polymerases that can withstand temperatures of around 100 °C without denaturing. These polymerases are usually obtained from thermophiles - special bacteria or archaea.
Design of a PCR thermal cycler
The central component of a PCR thermocycler is the heating block. The block is equipped with micro reaction wells, the number of which depends on the usual formats for microtiter plates – usually from 8 to 384 well, depending on the throughput requirement. To prevent evaporation, the vessels in early models were provided with a sealing of mineral oil. Today, evaporation is counteracted with heated lids. The heating block ensures uniform heating and cooling of the wells. Modern thermal cyclers have a gradient function that can scale the temperature control particularly gently. The basic technological principle of the heating block is the Peltier effect. By reversing the direction of current between two semiconductors, the heating and cooling phases are alternated. A PCR thermal cycler can thus very quickly reach temperatures between 4°C and 96°C required for PCR.
Process of PCR with a thermal cycler
PCR, i.e., the amplification (multiplication) of nucleic acids, takes place in the micro reaction wells of the thermal cycler. Usually, volumes between 10 and 100 µl are used. In addition to the DNA to be amplified, additional reagents and materials are required to perform PCR: 1. two primers that mark the start and end points of the DNA segment to be synthesized, 2. DNA polymerase to replicate the DNA, 3. deoxyribonucleoside triphosphates, the building blocks of the synthesized DNA segment, 4. Mg+ ions to stabilize the attachment of primers, and 5. buffer solutions that ensure optimal chemical conditions for the reaction.
The PCR process consists of four main steps: First, the polymerase must be activated during initial denaturation at high temperature, followed by the actual repetitive PCR cycles. Them follows the denaturation step, i.e., heating the wells splits the DNA double strands into single strands. At temperatures around 95°C, the hydrogen bonds that hold the double helix together are weakened. This is followed by the annealing step, also called primer hybridization. In this phase, the reaction wells are cooled down to allow the primers to bond – usually between 55 and 65°C. If the temperature is too high, there is a risk that the primers will not dock properly. If the temperature is too low, it is possible that the primers will attach to other non-specific DNA sequences. The optimal annealing temperature depends on the DNA sequence and length of the primers. The third and final phase is called elongation, in which the polymerase forms new DNA strands.
The PCR cycles are repeated until the desired amount of target DNA or RNA has been amplified. In standard PCR, detection is mostly done by an electrophoresis method. The amplified DNA is usually applied to a agarose gel to which a voltage is applied. Short DNA sequences then migrate faster than long ones to the positive pole. With the aid of a DNA ladder, the DNA sequence sought can then be identified on the gel. However, this only allows conclusions to be drawn as to whether the target DNA is present or not. Real-time PCR or qPCR (quantitative real-time PCR) is used to quantify the target DNA. It also allows real-time monitoring of the amplification process.
Industries and applications for PCR thermal cyclers
Today, PCR thermal cyclers have a wide variety of applications. As a result of the Corona pandemic, the PCR method has become known primarily for the detection of pathogens. The diagnosis of viruses and bacteria is one of the main applications of PCR. It provides valid evidence and data enabling physicians and other medical personnel to make informed decisions. PCR thermal cyclers can be found in almost every medical, veterinary or clinical laboratory around the world. In addition to diagnostics, however, PCR has many other applications. In the food industry, for example, PCR is a standard method for origin analysis of certain foods and their ingredients. Depending on the region of origin, products such as wine have different genetic characteristics. The climate and environment of a certain region leave genetic traces over thousands of years that can be detected via PCR. Closely related to this is the issue of food fraud – the declaration of false ingredients in a food product. PCR thermocyclers have been used by laboratories for a very long time to check manufacturers' declarations. Does a wine really come from France as stated by the manufacturer? Is a food product really 100 percent vegan or halal? These kinds of questions can be clarified with PCR. Even the smallest traces of plant or animal DNA can be detected. Environmental analysis is another field of application that has recently become increasingly important. PCR thermal cyclers are used here, for example, to detect pathogens in wastewater in order to establish comprehensive health monitoring and corresponding early warning systems. Of course, universities also use PCR thermocyclers for a wide variety of research and analyses. In forensics, PCR is also an established method for detecting genetic fingerprints, for example at crime scenes.
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