Biosensors Made of Synthetic Functional Nucleic Acids Toward Better Human Health

Selection of a metal ligand modified DNAzyme for detecting Ni2

Nickel is a highly important metal, and the detection of Ni²⁺ using biosensors is a long-stand analytical challenge. DNA has been widely used for metal detection, although no DNA-based sensors were reported for Ni²⁺. DNAzymes are DNA-based catalysts, and they recruit metal ions for catalysis. In this work, in vitro selection of RNA-cleaving DNAzymes was carried out using a library containing a region of 50 random nucleotides in the presence of Ni²⁺. To increase Ni²⁺ binding, a glycyl-histidine-functionalized tertiary amine moiety was inserted at the cleavage junction. A representative DNAzyme named Ni03 showed a high cleavage yield with Ni²⁺ and it was further studied. After truncation, the optimal sequence of Ni03l could bind one Ni²⁺ or two Co²⁺ for catalysis, while other metal ions were inactive. Its cleavage rates for 100 μM Ni²⁺ reached 0.63 h^-1 at pH 8.0. A catalytic beacon biosensor was designed by labeling a fluorophore and a quencher on the Ni03l DNAzyme. Fluorescence enhancement was observed in the presence of Ni²⁺ with a detection limit of 12.9 μM. The sensor was also tested in spiked Lake Ontario water achieving a similar sensitivity. This is another example of using single-site modified DNAzyme for sensing transition metal ions.

Advances in functional nucleic acid based paper sensors

This article provides an extensive review of paper-based sensors that utilize functional nucleic acids, particularly DNA aptamers and DNAzymes, as recognition elements.

Site-specific functionalization with amino, guanidinium, and imidazolyl groups enabling the activation of 10–23 DNAzyme

10–23 DNAzyme has been extensively explored as a therapeutic and biotechnological tool, as well as in DNA computing. Faster cleavage or transformation is always needed. The present research displays a rational modification approach for a more efficient DNAzyme. In the catalytic core, amino, guanidinium and imidazolyl groups were introduced for its chemical activation through the adenine base. Among the six adenine residues, A9 is the unique residue that realizes all the positive effects; the 6-amino and 8-position of adenine and the 7-position of 8-aza-7-deaza-adenine could be used for the introduction of the functional groups. A12 is a new choice for catalytic improvement with an 8-substituent. Therefore, more active DNAzymes could be expected by this nucleobase-modified activation approach.

Chemical activation of 10–23 DNAzyme was realized at A9 modified with active functional groups amino, guanidinium, and imidazolyl groups.