Synchronization of Two Assembly Processes To Build Responsive DNA Nanostructures

Nonenzymatic Autonomous Assembly of Cross-Linked Network Structures from Only Two Palindromic DNA Components for Intracellular Fluorescence Imaging of miRNAs

The abnormal expression of miRNA-21 is often found in tumor specimens and cell lines, and thus, its specific detection is an urgent need for the diagnosis and effective therapy of cancers. In this contribution, we demonstrate a palindrome-based hybridization chain reaction (PHCR) upon the stimuli of a short oligonucleotide trigger to perform the autonomous assembly of cross-linked network structures (CNSs) for the amplification detection of miRNA-21 and sensitive fluorescence imaging of cancerous cells. The building blocks are only two palindromic hairpin-type DNA strands that are separately modified with different fluorophores (Cy3 and Cy5), which is easily combined with the catalytic hairpin assembly (CHA) technique that can further amplify the signal output. Utilizing the CHA-PHCR assay system, a small amount of miRNA-21 can activate many triggers via CHA and in turn induce the PHCR-based CNS assembly from more DNA building blocks, bringing Cy3 and Cy5 into close proximity to each other and generating ultrasensitive fluorescence resonance energy transfer signals. As a result, target miRNA can be quantitatively detected down to as low as 10 pM with high assay specificity. The coexisting nontarget miRNAs and other biomacromolecules do not interfere with signal transduction. The developed assay system is suitable for screening different expression levels of miRNA-21 in living cells by fluorescence imaging. The palindrome-based cross-linking assembly can enhance the intracellular stability of assembled nanostructures by at least fivefold and exhibit the good universality for the detection of other miRNAs. Moreover, cancerous cells can be distinguished from healthy cells, and the CHA-PHCR assay is in good accordance with the gold standard PCR method, indicating a promising platform for the diagnosis of human cancers and other genetic diseases.

Construction of Smart Stimuli-Responsive DNA Nanostructures for Biomedical Applications

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.

Stimuli-Responsive DNA Self-Assembly: From Principles to Applications

Stimuli-responsive DNA self-assembly shares the advantages of both designed stimuli-responsiveness and the molecular programmability of DNA structures, offering great opportunities for basic and applied research in dynamic DNA nanotechnology. In this minireview, we summarize the most recent progress in this rapidly developing field. The trigger mechanisms of the responsive DNA systems are first divided into six categories, which are then explained with illustrative examples following this classification. Subsequently, proof-of-concept applications in terms of biosensing, in vivo pH-mapping, drug delivery, and therapy are discussed. Finally, we provide some remarks on the challenges and opportunities of this highly promising research direction in DNA nanotechnology.

Targeted Delivery of Rab26 siRNA with Precisely Tailored DNA Prism for Lung Cancer Therapy

Programmable DNA nanostructures are a new class of biocompatible, nontoxic nanomaterials. Nevertheless, their application in the field of biomedical research is still in its infancy, especially as drug delivery vehicles for gene therapy. In this study, a GTPase Rab26 was investigated as a new potential therapeutic target using a precisely tailored DNA nanoprism for targeted lung cancer therapy. Specifically, a DNA nanoprism platform with tunable targeting and siRNA loading capability is designed and synthesized. The as-prepared DNA prisms were decorated with two functional units: a Rab26 siRNA as the drug and MUC-1 aptamers as a targeting moiety for non-small cell lung cancer. The number and position of both siRNA and MUC-1 aptamers can be readily tuned by switching two short, single-stranded DNA. Native polyacrylamide gel electrophoresis (PAGE) and dynamic light scattering technique (DLS) demonstrate that all nanoprisms with different functionalities are self-assembled with high yield. It is also found that the cellular uptake of DNA prisms is proportional to the aptamer number on each nanoprism, and the as-prepared DNA nanoprism show excellent anti-cancer activities and targeting capability. This study suggests that by careful design, self-assembled DNA nanostructures are highly promising, customizable, multifunctional nanoplatforms for potential biomedical applications, such as personalized precision therapy.

A Case Study of the Likes and Dislikes of DNA and RNA in Self-Assembly

Programmed self-assembly of nucleic acids (DNA and RNA) is an active research area as it promises a general approach for nanoconstruction. Whereas DNA self-assembly has been extensively studied, RNA self-assembly lags much behind. One strategy to boost RNA self-assembly is to adapt the methods of DNA self-assembly for RNA self-assembly because of the chemical and structural similarities of DNA and RNA. However, these two types of molecules are still significantly different. To enable the rational design of RNA self-assembly, a thorough examination of their likes and dislikes in programmed self-assembly is needed. The current work begins to address this task. It was found that similar, two-stranded motifs of RNA and DNA lead to similar, but clearly different nanostructures.

A Signal-Passing DNA-Strand-Exchange Mechanism for Active Self-Assembly of DNA Nanostructures

DNA nanostructured tiles play an active role in their own self-assembly in the system described herein whereby they initiate a binding event that produces a cascading assembly process. We present DNA tiles that have a simple but powerful property: they respond to a binding event at one end of the tile by passing a signal across the tile to activate a binding site at the other end. This action allows sequential, virtually irreversible self-assembly of tiles and enables local communication during the self-assembly process. This localized signal-passing mechanism provides a new element of control for autonomous self-assembly of DNA nanostructures.