Stratos Genomics has raised $2.1 million in funding to further develop its nanopore-based DNA sequencing method.
The funding comes from existing shareholders and constitutes an "up round" to a $4 million Series A funding round that the company completed last year under the same terms. Last year's round was led by Fisk Ventures and included Stratos Group, the company's parent.
Spun off from Stratos in 2007, Seattle-based Stratos Genomics is developing a nanopore sequencing method it calls "sequencing by expansion," or SBX.
Last month, the company received a patent on the SBX method, US Patent No. 7,939,259 entitled "High Throughput Nucleic Acid Sequencing by Expansion."
Using the method, Stratos converts DNA into a longer polymer called an "Xpandomer," which encodes the base sequence through reporter molecules that have a high signal-to-noise ratio.
According to a video animation on Stratos Genomics' website, DNA is converted into the Xpandomer by a "modified DNA replication process" that uses modified 4-base oligonucleotides, or "x-probes," as building blocks that hybridize to the target DNA.
Each of the oligos carries a loop between the second and third base that consists of four "high signal-to-noise" reporters, which represent that oligo's base sequence. After the oligos are linked, the DNA is denatured to release the new strand and a reagent is added that breaks a cleavable bond between the second and third nucleotide of each original oligo. As a result, the loop of reporters between those nucleotides can expand, resulting in an Xpandomer molecule that is more than 50 times longer than the original DNA.
Stratos analyzes the Xpandomers using a nanopore detector, consisting of solid-state nanopores in a silicon chip. As each reporter passes through the nanopore, it causes a unique change in current that identifies the DNA base it represents. With several thousand nanopores in a silicon chip, measurement rates could exceed 10 million bases per second, according to the company.
Stratos provided no information on its website about how far the technology has progressed.