LITMIR.BIZ

Figure 1.10 Logic program (a) and automatically generated chemical reaction network (b) for a DNA strand displacement example.

      Source: Adapted from Spaccasassi et al. 2019 [80] with permission; open access paper.

1.3 DNA‐Based Information Storage Systems

Human civilization generates hugeamount of information increasing exponentially and required to be stored. The total digital information today amounts to 3.52 × 10²² bits globally and at its consistent exponential rate of growth is expected to reach 3 × 10²⁴ bits by 2040 [82]. Data storage density of silicon chips is limited, and magnetic tapes used to maintain large‐scale permanent archives begin to deteriorate within 20 years. Alternative methods/materials for storing high density/large amount of information with reliable preservation over long period of time are urgently needed. DNA has been recognized as a promising natural medium for information storage [83]. Indeed, the DNA molecules were created by nature to keep the genetic code, which can be easily “written” and “read” by biomolecular systems. With information retention times that range from thousands to millions of years, volumetric density 10³ times greater than flash memory, and energy of operation 10⁸ times less, DNA is a memory storage material viable and compelling alternative to electronic memory. Recent research in the area of information storage with DNA molecules resulted in the proof‐of‐the‐concept systems [82,84–87], while the practical use of the DNA memory systems is only limited by technological problems. Both processes in the information storage with DNA, “writing” and “reading” information, are available, but they are not as simple as needed to be implemented with the present computer technology. In other words, the DNA memory is technically possible, but it is not convenient enough to be integrated with standard Si‐based computers operated by end users.

Synthetic procedure for production of DNA molecules with specific nucleotide sequences is well known in organic chemistry [88] and can be used to “write” information in the DNA. Once the DNA molecules with the encoded information are prepared, they can be multiplied using a polymerase chain reaction (PCR) [89–92] (Figure 1.11), which is a technique to make many copies of a specific DNA in vitro (in a test tube rather than an organism). This technique is rather advanced in the instrumental realization but still requires special apparatus that cannot be connected easily to an electronic computer, at least at the end‐user convenience. “Reading” the DNA‐encoded information (DNA sequencing [93]) was advanced during the Human Genome Project [94] and presently is very technologically effective. Further improvements in sequencing throughput (>10⁴) and parallelization (>10⁷) are expected in the next five years [84]. Emerging technologies such as nanopore sequencing [95] will further reduce errors, cost, time, and energetics during reading the DNA‐encoded information. While future advances can result in novel technological approaches, already available techniques based on the DNA memo‐chips have been tested [96]. A simple chemical, rather than electronic, apparatus operating as the end‐to‐end automatic DNA data storage was designed and demonstrated the automatic “writing”–“reading” DNA processes [97] (Figure 1.12). The recent research efforts opened the way toward practical, high‐capacity, low‐maintenance information storage in synthesized DNA [98–100]. As an example, a 5.27‐megabit book was stored using DNA microchips and then read the book by using the DNA sequencing [101]. Other, even more impressive, examples demonstrated encoding the pixel values of black‐and‐white images and a short movie into the genomes of a population of living bacteria and then retrieving them back by the DNA sequencing [102].