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DNA nanostructures have recently attracted increasing interest in biological and biomedical applications by virtue of their unique properties, such as structural programmability, multi‐functionality, stimuli‐responsive behaviors, and excellent biocompatibility. In particular, the intelligent responsiveness of smart DNA nanostructures to specific stimuli has facilitated their extensive development in the field of high‐performance biosensing and controllable drug delivery. This minireview begins with different self‐assembly strategies for the construction of various DNA nanostructures, followed by the introduction of a variety of stimuli‐responsive functional DNA nanostructures for assembling metastable soft materials and for facilitating amplified biosensing. The recent achievements of smart DNA nanostructures for controllable drug delivery are highlighted. Finally, the current challenges and possible developments of this promising research are discussed in the fields of intelligent nanomedicine. [ABSTRACT FROM AUTHOR]

The Cu2+-dependent ligation DNAzyme is implemented as a biocatalyst for the colorimetric or chemiluminescence detection of Cu2+ ions, Hg2+ ions, or cocaine. These sensing platforms are based on the structural tailoring of the sequence of the Cu2+-dependent ligation DNAzyme for specific analytes. The tethering of a subunit of the hemin/G-quadruplex DNAzyme to the ligation DNAzyme sequence, and the incorporation of an imidazole-functionalized nucleic-acid sequence, which acts as a co-substrate for the ligation DNAzyme that is tethered to the complementary hemin/G-quadruplex subunit. In the presence of different analytes, Cu2+ ions, Hg2+ ions, or cocaine, the pretailored Cu2+-dependent ligation DNAzyme sequence stimulates the respective ligation process by combining the imidazole-functionalized co-substrate with the ligation DNAzyme sequence. These reactions lead to the self-assembly of stable hemin/G-quadruplex DNAzyme nanostructures that enable the colorimetric analysis of the substrate through the DNAzyme-catalyzed oxidation of 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid), ABTS2−, by H2O2 into the colored product ABTS.−, or the chemiluminescence detection of the substrate through the DNAzyme-catalyzed oxidation of luminol by H2O2. The detection limits for the sensing of Cu2+ ions, Hg2+ ions, and cocaine correspond to 1 n M, 10 n M and 2.5 μ M, respectively. These different sensing platforms also reveal impressive selectivities. [ABSTRACT FROM AUTHOR]

Polymerase/nicking enzymes and nucleic-acid scaffolds are implemented as DNA machines for the development of amplified DNA-detection schemes, and for the design of logic gates. The analyte nucleic acid target acts, also, as input for the logic gates. In the presence of two DNA targets, acting as inputs, and appropriate DNA scaffolds, the polymerase-induced replication of the scaffolds, followed by the nicking of the replication products, are activated, leading to the autonomous synthesis of the Mg2+-dependent DNAzyme or the Mg2+-dependent DNAzyme subunits. These biocatalysts cleave a fluorophore/quencher-functionalized nucleic-acid substrate, thus providing fluorescence signals for the sensing events or outputs for the logic gates. The systems are used to develop OR, AND, and Controlled-AND gates, and the DNA-analyte targets represent two nucleic acid sequences of the smallpox viral genome. [ABSTRACT FROM AUTHOR]