Polymerase chain reaction in high surface-to-volume ratio SiO2 microstructures.

We have performed the Taqman beta-actin PCR system in high-surface-to-volume ratio (0.02-0.13 microm(-1)) SiO2 microchannels and observed the reaction yield and uniformity. The concentrations of the enzyme, magnesium chloride, and reaction template were varied in the reaction mix, and PCR amplification was performed in devices of various surface-to-volume ratios. We found that microchannels with higher surface-to-volume ratios required higher enzyme concentrations to achieve the same amplification efficiency. We investigated the possibility that the observed reaction nonuniformity was related to the specific adsorption of magnesium ions to the negatively charged SiO2 surface. The effect of several modifications to the reaction chemistry, the addition of the caged-magnesium dye DM-Nitrophen, the replacement of human DNA template with PCR product, and the coating of the microchannel surface with Teflon were all studied. These modifications resulted in improved reaction uniformity in the microchannels and present opportunities for further studies on enhancing the efficiency and uniformity of PCR in high surface-to-volume ratio SiO2 microchannels.