“DNA Synthesis Technologies to Close the Gene Writing Gap”, Alex Hoose, Richard Vellacott, Marko Storch, Paul S. Freemont, Maxim G. Ryadnov2023-01-23 ()⁠:

Synthetic DNA is of increasing demand across many sectors of research and commercial activities. Engineering biology, therapy, data storage and nanotechnology are set for rapid developments if DNA can be provided at scale and low cost. Stimulated by successes in next generation sequencing and gene editing technologies, DNA synthesis is already a burgeoning industry. However, the synthesis of >200 bp sequences remains unaffordable.

To overcome these limitations and start writing DNA as effectively as it is read, alternative technologies have been developed including molecular assembly and cloning methods, template-independent enzymatic synthesis, microarray and rolling circle amplification techniques. Here, we review the progress in developing and commercializing these technologies, which are exemplified by innovations from leading companies.

We discuss pros and cons of each technology, the need for oversight and regulatory policies for DNA synthesis as a whole and give an overview of DNA synthesis business models.

[Timeline]
Figure 1: The state-of-the-art in DNA synthesis. (a) Productivity of DNA reading and DNA writing (synthesis) estimated in the number of nucleotides per person per day15. The grey arrow denotes the current gap in productivity between reading DNA and writing DNA. The dashed oval outline highlights the time frame within which the DNA synthesis industry achieved the majority of important milestones to close the gap. DNA synthesis data (red line) are available only for column-based synthesis instruments. The number of transistors per chip (Moore’s law) is shown for comparison. The graph uses the data available in the literature. (b) Timeline of milestones in DNA synthesis technologies discussed in the report20,25,26,34,35,37,42,71,146. For simplicity not all milestones are shown. Glossary: NTP, nucleoside 5ʹ-triphosphate; PCA, polymerase cycling assembly; TdT, terminal deoxynucleotidyl transferase; TiEOS, template-independent enzymatic oligonucleotide synthesis. Copyright Wiley-VCH GmbH. Reproduced with permission from15.

…Barriers to entry for customers: Custom DNA synthesis remains an expensive endeavour (for example, US$300–$1,000 per 3 kb gene or $0.1–$0.3 kb−1). Prices vary depending on vendor, sequence composition and length. A general trend is observed towards the decrease of price to $0.01 kb−1 for gene synthesis over several years15, for example, the current price offered by Twist Bioscience is $0.07 kb−1 for gene fragments.

More substantial funding is required to aid research aiming to make large DNA. More specialized equipment is required for the end users to make DNA that is more complex than plasmids. The provision of such complex and large DNA can be outsourced to DNA synthesis providers (for example, Ribbon Biolabs for assembly). The complexity of custom DNA made for a particular application defines the skill barrier required for the synthesis.

There are general trends for reducing the dependence on expert involvement by reducing the need to troubleshoot the DNA synthesis, which is achieved by advances in the performance of enzymes and DNA assembly methods.