Modeling the Adsorption of the miR-29a Cancer Biomarker on a Graphene Quantum Dot.

MicroRNAs (miRNAs) are small noncoding RNA molecules associated with the regulation of gene expression in organisms. MiRNAs are focused on as potential cancer biomarkers due to their involvement in cancer development. New potential techniques for miRNA detection are rapidly developed, while there is a lack of effective extraction approaches, especially for miRNAs. Recently, graphene quantum dots (GQDs) have been involved in many disease biosensor platforms including miRNA detection, but no application in miRNA extraction is studied. To extract miRNAs, miRNA adsorption and desorption on GQDs are the key. Thus, in this work, the adsorption mechanism of miRNA on GQDs in solution is revealed using molecular dynamics simulations. The aim is to explore the possibility of using GQDs for miRNA extraction. The folded miR-29a molecule, one of the key cancer biomarkers, is used as a miRNA model. Two systems with one (1miR) and four (4miR) chains of miR-29a were set. MiR-29a molecules in all systems are simultaneously adsorbed on the GQD surface. Our finding highlights the ability of the GQD in collecting miRNAs in solution. In 1miR, the whole miR-29a chain sits on the GQD face, whereas all miR-29a molecules in 4miR show the "clamping" conformation. No "lying flat" orientation of miR-29a is observed due to the existence of the preserved hairpin region. Interestingly, the 5' end shows tighter binding than the 3' terminus. A design of complementary DNA with the recognition segment involving the sequences close to the 3' end can promote effective miR-29a desorption.