br Synthesis and mechanism of fluorescent DNA
Synthesis and mechanism of fluorescent DNA-CuNMs
Application of fluorescent DNA-CuNMs
Summary and conclusions In summary, we introduce recent research progress in the synthesis and various applications of DNA-CuNMs. DNA-CuNMs with novel catalytic, electrical and optical properties can be obtained on various DNA scaffolds with special sequence design through chemical and electrochemical methods simply, rapidly and cheaply. On account of the advantages of fluorescent DNA-CuNMs, such as the large Stokes shift, high fluorescence efficiency, good photostability and non-toxic, DNA-CuNMs fluorophores gradually become a multipurpose tools promising for applications in logic gate construction, staining and biosensing of DNAs and RNAs, ions, proteins and enzymes, small molecules and so on (Fig. 7).
Introduction Deoxyribonucleic imipramine hcl (DNA) having genetic instructions are the cause of development and functioning of all living organisms , , , , , , . The research areas of DNA involved in vital processes such as mutagenesis, cell death, gene expression and transformation are of great importance , , , , , , . Interactions of small molecules with DNA have been investigated for decades in the hope of learning the design principle of targeting specific DNA sequences in order to control gene expression , , . Molecules or ligands can reversibly bind to DNA by three modes. These are (i) groove binding; (ii) electrostatical binding and (iii) intercalative binding , , . Among these three types of binding, intercalative binding is the most effective for drugs targeted to DNA . Intercalative binding, first proposed by Lerman et al. in 1961 , suggests that planar aromatic chromophore of typically intercalative small molecules becomes inserted between the adjacent base pairs of DNA. Small aromatic ligand molecules bind to DNA double helical structures by intercalating between stack base pairs thereby distorting the DNA backbone conformation and interfering DNA–protein interaction. DNA intercalators are used in chemotherapeutic treatment in order to inhibit DNA replication in the rapidly growing cancer cells . In general; intercalating dyes bind noncovalently to DNA through a combination of hydrophobic interaction with the DNA base pairs and ionic binding to negatively charged phosphate backbone. It is reported that the fluorescence of dye is ideally enhanced several fold upon binding to DNA, thereby enabling the detection of small amount of nucleic acid. Intensively studied DNA intercalators include ethidium bromide , , , daunomycin , acridine orange , nile blue , proflavine  and so on. Among them, ethidium bromide (EB) is a well known and widely used intercalating dye because of its striking enhancement of fluorescence upon binding to DNA , , . In solution, an unbound ethidium cation under photoirradiation donates a proton to the solvent which significantly increases its nonradiative decay rates . On the other hand, ethidium cation is shielded from contact with the solvent molecules after intercalation between the base pairs of the double helix of DNA, thereby inhibiting the fluorescence quenching via the proton transfer mechanism . The mechanism of EB intercalation with DNA, as well as the increase in EB excited state lifetime from 1.8ns in water to 23ns upon binding to DNA is well understood , , , , . These unique spectral characteristics make EB relatively accessible to utilize for measuring DNA concentration in solution. Another commonly used intercalating dye is Propidium Iodide (PI), derivative of ethidium ion. There are several reports on the interaction of PI with nucleic acids for the detection and quantification of nucleic acids , , . The use of PI as a fluorescent DNA intercalating label in the simpler and quicker staining method for the analysis of DNA per cell by flow cytometry has been described by Krishan .