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Since last decade, microRNAs have been identified as promising biomarkers for specific diseases, one common type is cancer. miRNA, usually of around 22 nucleotides long, are made inside our body via complex mechanisms. They play important roles in gene regulation through several ways, such as binding with messenger-RNA (mRNA) to inhibit translation and speeding up mRNA degradation to cause gene silencing. Dysregulation of miRNA expression may lead to under- or over-expression of genes and hence diseases.
G-quadruplexes (Gq) are formed by 4 strands of DNA made up of Guanine bases. When Gq forms a complex with Hemin, it exhibits peroxidase activity and functions as a DNAzyme. Its catalytic activity is utilized in many DNA nanostructures where a colour change is produced by target-induced conformational change.
During the strand displacement reactions, two strands with partly or fully complementary sequences hybridize to each other, displacing one or more pre-hybridised strands. This process is initiated at a single-stranded site called a ‘toehold’. Seeing this as a commonly-employed reaction in DNA nanostructure designs, we of course include this as one of our the main properties we have in our designs.


In vivo synthesis of DNA nanostructures for disease diagnosis through miRNA-induced structural transformation

DNA has emerged as a promising material for the creation of novel functional nanostructures. Here we present DNA nanostructures capable of simultaneous detection of multiple microRNA (miRNA) targets which are identified as promising disease biomarkers. Logic gates can be easily incorporated into our designs to test various combinations of miRNA targets. G-quadruplexes form when the specified target hybridizes with the probe, generating fluorescence in the presence of substrate. We endeavor to demonstrate intracellular synthesis, self-assembly and functioning of our nanostructures inside E. coli. Our constructs open up new possibilities in future research on DNA nanotechnologies as diagnostic tools, and promote the applications of miRNA testing in clinical conditions.

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