Sequencing Platform Technologies

Sequencing by Expansion (SBX)

Stratos Genomics, a Roche company, has developed a novel next generation sequencing (NGS) chemistry called sequencing by expansion (SBX). This chemistry translates the sequence of DNA into a simple to measure surrogate molecule called an Xpandomer. Much like with polymerase chain reaction (PCR), Xpandomer synthesis is based on the natural function of DNA replication where expandable nucleoside triphosphates (X-NTPs) act as substrates for template-dependent, polymerase-based replication.

Four easily differentiated X-NTPs (also called High Signal-to-Noise Reporters) are used during Xpandomer synthesis, one for each DNA base, and engineered polymerases incorporate the X-NTPs into an Xpandomer, which serves as a surrogate for the complement of the nucleic acid template. As the Xpandomer molecule transits through a nanopore, the distinct electrical signal of each base reporter is easily identifiable to enable highly accurate and high throughput nanopore-based nucleic acid sequencing.

What is nanopore-based sequencing?

Sequencing using nanopores—tiny apertures on the cell membrane—enables the sequencing of single DNA molecules. A semiconductor-based electronic detection system detects the unique electrical signals of different molecules as they pass through the nanopore. This sequencing technology offers several advantages over existing modalities that use optical or pH change methods to detect DNA sequences (1) :

  • Flexibility and versatility
  • Both short and longer read lengths
  • Ultra-rapid data generation and analysis
  • Cost-effectiveness


SBX can be paired with the nanopore and electronic sensor technology to enable high throughput, high accuracy, and cost-effective sequencing with faster time-to-data.


  1. Fuller C, Kumar S, et al. 2016. PNAS. Real-time single-molecule electronic DNA sequencing using polymer-tagged nucleotides on a nanopore array.

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