Toward Effective PCR-Based Amplification of DNA on Microfabricated Chips

The polymerase chain reaction (
PCR
) has rapidly become the most valuable tool in the clinical diagnostic arsenal for determiningspecific diseases or detecting infectious agents. Primers, short pieces of
DNA
complementary to the DNA sequence of interest,are mixed with nucleotides, a small amount of template DNA from the sample of interest, and
Taq
DNA polymerase enzyme in the appropriate buffer. Using temperature cycling, a short piece of DNA (50-1000 bp in length),defined by the primers chosen, is rapidly amplified from the few initial template molecules added to the mixture. The amplificationproduct is then analyzed using an electrophoretic separation. The entire process, shown in Fig. 1, includes the “sample preparation” which typically involves isolating the appropriate cells, from which the DNA is extractedprior to PCR amplification. To utilize this sequence most efficiently there should be a continuous flow from sample collectionto diagnosis. This would eliminate both delays due to the transfer of material between each step and the need for interventionbefore the next step could begin. In the ideal world, this diagnosis would be immediate—the real goal is to decrease the timeto as short as possible. Towards this end, the integration of the steps detailed in Fig. 1into a single platform is of obvious and critical importance (
see
Note 1).
Fig. 1.
Overall scheme for clinical and genetic analyses.