Noncontact infrared-mediated thermocycling for effective polymerase chain reaction amplification of DNA in nanoliter volumes

We demonstrate that accurate thermocycling of nanoliter volumes is possible using infrared-mediated temperature control. Thermocycling in the presence of Taq polymerase and the appropriate primers for amplification of lambda -DNA in a total volume of 160 nL is shown to result in the successful amplification of a 500-base pair fragment of lambda -DNA. The efficiency of the amplification is sufficiently high so that as few as 10 cycles were required to amplify an adequate mass of DNA for analysis by capillary electrophoresis. This indicates that, as expected, PCR amplification of DNA in nanoliter volumes should not only require less Tag polymerase but require less cycling time to produce a detectable amount of product. This sets the stage for microchip integration of the PCR process in the nanoliter volumes routinely manipulated in electrophoretic microchips.