Automating Microsatellite Genotyping with Array Tape

Our laboratory has been testing ways to reduce costs, sample volumes, and decrease labor in microsatellite (or short tandem repeat polymorphism) genotyping. Microsatellite genotyping involves polymerase chain reaction amplification of a short (100–400 bp) fragment of chromosomal DNA that encompasses the tandem repeats followed by electrophoresis to size the amplification products. Using a continuous polypropylene tape (array tape) embossed with 384-well arrays, conforming to the microtiter plate standard, we have been able to perform the amplification reactions in smaller volumes and to decrease handling of stacks of microtiter plates. Instruments were constructed in-house to achieve these results. However, the problem of removal of the samples from the tape for electrophoresis remained. We report here efficient piercing of the tape seal for extraction of the samples using a CO 2 laser. Scoring of the seals with the laser weakens it sufficiently to permit extraction of the samples with a syringe array. CO 2 lasers are robust systems that do not contain a lot of frequently replaced parts, and do not require frequent recalibration. In addition, the laser is software controlled allowing for highly reproducible scoring and easily switching between 384-, 1536-, and 96-well formats. (JALA 2006;11:260–7)