Abstract
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The high costs and slow speeds associated with DNA synthesis, or writing data in DNA, currently hinder the widespread adoption of DNA data storage. Proteins such as ligases that are used to join DNA strands together end-to-end during the assembly process are the most expensive components of a DNA assembly reaction, and are prohibitively expensive at the scale suitable for data storage. DNAzymes, or DNA strands that act as enzymes, are much cheaper at scale than protein-based enzymes. Utilizing a ligating DNAzyme as a catalytic splint, we achieve room-temperature, enzyme-free assembly, offering a cost-effective alternative to traditional enzyme-based ligation methods. We demonstrate this technique by assembling three different constructs where DNA symbols, or oligos designed to encode information for data storage, are joined to linker sequences at either end. This linker-directed assembly technique allows data-encoding symbols to be assembled in any desired order in a single reaction. Leveraging the linker-directed assembly technique, rather than base-by-base synthesis on-demand, brings two advantages: The cost of the writing is reduced since the oligos can be purchased in bulk, and the data can be written faster since multiple symbols can be assembled simultaneously. To automate the DNAzyme-based assembly process and reduce the volume of liquid reagents required for assembly, we employed a digital microfluidic platform, a lab-on-a-chip system which relies on electrowetting on dielectric to manipulate droplets on an array of electrodes. Our work aims to reduce the cost and increase the speed of DNA writing by linker-directed assembly of prefabricated DNA blocks that can be synthesized in bulk, by substituting protein ligase for DNA-based ligase, and by leveraging a digital microfluidic platform to automate and reduce the reagent volumes required for the DNA write process.