Long term conservation of DNA at ambient temperature. Implications for DNA data storage

Abstract

DNA conservation is central to many applications. This leads to an ever-increasing number of samples which are more and more difficult and costly to store or transport. A way to alleviate this problem is to develop procedures for storing samples at room temperature while maintaining their stability. A variety of commercial systems have been proposed but they fail to completely protect DNA from deleterious factors, mainly water. On the other side, Imagene company has developed a procedure for long-term conservation of biospecimen at room temperature based on the confinement of the samples under an anhydrous and anoxic atmosphere maintained inside hermetic capsules. The procedure has been validated by us and others for purified RNA, and DNA in buffy coat or white blood cells lysates, but a precise determination of purified DNA stability is still lacking. We used the Arrhenius law to determine the DNA degradation rate at room temperature. We found that extrapolation to 25 degree C gave a degradation rate constant equivalent to about 1 cut per century per 100000 nucleotides, a stability several orders of magnitude larger than the current commercialized processes. Such a stability is fundamental for many applications such as the preservation of very large DNA molecules (particularly interesting in the context of genome sequencing) or oligonucleotides for DNA data storage. Capsules are also well suited for this latter application because of their high capacity. One can calculate that the 64 zettabytes of data produced in 2020 could be stored, standalone, for centuries, in about 20 kg of capsules.

La révolution de l’ADN: biocompatible and biosafe DNA data storage

“…0.45 Zettabytes (ZB) equivalent to 450 x 10 6 Terabytes (TB) per gram of DNA, all of humanity's digital data in 2019 (45 ZB) could fit in 100 g of DNA ( 3 ). Moreover, DNA storage does not require energy since these molecules are perfectly stable at room temperature under appropriate conditions ( 4, 5 ).…”

“…Each bit of the binary file is converted into DNA using the one bit per base Church-Gao-Kosuri (CGK) encoding scheme ( 4 ) attributing randomly A or C for 0 and T or G for 1. Combinatorial effect of the CGK method confers flexibility in the conversion of binary information into DNA, allowing to apply multiple constraints on the final sequence, which are necessary for (i) DNA synthesis and sequencing (limitation of homopolymer length, controlled GC content), (ii) DNA assembly (forbidden restriction sites) and (iii) DNA biosafety (limiting transcription and translation).…”

“…the Declaration of the Rights of Woman and of the Female Citizen. The two DNA Drives were assembled and stored dried in metallic minicapsules (DNAshell® from Imagene) ensuring their stability for thousands of years ( 4 ). The data could be read many times with 100% fidelity.…”

“…100 billion copies per DNA Drive). The DNA of each DNA Drive was lyophilized and encapsulated in DNAShell® metallic minicapsules by Imagene SA (Evry, France) to ensure their conservation at ambient temperatures for thousands of years ( 4, 5 ). After conservation of the capsules at ambient temperatures for several months (up to 6 months), a capsule was opened, DNA was resuspended in pure water and a fraction was sequenced using an Oxford Nanopore MinION™ sequencer (Oxford Nanopore Technologies, Oxford, UK) (Fig.…”