Thursday October 19, 2006
The RoboCycler® temperature cycler is quite different in design than most traditional PCR machines. As such, it can be used with more applications than most other machines. The RoboCycler® has 4 temperature blocks. The first 3 blocks can be used for temperatures ranging from 25ºC to 99ºC, and Block 4 can be used for temperatures ranging from 6ºC to 25ºC. One of the blocks (Block 2) can even be programmed for a temperature gradient. This allows samples within the same run to be exposed to temperatures varying in the range of 45º to 99ºC or 35ºto 99ºC, depending on the model. Samples are moved from one block to the next via a rotating, robotic arm. Because of the movement from one temperature block to the next, it is not necessary for the machine to take time ramping like most PCR machines. This is a nice feature, because it saves time.
An LCD screen on the front of the machine is used for setting up programs. The screen is easy to read, and the set-up procedures for programming the cycles are easy to follow. All information (such as time remaining, set temperature for the blocks, actual temperature for the blocks, and cycle number) is shown clearly on the screen. The RoboCycler® can hold up to 99 programs. Beyond that, it is possible to link up to 10 programs together to run in sequence. The instruction manual is quite helpful and gives detailed instructions for assembly and programming of the machine.
The rotating arm has a heated cover, called the Hot Top, which fits over the tubes. This eliminates the need for an oil overlay. Our lab has one earlier model of the RoboCycler® which has a simple On/Off switch controlling the Hot Top. For some reason, the newer model is without this switch, requiring the user to press successive buttons on the front of the machine to toggle the Hot Top on and off if it needs to be switched during a cycle. This is only slightly more cumbersome, but the users in our lab still prefer the switch on the older model. The need for switching the Hot Top off and on only occurs with certain applications. For example, in our lab we frequently use the RoboCycler® when reverse transcribing RNA into cDNA. In this application, samples are kept in a relatively cool block for a period of time then moved to a high temperature block. The Hot Top is necessary for the hot block, but not for the cooler block. If the Hot Top is turned off to begin with, then you must turn it on using the buttons on the front of the machine, a few minutes before it moves to the hot block. With the older model, you can simply flip the switch when you are ready to turn the heated cover on.
The rotating arm which moves the tubes from one block to another has caused frustration for our lab as well. Even after following the alignment procedures for the arm, it occasionally misaligns during rotation. This causes the arm to return to Block 4 (the final block) and hold. Four different users have used this machine, and each person has had this problem once, if not multiple times. This requires users to keep a fairly close eye on the machine, especially on the first cycle, to make sure it hasn’t encountered an alignment problem. Clearly, this is a big disadvantage since many labs prefer to set-up a PCR to run unsupervised overnight.
In general, this machine has produced nice products, but not without its share of frustrations.
Kathryn Boyd
Research Assistant
Conceptual MindWorks, Inc.
Air Force Research Laboratory, HEPC