Since the development of DNA sequencing, scientists have been trying to do it less expensively and with less sample. There are various ways to sequence DNA, but the Sanger method generates long and accurate sequence reads, which is important for comparative analysis of variations such as insertions and deletions in mammalian genomes.

Richard A. Mathies and colleagues at the University of California campuses in Berkeley and in San Francisco have created a microdevice that can perform Sanger sequencing using only 1 fmol of DNA template. The device is made of a hybrid glass PDMS assembly, a critical change from the monolithic substrate used before. It incorporates miniaturized temperature sensing, nanoliter scale Sanger extension reactions, microvalves/pumps, DNA affinity-capture and high-performance capillary electrophoresis.

In the May 9 issue of PNAS, the researchers report that the device can sequence up to 556 continuous bases with 99 percent accuracy, which is adequate for de novo sequencing (determining DNA sequence without any prior knowledge of that sequence) of human and other genomes. They used this information to predict an ultimate limit of Sanger sequencing miniaturization. They believe that, by incorporating other advancing technologies such as more efficient injection techniques and scanners with improved sensitivity, the 1-fmol sample required could be reduced, conservatively, to 100 amol and possibly to as little as ~10 amol.