The well-known DNA double helix is composed of two DNA molecules of complementary sequence: an A in a DNA strand will face a T in the other strand, while a G will face a C. And vice versa. Such is the mechanism by which genetic information can be read and copied. This molecular recognition process, called hybridization, is the central component of not only the expression of genes, but also of essentially all DNA-related research. Because these rules are strict and apply to any and all DNA, genomes and DNA-encoded digital information can be accurately copied and read.
Biotechnology applications such as these require an ever increasing amount of DNA, yet widespread and inexpensive access to DNA-based information raises the question of security and traceability. We developed a chemical way to authenticate and encrypt information using a novel form of DNA that uses the same set of rules but without interfering with natural DNA. The key to this technique is to employ and produce the mirror image of natural DNA, which results in double helices being left-handed structures instead of the standard right-handed DNA double helix. Because of this, (natural) D-DNA can only recognize a complementary D-DNA sequence while its mirror-image, L-DNA, only associates with L-DNA.
Mirror, mirror on the array
This unusual property was used to design L-DNA signatures that are easy to identify but which remain absolutely invisible to anyone working with natural DNA. These signatures are created by arranging L-DNA sequences in a precise order on the flat surface of a microarray slide; they cannot be deciphered without a key given their sequence complexity and are also indelible since L-DNA molecules are resistant to enzymatic degradation, while natural D-DNA is not. And both DNA forms can be synthesized in parallel, on the same surface, with complete control over sequence and space. "L-DNA acts as some sort of invisible ink which can only be revealed with the appropriate tool and can be the key to decrypt information stored on natural D-DNA," says Jory Liétard, principal investigator of this study conducted at the Department of Inorganic Chemistry.
We applied this signature concept to QR codes and to steganography, by hiding a message composed of L-DNA in a few pixels within a D-DNA picture. The message is invisible to the naked eye but is accessible to an operator aware of the presence of an L-DNA "ink" Mirror-image L-DNA synthesis is a simple and extremely robust way to watermark and encrypt information without leaving the realm of nucleic acids.
The research was funded by the Austrian Science Fund (FWF project 30596).
S E R V I C E: Publication in "Chemistry – A European Journal"
E. Schaudy, M. M. Somoza and J. Lietard: L -DNA Duplex Formation as a Bioorthogonal Information Channel in Nucleic Acid-Based Surface Patterning, published online 09/06/2020. Doi: 10.1002/chem.202001871
Contact
Dr. Jory Lietard
Institut für Anorganische Chemie
Fakultät für Chemie
Althanstraße 14 (UZA II)
1090 Wien
+43-1-4277-52643
