PCR in Integrated Microfluidic Systems

Miniaturized integrated DNA analysis systems offer the potential to provide unprecedented advances in cost and speed relative to current benchtop-scale instrumentation by allowing rapid bioanalysis assays to be performed in a portable self contained device format that can be inexpensively mass-produced. The polymerase chain reaction (PCR) has been a natural focus of many of these miniaturization efforts, owing to its capability to efficiently replicate target regions of interest from small quantities template DNA. Scale-down of PCR has proven to be particularly challenging, however, due to an unfavorable combination of relatively severe temperature extremes (resulting in the need to repeatedly heat minute aqueous sample volumes to temperatures in the vicinity of 95°C with minimal evaporation) and high surface area to volume conditions imposed by nanoliter reactor geometries (often leading to inhibition of the reaction by nonspecific adsorption of reagents at the reactor walls). Despite these daunting challenges, considerable progress has been made in the development of microfluidic devices capable of performing increasingly sophisticated PCR-based bioassays. This chapter reviews the progress that has been made to date and assesses the outlook for future advances.