Hexadecimal data encryption in paranemic crossover (PX) DNA

DNA is highly programmable and efficient for encoding information. In this work, we use the paranemic crossover (PX) DNA structures for a binary-encoded system. As substrates for data storage, we designed a combination of PX and anti-PX structures where the four strands of the PX motif are complementary to those in the anti-PX motif. To write data, we programmed encoding elements in each of the four strands of the PX and anti-PX motifs. The encoded data remains encrypted until the samples are processed at a specific temperature, when the PX and anti-PX motifs reassociate to four distinct duplexes, defined by the encoding elements and retrieved using an electrophoretic readout. We show that the encoded information is stable for several days when stored at 20 {degrees}C, 37 {degrees}C or outdoors, with the encrypted structures showing higher nuclease resistance compared to the decrypted structures. Using this strategy, we demonstrate hexadecimal encoding using a combination of 4 bits, encrypting specific words and color codes. We envision such systems could find use barcoding, secure messaging and authentication.